Neutrino Os illations and the LMC dete tor atMiniBooNEHoyt KoepkeApril 26, 2004Undergraduate Honors ThesisPhysi sSpring 2004Adviser: Prof. Eri ZimmermanThesis Committee: Prof. John Cumalat, Physi s, ChairProf. Eri Zimmerman, Physi sProf. Homer Ellis, Mathemati s.

Neutrino Os illations and the LMC dete tor at MiniBooNEHoyt Koepke, Physi sAbstra tNeutrino os illations, one of the urrent hot topi s in physi s, is the subje t ofthe Booster Neutrino Experiment (BooNE). Experimental eviden e ontinues tobuild for neutrino os illations; however, the data are in onsistent with os illationsbetween only 3 neutrino types. BooNE is designed to investigate this on i t,dupli ating the most ontroversial experiment but with far higher statisti s. Itgenerates a beam of ��'s and looks for the appearan e of �e's. Within BooNE, anear-line dete tor alled the \Little Muon Counter" (LMC) provides informationabout the intrinsi �e ontamination in the �� beam.

Contents1 The Physi s of Neutrinos 11.1 Theory Behind Neutrino Os illations . . . . . . . . . . . . . . . . . . . . 21.2 Consequen es . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Dete ting Neutrinos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.4 Early Signs of Neutrino Os illations . . . . . . . . . . . . . . . . . . . . . 61.4.1 Solar Neutrino Experiments . . . . . . . . . . . . . . . . . . . . . 61.4.2 Atmospheri Neutrino Experiments . . . . . . . . . . . . . . . . . 91.4.3 LSND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.5 The Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 MiniBooNE 172.1 Physi s and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172.1.1 Intrinsi �e Contamination . . . . . . . . . . . . . . . . . . . . . . 182.1.2 The Main Dete tor . . . . . . . . . . . . . . . . . . . . . . . . . . 202.2 Bla k Box Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.3 The Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 The LMC Dete tor 233.1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.2 Testing the Prototype Dete tors . . . . . . . . . . . . . . . . . . . . . . . 263.3 Constru tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283.3.1 The Spe trometer Magnet . . . . . . . . . . . . . . . . . . . . . . 283.3.2 The Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323.3.3 The Preamp Cir uits . . . . . . . . . . . . . . . . . . . . . . . . . 333.3.4 Data A quisition . . . . . . . . . . . . . . . . . . . . . . . . . . . 343.4 Current Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 Analysis 354.1 Tra k Re onstru tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354.2 Software and The Analysis Framework . . . . . . . . . . . . . . . . . . . 364.3 The Experimental Data Side . . . . . . . . . . . . . . . . . . . . . . . . . 374.4 The Monte Carlo Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384.4.1 Greys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384.4.2 InputGreys & Pro essGreys . . . . . . . . . . . . . . . . . . . . . 394.5 The Event Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.6 Current Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 Con lusion 43i

A Appendix: The Event Display Design 45A.1 Stru ture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46A.2 Possible Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

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1 The Physi s of NeutrinosOne of the urrent hot topi s in physi s today is the study of neutrinos. These light (ormassless), diÆ ult-to-dete t parti les are hallenging both experimental and theoreti alphysi ists and pushing them to the limits of urrent te hnology and understanding. Theirproperties, even down to the question of whether they have mass, are still being exploredby theorists and experimentalists alike. Several experiments, in luding MiniBooNE (�rststage of BooNE, Booster Neutrino Experiment) at Fermi National A elerator Labora-tories (FNAL), are expanding the edges of our knowledge about these weakly-intera tingparti les, attempting to dis over their properties.One phenomenon in parti ular fuels the

Figure 1: The Standard Model of Parti lePhysi s.

interest. There are three known avorsof neutrinos, �e, ��, and �� , and severalexperiments have dis overed that one a-vor of neutrino will swit h, or \os illate,"to another avor mid- ight. Currently,the a epted quantum me hani al expla-nation says that if neutrino avors havedi�erent masses, one avor of neutrino mayos illate into another avor at a rate re-lated to the di�eren e in squared massesof the neutrinos. Thus a onsequen e ofobserving neutrinos os illate is that theyhave some mass. It's a topi of interestbe ause the standard model, the widelya epted and veri�ed model of parti le physi s, says they're massless. This intrigu-ing situation has led to a number of neutrino experiments around the world, in ludingMiniBooNE. 1

Neutrino physi s essentially began with a letter from Wolfgang Pauli to the Physi alSo iety of Tubingen. In this letter, he postulated the existen e of a new parti le, nowknown as the neutrino, as a way to resolve the ontinuous momentum spe trum observedin ele trons from nu lear beta de ay. If the de ay was indeed a two body de ay, as wasbelieved, then the momentum of the ele tron in the rest frame of the parent parti lewould have had a single value. A three body de ay allowed for the spe trum observed.Sin e then, neutrinos been instrumental in developing a theoreti al understandingof weak for e intera tions, being that they only intera t with matter via the weak for e(and possibly gravity, if they do indeed have mass). Weak for e theories are now abuilding blo k in the Standard Model of parti le physi s, a model apable of des ribingall the weak for e intera tions (see Figure 1)[1℄.1.1 Theory Behind Neutrino Os illationsPhysi ists have known for a while that the avor eigenstates of quarks are not equivalentto their mass eigenstates. The states transform a ording a matrix alled the CKMmixing matrix, and some os illation e�e ts, su h as K0 $ K0, have been observed[2℄.However, the CKM transformation matrix is very lose to the unit matrix, so mixinge�e ts are rarely observed.The theory of neutrino os illations is essentially based on the same assumption {that the avor eigenstates are not equivalent to the mass eigenstates. To illustrate thetheory, let us onsider os illations between two neutrino types1. The transformationwould be: � j�e >j�� > � = � os� sin��sin� os� � � j�1 >j�2 > � (1)where j�1 > and j�2 > are the mass eigenstates with masses m1 and m2, respe tively.Thus, for a given avor state �,1Of ourse the three-neutrino ase is a little more ompli ated; I am using the two avor ase merelyto show on eptually what is going on. For a thorough derivation of os illations (with three neutrinotypes), see [3℄ pages 323-329. 2

j�� >= os �j�1 > +sin �j�2 > (2)The mass eigenstates j�1 > and j�2 > evolve a ording to Shr�odinger's equation:j�i(t) >= e�i(Eit�piL)j�i > (3)In this equation, L = t (taking = 1), and Ei = pp2 +m2i ' p + m2i =2p. Thus, theevolution of a neutrino of avor � is:j��(L) >= e�im21L=2E os �j�1 > +e�im22L=2E sin �j�2 > (4)The os illation probability, for � 6= �, is given by:P��!��(L) = j < ��j��(L) > j2 (5)This be omes, after a fair amount of algebra:P��!��(L) = sin2 2� sin2�1:27�m2 LE� (6)where �m2 = m22 � m21 (in eV2), L is the distan e from the sour e to the dete torin km, and E is the energy in GeV. This equation is essentially the basis of neutrinoos illations2.1.2 Consequen esThe standard model of parti le physi s has been very su essful. It explains basi allyeverything we've seen in experiments, from parti le de ays to strong and weak for eintera tions. As a testament to this, it has remained virtually un hanged for severalde ades.2The derivation above is for neutrino os illations in a va uum. Matter also a�e ts the os illationprobability (see [3℄, pp. 348-363, for more information), an e�e t signi� ant in neutrinos from the sunor those that travel through the earth. 3

However, there are signs that it's not the end of the story. It has a number offree parameters that have to be determined by experiment, and the ultimate theorywould ideally predi t all we observe from �rst prin iples. Furthermore, there are thingsit doesn't explain { why there appear to be three families of quarks and leptons, forinstan e. Not only that, but the urrent standard model of ele troweak intera tions,one of the pillars of the standard model, assumes that neutrinos are massless (there areextensions that allow for massive neutrinos, seemingly required by the observations ofos illations, but adopting one of those would be a huge deal in parti le physi s) [1℄. Allthese ombined hint that there's physi s beyond the standard model.That's why there's so mu h interest in neutrino os illations. A number of theories,parti ularly super-symmetry and several Grand Uni� ation Theories (GUTs), have beenproposed as extensions to the Standard Model, and some of these in lude massive neutri-nos that an os illate. However, these theories have yet to be on�rmed experimentally,and neutrino os illations present one of the few roads open to us in testing them andexploring physi s beyond the standard model. Ultimately, then, urrent resear h intoneutrino os illations may ause the urrent theory of the Standard Model to be amended.However, high-energy parti le physi ists are not the only people interested in thisresear h. In astrophysi s, massive neutrinos may very likely be a part of the missing darkmatter in the universe. Be ause they intera t via the weak for e only at higher energies,these neutrinos would be inert and undete ted, with possibly the only e�e t being agravitational �eld. A lot of theoreti al work has been done on this possibility, and it'sstill an intriguing hypothesis waiting for on�rmation from neutrino experiments.1.3 Dete ting NeutrinosNeutrinos are very diÆ ult to dete t. They intera t only via the weak for e; in otherwords, by ex hanging a W or Z boson with a nu leon in the dete tor.There are two possible rea tions when a neutrino ex hanges a W+ or W� boson,4

alled a Charged Current (CC) event:�` + n! p+ `� (7)�` + p! n + `+ (8)where ` represents the lepton number or family (an ele tron neutrino will produ e anele tron, and so on)3. The nu leus of the atom and resulting harged lepton arrieso� the energy of the neutrino. There is also a lower energy uto� on these rea tionsthat depends on the lepton avor; the neutrino must have enough energy to reate the harged lepton before the rea tion an o ur. Many urrent dete tors look for theserea tions and identify the resulting lepton to get the avor of the original neutrino.Others look for atoms in whi h a neutron has hanged to a proton or a proton to aneutron, indi ating a neutrino harged urrent event.The other way a neutrino intera ts with matter, by ex hanging a neutral Z bosonwith a nu leon, is alled a Neutral Current (NC) event. In this rea tion, the startingparti les are the same as the produ ts, but the nu leon takes some of the neutrino's en-ergy, possibly dislodging it from the nu leus if suÆ ient energy is transferred. Dete torsusing NC rea tions look for a dislodged nu leon. This rea tion does not reveal the avorof the neutrino, however.One of the most ommon te hniques now to sear h for these rea tions is to line a tankof some transparent liquid (usually water or mineral oil) with photomultiplier tubes. A harged parti le, be it a proton or a harged lepton, arrying away enough energy fromthe CC or NC event, would often travel faster than the speed of light in that medium.This produ es Cerenkov radiation, an e�e t analogous to waves emitted from a shiptraveling faster than the waves or to a soni boom. It produ es a one of light, wherethe emission angle � is related to the velo ity of the parti le by os� = =vn, where isthe speed of light, n is the refra tive index of the medium, and v is the parti le's velo ity[2℄. The phototubes pi k up a ring on the edge of the tank, and possibly the rings of3These intera tions are valid only in the energy range where the nu leon doesn't break up; if it does,the intera tion is alled Deep Inelasti S attering. 5

de ay parti les in the ases of muons (or taus) as well. Charged urrent intera tions anbe found and the lepton avor identi�ed by looking for the hara teristi rings.1.4 Early Signs of Neutrino Os illationsAlthough the theory is fairly straightforward, the fa t that the onsequen es of thetheory don't dire tly �t into the Standard Model aused experiments to provide theimpetus behind exploring the physi s of neutrinos. It started when a handful of ex-periments looking at neutrinos emitted by rea tions within the sun noti ed a fra tionof the neutrinos that the standard model of solar pro esses predi ted they would see.Physi ists proposed neutrino os illations as one solution, along with alternate modelsfor the sun or a ooler solar ore than expe ted[4℄[5℄. As other subsequent experimentsinvestigated the phenomenon and on�rmed the standard solar model in other ways, theeviden e be ame more and more ertain. Now there are a number of neutrino os illationexperiments investigating os illations from three angles: Solar neutrino experiments lookat neutrinos generated by well-understood nu lear rea tions in the sun, atmospheri ex-periments look at neutrinos resulting from ollisions between osmi rays and mole ulesin the upper atmosphere, and experiments like MiniBooNE look at neutrinos generatedby a elerators or nu lear rea tors.1.4.1 Solar Neutrino ExperimentsSolar neutrino resear h was �rst driven by the Standard Solar Model as a way to on�rmits theoreti al understanding of the pro esses at the enter of the sun[6℄. Neutrinos inter-a t with matter rarely enough that many of those produ ed by internal solar pro esses,virtually all ele tron neutrinos, would es ape, and some of these ould be dete ted onearth. At that time, the harged urrent weak-for e rea tions whi h determine when(and how) the neutrinos intera t with matter { were well understood theoreti ally [6℄,so an a urate predi tion of the dete ted neutrino ux on earth was possible (see Figure2). The �rst signi� ant experiment to investigate solar neutrinos was the Homestake6

Mine experiment, built from 1965-1967. It used the �e+37Cl!37Ar+� rea tion (inverse�-de ay), where the �e e�e tively turns one of the neutrons inside the 37Cl nu leus intoa proton via a harged urrent intera tion and emits a beta parti le (ele tron) [7℄. Itdete ted �e's from 8B fusion in the sun (see Figure 2) by sear hing for Ar atoms in atank ontaining 390,000 liters of tetra hloroethylene [8℄. A ording to the solar theory,the Homestake experiment should have seen about 6� 2 SNU (Solar Neutrino Units, or10�36 aptures per target parti le per se ond); as it was, they only saw 2:2 � 0:2 SNU[9℄[10℄.The s ienti� ommunity was surprised, and though some people began to questionthe urrent solar models, many people simply assumed that the results were wrong.More experiments were built, in luding the GALLEX experiment in Italy, whi h usedgallium (�e+71Ga! e�+71Ge) to lower the neutrino dete tion threshold to in lude the

Figure 2: A diagram of the predi ted neutrino ux (in neutrinos per m2) versus energy fromvarious fusion pro ess in the sun. The energy sensitivity of several kinds of dete tors is shownon top. 7

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(b)Figure 3: (a). The ombined allowed regions for os illations of solar neutrinos from �e ! �xfor tan22� and �m2. The regions inside the lines are those shown at the 95% on�den e level.(b). The same region showing the area (shaded) ex luded by KamLAND, a rea tor experiment.Diagrams from [13℄.mu h higher ux of neutrinos from proton-proton fusion. The Standard Solar Modelpredi tion of their dete tion rate was 132 SNU, but they dete ted only 79 � 13 SNU,a ording to their �nal results published in 1994 [6℄. A similar gallium dete tor built inRussia, SAGE, released its results at about the same time, also seeing only 56% { 60%of the neutrino ux they expe ted [11℄.A third experiment alled Kamiokande (now upgraded with a larger dete tor and alled Super-Kamiokande, or Super-K), was a water-�lled Cerenkov dete tor originallybuilt to look for proton de ay but was set up to also look for neutrinos. It beganobservations in January of 1987, and published the �rst results in 1989, observing aneutrino ux of 2:5 � 106 m�2s�1 ompared to a standard model predi tion of 5:6 �8

106 m�2s�1. It agreed with the previous experiments within un ertainties.One of the most re ently built solar neutrino experiments is the Sudbury NeutrinoObservatory (SNO), another Cerenkov dete tor. SNO, however, uses heavy water (D2O),whi h has the added advantage of observing both CC rea tions, sensitive only to �e'sin the solar neutrino energy range (d + �e ! p + p + e�), and Elasti S attering4 (ES)(�x + e� ! �x + e�) and NC (�x + d ! n + p + �x) rea tions, equally sensitive to allnon-sterile neutrino types [12℄. This allowed them to fully look at the neutrino spe trumfrom the sun and the ase for neutrino os illations. The results released in 2001 indeedseemed to indi ate neutrino os illations from �e to other avors. The ux from the CCrea tions was (1:75 � 0:07) � 106 m�2s�1, whereas the ux from the ES rea tions was(2:39� 0:34)� 106 m�2s�1 [12℄, onsistant with the Standard Solar Model.The solar neutrino observations make a strong ase for neutrino os illations [14℄.A ombined analysis, then, of the results from these experiments should yield somestatisti al answers about these neutrino os illations, and indeed it does. The allowed�m2 to sin22� regions from the solar experiments are shown in Figure 3(a).KamLAND (for Kamioka Liquid s intillator Anti-Neutrino Dete tor) in Japan is area tor experiment worth mentioning as it gets similar results to the solar neutrinoexperiments. It looks for the disappearan e of �e's generated during �ssion pro essesinside several nearby nu lear rea tors. The \solar" neutrino os illation region ex ludedby the KamLAND result is shown in Figure 3(b).1.4.2 Atmospheri Neutrino ExperimentsAnother lass of neutrino experiments look at neutrinos resulting from the de ays ofmesons and muons produ ed in osmi ray showers (see Figure 4(a)) [3℄. These showersprodu e twi e as many ��=��'s than �e=�e's (see Figure 4(b)) [3℄. By looking at theneutrino ux as a fun tion of angle { in other words, from what lo ation on the earththey ome from { dete tors an look at the neutrino ux essentially as a fun tion of thedistan e traveled. One experiment in parti ular (that is also looking at solar neutrinos)4Elasti S attering te hniques look for the re oil of the atomi nu leus after either a CC or NC event.9

(a) (b)Figure 4: (a). An artist's rendition of a small osmi ray shower; a high-energy shower mayprodu e 108 parti les or more. (b). The atmospheri neutrino ux from zenith-angle. Several al ulations are shown by the lines, and the observations from Super-K are shown as the datapoints. Figure from [15℄.is doing this, Super-K. Two others experiments, Soudan 2 and the IMB (for IrvineMi higan Brookhaven) experiment also investigated atmospheri neutrino signals.Though not as many experiments have been devoted to studying atmospheri neu-trinos as to solar neutrinos, the results from atmospheri neutrino data have made themost onvin ing ase for os illations. In omparing the zenith-angle ux to the ux ofneutrinos traveling through the earth, Super-K has noti ed a signi� ant disappearan eof ��'s, ruling out the possibility of nothing happening { i.e. no os illations or otherunpredi ted behavior { by 15.9� [16℄.The disappearan e seems to be best explained by os illations, as the data losely �tthe simulations if os illations are in luded, as shown in Figure 5. Though other, moreexoti theories have been proposed as to the �� disappearan e (su h as neutrino de ay,where the neutrino de ays into another possibly unknown or undete ted parti le [17℄),10

Figure 5: The atmospheri neutrino ux as a fun tion of os(�). The solid line shows theMonte Carlo simulation without os illations, and the dashed line shows the simulation withos illations with the parameters �m2 ' 2:2 � 10�3(eV )2 and sin22� ' 1.the high statisti s obtained from Super-K favor os illations from �� ! �� over any otheryet proposed by 4� [16℄. Based on the �� ! �� solution, the allowed region of �m2 tosin22� is shown in Figure 6.1.4.3 LSNDLSND, whi h stands for Liquid S intillator Neutrino Dete tor, was an a elerator ex-periment lo ated at Los Alamos National Laboratory. It generated neutrinos using abeam of 798 MeV protons hitting a target to generate pions. These pions, mostly �+'s,de ay predominately into a �+ and a ��, and the �+ then de ays almost ex lusively into11

Figure 6: The Super-K allowed regions for atmospheri neutrino os illations from �e ! �� forsin22� and �m2.e++�e+��. LSND sear hed for the appearan e of �e's, as the intrinsi �e ontaminationwas very low (�e=�� ' 8� 10�4) [18℄.It looked for these neutrinos by sear hing for the positron from a �e+p! n+e+ CCevent in a ylindri al tank, 8.3m long by 5.7m in diameter, that was �lled with mineraloil doped with a liquid s intillator5 and lined with photomultiplier tubes. The positronfrom the rea tion would ause Cerenkov radiation and thus a ring on the edge of thetank. By re ording the time the photons hit ea h of the phototubes, the s intillationlight would yield further information about the lo ation of the event and travel path of5S intillators are materials that emit photons whenever a harged parti le with suÆ ient energypasses through them. 12

Figure 7: The LSND allowed region for sin22� and �m2 for a elerator neutrino os illationsfrom �� ! �e. Also shown are the regions (to the right of the lines) ex luded by Karmen,another a elerator experiment, and Bugey, a rea tor experiment.the resulting parti le. In addition, the neutron produ ed by the CC intera tion then aptured on another proton in the oil, produ ing a deuteron and a 2.2 MeV . The was also re orded in the dete tor, allowing distin tion between �e's and ��'s.LSND ran from 1993 to 1998 and saw a total of 89:4�24 �e os illation andidates afterba kground subtra tion, orresponding to an os illation probability of approximately0:26 � 0:08 per ent [19℄. The allowed regions for their data, along with the ex ludedregions from two other experiments sensitive to LSND's sin22� to �m2 region, are shownin Figure 7. 13

1.5 The ProblemThe LSND result presents a mystery for neutrino os illation theory, however. With threeneutrinos, there an only be 2 independent �m2's, as �m212 + �m223 = �m213, wherethe subs ripts denote the two mass eigenstates involved. However, what we observe arethree distin t values for �m2 oming from the three types of experiments (the �m2values are based on the 95% on�den e allowed regions):Experiment Type Os illation Type log10(�m2) RangeSolar + KamLAND �e ! �� or �� �5 to �4Atmospheri �� ! �� or X �3 to �2:1LSND �� ! �e �1 to 1:2These three distin t values are impossible to �t together given only three neutrino types.Physi ists have proposed a number of possible solutions to this problem. One of themost prominent is that there are a tually four neutrino avors, the three mentioned plusa fourth, sterile6 neutrino. This solution would require two nearly degenerate pairs ofmass eigenstates, with the mass di�eren e between the pairs being in the LSND (largest)region and ea h of the masses in these pairs being separated by one of the other results[20℄. This would be physi s beyond the standard model and ould indi ate a fourthfamily of parti les beyond the three already dis overed.Another possible solution whi h would also ex ite theorists is that the neutrinos andtheir antimatter ounterparts do not have the same mass spe trum. Thus the LSNDresult, whi h looked at �� ! �e os illations, would not �t with the other two. This wouldbe the �rst observed ase of CPT (Charge Parity Time) violation, a matter-antimatterasymmetry in ompatible with Quantum Field Theory [21℄, and would de�nitely give thetheorists something to think about.But new additions to the theory aren't the only way to resolve the problem. It isde�nitely possible that the analysis of one of the experiments is wrong. It may be thatthe higher �m2 is a tually around 10�2eV 2, at the boundary between the atmospheri 6A sterile parti le does not intera t with matter in any observable way, with the possible ex eptionof gravity. 14

and a elerator neutrino results. If improper analysis is at fault, than the LSND resultis the most suspe t as it is not orroborated by other experiments. This requires moreexperimental investigation, and the main experiment designed to look at the LSNDresult is MiniBooNE.

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2 MiniBooNEThe purpose of MiniBooNE is to on�dently on�rm or on�dently disprove the LSNDresult. It was designed to look at �� ! �e os illations at the same L/E ratio as LSND,allowing it to investigate the same �m2 to sin22� region (see Figure 8). The statisti s,however, will be far higher { MiniBooNE expe ts to see several hundred os illationevents and about 1 million total events over its three years of running. The MiniBooNEproposal was �rst submitted in De ember 1997 [22℄, and the experiment began takingdata in August 2002.2.1 Physi s and DesignMiniBooNE uses 8 GeV protons from the

Figure 8: The �m2 to sin22� region(inside the solid blue line) being inves-tigated by MiniBooNE with a 90% on�-den e level.

Booster a elerator ring at Fermilab to ulti-mately generate a beam of ��'s in whi h tolook for os illations to �e at a dete tor half akilometer downstream (see Figure 9). The pro-tons strike a stationary beryllium target wherethey produ e a shower of pions and kaons. Ap-proximately 80 bun hes, or \bu kets," of pro-tons hit the target every 67 millise onds, withea h bu ket ontaining upwards of 1010 protons.Adja ent bu kets are separated in time by 19nanose onds, and ea h train of 80 bu kets rep-resents one a elerator y le or \spill."A magneti fo using horn, generating a mag-neti �eld using 176 kA pulses in time with theproton bu kets, fo uses the positively harged parti les toward the dete tor. These de-bris parti les, mainly pions, de ay inside a pipe about 6 ft. in diameter and 50m long alled the de ay pipe, the primary de ay mode being �+ ! �+ + ��. All the non-17

neutrino parti les are stopped by a beam absorber at the end of the de ay pipe, and theneutrinos then travel through 500m of earth to our dete tor, a 12m sphere �lled withmineral oil and lined with photomultiplier tubes. Some of these neutrinos intera t via aCC rea tion in the tank, �e's produ ing an ele tron and ��'s produ ing a muon. Thesemuons then produ e a solid, distin t ring on the wall of the tank, and ele trons, sin ethey are lighter and more prone to radiation, produ e a less distin t ring.At ea h step along this pro ess, a number of physi s issues have to be well understoodto minimize the un ertainties in our result. There are two major issues that all theothers revolve around in some way: understanding exa tly what neutrinos left the de ayregion and understanding exa tly what neutrinos intera ted in the target. Be auseit is impossible to produ e an absolutely pure beam of muon neutrinos { and this isespe ially true at the energy range we're dealing with { we must understand what theintrinsi �e ontamination is before we an on�dently identify os illations. A lot ofe�ort in MiniBooNE is going toward that issue. The other primary physi s issue isevent re onstru tion inside the tank, a hallenging and di�erent puzzle to solve.2.1.1 Intrinsi �e ContaminationA signi� ant sour e of un ertainty in our �nal result is the intrinsi �e ontamination inour �� beam { we expe t 1.5 times as many of the �e events in the dete tor to be from ontaminations as from os illations, assuming we on�rm LSND's result. (see Figure 10).

Figure 9: The MiniBooNE Experiment.18

The ontamination omes from two sour es, �+ ! e++��+�e and K+=K0L ! �+e+�e,the se ond one being harder to quantitatively understand and the one we espe ially needto examine. The task, then, is essentially �guring out the relative ux of kaons to pions,and we are using detailed Monte Carlo simulations based on two sour es of informationand to �gure this out, data from HARP, another experiment, and the LMC.One signi� ant sour e of data for this

Figure 10: The expe ted breakdown of the andidate �e events. Out of 3500 events, weexpe t about 1500 from intrinsi �e ontami-nation, 1000 from misidenti� ation in the al-gorithm, and, if the LSND result is orre t,1000 from os illations.

detailed Monte Carlo work is from an ex-periment alled HARP (for Hadron Pro-du tion experiment) at CERN. HARP's pur-pose was to measure within 3% the ux ofpions, kaons, and other de ay parti les re-sulting from intera tions of 1.5 GeV - 15GeV protons with various targets. In ol-laboration with MiniBooNE, they tested in-tera tions between beryllium and 8 GeVprotons in August 2002. MiniBooNE is work-ing with HARP's data to produ e MonteCarlo simulations that re e t reality as loselyas possible.The se ond sour e of data to guide the analysis pro ess is the Little Muon Counter(LMC), an o�-axis near-line dete tor lo ated at the end of a 60 ft. long and 10 in.diameter pipe emerging from the main de ay pipe at a 7o angle, the optimum anglefor pi king up a muon from a kaon de ay. Su h muons are in the 1:2 � 3 GeV energyrange, while those from pion de ay at this angle are signi� antly lower, in the 0:2� 0:4GeV range. The LMC is essentially a momentum spe trometer, measuring the energyspe trum of muons from these de ays and thus giving a key data point for the MonteCarlo simulations to mat h up with. As this is the part of the experiment I worked on,I will dis uss it in detail in the next se tion.19

(a) (b)Figure 11: (a). A diagram of the main dete tor. (b). A photograph of the inside of the tankbefore it was �lled with mineral oil.2.1.2 The Main Dete torThe main dete tor (see Figure 11(a)) is a Cerenkov dete tor �lled with 800 tons ofmineral oil and lined with 1560 phototubes (see Figure 11(b)). The veto region, anoil-�lled area lined with phototubes surrounding the tank, is painted white to at h anyphotons produ ed by a harged parti le entering from outside the tank. This allows usto treat signals from parti les originating from outside the tank as ba kground in theanalysis pro ess.The primary hallenge involving the main dete tor is properly identifying the parti- les and intera tions generating the rings of light in the tank. Ea h of the intera tionshas a de�nite signature. Ele trons oming from �e CC events produ e a thin, less distin t20

(a) (b)Figure 12: (a). A ring produ ed by an ele tron from a muon de ay. (b). A ring from amuon, indi ating a andidate �� CC event. In both of these, the olor indi ates the timing ofthe event, with red-orange o urring before blue. The size of the ir le indi ates the strengthof the signal from the phototube; more photons hitting it produ es a stronger signal.ring as the ele tron is light and more prone to s attering and bremsstrahlung radiation7in the oil (see Figure 12(a)). Muons oming from ��'s produ e a distin t, thi k ring (seeFigure 12(b)), followed by an ele tron ring about 2�s later when the muon de ays.But the analysis itself is not as straightforward as this might indi ate. There isa nontrivial ba kground from osmi rays, some even produ ing new parti les in thedete tor. The veto region re ords when and approximately where a harged parti lepasses through the wall of the tank, allowing us to disqualify any rings produ ed bysu h parti les for anada y as an neutrino CC event. Cutting out these rings, plusimposing uts requiring a andidate event to be in time with the beam pulses, provideways to eliminate mu h of the ba kground.7Bremsstrahlung, or \Braking Radiation," o urs when an ele tron ex hanges a photon with anu leus and emits a photon. It an signi� antly hange the momentum of a light parti le like anele tron. For more information, see [2℄ pp. 27-32.21

2.2 Bla k Box AnalysisA lot of people are wat hing MiniBooNE losely. The result, whether it on�rms theLSND result or dis overs something new, will be a major step forward in neutrinophysi s. If it does on�rm the results, then the urrently a epted theory needs to beamended. If it instead omes up with something in line with os illations between threeneutrinos, then that on�rmation of os illation theory will itself be signi� ant. Thesehigh stakes will draw the lose s rutiny of the s ienti� ommunity.As a result of this a ountability in the s ienti� ommunity, MiniBooNE has de idedto do something alled a `bla k box' analysis, where they store the data on all the eventsbut only look at events whi h annot be os illation andidates when developing theanalysis algorithms. On e all the analysis algorithms are oded in the software and allthe variables determining uts, et . are optimally set, we will open up all the data.On e we do, none of the analysis algorithms an hange. This te hnique ensures thatthe result will be as free of bias as possible and ensure its redibility in the s ienti� ommunity.2.3 The FutureAs mentioned in the introdu tion, MiniBooNE is the �rst stage of BooNE, a largerproje t. If MiniBooNE on�rms LSND's result (and possibly if they �nd somethingelse), they will build another Cerenkov dete tor, similar to the urrent one, fartherdownstream to get a se ond data point on the neutrino os illations and re�ne the �m2to sin22� region. This will be de ided for sure on e we know the result of the urrentstage.If MiniBooNE �nds something other than LSND's result, we may hoose to run inanti-neutrino mode. To do this, we would reverse the urrent in the horn so that themagneti �eld fo uses �� parti les into the de ay region instead of �+'s. ��'s de ay intoa �� and a ��, so we would then look for os illations from �� to �e. This will allow usto investigate the possibility of anti-neutrinos behaving di�erently than neutrinos.22

3 The LMC Dete torThe LMC dete tor, ombined with detailed Monte Carlo work modeling the target areaand the data from HARP, will signi� antly improve our understanding of the parti les inthe de ay region and redu e the un ertainty on the initial ele tron neutrino ux. This is riti al, as it is essentially the limiting fa tor in determining the allowed �m2 to sin22�region.3.1 DesignStated in more pre ise terms, the purpose of the LMC is essentially to get as a uratean energy spe trum of muons as possible for a known area of the de ay pipe, providing adata point to mat h our simulations against. The 60 foot long 8 in h diameter va uum-�lled drift pipe onne ting the LMC hamber with the de ay pipe ombined with atapered ir ular ollimator built from tungsten plates (the interse tion of the de ay pipeand the drift pipe being the proje tion of the tapering) provide a well de�ned areal

Figure 13: A simulation of the LMC dete tor, showing muons (�+'s) in purple and ele tronsin yan. 23

(a) (b)Figure 14: (a). A diagram showing the �ber holders. Aluminum bra kets hold s intillating�bers in alignment with regular opti al �bers. The regular �bers then arry the signal tophototubes below the table. (b). A diagram showing the planes of s intillating �bers heldby the aluminum bra kets. Two planes a hieve greater resolution than a �ber diameter by onsidering whether a parti le also hits an adja ent �ber in the other plane (B). If not, theparti le probably went through the spa e between the other �bers (A). ross se tion to work with. Simulations (see Figure 13) showed that virtually all themuons passing through our dete tor would have passed through the ollimator hole,eliminating muons not passing through the entran e to the drift pipe as a signi� antsour e of un ertainty in our result.Though there are a number of di�erent ways to dete t the lo ations of moving hargedparti les like muons { wire hambers, drift hambers, to name a few { we hose a designfor the LMC dete tor based on s intillating �bers. Planes of short, parallel s intillating24

(a) (b)Figure 15: (a). A diagram of the tra ks bending through the magnet. The �ber planes re ordthe position of ea h of the parti les, allowing us to onstru t a linear tra k on ea h side of themagnet and note how mu h the tra k bends. (b). a pi ture of the dete tor before installation,showing the �ber planes without the magnet or onne ting opti al �bers.�bers interfa ed to lear opti al �bers re ord the horizontal and verti al position of theparti les entering the dete tor as shown in Figure 14(a). When a harged parti le travelsthrough one of the s intillating �bers, it generates a few photons whi h then propagatethrough an adjoined opti al �ber to a phototube whi h re ords the hit. Aluminumbra kets hold �bers in grooved slots, aligned so that ea h of the s intillating �bersinterfa es dire tly to one of the opti al �bers.Ea h plane of �bers is a tually two lose planes parallel to ea h other, arranged su hthat the �bers in one line up with the spa es in the other (see Figure 14(b)). This notonly ensures that every parti le that travels through the dete tor will en ounter at leastone �ber, it also in reases the resolution of the dete tor as explained in Figure 14(b).To determine the momentum of the in oming parti les, we used a total of 6 planes {or pairs of planes { two aligned so the �bers are horizontal and the rest aligned so theyare verti al, with a magnet between the middle two verti al planes. The two horizontalplanes, lo ated upstream of the magnet, allow us to determine the verti al omponentof the parti le's momentum. The verti al plan es allow us to tra k the parti le through25

the magnet and determine the momentum by how mu h the overall tra k bends in themagneti �eld (see Figure 15).3.2 Testing the Prototype Dete torsSin e these s intillating �ber dete tors were in a new and previously untested on�gu-ration, testing them before installation in the LMC was a must. To do this, we usedthe Indiana University Cy lotron Fa ility in Bloomington, IN in June 2002 to test thee�e tiveness of our design. We used 200 MeV protons and several di�erent prototypedete tor on�gurations to ultimately show that the design was a su ess.To keep any light out, the prototype was assembled and put inside a sealed bla kplywood box whi h ontained the phototubes, ampli�er ir uits, �bers, and dete tors.For our trigger, we pla ed a \paddle" { a s intillating plane wrapped with bla k ele tri altape atta hed to a phototube { dire tly upstream of the dete tor and a se ond onedownstream. Coin ident hits on both paddles indi ated a proton rossed the dete tor.A �5 Volt power supply, whi h I designed and built using HP7805 voltage regulatorsand two motor y le batteries, powered the ir uitry. Coaxial ables arried the pulsesfrom the ampli�ers in the box to our instruments outside the beam area.Our two main on erns were how eÆ iently the �bers and phototubes dete ted the harged parti les and whether rosstalk { photons from one �ber jumping to another {at the s intillating �ber to opti al �ber interfa e was a problem. To test the former, wesimply looked at the simultaneous hits on the trigger and the �ber plane. For omparison,we also tested a prototype made from purely s intillating �ber, without an opti al �berinterfa e, and ompared the results.To test rosstalk between �bers, we monitored 5 adja ent �bers at the enter ofthe bundle individually and the rest of the �bers together. This allowed us to lookfor simultaneous hits on two side-by-side �bers, the signature of rosstalk between the�bers. During the 96 hours we had the beam, we took 150+ runs of data over di�erent on�gurations, tube voltages, and trigger thresholds.26

Figure 16: A s atter plot of hits simultaneous in a spe i�ed time window on two side-by-side �bers as a fun tion of integrated signal strength. A value less than about 200 indi atesnegligible energy in that tube. Crosstalk would appear as a signi� ant amount of hits witha hit strength signi� antly above baseline energy on both tubes. As the plot shows, we seerelatively few hits in this region (and those there ould easily be due to two separate parti les),indi ating negligible rosstalk between �bers.The results were overall quite satisfa tory. The eÆ ien y of any individual �berwas over 99.99 per ent { out of approximately 208,000 triggered events, only 11 did27

not register simultaneous hits on both planes. Crosstalk between the �bers was alsonegligible, as shown and explained in Figure 16. Noise levels were tolerable, and thedesign appeared to be a su ess.The only problem we observed was rosstalk in the ir uitry, when the preamp onone tube (sensitive to millivolts) pi ked up the output pulse of one of the other postamps(volts). The signature of this was a se ondary pulse about 250 nanose onds after theprimary pulse (the delay inherent in the opamp), and it o urred often enough to be aproblem. A later redesign of the ir uitry with better shielding, however, solved thatproblem.3.3 Constru tionConstru tion on the full LMC dete tor �nished approximately one year ago at CU. Eri Erdos, a CU te hni ian, did most of the onstru tion work, with Prof. Zimmerman andme helping when needed. The pro ess took several months, and the dete tor was �nallyinstalled in September 2003 and began taking data later that year.3.3.1 The Spe trometer MagnetDesigning, onstru ting and testing the spe trometer magnet was my primary proje tduring the summer of 2002. We al ulated that spring using Monte Carlo simulationsthat we needed a 500 Gauss-m �eld integral to bend the parti les the orre t amount(see Figure 17). Furthermore, we needed a very uniform �eld to minimize un ertaintiesin our al ulations and, be ause spa e was limited, we needed the magnet to be as shortas reasonable. These provided the initial onstraints for designing the magnet.I worked with Bru e Brown, a magnet expert at FNAL, in designing the magnet.After several weeks of deliberations and drafts, we designed a magnet that was 14 in.wide by 12 in. high by 17 in. tall and, a ording to al ulations, would produ e therequired �eld. It used 32 4 � 4 � 1 in. ferrite bri k magnets to generate the �eld, andtwo 4.5 � 8 � 10 in. steel blo ks to pull the �eld into a uniform pattern (see Figure18). 1 in. and 2 in. steel plates on the outside returned the ux, so there was no stray28

Figure 17: Four plots of Monte Carlo simulations using GEANT, a parti le physi s simulationpa kage [23℄. They show the horizontal position of the parti le when it hits the �nal plane of�bers (x axis), with the edge of the dete tor being about �0:1, versus energy (y axis). Theleft two plots show �� parti les, whi h bend to the left in the magnet, and the two right plotsshow �+ parti les. Parti les in the top plots travel through a 1000 Gauss-m �eld, and a 500Gauss-m �eld in the lower plots. Sin e we wanted the lower energy parti les around 0.2 GeV totravel through the dete tor, we hose 500 Gauss-m for the magnet { noti e that in the stronger�eld the lower energy uto� is around .3 GeV and in the weaker �eld, the uto� is less than0.2 GeV.29

Figure 18: A beamline view of the magnet. Steel is shown in dark gray, aluminum in lightgray, ferrite magnets in red, ompensator in blue, and approximate magneti �eld lines ingreen. The parti les travel into or out of the �gure through the empty slot in the enter.30

Figure 19: Assembling the LMC spe trometer magnet. The thi k steel blo ks pull the mag-neti �eld into a uniform distribution, and the �eld is reated by ferrite bri ks that we'll sti karound the two blo ks. The outside is overed with 3/4 in. and 2 in. thi k steel ux returnplates to minimize any magneti �eld outside the magnet. The parti les travel through theslot in the enter of the magnet.magneti �eld outside the magnet. Furthermore, sin e the �eld strength of the ferritebri ks was somewhat temperature dependent, we inserted strips of a spe ial ompensatorthat would pull o� the magneti �eld at a strength per ÆC that was ten times that ofthe magnet, the net result being a magneti �eld nearly onstant over the temperaturerange we'd be dealing with.After we ompleted the magnet design, we found the materials and got the partsma hined, a pro ess that took several weeks. On e all the parts were in the same pla e,Jim Volk, a Fermilab physi ist, and I assembled the magnet in a morning and tested itthat afternoon (Figure 19).The tests on the magnet were quite satisfa tory. We used a hall probe mounted to31

Figure 20: The �eld strength in the LMC magnet. We measured the �eld at 1/2 in. intervalsthrough the magnet and at 1 in. intervals side to side. Noti e the sharp uto� at the edges,where the parti le enters the magnet, and the uniform �eld inside the magnet, exa tly whatwe were hoping for.a movable art to measure the �eld inside the magnet, taking data at ea h point ona 1 � 0.5 in. grid plus at 1/8 in. intervals at the edges. The results showed a veryuniform �eld strength inside the magnet and sharp uto�s at the edges (see Figure 20),exa tly what we were hoping for. And the designing pro ess was de�nitely a su ess {the approximate �eld integral is 503 Gauss-m.3.3.2 The TableThe table was engineered out of aluminum beams and plates, with a lower se tion to holdthe ir uitry and phototubes and an upper se tion on whi h to mount the �ber planesand magnet (see Figure 21(a)). We arranged the ir uitry in rows for ompa tness andeasy a ess (see Figure 21(b)). All the onne tions were aulked and an aluminum sheet32

(a) The Dete tor Table (b) The Cir uitry RowsFigure 21: The dete tor table during the onstru tion pro ess. The s intillating �ber planeswill be mounted on the verti al holders, with the opti al �bers arrying the messages to thephototubes and preamp ir uits below, whi h are arranged in rows. The signals then leave thebox via the onne tors on the right.metal over goes over the magnet and dete tors to make the box light-tight. We installedfans and light-tight vents to move air through the dete tor and keep the ir uitry ool.3.3.3 The Preamp Cir uitsEri Erdos and I assembled 48 preamp and postamp ir uits8 for our dete tor (see Figure21(b)), ea h onsisting of four hannels. Ea h hannel had a ir le of pins with high-voltage ir uitry in whi h to mount a phototube, two op-amps with supporting resistersand transistors, and a onne tor for the signal output. They were designed to output a1 Volt signal when the phototube was hit.To test the preamp ir uits, I �rst hooked the ir uit up to a high-voltage supply andtested ea h pin, noting any dis repan ies. Next I put in a 15 MHz low-voltage sine wave,as the wave form is similar in slope, frequen y, and amplitude to what our tube pulseswould look like, and looked at the output on an os illos ope. Again I noted anythingwrong (whi h varied from mild lipping to bizarre waveforms.) We then lo ated and8We only needed 36, but required extras for repla ements and in ase some didn't work.33

�xed bugs in the ir uitry (a pain!) until we had enough for the dete tor and a few leftover.3.3.4 Data A quisition A signal from a phototube, after it is ampli�ed in the

Figure 22: Approximate sig-nals from the preamp ir uitand the dis riminator. Volt-ages are not to s ale.

preamp ir uit, travels through a oaxial able to the dataa quisition equipment. It �rst passes through a dis rimi-nator ir uit that reates another pulse only if it the signalbelow (the pulse voltages are negative) a ertain thresholdvoltage (see Figure 22). By setting this threshold voltage,we an redu e the ba kground from \dark noise," or sig-nals aused by mis�res in the phototube.If a signal passes the dis riminator, it then goes to aTime to Digital Converter (TDC). The TDC emits a dig-ital signal as soon as it re eives the signal from the dis- riminator. On e this signal is emitted, it is time-stampedby a GPS unit with the pre ise time and re orded by a omputer, alled the DAQ (for Data A quisition).3.4 Current StatusCurrently, the dete tor is taking data and everything is running without a problem.We are developing our tra k re onstru tion algorithm and other software while verifyingthat the data we're seeing is indeed what we'd expe t. We hope to omplete the analysisthis year and report our �nal result to MiniBooNE soon after.34

4 AnalysisAnalysis of the data starts from the hits on the �bers and ends by produ ing the energyspe trum of the muons exiting the de ay region and entering our drift pipe and the LMCdete tor. The �rst step in this pro ess is separating the hits that ome from a tra k fromthose oming from noise ( osmi muons, muons not from the drift pipe, hadron showers,et .). On e we lo ate a lean tra k, we need to re onstru t the probable geometry ofthe tra k, obtaining the momentum and harge of the parti le from that.One thing a�orded us in the LMC that helps signi� antly at the �rst step is anabundan e of data. Be ause of the long running time required in the overall experiment,we an a�ord to throw out events with too mu h noise (this would not introdu e anyadditional un ertainty into the analysis, as the the probability of noise on a given eventis onstant.) Thus our approa h to utting out noise is essentially to bypass it { if thetra king algorithm an't �nd a good tra k, it simply throws that event out.4.1 Tra k Re onstru tionThe idea behind the tra king algorithm itself (still in development) is fairly simple. It�rst looks for oin ident hits on ea h of the �ber planes. If it �nds at least one hiton ea h plane, it lo ates all the possible linear tra ks in the planes upstream of themagnet, throwing out those that do not tra e ba k to the ollimator hole, and likewisedetermines the downstream tra ks. Finally, to sele t whi h downstream tra k mat hesup with whi h upstream tra k, it looks at the interse tion of ea h possible pair of lineartra ks. If a given pair of tra ks do not interse t in the enter of the magneti �eld, all thehits probably did not ome from the same parti le. If the algorithm �nds no a eptablepair of tra ks or �nds multiple possible pairs, it throws the event out.The momentum of a relativisti parti le with harge q in a magneti �eld B is relatedto the radius of urvature R of its tra k by [24℄:p? = 0:3qeBR (9)35

where p? is the momentum omponent of the parti le perpendi ular to the magneti �eld, B is in tesla, and R is in meters. In our geometry de�nitions, the downstreambeam dire tion is parallel to the z axis, the magneti �eld is in y, and the tra kingplanes measure the position of the parti le in x. Be ause the parti les in the dete tor ome from the ollimator, p? = pz. Thus, in the approximation that the initial x andy omponents of the parti le's momentum are zero, we an rewrite (9) in terms of thelength L of the magnet �eld (in z) and the bending angle, ��:pz = 0:3qeBy Lsin�� (10)Now the harge of a muon equals �e, so the �nal equation for a �� parti le be omes:pz = �0:3By Lsin�� (11)4.2 Software and The Analysis FrameworkAll the software analysis in the MiniBooNE experiment is done within an integratedenvironment alled the Analysis Framework, a program designed to provide an organizedand exible way to pro ess and analyze data. It is stru tured around program modules,whi h an pro ess, �lter, analyze, or display the data, and data \ hunks," olle tionsof data produ ed by a framework module from events, simulations, or analysis routines.Furthermore, it has a entral database, alled BooDB, whi h ontains all the onstantsin the experiment su h as physi al dimensions and hardware information. To pro ess oranalyze some data, the user puts a string of modules together, usually with one readingin the data at the beginning, followed by modules to �lter and analyze the data, andending with one displaying the results. A set of run ontrol parameters, or RCP's, ontrols all the modules.The modules in the LMC are organized into two ategories, those dealing with thea tual data from the table and those dealing with the Monte Carlo simulated data (seeFigure 23). Both begin with data �les outside the framework. The DAQ reates data �les36

Figure 23: A ow hart of the software modules in the LMC analysis pro ess. The experimentaldata from the dete tor omes in at the top, with InputDAQFormat, and the Monte Carlosimulations begin at Greys in the bottom of this diagram.of un alibrated data from the dete tor, and Greys, the Monte Carlo program, reates aset of simulated data �les. All these �les an be read into the analysis framework andpro essed with the various modules. Be ause I worked primarily on the Monte Carloside of the framework, I will on entrate on that aspe t of the analysis.4.3 The Experimental Data SideThe analysis pro ess essentially begins with InputDAQFormat and Unpa kLMC, twomodules whi h simply read in the data and turn it into data hunks usable in the frame-work. CalibrateLMCHits reads in these data hunks and ombines the hit data with alibration data, su h as the time delay between hit and registered time for ea h of thephototubes. It then outputs a CalibratedLMCData hunk that holds all the informationabout events in our dete tor for the event re onstru tion module, Tra kLMC, to pro ess.37

4.4 The Monte Carlo SideIn an experiment like this one, simulations and modeling of the dete tor are riti al togetting an a urate result. In designing the dete tor, they provide the most reliablemethod of verifying the e�e tiveness of the design. In analysis, they provide a powerfultool to allow us to investigate almost any physi s issue we believe might be a�e ting ourdata; for instan e, �guring out to what extent pions or other non-muon parti les willa�e t our results or how mu h we need to worry about muons oming from the dirt orpassing through the aluminum or steel in our dete tor. The most important use of theMonte Carlo simulations in developing the analysis algorithm, however, is in providinga way for us to he k our analysis routines against tra ks with a known momentum andpath. If they ome up the same parti le energy and orre tly identify the parti le, theywill likely give orre t results when looking at the real data, assuming the simulationsa urately mat h the dete tor performan e and parti le ux the dete tor is looking at.To enable us to use the simulations for all these purposes, I modi�ed Greys, a MonteCarlo program we've used with the LMC for a number of years, to output all the in-formation on erning the parti le, tra k, momentum, and �bers hit into a �le I alleda hit registry �le. I then wrote a module in the framework, InputGreys, to read inany number of these hit registry �les and ombine them into a simulated hunk alleda GreysData hunk. This hunk holds data about hit �bers and times that the nextmodule, Pro essGreys, uses to output a CalibratedLMCData hunk that mimi s onefrom the dete tor. The mat hing GreysData hunk, however, holds the full informationabout the tra ks for us to ompare with the re onstru ted tra ks later on.4.4.1 GreysGreys uses a parti le simulation library put out by CERN alled GEANT 3.2.19. Theprogram itself loads in the geometry from a spe i� ation �le, gives GEANT the initial onditions of ea h parti le, then re ords the information as GEANT simulates the path9For more information on GEANT, see http://wwwasd.web. ern. h/wwwasd/geant/.38

and possible intera tions or de ay of that parti le. As soon as one parti le is done, Greysdumps the data to a �le (or �les) and starts the pro ess again with another parti le.The user an then on�gure this program to produ e �les of pions, muons from kaons,muons from pions, et .To model the geometry of our beamline and dete tor, I had to write more sophis-ti ated ode to properly implement all the �bers. To do this, I implemented ode tohandle an option in the spe i� ation �le to repeat a given geometri al feature a spe i-�ed number of times in any dire tion. On e this was in pla e, I was able to implementhundreds of �bers easily.The se ond major modi� ation I had to do to Greys was enable it to re ord the dataabout parti le tra ks and hit �bers. Before, the ode was set up merely to register theenergy and lo ation of a parti le when it en ounters one of a few geometries hard- odedinto the program and output it to a �le. It was nearly impossible to get that to workfor hundreds of �bers, so I ame up with an additional data handling routine to re ordall the information we would need later on. At the end, it produ es, for ea h parti le,a list of the energy deposited in ea h �ber hit and all the information about the energyand tra k of the parti le. This information is then read in with InputGreys.4.4.2 InputGreys & Pro essGreysInputGreys is divided into two parts, MCData and FormSpill (see Figure 24(a)). MC-Data handles all the intera tions with the data and FormSpill does exa tly what thename implies { it forms a data hunk resembling a beam spill10. The user spe i�es theaverage number of parti les from ea h �le to go into a spill in the RCP's. From this,FormSpill al ulates, using a Poisson distribution, how many parti les of ea h type touse and de ides randomly where to put them. It then asks MCData for the events (MC-Data keeps tra k of all the bookkeeping internally) and forms the spill. All this data issent on to Pro essGreys in the form of a GreysData hunk.Most of the physi s in building the simulated spill o urs in Pro essGreys. It uses10See se tion 2.1 for a brief des ription of the beam.39

(a) (b)Figure 24: (a). A ow hart of InputGreys. (b). A ow hart of Pro essGreys.the geometry of the beamline, the momentum and path of ea h of the parti les, and thetype of the parti le to al ulate the likely time of ight from the target to the LMC.It then uses this and the time separation of the bu kets to al ulate a time for ea hhit, referen ed from the beginning of the spill. Finally, it looks in BooDB for the �berto phototube mappings and the energy thresholds of the phototubes, al ulating whi h�bers would have enough energy deposited in them for a hit to register in the givenphototube. It �nishes by produ ing another data hunk simulating the real data, simplya list of whi h phototubes would re eive a signal and when. A graphi al explanation ofthis is found in Figure 24(b).4.5 The Event DisplayOne of the �nal modules in the analysis pro ess is the event display. This module displaysthe data hunks from the rest of the analysis pro ess in a graphi al way, fa ilitating ourinvestigation of the data and tra k re onstru tion algorithm. It uses a graphi s library40

Figure 25: A s reenshot of the event display, showing generated parti le tra ks. The windowson the right with blue sidebars are linked together; the sele tion on the zoomed-in histogramon the bottom is displayed in the viewer on top. The user an have multiple linked windows;the windows with red sidebars are looking at the same data set but a di�erent sele tion. Thered ir les indi ate multiple hits within the sele tion on one phototube. alled QT11 to display the �bers (see Figure 25). The user sele ts whi h hits to displayin a orresponding timing histogram, the unhit �bers appearing as blue ir les and thehit �bers appearing in white. Multiply hit groups �bers in a given sele tion are displayedin shades of pink and red, with darker shades indi ating more hits.11See the QT website, www.trollte h. om, for more information on this library.41

When the event display loads in a data hunk from the framework, it reates two win-dows ( alled \modules," not to be onfused with framework modules) in the workspa earea for the user to view the data with, one being the hit-time histogram sele tor and theother being a graphi al display of the dete tor. Should users want to look at di�erentparts of the data, they an open up new histogram and viewing windows that operateindependently of the others. Figure 25 demonstrates this, where windows with the same olor of bar on their left are linked together.Stru turally, the program is designed to be exible and extendable. All the databookkeeping is handled automati ally, independently of the data type, allowing theprogram to be easily adapted to handle other types of data (in our ase, re onstru tedtra k and Monte Carlo data). Furthermore, it's relatively easy for a programmer towrite another type of viewer or data sele tor, as the interfa e between it and the rest ofthe program is also designed to work with any type of module. The a tual stru ture ofthe ode is des ribed in detail in appendix A.4.6 Current StatusThe LMC's analysis software development is going well. We have seen de�nite tra ksin the data, and Eri Zimmerman and others are urrently working on ode to identifypossible tra k andidates among the hit �bers. My urrent area of responsibility is stillthe Monte Carlo side of the analysis and the event display, both of whi h need someslight work before we an use them to he k our tra k re onstru tion algorithm. Thiswork will hopefully be ompleted within the next month or so. On e the basi algorithmworks, we will spend several months �ne-tuning it, then hopefully report our results tothe rest of MiniBooNE and the world soon after.42

5 Con lusionThis is an ex iting time for physi s. Whether MiniBooNE on�rms LSND's result or�nds something entirely di�erent, the result will have ex iting onsequen es for theoret-i al physi s. Neutrino os illations are opening up new doors for experimentally-veri�edtheoreti al work and may soon begin to put new theories to the test. Physi s beyondthe Standard Model will ontinue to be purposefully investigated, and MiniBooNE's re-sult may soon open new windows through whi h to glimpse what is urrently unknown.Indeed, the next few de ades may revolutionize part of our view of the fundamentalproperties of nature.

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A Appendix: The Event Display DesignWhen I began to work on the event display, I formed several riteria to guide the design.These were partly for personal reasons { namely, that I wanted to develop quality C++skills while writing the program { but mainly be ause other people will probably beusing and modifying the ode. Along these lines, I ame up with three requirements.First, it had to follow established guidelines for C++ design. These guidelines in ludehaving a fully obje t-oriented stru ture, with obje ts12 being as abstra t as possible.This simply means that ea h operation or fun tion of the program should be odedinto only one obje t, that it should do the operation in the most exible way possible,and that ea h obje t should be able to fun tion as independently of the other obje tsas possible. Thus, if a programmer has to hange something, he should only need to hange it in one pla e, and similar operations should not have to be oded up more thanon e.Se ond, it had to be stru tured in su h a way as to be easily extendable. Be ausewe are dealing with several di�erent data stru tures in the event display, namely MonteCarlo data, re onstru ted tra k data, and the basi hit data, the program was stru turedso that multiple data stru tures ould be easily handled. Furthermore, be ause there area number of possible features beyond the basi viewer that ould fa ilitate our analysiswork, it makes sense to stru ture the program so that these ould be easily added onlater.Third, it had to be designed su h that others ould easily use and modify it. Therewere two spe i� guidelines I followed as part of this. The �rst was to use lear variablenames and lear �le names (like fa tory. pp, modulebase. pp, et .), and the se ond wasto make the ode, espe ially the spe i� fun tion of ea h obje t, well ommented. Mygoal is to make it possible for a programmer, reasonably familiar with the stru ture ofthe ode, to �nd a spe i� operation in the program without mu h diÆ ulty.12Obje ts in C++ (also alled lasses) are simply a olle tion of variables with a set of fun tions thatwork spe i� ally with those variables. On e de�ned, they an be treated just like any other variabletype, with multiple obje ts of the same type able to exist at the same time.45

Figure 26: The internal stru ture of the event display. The DataGroup obje t holds all thedata stru tures, in luding DataSets and DataChunks, the DataLinks handle all the ommu-ni ations between the obje ts and link the Modules with the data, the Modules are used toview and sele t the data, the DataSele tors ontrol whi h events are viewed, and the rest ofthe obje ts support this stru ture. Bla k lines represent two-dire tional lines of ommuni a-tion between obje ts, red lines represent one dire tional ommuni ation lines, and green linesrepresent ommuni ations that happen only during initialization.A.1 Stru tureIn light of these requirements, I ame up with the stru ture represented graphi ally inFigure 26. The stru ture of this ode allows for anyone to extend the event display toin lude additional data types, viewing and sele ting modules, and features with minimale�ort. Furthermore, it is straightforward, exible, and powerful to use.The entral data handling obje t is the DataGroup, and the stru ture of the eventdisplay is designed around it. It holds all of the data in two ontainer13 lasses, alled13Containers in C++ an be though of as enhan ed arrays of data. Essentially, they are obje ts witha way of holding as many instan es of a given type of obje t as needed. They automati ally handle all46

DataSet and DataGroup. The viewing and sele ting modules intera t with it to getpointers to given data stru tures through a DataLink (explained below). Multiple Data-Groups an exist in the program, but ea h ontains distin t data and has distin t viewingmodules intera ting with it. In this ase, one DataGroup is reated and �lled with allthe data hunks from the framework.The data are held within a template14 ontainer lass alled a DataChunk. Thesehold the data, sorted by a given spe i� ation, in this ase the time of the event, insidean internal array.Be ause the event display deals with multiple types of data events, a template obje t, alled a DataSet, interfa es to the DataGroup and holds all the DataChunks of that giventype. Whenever a new type of data is inserted into the DataGroup, the DataGroupautomati ally onstru ts a DataSet to hold data of that parti ular type. The powerof this is that none of the data handling ode needs to be modi�ed when a new dataevent stru ture is written { the ompiler does it automati ally. The only ode thathas to be written or modi�ed is the stru ture holding the datum itself and the viewingmodule ode. This feature bene�ts our purposes as we are dealing with three data types{ re onstru ted tra ks, alibrated hits, and Monte Carlo simulation data { and allowsothers to turn the ode into an entirely di�erent event display with minimal e�ort,ful�lling the se ond requirement.The �nal interfa e between the viewing and sele ting modules is the DataLink obje t.This obje t serves two main purposes, the �rst being simply to onne t the moduleswith the data in su h a way that the DataGroups don't need to know anything aboutthe modules themselves. This allows multiple DataLinks to be onne ted to the sameDataGroup, so the user an have di�erent data sele tions in di�erent viewing windowswhile looking at the same data. By allowing the user to so ompare data, this will be apowerful tool for analyzing the data.the memory allo ation issues, making them very onvenient.14Templates are a very powerful C++ feature that allows a lass to be oded in su h a way so thatthe ompiler a tually builds it based on a given obje t or variable type. In this ase, the ompiler buildsthe DataChunk around a given data event stru ture. This makes the lass extremely exible and fast.47

The se ond fun tion of the DataLink is as a ommuni ation enter, transmittingmessages (obje ts ontaining information about data sele tion or hanges in the dataitself) between the DataSele tors and the modules. When any obje t onne ted to aDataLink tells it to broad ast a message, the DataLink will send it to every module orDataSele tor ex ept the one sending the message. This allows for the modules themselvesto be entirely independent of one another, ful�llingmy �rst requirement of having obje tsbe as independent as possible.The DataSele tors are template obje ts onne ted to the DataLink that ontrol,hold, and send out information about data sele tion. When a new DataSet is reatedinside a DataGroup, or a new DataLink is onne ted to the DataGroup, the DataSettells the DataLink to reate a new DataSele tor of the same type as itself. These twothen syn hronize with ea h other, and the DataSele tor then holds information aboutwhi h events inside the DataSet are sele ted and whi h ones are not. This reates avery failsafe way of handling sele tion operations, ensuring that the same event is neversele ted twi e and that all events within a requested time window are displayed15.The modules themselves are the front end part of the entire stru ture. They appearas windows in a entral, main window, (see Figure 25). A olored bar on the left sidetells the user what DataLink the module is a part of { ea h DataLink is given a unique olor. There are urrently three di�erent modules, one to view the data, one to sele tthe data, and one to print o� information about the program and the data (mainlyused for debugging, but an also have other purposes). The sele ting module displaysa histogram, binned by time (the user sele ts the bin width, et .), of all the data andallows the user to sele t the time window to display. When the user modi�es a sele tion,it sends a message to the appropriate DataSele tor, whi h then broad asts the spe i� data events to display. The viewing module, showing the �bers in the �ber plane as ir les, displays these events as highlighted ir les as shown in the �gure.All the di�erent kinds of modules are built on top of a single obje t, alled Module,15Within the DataSele tor lass, there is a simple and eÆ ient way for �lters on whi h events aresele ted to be instated while the program is running, but urrently there is no implementation of this.48

using inheritan e16. This makes it very easy to implement new types of modules { theprogrammer only has to reate the user interfa e on top of the Module lass, and theprogram takes are of the rest17. This, along with using templates for the DataSets,helps ful�ll my se ond requirement by making the ode easily extendable.The other parts of the program help support this entral stru ture. One obje t,Dete torGeom, holds all the information about the dete tor and its geometry. An obje t alled Interfa e18 handles all the intera tions between the framework and the a tualevent display. EDControl ontrols the initialization and exiting of the program, allingfun tions in the Interfa e obje t to load in data and information about the dete tor. Amenu handling obje t standardizes and handles almost all the menus in the program.A Fa tory obje t handles all the reation of new modules, DataGroups, and DataLinks,and another obje t, ModKeeper, keeps tra k of all of them. Finally, another obje t,Globals, holds all the program-wide ags and variables. These are all held in a globalnamespa e19, allowing any obje t to a ess them.A.2 Possible ExtensionsAs I might have suggested, there are many possible ways to develop this program further.In the near future I plan to implement basi printing support for the various modules.Also, the 2-d viewing module only displays the alibrated hit data, so I plan to updateit to in lude both the Monte Carlo tra ks and the re onstru ted tra ks. This should16In C++, when one obje t inherits another obje t or lass, the �rst obje t is essentially built on topof the inherited lass ( alled the base lass), taking on its properties. Furthermore, other obje ts antreat the full deal as if it were simply the base lass.17The user does have to hange the program ode in two pla es so the program re ognizes the newmodule, in one array de�ning the module types and another pla e that reates them.18The Interfa e lass makes the event display ode easily adaptable, as another programmer onlyneeds to reimplement this lass to adapt the ode to something else. The ode stri tly in the eventdisplay itself that deals with the analysis framework is entirely onsolidated to this lass (of oursethere are other routines outside this that, for instan e, laun h the event display ode, but I onsiderthat separate from the inner workings of the event display.19In C++, a namespa e is simply a way to group global variables and obje ts into similar ategories.Think of it like a room inside a house; it is not an obje t in the house, in the same sense that a tableor piano might be, but its purpose is to hold obje ts. It's a very onvenient tool in making a programwell organized. 49

be reasonably straightforward. Furthermore, as for more optional but still desirablefeatures, QT, the graphi s development library I used to write the event display, hasgood OpenGL20 support, so it wouldn't be too diÆ ult to reate a 3-d version of theevent viewer.

20OpenGL is an industry-standard 3-d graphi s library, used ommonly in everything from games to3-d modeling programs. For instan e, the event display for the primary MiniBooNE dete tor uses anOpenGL based library. 50

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[13℄ http://sandman.berkeley.edu/neutrino/.[14℄ Bah all, J.N. (2001). How well do standard solar models des ribe the results of solarneutrino experiments? astro-ph/9606161.[15℄ Tserkovnyak, Y. (2003). A Three-Dimensional Cal ulation of Atmospheri NeutrinoFluxes. hep-ph/9907450[16℄ Messier, M.D. (2001). Status of the atmospheri neutrino studies. In Suzuki, B.Nakahata, M., et. al., eds. (2002). Neutrino os illations and their origin. River Edge,NJ: World S ienti� Publishin Co. Pte. Ltd., pp. 100{109.[17℄ Barger, V. D., Learned, J. G., et. al. (1999). Phys. Lett. B 462, 109[18℄ Chur h, E.D., Eitel, K. Mills, G., Steidl, M. (2002). Statisti al analysis of di�erentmuon-antineutrino! ele tron-antineutrino sear hes. hep-ex/0203023[19℄ Aguilar, A., Auerba h, L.B, et. al. (LSND Collab.) (2001). Eviden e for neutrinoos illations from the observation of ele tron anti-neutrinos in a muon anti-neutrinobeam. Phys.Rev. D64 112007[20℄ Caldwell, D. O. (ed.) (2001). Current aspe ts of neutrino physi s. New York:Springer-Verlag.[21℄ Barenboim, G. & Lykken, J. (2003). A model of CPT violation for neutrinos. hep-ph/0210411[22℄ http://www.neutrino.lanl.gov/BooNE/boone proposal.ps[23℄ http://wwwasd.web. ern. h/wwwasd/geant/.[24℄ Weinberg, E. J., & Nordstrom, D. L., eds. (1996).Physi al review D: parti les and �elds. Woodbury, NY: Ameri an Physi al So- iety. 52