Experimental Summary TalkPhysics at the End of the Galactic
Spectrum
Pierre Sokolsky
Univ. of Utah
The Hedgehog and the Fox(The Greek poet
Archilochus)
“The Fox knows many things, but the the Hedgehog knows one
big thing”
One of the emergent themes of this meeting is the ‘excluded
middle’• HESS results - first sign of CR galactic sources• What is the max energy of the accelerator
associated with these sources• What about the knee - propagation vs. acceleration• Kascade results very important - BUT indirect and
still model dependent and likely to remain so.• HiRes data shows ankle region is now clearly
established, second knee less so but transition to ankle must occur somewhere
‘Excluded middle’ continued
• Transition from galactic to extragalactic
• Dip as evidence for extragalactic origin and protonic composition (“more reliable than GZK cutoff” (Berezinsky)
• There are “reasonable” pictures of the low and the high energy situation
• But - Plan B ( Hillas ) - the missing middle
Hess Results - First evidence (still putative?) of SN CR.
• Extended objects
• Association with SN remnants
• Hard spectra
• Detailed comparison with models and X-ray and radio structures
RX J1713 – H.E.S.S & ASCA• Gamma-ray and X-ray morphology quite similar
ASCA1 – 3 keVUchiyama 2002
HESS Preliminary
RX J0852.0-4622 – 'Vela Junior'
2004
- 3hr observation
- 4 tels
- dN/dE E-2.2
- 12 sigma from entire SNR (rad < 1 deg)
~ 1 Crab flux
2005
--> further obs. ~15hr expected soon
--> high ZA obs!
ASCA0.7 – 10 keVSlane 2001
HESS Preliminary
Direct measurements below the knee
• Presumably propagation modified reflections of supernova sources
• Should reflect max energy of accelerator and (modified) chemistry of the source
• Binns talk - evidence for acceleration in superbubbles.
• Cannot see turn over in spectra!• Consistency problems at higher energies
CRIS GCR Isotopic Measurements
•Two component models•Wolf-Rayet winds from stars with various initial masses, with and without rotation.•Adjust the WR fraction mixed with ISM to match CR 22Ne/20Ne.(Goriely, Arnould & MeynetModeling)
“Combined” data points (red) are mean values of ratios from Ulysses, Voyager, ISEE-3 and HEAO-3-C2
Model WR Fraction
M60-no rot 0.20
M85-no rot 0.12
M120-no rot 0.16
M40-rot 0.22
M60-rot 0.16
M85-rot 0.41
M120-rot 0.35
Fraction of WR materialmixed with ISM with solarsystem composition tonormalize to 22Ne/20Ne ratio
300 km/s
But what about the 14N/16O and N/Ne ratios???
Summary (cont)
• We take agreement as evidence that WR star ejecta is likely an important component of cosmic-ray source material.
• Since most WR stars & core-collapse SN reside in SBs, then SBs must be the predominant site of injection of WR material and SN ejecta into the GCR source material.
• Picture that emerges is that SBs appear to be the site of origin and acceleration of at least a substantial fraction of GCRs.
Balloon borne measurements just below knee
Fill gap between low energy AMS and high energy JACEE with accurate measurements
Preliminary indication that H and He spectral indices are very similar Measurements of Iron group show flattening of spectrum Have measured GCR electrons up to about 2 TeV At the highest energies, the heavy ion spectra show deviations, which
might suggest that a modified Leaky Box Model, including a constant residual pathlength (0.13 g/cm2), is needed.
Preliminary charge histograms for E > 50 GeV from the ATIC-2 flight
Preliminary Results from ATIC-1 and ATIC-2
C O Ne Mg Si
S
Fe
S Ca
Testing of models with the ATIC-2 spectra of protons and HeliumAMS
CAPICE98
ATIC-2
Diffusion model (Kolmogorov spectrum offluctuations)
at high energies
V. S. Ptuskin et al.astro-ph/0301420
at low energies(reacceleration process)
Energy spectra of abundant nuclei
C
O/10
Ne/100
Mg
Si/10
Fe/100
HEAO-3-C2
CRN
ATIC-2
Direct measurements
• Some disagreement at the higher energies
• Approximately equal power law spectra for different elements
• No evidence of turnover to highest energies measured
All particle spectrum: ATIC, emulsion, and EAS data
RUNJOB
JACEE
CASA-BLANCA
TibetKASKADETUNKA
ATIC-2
The knee
• Change of slope appears in all particle spectrum in indirect experiments.
• Structure MUST appear in elemental spectra
• But many possible combinations can produce same overall spectrum
• Indirect experiment mass resolution is poor
Fit to the all-particle spectrum with rigidity dependent cut-off
common c
0.1162/dof
1.87 +- 0.18c
-4.68 +- 0.23c
4.51 +- 0.52Ep [PeV]
c
Zc
c
Z
å
ããå
p
0ã0
0Z0
0
Z
EZ
E1EÖ)(E
dE
dÖ
−
⎥⎥
⎦
⎤
⎢⎢
⎣
⎡
⎟⎟⎠
⎞⎜⎜⎝
⎛
⋅+=
0.1132/dof
1.90 +- 0.19c
2.10 +- 0.24
4.49 +- 0.51Ep [PeV]
common
cc
Z
å
Äãå
p
0ã0
0Z0
0
Z
EZ
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dE
dÖ
−
⎥⎥
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⋅+=
Two dimensional shower size spectrum lg Ne vs. lg N
M Roth et al, 28th ICRC, Tsukuba 1 (2003) 139
KASCADE
derive E0 and A from Ne and N data
∫∞
=0
)()|lg,(lg)lg,(lg dEEpENNtNNg ieiei μμ
Fredholm integral equations of 1st kind:
E0
A
All-particle energy spectrum
two hadronic interaction models:CORSIKA 6.018/GHEISHA 2002
- QGSJET 01- SIBYLL 2.1
T. Antoni et al., Astropart. Phys. in press
QGSJET
KASCADE: Energy spectra for individual elemental groups
distribution
!
distribution
!
SIBYLL
H. Ulrich et al., Int. J. Mod. Phys. A (in press)
Kascade Results
• Careful measurement of Ne and Nmu + hadronic model can yield a remarkable amount of information
• However, significant model dependence remains
• Rather indirect, complex analysis
• That being said, results are ‘sensible’
Now for the High Energy end
• Evidence for second knee
• Evidence for ankle
• Composition change
• Models based on transition from Galactic to Extragalactic flux
Best Evidence (cont’d)Second Knee at 1017.6 eV
• Yakutsk, Akeno, Fly’s Eye Stereo, HiRes Prototype/MIA all saw flat spectrum followed by a steepening in the power law. The break is called the second knee.
• Correct for varying energy scales: all agree on location of the second knee.
• There are THREE spectral features in the UHE regime.
• But location of second knee is unknown.
• The ULTIMATE experiment is one which would see the three UHE cosmic ray features with good statistics!
Physics in the UHECR Regime: Best Evidence so far…
HiRes observes the ankle; Has evidence for GZK suppression;Can not claim the second knee.
Galactic/Extragalactic Transition:HiRes/MIA hybrid experiment, and HiRes Stereo results.
Fitting the Spectrum
• It is important to fit the spectrum to a model that incorporates known-physics.– Position of the ankle is
important for determining the distance to sources.
– Regions of poor fit quality indicate where the model may break down.
• Problem near 1019.5 eV? Six points with chi squared 10.
• Problem at 1017.5 eV? The second knee is too weak.
SECOND KNEE and EXTRAGALACTIC PROTONS
Second knee automatically appears in the total spectrum (galactic +extragalactic) due to low-energy flattening of extragalactic spectrum, which appears at Ec~ 1×1018 eV.This energy is universal for all propagation modes (rectilinear or diffusive) and it is determined by transition from adiabatic to e+e- -energy losses .
rectilinear propagation diffusive propagationLemoine 2004, Aloisio, V.B. 2004
DIP as SIGNATURE of PROTONS INTERACTING with CMB
(model independent analysis in terms of modification factor)Definition:
(E) = Jp(E)/Jpunm (E) (3)
Jp(E) is calculated with all energy losses included.
Jpunm (E) - only adiabatic energy losses included.
Dip is stable:
• to propagation modes (rectilinear or diffusive),
• to variation of source separation (d=1-60 Mpc),
• to inhomogeneities in source distribution,
• to fluctuations in interaction.
DIP and DISCREPANCY between AGASA and HiRes DATA
(energy calibration by dip)
We have shifted the energies to obtain the best fit to the dip: AGASA : E→kAE (best fit kA=0.90) HiRes : E→kHiRE (best fit kHiR=1.25)
Aside on energy adjustments
• While it is not unreasonable to assume a fixed energy scale systematic - this may not be the source of the problem
• Differences in energy resolution and tails in energy resolution may also be important
• Systematic errors in calculating the detector aperture can induce apparent slope changes.
• This can be important for ground array experiments at energies below full efficiency as well as fluorescence experiments near threshold.
TRANSITION from GALACTIC to EXTRAGALACTIC CR in DIFFUSIVE PROPAGATION
Assumptions:• power-law Qgen(E) ~ E-2.7 generation spectrum for extragalactic protons• Lp = 3.0×1048 erg/s for source separation d=30 Mpc• Lp = 1.5×1048 erg/s for source separation d=50 Mpc• magnetic field with Kolmogorov spectrum B0 =1 nG on the basic scale lc=1 Mpc• several different regimes in low-energy region (Kolmogorov, Bohm and D(E) ~ E2 ).
In principle, the observed dip can be explained by the galactic component. In the absence of the detailed theory of propagation in galactic magnetic fields, the precise description of the dip shape in this case looks like a formal fitting exercise with many free parameters.
knee 2nd kneeankle
?
x 92
The Fox - how do we improve the low and high energy data?
• Low energy - how far up can direct measurements go?
• Working group answer ~ 2 x 10^14 eV
• High altitude proton detector
• Transition radiation balloon flights for high Z spectra
• Subtract high Z from all- particle spectra
Conclusion:
If we use balloon observations we need larger instruments than
currently exist. (We also may have to be concerned about nuclear
interactions in the residual atmosphere).
For calorimeters, a significant increase is not be possible because of
weight constraints.
For TRD’s, an increase to a detector area of about 5x5 m2 (as opposed
to the current 2x2 m2) may be possible. This would reduce the number
of required TRD flights from 60 to 10.
For protons and helium, balloon measurements cannot reach the ACCESS goal. For the heavier nuclei, the gap between balloon flights and ACCESS is considerably smaller.
A POSSIBLE (?) ALTERNATIVE TO MEASURE THEENERGY SPECTRUM OF PROTONS 1011 TO 1016 eV:
Hadron Calorimeter (such as the one of Kascade),at high mountain altitude; detect surviving single protons.
Some numbers:assume residual atmosphere to have 5 proton interactionlengths. Then 0.67% of protons will survive (factor 400 morethan at sea level). If the hadron calorimeter has the same sensitivity as that of Kascade (320 m2 sr) its effective geometricfactor would be 2.14 m2 sr. The ACCESS goal for protons would be achieved within 0.5 years of observation!
How to improve indirect data around the knee
• Kascade type detector enhanced by Cherenkov array that is sensitive to Xmax
• Overlap with direct measurements near 10^14 eV.• Xmax measurement reduces reliance on hadronic
models, reduces shower fluctuations in Ne and Nmu
• Detector with improved logA resolution and improved systematics
• Kascov or Cherenkade?
Basics of the Technique
• Light near the core are emitted deeper in the atmosphere
Proposed Cherenkade Detector
• Combination fluorescence + Cerenkov + muon array
• 3km 3km• Can probably sparsify
the Cerenkov spacing from BLANCA
• May need larger light collectors to reach down to 1014 eV
• Infill scintillator array needed for lowest energies.
Another approach
• Snow-top detector has unique ability to study multi-hundred GeV muon content of shower.
• Important check on hadronic models• Very good energy resolution• This would be even better with a Cherenkov
detector to determine Xmax!• Snow-kov
IceTop
• Concept– Surface array is unique
opportunity for -telescope in deep ice
• Purpose– To detect cosmic-ray showers
related to events deep in IceCube
• Calibration of IceCube– Pointing– E/E (energy resolution)
• Tagging background for study and rejection
• Related cosmic-ray physics from “knee” to “ankle”
1400 m
2400 m
AMANDA
South Pole
IceTop
• 4800 PMT • Instrumented volume: 1 km3
(1Gt)
• 80 Strings• IceCube is designed to detect
neutrinos of all flavors at energies from
107 eV to 1020 eV
IceCube
•1 station on top of each IceCube string•2 ice tanks per station•2 DOMs in each tank
•IceTop will detect Air Showers of energies 3x1014 eV to 1018 eV
IceTop Tank
2 m
0.9 m ice
Diffusely reflecting liner
The IceTop km2 array
• Array consists of 160 tanks at 80 stations– each station near top of string– each tank connected to surface cable at
junction with down-hole cable
• Single low-energy : 1.3 kHz / tank• flux measured at SP with telescope
• Tank rate inferred from geometry
• Soft Component (>30 MeV): 1.2 kHz
Using TeV Gamma Ray detectors ?
• HESS/Veritas and extensions have ~ 1 km^2 collecting areas and ~ 5-10 deg acceptance.
• Background hadrons could in principle be analyzed a-la DICE ( stereo reconstruction of shower centroid to get Xmax ).
What about the second knee and ankle?
• Present fluorescence experiments have difficulty going below 10^17 eV - short lever arm for second knee.
• Composition measurement is crucial. Xmax composition requires careful control of resolution function - stereo important
• Detectors should have smoothly and slowly changing acceptance over the structures they are trying to measure
Cont.
• Smooth acceptance for Fe and p implies higher elevation angles for mirrors near 10^17 eV ( Tower of Power)
• Smooth acceptance as function of energy implies HiRes type of stereo separation (12km) is too large.
Observe the Ankle in Stereo Mode
• HiRes stereo (12.6 km separation) has rapidly-changing aperture below 1018.5 eV (Auger and STA stereo and hybrid are not better).
• Flatten the aperture by having the two stereo detectors be closer: STA and HiRes fluorescence detectors 6 km apart.
• Perform composition-correlated measurement of spectrum.
Lower-energy Limitations
• HiRes observes elongation above 1018.0 eV clearly.
• HiRes looks up to 31o, can’t see Xmax for close-by (low energy) events.
• Makes spectrum measurements difficult below 1017.5 eV.
• Composition bias for E < 1018.0 eV.
Before bracketing and Cerenkov cuts
Observe the Second Knee in Hybrid Mode with a Tower Detector
• Two methods of lowering the minimum energy:– Use bigger mirrors.– Look higher up.
• Tower detector with 3x larger mirrors:– 750 cm radius of curvature.– Cluster box at 97% of focal
length.– Use HiRes-type phototubes
with Winston cones.– Collect 2.88 times as much
light.
Tower Detector
• Simulate a five-ring detector.
• Rings 1 and 2 have standard HiRes mirrors.
• Rings 3-5 have 3x larger mirrors and Winston cones.
• Compare with HiRes2 (data set 2).
• Compare with a tower detector with standard HiRes mirrors throughout.
Lower Emin by order of magnitude.
• Test tower detector design: MC ~ 2 mo running. – cover 90o azimuthally.
– 15 mirrors in rings 3-5.
– HiRes-size mirrors reach down ½ order of magnitude.
– 3x larger mirrors reach down full order of magnitude.
How would this be realized?TA/TALE version
• Use TA fluorescence detectors as pair partners with reconfigured HiRes detectors to provide Stereo aperture for ankle region
• Add a Tower of Power with larger mirrors to extend low energy response to 10^16.5.
• Add an infill array to TA array to have hybrid detection for Tower of Power.
• Addition of Auger water tanks would be ideal for muon detection ( co-siting of N. Auger would be great)
TA Design• SA: 576 scintillation counters,
each 3 m2 area, 1.2 km spacing.• 3 fluorescence stations, each
covering 108o in azimuth, looking inward.
• Central laser facility.• Millard County, Utah, flat
valley floor for SA, hills for fluorescence, low aerosols.
• A 1020 eV event (on a night when the moon is down) will be seen by SA and all three fluorescence detectors.
• A powerful detector for hybrid and stereo cross correlation with SA.
TA Progress (FD)
Increase the High Energy Fluorescence Aperture of TA by Factor of 3.6
• Two HiRes detectors, moved to Millard Co.
• One is a TA fluorescence detector (360o azimuth).
• 6 km stereo with Black Rock Mesa TA fluorescence detector.
• Each detector has two rings.• High enegy instantaneous
aperture of 18000 km2 ster.• Increase high energy
fluorescence aperture by factor of 3.6
• Total high energy aperture of 3200 km2 ster.
TA FD, Tower, Infill Array
• 15 mirrors, 3xHiRes area, in rings 3,4,5.
• 111 AGASA counters, spacing of 400m, shown in red. Can see events hitting outside also.
• 10 x HiRes/MIA hybrid aperture.
TA/TALE Apertures
How would this be realized/ S. Auger version
• Build additional Auger fluorescence mirrors to reach higher elevation angles and improve acceptance to lower energy Fe showers.
• Infill array of Auger water tanks to provide hybrid reconstruction.
FD telescopes: vertical field of view vs. minimal distance
600 viewing angle 300
Height a.s.l. [km]
distance from eye[km] 5 10
5.0
2.5
7.5
X ~ 430 g/cm² vertical ~ 500 g/cm² at 300 zenith angle
~ 3 km ~ 9 km
summer
atm.winter
~ eye level1400 m
Possible FD upgrade proposal(for 2006/2007, after Auger South experiment is fully commissioned)
• 3 additional FD telescopes at Loma Amarilla increasing vertical f.o.v. to 600 for ~ 900 in azimuthstandard or new telescope design for R&D ?
• Additional infill SD array with (50-100) tanks at R = 3 – 9 kmwith an area ~ 50 - 100 km²
• Hybrid detection and engineering array for Auger North
threshold for high quality data : < 2 x 1017 eV
statistics for LE hybrid data ~ 10.000 / year
1,5 km1,5 km
866 m866 m
A simple layout for an infill array
What about the Hedgehog?
• How do we connect the low energy and the high energy measurements?
• Push fluorescence measurement as low as possible ( 10^16.5 eV?)
• Build Cherenkade as big as possible - reach 10^17 eV
• Direct cross calibration of Xmax techniques is then possible - event by event
• Overlap in physics reach with direct measurements at 10^14 eV
The CR Grand Staircase V1.0
• Isotopic measurements (balloon flights)• TR type detector (balloon flights)• High mountain proton flux measurement• Cherenkade *• TALE TOP detector *• TALE Stereo detector *• TA *• TA (+) N. Auger *(?) * = co-sited
The CR Grand Staircase ( V1.1)
• As before
• S. Cherenkade *
• S. Auger low energy hybrid extension *
• S. Auger *
• EUSO
• OWL
The Hedgehog and the Fox, cont.
• If we are like the Fox, by 2010 we will have:
- Continuing balloon flights
- Snow-top + (Tunka?)
- S. Auger low energy extension
- TALE (?) not guaranteed
- TA
Fox, cont.
• This leaves very unpleasant gaps between direct measurements and snow-top
• Snow-top has no Xmax measurement
• No event by event correlation is possible with fluorescence
How expensive is the Hedgehog?
• Can we afford all of this?• S. Auger extension money is identified• TA is fully funded.• HiRes equipment can be moved from Dugway for
TALE.• Major expense is TR balloon flight program, high
altitude proton detector (re-use existing calorimeter?), TALE tower of power and Cherenkade detector(s)
Contra Mike Turner
• Competition is good
• Some duplication is essential
• Planning is just the beginning!
• Government exists by the consent of the governed (Thomas Jefferson)
• This applies to funding agencies too!
Importance of other particles
• Gamma rays and neutrinos are also cosmic rays.
• Some breakthroughs relating to charged particle CR come from neutrals (HESS)
• Example: Anita-light may have ruled out Z-burst model in two day balloon flight.
• The picture will always remain incomplete if we don’t put all the information together.
Importance of Connections to Other Disciplines
• The “Vapor pressure of Copper” problem• Implications and integration with
- Astronomy/Astophysics
Magnetic fields
SN modeling
Galactic structure
Is clustering scale relevant?
Galactic evolution
Integration, cont.
• Particle Physics– GZK resolution may bring in new physics– String theoretical predictions - modifications of
cross sections ( strong neutrinos )- Framgmentation physics
- Total cross-sections
Let’s Get Busy!