7 - 11 june 2004l. benussi - dafne 2004 first results on hyper-nuclear spectroscopy from the finuda...
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7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
First results onFirst results onhyper-nuclear spectroscopy hyper-nuclear spectroscopy from the FINUDA experimentfrom the FINUDA experiment
at DAat DANENE
Luigi BenussiLuigi BenussiINFN, Laboratori Nazionali di FrascatiINFN, Laboratori Nazionali di Frascati
On behalf of FINUDA CollaborationOn behalf of FINUDA Collaboration
DAFNE 2004 - Frascati, June 4-8,2004DAFNE 2004 - Frascati, June 4-8,2004
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
•Bari University and I.N.F.N. Bari, ItalyBari University and I.N.F.N. Bari, Italy
•Brescia University and I.N.F.N. Pavia, ItalyBrescia University and I.N.F.N. Pavia, Italy
•KEK, JapanKEK, Japan
•Laboratori Nazionali di Frascati I.N.F.N., ItalyLaboratori Nazionali di Frascati I.N.F.N., Italy
•Pavia University and I.N.F.N. Pavia, ItalyPavia University and I.N.F.N. Pavia, Italy
•Seoul National University, KoreaSeoul National University, Korea
•Shahid Beheshty University, Teheran, Iran Shahid Beheshty University, Teheran, Iran
•Torino University and I.N.F.N. Torino, ItalyTorino University and I.N.F.N. Torino, Italy
•Torino Polytechinc and I.N.F.N. Torino, ItalyTorino Polytechinc and I.N.F.N. Torino, Italy
•Trieste University and I.N.F.N. Trieste, ItalyTrieste University and I.N.F.N. Trieste, Italy
•TRIUMF, Vancouver, Canada TRIUMF, Vancouver, Canada
The FINUDA collaborationThe FINUDA collaboration
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
50 Years after the discovery of the50 Years after the discovery of thefirst hyper-nucleus, FINUDA has started first hyper-nucleus, FINUDA has started
its production of strange nuclei in Frascatiits production of strange nuclei in Frascati
Talk outlines:Talk outlines:• Performances and events reconstructionPerformances and events reconstruction• First preliminary results on hyper-nuclear First preliminary results on hyper-nuclear
spectroscopyspectroscopy
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
FINUDAFINUDAFIFIsicasica NU NUclearecleare aa DADANENE
The The ’s’sproduced by DAproduced by DANE provide a unique “KNE provide a unique “K beam”…. beam”….
1.1. Monochromatic, low momentum (127 MeV/c)Monochromatic, low momentum (127 MeV/c)
2.2. trigger tagging Ktrigger tagging Kstop stop event through the associate Kevent through the associate K
3.3. no hadronic backgroundno hadronic background
…….that can be stopped in thin targets to produce hypernuclei .that can be stopped in thin targets to produce hypernuclei
KKstop stop + + AAZ Z AA
Z + Z +
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
FINUDA main physics programFINUDA main physics program
• Production of Production of -hyp. : K-hyp. : Kstop stop + + AAZ Z AA
Z + Z +
– spectroscopy of hyp. via the spectroscopy of hyp. via the promptprompt momentum momentum
• Decay of Decay of -hyp.-hyp.
mesonic decays is Pauli blockedmesonic decays is Pauli blocked
non-mesonic decays prevalentnon-mesonic decays prevalent
• Lifetime of Lifetime of -hyp.-hyp.
• Search for neutron rich Search for neutron rich -hyp.-hyp.
0; np
nnnnpp ;
FINUDA can study
FINUDA can study
simultaneously
simultaneously
hyp. spectroscopy
hyp. spectroscopy
and hyp. decays
and hyp. decays
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
3 targets of 3 targets of 1212C C 2 targets of 2 targets of 66Li Li 1 target of 1 target of 77LiLi1 target of 1 target of 2727AlAl1 target of 1 target of 5858VV
OSIMOSIM
ISIMISIM
TOFINOTOFINO
TargetsTargets
Beam pipeBeam pipe
Interaction-Target regionInteraction-Target region
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
Segmented Segmented targettarget in 8 different modules: in 8 different modules:
2 of 2 of 66Li, 1 of Li, 1 of 77Li, 3 of Li, 3 of 1212C, 1 of C, 1 of 2727Al and 1 of Al and 1 of 5151VV
66LiLi: Source of : Source of 44He and He and 55
He (He (66Li unstable); study of the decay of light Li unstable); study of the decay of light
hypernuclei (never examined);hypernuclei (never examined);
77LiLi: Comparison with the : Comparison with the 66Li target, available data of poor quality w.r.t Li target, available data of poor quality w.r.t
FINUDA performance;FINUDA performance;
1212CC: Reference target for spectroscopy and weak decays studies, search : Reference target for spectroscopy and weak decays studies, search
for states weakly excited, for states weakly excited, 10 1055/K/Kstopstop (present limit 10 (present limit 104 4 /K/Kstopstop););
2727AlAl: Never studied before; measurement of the capture rate in the : Never studied before; measurement of the capture rate in the
medium A hyper-nuclei;medium A hyper-nuclei;
5151VV: No measurements available with K: No measurements available with K-- at rest, useful for weak decay at rest, useful for weak decay
studies; important to assess the capture rate for the medium and heavy studies; important to assess the capture rate for the medium and heavy
hyper-nuclei;hyper-nuclei;
Target ChoiceTarget Choice
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
e+
e
ee invariant mass (GeV/c)
Ks
e+e e+e
FINUDA performances: FINUDA performances: Bhabha eventBhabha event
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
FINUDA performances: FINUDA performances: Hyper-nuclear formation eventHyper-nuclear formation event
+
-
K-
K+
+
-
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
FINUDA performances: FINUDA performances: Hyper-nuclear formation and decay eventHyper-nuclear formation and decay event
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
KK stopping point stopping point distributiondistribution
Scatter plot of the reconstructed y vs x Scatter plot of the reconstructed y vs x coordinates of the Kcoordinates of the K stopping points stopping points
– most external octagon: 8 target modules, most external octagon: 8 target modules, where most of the Kwhere most of the K stop. stop.
– Inner layers: stops on the microstrip ISIM Inner layers: stops on the microstrip ISIM modules which give us an additional target: modules which give us an additional target: 2828
Si can be studied Si can be studied
7Li
6Li
27Al 51V
12C12C
12C
6Li
Isim 8
Isim 7
Isim 2
Isim 1
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
Momentum distribution of KMomentum distribution of K++ charged decay productscharged decay products
K+ +
K+ + o
KK++ ++
KK++ ++oo
The width of the The width of the ++ peak gives a peak gives a momentum momentum resolution of: resolution of:
p/p< 0.9% p/p< 0.9%
(Goal (Goal p/p< 0.35%)p/p< 0.35%)
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
Event and track selectionEvent and track selection Selection criteria for Selection criteria for -- Candidates from hypernuclear formation: Candidates from hypernuclear formation:
• negative track from Knegative track from K vertex; vertex;• 4 points/track, in detectors:4 points/track, in detectors:
Outer microstrip OSIMOuter microstrip OSIMfirst layer LMDCfirst layer LMDCsecond layer LMDCsecond layer LMDCStraw Tubes tripletStraw Tubes triplet
• forward track forward track (more clean events….backward tracks will be used mainly for decays study)(more clean events….backward tracks will be used mainly for decays study); ; • angle w.r.t. target 0angle w.r.t. target 0oo 70 70oo;;• momentum corrected for the energy loss in the target material momentum corrected for the energy loss in the target material
crossed;crossed;• Quality cuts onQuality cuts on track fitting;track fitting;
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
reconstructed momentum spectrumreconstructed momentum spectrumin the 8 targetsin the 8 targets
Clean hypernuclear structures Clean hypernuclear structures present in all targetspresent in all targets
sel. sel. cutscuts
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
Target N.1 Target N.1 1212C nucleusC nucleus1212C is the reference Nucleus C is the reference Nucleus
In the following data only from In the following data only from 1212C target (target n.1) C target (target n.1) about 20% of the available statistics for about 20% of the available statistics for 1212CC
Different targets have different systematic mainly due to the geometrical alignment of Different targets have different systematic mainly due to the geometrical alignment of the detectors, that are currently being improved…. the detectors, that are currently being improved….
The measured momentum spectrum is transformed into binding The measured momentum spectrum is transformed into binding energy (Benergy (B) spectrum of the lambda) spectrum of the lambda
BB=M=MA-1A-1+M+MMMA A M MKK+M+M +T+T
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
Background reactions: Background reactions: - spectra- spectra
K- n -
p -
K- p+ -
K- p- +
- n -
K- (NN)- N - n -
K- n0 -
TOT
Background reactions giving a Background reactions giving a following K following K Nucleus Nucleus interactions have been simulated in the apparatusinteractions have been simulated in the apparatus with with FINUDA Monte Carlo:FINUDA Monte Carlo:
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
(K(K--stopstop, , -)-) 1212
C spectrum C spectrum
• Simulated background particles have been Simulated background particles have been reconstructed andreconstructed and selected following the selected following the same selection criteria as for the hyper-same selection criteria as for the hyper-nucleus formation nucleus formation candidates candidates
• The shape of the background simulated The shape of the background simulated and reconstructed spectrum is and reconstructed spectrum is parameterized and subtracted from the parameterized and subtracted from the experimental spectrum.experimental spectrum.
• Resolution (Resolution (E E =600keV) set by peak #2 =600keV) set by peak #2 p/p p/p 0.6% 0.6%
#2
#1
FINUDA P
relim
inar
y
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
Exclude region between peaks Exclude region between peaks #1 , #2. #1 , #2. We fit with 2 gauss with We fit with 2 gauss with EE=600 =600 keV fixed keV fixed There is more than 1 object in There is more than 1 object in #2 (?)….#2 (?)….
…….try to fit peak #2 with 2 .try to fit peak #2 with 2 gauss….Seems better but….gauss….Seems better but…. ……add a third gauss for the add a third gauss for the
peak #2peak #2…….Now better fit. .Now better fit.
#1
#2
preliminary
preliminary
preliminary
FINUDA preliminary 12C spectrum
#1
#2
#1
#2
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
• Partial statistics, only one of the Partial statistics, only one of the three three 1212C targets C targets • Best fit with the sum of 4 gauss Best fit with the sum of 4 gauss distributions, 1 for the ground distributions, 1 for the ground state peak (#1), 3 needed to state peak (#1), 3 needed to describe the excited state peak describe the excited state peak (#2) (#2) • Region between main peaks Region between main peaks excluded from fit.excluded from fit.
preliminary#2
#1
Capture Rates: #1 ground state: ~ 1.8x10-3/K-
stop
#2 excited state: ~ 3.3x10-3/K-stop
FINUDA preliminary FINUDA preliminary 1212C spectrumC spectrum
#3#4
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
1212C spectroscopy: C spectroscopy: FINUDA vs KEKFINUDA vs KEK
H.Hotchi, Phys.Rev. C 64 (2001) 044302
Previous results: KEK E369Previous results: KEK E369Energy resolution Energy resolution 1.45 MeV FWHM 1.45 MeV FWHM production reaction (production reaction (KK
FINUDA preliminary FINUDA preliminary Energy resolution Energy resolution 1.4 MeV FWHM 1.4 MeV FWHM production reaction (Kproduction reaction (K
stopstop, , ) )
#1
#2 = #5
#3 = #6
#4 = ?
7 - 11 June 20047 - 11 June 2004 L. Benussi - DAFNE 2004L. Benussi - DAFNE 2004
ConclusionsConclusions• FINUDA HAS SUCCESSFULLY ENDED the FIRST FINUDA HAS SUCCESSFULLY ENDED the FIRST
DATA TAKING PERIOD COLLECTING 30XDATA TAKING PERIOD COLLECTING 30X10106 6
EVENTSEVENTS
• FINUDA preliminary results, with partial statistics FINUDA preliminary results, with partial statistics
(~1/5) and not yet final momentum resolution (~1/5) and not yet final momentum resolution
(~40% worst), are already at the same level of (~40% worst), are already at the same level of
the best published results on hyper-nuclear the best published results on hyper-nuclear
spectroscopyspectroscopy