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Proposal for Experiment at RCNP Measurement of Proton-Induced Subthreshold Pion Pair Production ( p+A + +X ) Atsushi Sakaguchi (Osaka Univ.)
Proposal for Experiment at RCNP
Measurement of Proton-Induced Subthreshold Pion Pair Production
( p+A ++X )
Atsushi Sakaguchi (Osaka Univ.)
5 August, 2004 RCNP B-PAC 2
Physics Motivation
LQCD and strong interaction
Chiral symmetry is broken dynamically
Origin of constituent quark mass
Pion as Goldstone boson
Gap: QCD and low energy phenomena
00 qqqq
qqmmffMM hud 22,,
mm
5 August, 2004 RCNP B-PAC 3
How can we prove it to be true ?Phase transition broken conserved
• High temperature (T>200MeV)
• High baryon density (>100)
• Transient phenomena, dynamical effects
Partial restoration of symmetry• Precursor of phase transition• Nuclei as static environment with finite
baryon density (0<<0)
5 August, 2004 RCNP B-PAC 4
Meson productions in nuclei meson (two pions)
• CHAOS : +A ++X• Crystal Ball: +A ++X• TAPS : +A ++X
// mesons• KEK-E325 : p+A e++e+X
Still not clear• Drastic effect, elementary proc., absorption
5 August, 2004 RCNP B-PAC 5
CHAOSDrastic change in
channel
Spike in M<300 MeV/c2
Elementary process seems to be not simple
(pion induced)
5 August, 2004 RCNP B-PAC 6
TAPSRPb/C has spike inM<300 MeV/c2
Elementary process seems to be simple
( induced)
5 August, 2004 RCNP B-PAC 7
Proposed Experiment p+A++X
Subthreshold
Sensitive to low M component• Cross section enhancement
• Modification of M shape
• Target mass dependence (future)
MeVT
MeVTMeVT
pAthre
pNthreBeam
300
600416
)(
)(
Above threshold
A
Subthreshold
CERSIUSPRL 88 (2002) 192301
5 August, 2004 RCNP B-PAC 8
Cross section
Simple model calculation• Realistic Fermi motion• Experimental pppp cross section• Target nucleon binding effect• MC calculation
1nb/nucleon (@416MeV)
Strong Tbeam dependence
1.34nb
0.74nb
0.38nb
5 August, 2004 RCNP B-PAC 9
Existing Setup Ohsho spectrometer at WSS
Large acceptance
Efficient trigger• Improve /p ratio 2.5 orders• About 4M /day
4.2
5 August, 2004 RCNP B-PAC 10
Preliminary spectrumSearch for like pairs
• Byproduct of R&D for pnp experiment
• TBeam=392MeV
• 8 hours run with Cu target (2.7 h live time)• One and another h+
Sensitivity down to 0.1nb/nucleon
5 August, 2004 RCNP B-PAC 11
New Experiment Proposal About 100 times larger yield
Establish measurement• Present yield is too few
Discuss production more clearly• M, p and distributions
First step to measure A-dependence• At least 2 more targets
5 August, 2004 RCNP B-PAC 12
System Update DAQ
Decrease dead time• Optimize DAQ sequence
• VME+FASTBUS
• Double memory buffer in VME
High statisticsBeamtimeBeam energy
10 (8h80h)
3 (0.4nb1.3nb)
5 August, 2004 RCNP B-PAC 13
New triggerTwo track trigger
• 2 cluster in Outer hodoscope (available)• 2 cluster in CDC hits (need update)• Combination of Outer and CDC hits
Trigger system w/ ULM (FPGA based)
1.02
all
eventstrack
5 August, 2004 RCNP B-PAC 14
CDC-Outer trigger
Offline analysis results
5 August, 2004 RCNP B-PAC 15
Requests Beam time
Trigger study: 1 dayDetector tuning: 1 dayPhysics run: 4 days
BudgetULM: 600,000 yenCables: 200,000+150,000 yen
5 August, 2004 RCNP B-PAC 16
Accidental Coincidence
NextBunch
NextBunch
1%
5 August, 2004 RCNP B-PAC 17
opening angle (MC)
70
