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 alleventstrack

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