Proposal for Experiment at RCNP

1
Proposal for Experiment at RCNP

• Measurement of Proton-Induced Subthreshold Pion
  Pair Production
• ( pA ? pp-X )
• Atsushi Sakaguchi (Osaka Univ.)

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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

3

• How can we prove it to be true ?
• Phase transition broken ? conserved
• High temperature (Tgt200MeV)
• High baryon density (rgt10r0)
• Transient phenomena, dynamical effects
• Partial restoration of symmetry
• Precursor of phase transition
• Nuclei as static environment with finite baryon
  density (0ltrltr0)

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4

• Meson productions in nuclei
• s meson (two pions)
• CHAOS pA ? pp-X
• Crystal Ball p-A ? p0p0X
• TAPS gA ? p0p0X
• r/w/f mesons
• KEK-E325 pA ? ee-X
• Still not clear
• Drastic effect, elementary proc., absorption

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?
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5

• CHAOS

Drastic change in pp- channel Spike in
Mpplt300 MeV/c2 Elementary process seems to be
not simple (pion induced)
6

• TAPS

RPb/C has spike in Mpplt300 MeV/c2 Elementary
process seems to be simple (g induced)
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Proposed Experiment

• pA?pp-X
• Subthreshold
• Sensitive to low Mpp component
• Cross section enhancement
• Modification of Mpp shape
• Target mass dependence (future)

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• Cross section
• Simple model calculation
• Realistic Fermi motion
• Experimental pp?pp-pp cross section
• Target nucleon binding effect
• MC calculation

s ? 1nb/nucleon (_at_416MeV)
Strong Tbeam dependence
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Existing Setup

• Ohsho spectrometer at WSS
• Large acceptance
• Efficient p- trigger
• Improve p-/p ratio 2.5 orders
• About 4M p-/day

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• Preliminary spectrum
• Search for pp- like pairs
• Byproduct of RD for pn?pL experiment
• TBeam392MeV
• 8 hours run with Cu target (2.7 h live time)
• One p- and another h

Sensitivity down to 0.1nb/nucleon
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New Experiment Proposal

• About 100 times larger yield
• Establish pp- measurement
• Present yield is too few
• Discuss pp- production more clearly
• Mpp, ppp and qpp distributions
• First step to measure A-dependence
• At least 2 more targets

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System Update

• DAQ
• Decrease dead time
• Optimize DAQ sequence
• VMEFASTBUS
• Double memory buffer in VME
• High statistics
• Beamtime
• Beam energy

?10 (8h?80h)
?3 (0.4nb?1.3nb)
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• New trigger
• Two 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)

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• CDC-Outer trigger

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Requests

• Beam time
• Trigger study 1 day
• Detector tuning 1 day
• Physics run 4 days
• Budget
• ULM 600,000 yen
• Cables 200,000150,000 yen

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Accidental Coincidence
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pp opening angle (MC)