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Proposal for Experiment at RCNP

Proposal for Experiment at RCNP. Measurement of Proton-Induced Subthreshold Pion Pair Production ( p+A  p + + p - +X ) Atsushi Sakaguchi (Osaka Univ.). Physics Motivation. L QCD and strong interaction Chiral symmetry is broken dynamically Origin of constituent quark mass

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Proposal for Experiment at RCNP

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  1. Proposal for Experiment at RCNP Measurement of Proton-Induced Subthreshold Pion Pair Production ( p+A  p++p-+X ) Atsushi Sakaguchi (Osaka Univ.)

  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 RCNP B-PAC

  3. How can we prove it to be true ? • Phase transition broken  conserved • High temperature (T>200MeV) • High baryon density (r>10r0) • Transient phenomena, dynamical effects • Partial restoration of symmetry • Precursor of phase transition • Nuclei as static environment with finite baryon density (0<r<r0)  RCNP B-PAC

  4. Meson productions in nuclei • s meson (two pions) • CHAOS : p++A  p++p-+X • Crystal Ball: p-+A  p0+p0+X • TAPS : g+A  p0+p0+X • r/w/f mesons • KEK-E325 : p+A  e++e-+X • Still not clear • Drastic effect, elementary proc., absorption     RCNP B-PAC

  5. CHAOS Drastic change in p+p- channel Spike in Mpp<300 MeV/c2 Elementary process seems to be not simple (pion induced) RCNP B-PAC

  6. TAPS RPb/C has spike in Mpp<300 MeV/c2 Elementary process seems to be simple (g induced) RCNP B-PAC

  7. CERSIUS PRL 88 (2002) 192301 Subthreshold Proposed Experiment • p+Ap++p-+X • Subthreshold • Sensitive to low Mpp component • Cross section enhancement • Modification of Mpp shape • Target mass dependence (future) RCNP B-PAC

  8. 1.34nb 0.74nb 0.38nb • Cross section • Simple model calculation • Realistic Fermi motion • Experimental ppp+p-pp cross section • Target nucleon binding effect • MC calculation s 1nb/nucleon (@416MeV) Strong Tbeam dependence RCNP B-PAC

  9. Existing Setup • Ohsho spectrometer at WSS • Large acceptance • Efficient p- trigger • Improve p-/p ratio 2.5 orders • About 4M p-/day RCNP B-PAC

  10. Preliminary spectrum • Search for p+p- like pairs • Byproduct of R&D for pnpL experiment • TBeam=392MeV • 8 hours run with Cu target (2.7 h live time) • One p- and another h+ Sensitivity down to 0.1nb/nucleon RCNP B-PAC

  11. New Experiment Proposal • About 100 times larger yield • Establish p+p- measurement • Present yield is too few • Discuss p+p- production more clearly • Mpp, ppp and qpp distributions • First step to measure A-dependence • At least 2 more targets RCNP B-PAC

  12. System Update • DAQ • Decrease dead time • Optimize DAQ sequence • VME+FASTBUS • Double memory buffer in VME • High statistics • Beamtime • Beam energy 10 (8h80h) 3 (0.4nb1.3nb) RCNP B-PAC

  13. 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) RCNP B-PAC

  14. Offline analysis results • CDC-Outer trigger RCNP B-PAC

  15. Requests • Beam time • Trigger study: 1 day • Detector tuning: 1 day • Physics run: 4 days • Budget • ULM: 600,000 yen • Cables: 200,000+150,000 yen RCNP B-PAC

  16. Next Bunch Next Bunch 1% Accidental Coincidence RCNP B-PAC

  17. 70 pp opening angle (MC) RCNP B-PAC

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