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Experimental study of hadron mass

Experimental study of hadron mass. K. Ozawa (University of Tokyo). Contents: Physics motivation Current results Future Experiments Summary. Origin of quark mass. Figure by Prof. I. Tserruya. Current quark masses generated by spontaneous symmetry breaking (Higgs field).

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Experimental study of hadron mass

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  1. Experimental study of hadron mass K. Ozawa (University of Tokyo) Contents: Physics motivation Current results Future Experiments Summary

  2. Origin of quark mass Figure by Prof. I. Tserruya Current quark masses generated by spontaneous symmetry breaking (Higgs field) Constituent quark masses should be generated by QCD dynamical effects 95% of the (visible) mass is dynamically generated by the strong interaction. This mechanism isactively studied both theoretically and experimentally. Weizmann seminar, K. Ozawa

  3. Naïve Theory High Temperature High Density Chiral symmetry exists. Mass ~ 0 (Higgs only) When T and r is going down, q Vacuum Vacuum Quark – antiquark pairs make a condensate and give a potential. Chiral symmetry is breaking, spontaneously. q Vacuum contains quark antiquark condensates. So called “QCD vacuum”. p as a Nambu-Goldstone boson. Weizmann seminar, K. Ozawa

  4. Experimental approach? “QCD vacuum”, i.e. quark condensates can be changed in finite density or temperature. Then, chiral symmetry will be restored (partially). Vacuum r  0 T  0 In finite r/T Chiral properties can be studied at finite density and temperature. mass a1 (JP = 1+) Observable? 1250 Dm When chiral symmetry is restored, mass of chiral partner should be degenerated. Degenerate 770 Dm = 0  (JP = 1-) r/T Dm will decrease in finite r/T matter. However, measurements of chiral partner is very difficult. We can measure only mass modification of narrow resonance. Weizmann seminar, K. Ozawa

  5. Predicted “spectra” As the first step, measurements in hot/dense matter are compared with predicted mass spectra. • several theories and models predict spectral function of vector mesons (r, w, f) in hot and/or dense matter. • Lowering of in-medium mass • Broadening of resonance P. Muehlich et al. , Nucl. Phys. A 780 (2006) 187 r- meson - meson R. Rapp and J. Wambach, EPJA 6 (1999) 415 Weizmann seminar, K. Ozawa

  6. Current Experiments Weizmann seminar, K. Ozawa

  7. Generate hot/dense media • Measurements of Vector Meson mass spectra in hot/dense medium will provide QCD information. Hot matter experiments SPS heavy ion reactions: A+AV+X mV(>>0;T>>0) RHIC LHC Leptonic (e+e-, m+m-) decays are suitable, since lepton doesn’t have final state interaction. 7 Weizmann seminar, K. Ozawa

  8. SPS-CERES results D. Miskowiec, QM05 talk PLB663, 43 (2008) Weizmann seminar, K. Ozawa Existing of Mass modification is established.

  9. NA60 Results @ SPS • Muon pair invariant mass in Pb-Pb at sNN=19.6 GeV [van Hees+R. Rapp ‘06] PRL 96, 162302 (2006) Spectrum is well reproduced with collisionalbroadening. Next, We should try to understand QCD nature of the modification. Weizmann seminar, K. Ozawa 9

  10. RHIC&PHENIX Weizmann seminar, K. Ozawa

  11. Results @ RHIC • Electron pair invariant mass in Au-Au at sNN=200 GeV • Advantages of RHIC • Clear initial condition • Clear Time develop • calculated by Hydrodynamics arXiv:0706.3034 No concluding remarks at this moment. New data with New detector (HBD) can answer it. Weizmann seminar, K. Ozawa • Black Line • Baseline calculations • Colored lines • Several models Low mass • M>0.4GeV/c2: • some calculations OK • M<0.4GeV/c2: not reproduced • Mass modification • Thermal Radiation

  12. signal electron e- partner positron needed for rejection Cherenkov blobs e+ qpair opening angle ~ 1 m New detector! Constructed and installed by Weizmann and Stony Brook group. Hadron few p.e. Single electron ~20 p.e. Great performance! Weizmann seminar, K. Ozawa

  13. Now, Nucleus! At Nuclear Density , . p - beams J-PARC CLAS elementary reaction: , p,   V+X mV(=0;T=0) Cold matter experiments • Experiments, • CBELSA/TAPS • KEK-E325 @KEK-PS (Japan) • CLAS g7 @ J-Lab Stable system Saturated density 13 Weizmann seminar, K. Ozawa

  14. gA   + X after background subtraction p g p0g g  w p0 g g Results from CBELSA/TAPS TAPS, w p0g with g+A D. Trnka et al., PRL 94 (2005) 192203 advantage: • p0g large branching ratio (8 %) • no -contribution (  0 : 7  10-4) disadvantage: • p0-rescattering m =m0 (1 -  /0) for  = 0.13 NQCD symposium, K. Ozawa

  15. E325 @ KEK-PS 12 GeV proton induced. p+A f + X Electrons from f decays are detected. • Target • Carbon, Cupper • 0.5% rad length KEK E325 Weizmann seminar, K. Ozawa

  16. E325 Spectrometer Weizmann seminar, K. Ozawa

  17. Mass spectra measurements KEK E325, r/w  e+e- Induce 12 GeV protons to Carbon and Cupper target, generate vector mesons, and detect e+e- decays with large acceptance spectrometer. M. Naruki et al., PRL 96 (2006) 092301 w/r/f Cu we+e- The excess over the known hadronic sources on the low mass side of w peak has been observed. re+e- mr=m0 (1 -  /0) for  = 0.09 Weizmann seminar, K. Ozawa

  18. w/r/f g CLAS g7a @ J-Lab Induce photons to Liquid dueterium, Carbon, Titanium and Iron targets, generate vector mesons, and detect e+e- decays with large acceptance spectrometer. R. Nasseripour et al., PRL 99 (2007) 262302 No peak shift of r Only broadening is observed mr=m0 (1 -  /0) for  = 0.02 ± 0.02 Weizmann seminar, K. Ozawa

  19. Contradiction? R.S. Hayano and T. Hatsuda, Ann. Rev. • Difference is significant • What can cause the difference? • Different production process • Peak shift caused by phase space effects in pA? • Need spectral function of r without nuclear matter effects Note: • similar momentum range • E325 can go lower slightly CLAS KEK We need to have a new experiment to investigate the problem. Weizmann seminar, K. Ozawa

  20. Results: f e+e- bg<1.25 (Slow) R. Muto et al., PRL 98(2007) 042581 Invariant mass spectrum for slow f mesons of Cu target shows a excess at low mass side of f. Cu Excess!! Measured distribution contains both modified and un-modified mass spectra. So, modified mass spectrum is shown as a tail. First measurement of f meson mass spectral modification in QCD matter. Weizmann seminar, K. Ozawa

  21. 1.75<bg (Fast) bg<1.25 (Slow) 1.25<bg<1.75 Target/Momentum dep. Mass modification is seen only at heavy nuclei and slowly moving f Mass Shift: mf=m0 (1 -  /0) for  = 0.03 Weizmann seminar, K. Ozawa

  22. New EXPERIMENT@ J-PARC Weizmann seminar, K. Ozawa

  23. Performance of the 50-GeV PS Numbers in parentheses are ones for the Phase 1. • Beam Energy： 50ＧｅＶ (30GeV for Slow Beam) (40GeV for Fast Beam) • Repetition: 3.4 ~ 5-6s • Flat Top Width： 0.7 ~ 2-3s • Beam Intensity: 3.3x1014ppp, 15mA (2×1014ppp, 9mA) ELinac = 400MeV(180MeV) • Beam Power: 750kW (270kW) Weizmann seminar, K. Ozawa

  24. J-PARC • Cascaded Accelerator Complex: Hadron Hall (Slow Extracted Beams) Materials and Life Science Facility 3GeV Rapid Cycling (25Hz) Synchrotron Hadron Hall Linac Neutrino Beamline to Super-Kamiokande 50GeV Synchrotron Weizmann seminar, K. Ozawa

  25. NP-HALL 56m(L)×60m(W) Hadron Hall Stopped w for Clear mass modification Upgrade of E325 Large statistics Weizmann seminar, K. Ozawa

  26. Upgrade of KEK-E325 • Large acceptance (x5 for pair ) • Cope with high intensity beam and high rate (x10) • Good mass resolution ~ 5 MeV/c2 • Good electron ID capability 100 times higher statistics!! Weizmann seminar, K. Ozawa

  27. Pb f Modified f [GeV/c2] Invariant mass in medium What can be achieved? f f f f f f f f f from Proton p dep. High resolution Weizmann seminar, K. Ozawa Dispersion relation

  28. Detector components • Tracker • ~Position resolution 100μm • High Rate(5kHz/mm2) • Small radiation length • (~0.1% per 1 chamber) • Electron identification • Large acceptance • High pion rejection @ 90% e-eff. • 100 @ Gas Cherenkov • 25 @ EMCal Weizmann seminar, K. Ozawa

  29. R&D Items ① GEM foil Develop 1 detector unit and make 26 units. ② GEM Tracker CsI+ GEM photo-cathode • 50cm gas(CF4) radiator • ~ 32 p.e. expected • CF4 also for multiplication in GEM • Ionization (Drift gap) • + Multiplication (GEM) • High rate capability • + 2D strip readout • ③ Hadron Blind detector • Gas Cherenkov for electron-ID Weizmann seminar, K. Ozawa

  30. GEM foils Stability of GEM gain 100mm 1 foil 103 • Dry etching method is developed in Japan. • Hole shape is improved and cylindrical hole GEM has better Gain stability. • Thicker GEM foils is generated. 50mm 3 foils 102 wet etching dry etching 300 350 Hole shape Applied Voltage per 50 mm [V] Thicker GEM foil A hole with cylindrical shape A hole with double-conical shape Dry Wet Weizmann seminar, K. Ozawa

  31. GEM Tracker Test @ KEK Gas: Ar/CO2 290 mm • 2D readout: • kapton t=25mm • (Cu: t=4mm both side) σ~105μm Residual[mm] Weizmann seminar, K. Ozawa

  32. HBD: in the beginning… Compare Measured Charge w/wo Cherenkov light blind dE/dx (Blind ON) This part of evaporated CsI looksgone!! Low Q.E.? dE/dx + Light (Blind OFF) 1~2 photo electrons Too small… Charge [A.U.] Weizmann seminar, K. Ozawa

  33. p-A   + N+X n p p0g g  w p0 g g Exp 2: stopped w meson Generate w meson using p beam. Emitted neutron is detected at 0. Decay of w meson is detected. If p momentum is chosen carefully, momentum transfer will be ~ 0. To generate stopped modified w meson, beam momentum is ~ 1.8 GeV/c. (K1.8 can be used.) As a result of KEK-E325, 9% mass decreasing (70 MeV/c2) can be expected. Focus on forward (~2°). 0.4 w momentum [GeV/c] 0.2 4 2 0 0 p momentum [GeV/c] Weizmann seminar, K. Ozawa

  34. Experimental setup • p-p  wn @ 1.8 GeV/c •  p0g  gg • Target: Carbon 6cm • Small radiation loss • Clear calculation of w bound state • Ca, Nb, LH2 are under consideration. • Neutron Detector • Flight length 7m • 60cm x 60 cm (~2°) • Gamma Detector • Assume T-violation’s • 75% of 4p • SKS for charge sweep Neutron Beam Gamma Detector Weizmann seminar, K. Ozawa

  35. Detectors Neutron Detector EM calorimeter • CsIEMCalorimeter • Existing detector + upgrade （D.V. Dementyevet al., Nucl. Instrum. Meth. A440(2000), 151） 912 • Timing resolution • Timing resolution of 80 psis achieved (for charged particle). • It corresponds to mass resolution of 22MeV/c2. • Neutron Efficiency • Iron plate (1cm t) is placed. • Efficiency is evaluated using a hadron transport code, FLUKA. • Neutron efficiency of 25% can be achieved. mass resolution of 18MeV/c2 can be achieved. Weizmann seminar, K. Ozawa

  36. Expected results Final spectrum is evaluated based on a theoretical calculation and simulation results. Expected Invariant mass spectrum Generation of w is based on the above theoretical calculation. Detector resolution is taken into account. Yield estimation is based on 100 shifts using 107 beam. Estimated width in nucleus is taken into account. H. Nagahiro et al, Calculation for 12C(p-, n)11Bw Stopped w is selected by forward neutron Weizmann seminar, K. Ozawa

  37. “Mass” correlation? Expected Missing mass spectrum (Mass @ generation) Neutron energy spectrum No interact No mass mod. Smearing Interact w. nuclei and Mass modification Correlation to invariant mass reconstructed by p0g(Mass @ decay) Non-correlation? Same mass? Weizmann seminar, K. Ozawa

  38. Summary • According to the theory, Hadron mass is generated as a results of spontaneous breaking of chiral symmetry. • Many experimental efforts are underway to investigate this mechanism. Some results are already reported. • Next, we need to extract QCD information. • New experiments for obtaining further physics information are proposed. • Explore large kinematics region • Measurements with stopped mesons Weizmann seminar, K. Ozawa

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