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原子核媒質中の 中間子質量測定の 現状と将来

原子核媒質中の 中間子質量測定の 現状と将来. 小沢　恭一郎（東京大学）. Contents: Physics motivation Current results Future Experiments Summary. ハドロン質量の起源. Current quark masses generated by spontaneous symmetry breaking (Higgs field). Constituent quark masses generated by

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原子核媒質中の 中間子質量測定の 現状と将来

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  1. 原子核媒質中の中間子質量測定の現状と将来 小沢　恭一郎（東京大学） Contents: Physics motivation Current results Future Experiments Summary

  2. ハドロン質量の起源 Current quark masses generated by spontaneous symmetry breaking (Higgs field) Constituent quark masses generated by QCD dynamical effects (spontaneous chiral symmetry breaking ). 95% of the (visible) mass is generated by the strong interaction, dynamically. Only 5% of the mass is due to the Higgs field. The hadron mass is strongly related to chiral properties of “QCD medium”, which can be changed as a function of Temperature and Density. J-PARC seminar, K. Ozawa

  3. QCD medium High Temperature High Density • Quark is not confined. • Mass ~ 0 (Higgs only) • It looks real “vacuum”. q When T and rare going down, Vacuum Vacuum Quark – antiquark pairs make a condensate and give a potential. Symmetry is breaking. q Quark is confined. Vacuum contains quark antiquark condensates. So called “QCD vacuum”. p as a Nambu-Goldstone boson. J-PARC seminar, K. Ozawa

  4. How to study? “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. What is observable? Mass of chiral partner should be degenerated in restored medium. •  (JP = 1-) m=770 MeV：　a1 (JP = 1+) m=1250 MeV • N (1/2+) m=940 MeV　：　 N* (1/2-) m=1535 MeV？ Dm will decrease in finite r/T matter. However, measurements of chiral partner is very difficult Connect hadron properties and quark condensate using QCD and/or phenomenology. J-PARC seminar, K. Ozawa

  5. Theoretical efforts Vector meson mass • Nambu-Jona-Lasino model • Nambu and Jona-Lasino, 1961 • Vogl and Wise, 1991 • Hatsuda and Kunihiro, 1994 • Chiral Perturbation theory • Weinberg 1979 • Gasser and Leutwyler, 1984, 1985 • QCD sum rule • Shifmanet al., 1979 • Colangelo and Khodjamirian, 2001 • Hatsuda and Lee, 1992 • Lattice QCD • Wilson, 1974 • Karsch, 2002 • Empirical models • Potential model (De Rujulaet al., 1975), Bag model (Chdoset al., 1974) • In addition, Collisional broadening, nuclear mean field … G.E.Brown and M. Rho, PRL 66 (1991) 2720 ‘ T.Hatsuda and S. Lee, PRC 46 (1992) R34 J-PARC seminar, K. Ozawa

  6. Predicted “spectra” As the first step, experiments try the comparison between predicted spectra and measurements. • several theories and models predict spectral function of vector mesons (r, w, f). • Lowering of in-medium mass • Broadening of resonance P. Muehlich et al. , Nucl. Phys. A 780 (2006) 187 r- meson - meson structure due to coupling to S11,P13 resonances R. Rapp and J. Wambach, EPJA 6 (1999) 415 J-PARC seminar, K. Ozawa

  7. Measurements J-PARC seminar, K. Ozawa

  8. Create QCD medium At Nuclear Density , . p - beams J-PARC CLAS elementary reaction: , p,   V+X mV(=0;T=0) • Measurements of Vector Meson mass spectra in QCD medium will provide QCD condensates information. 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. 8 J-PARC seminar, K. Ozawa

  9. Results @ SPS (NA60) • Muon pair invariant mass in In-In at sNN=19.6 GeV [van Hees+R. Rapp ‘06] PRL 96, 162302 (2006) Spectrum is reproduced with collisionalbroadening. Next, We should try to extract of a quark condensate information from the data. J-PARC seminar, K. Ozawa 9

  10. RHIC&PHENIX J-PARC seminar, K. Ozawa

  11. Results @ RHIC • Advantages of RHIC • QGP generated • Clear initial condition • Time developing • calculated by Hydrodynamics • Electron pair invariant mass in Au-Au at sNN=200 GeV arXiv:0706.3034 No concluding remarks at this moment. Currently, we are working for detector upgrade. J-PARC 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. Then, Nucleus Two approaches, • Link vector meson masses and the quark condensate. • Link meson bound states and the quark condensate. Nucleon Hole Bound State (Emitted Proton/Neutron) p, p, g Meson Decay 12 • Stable system • No (small) need for time development • Saturated density ECT*-WS, K. Ozawa J-PARC seminar, K. Ozawa Target

  13. p bound state pas a NG boson K. Suzuki et al., Phys. Rev. Let., 92(2004) 072302 • bound state is observed in • Sn(d, 3He) pion transfer reaction. Reduction of the chiral order parameter, f*p(r)2/fp2=0.64 at the normal nuclear density (r = r0 ) is indicated. Jido-san et al. shows that p-nucleus scattering length is directly connected to quark condensate in the medium. D. Jido et al., arXiv:0805.4453 PLB670 (2008) 109 New exp. is in preparation at RIKEN J-PARC seminar, K. Ozawa

  14. Mass spectra measurements 注意 得られるものは、自由空間中で崩壊した粒子の分布との重ね合せ 予想される質量分布（KEK実験、銅標的の場合） 14 • 現在までに主に4例の実験結果 • TAGX 実験 • CBELSA/TAPS 実験 • KEK陽子シンクロトロン（KEK-E325実験) • J-Lab CLAS実験 • 軽い原子核と重い原子核で比較することで、媒質効果を導き出す。 J-PARC seminar, K. Ozawa

  15. INS-ES TAGX experiment Eγ~0.8-1.12.GeV, sub/near-threshold ρ0 production • PRL80(1998)241,PRC60:025203,1999.: mass reduced in invariant mass spectra of 3He(γ, ρ0)X ,ρ0 --> π+π− • Phys.Lett.B528:65-72,2002: introduced cosq analysis to quantify the strength of rho like excitation • Phys.Rev.C68:065202,2003. In-medium r0 spectral function study via the H-2, He-3, C-12 (g,p+ p-) reaction. Try many models, and channels Δ, N*, 3π,… J-PARC seminar, K. Ozawa

  16. gA   + X after background subtraction p g p0g g  w p0 g g 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 J-PARC seminar, K. Ozawa

  17. 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 J-PARC seminar, K. Ozawa

  18. E325 Spectrometer J-PARC seminar, K. Ozawa

  19. 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 J-PARC seminar, K. Ozawa

  20. 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 J-PARC seminar, K. Ozawa

  21. Contradiction? CLAS • 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 KEK In addition, background issue is pointed out by CLAS J-PARC seminar, K. Ozawa

  22. Background is not an issue The problem: Each experiment can’t apply another method. • Combinatorial background is evaluated by a mixed event method. • Form of the background is determined by acceptance and reliable. • We should be careful on normalization. CLAS KEK Normalized using mass region above f. There is enough statistics Absolute normalization using like-sign pairs J-PARC seminar, K. Ozawa

  23. Results: f e+e- (E325) 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. Mass Shift: mf=m0 (1 -  /0) for  = 0.03 J-PARC seminar, K. Ozawa

  24. 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 J-PARC seminar, K. Ozawa

  25. Next step@ J-PARC J-PARC seminar, K. Ozawa

  26. Condensates to Spectrum We should revisit the relation between quark condensate and vector meson spectrum Original idea by Hatsuda and Lee shows the relation q • Average of Imaginary part of P(w2) • vector meson spectral function Vacuum Vacuum q QCD sum rule Using this relation, Assume Prediction mV T.Hatsuda and S. Lee, PRC 46 (1992) R34 Spectrum J-PARC seminar, K. Ozawa

  27. Spectrum to condensate Condensates and Spectrum Replace by average of measured spectra • Average of Imaginary part of P(w2) • vector meson spectral function q Vacuum Vacuum QCD sum rule p q Evaluate quark condensate using QCD-SR. Not comparison btw models and measurements. High statics Clear initial condition Experimental requirements J-PARC seminar, K. Ozawa

  28. Let’s go to J-PARC • Beam Energy： 50ＧｅＶ (30GeV for Slow Beam) • Beam Intensity: 3.3x1014ppp, 15mA (2×1014ppp, 9mA) Hadron Hall J-PARC seminar, K. Ozawa

  29. New exp 1: High Statistics • Extended to vertical direction KEK spectrometer Side view Plain view Cope with 10 times larger beam intensity!! 100 times higher statistics!! J-PARC seminar, K. Ozawa

  30. NP-HALL 56m(L)×60m(W) Beam Line ここでやります。お願いします。 J-PARC seminar, K. Ozawa

  31. 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 calculate quark condensate J-PARC seminar, K. Ozawa

  32. gA   + X n p p0g g  w p0 g g New exp 2: Clear Initial condition Stopped w meson Generate w meson using p- + p. Emitted neutron is detected at 0. Decay of w meson is detected. If p momentum is chosen carefully, momentum transfer will be ~ 0. 0.4 Mass dependence (Mw = 783 MeV/c2) As a result of KEK-E325, We can expect 9% mass decreasing. It corresponds to 70 MeV/c2. To generate stopped modified w meson, beam momentum is ~ 2 GeV/c. (K1.8 can be used.) w momentum [GeV/c] 0.2 -100 MeV/c2 -50 MeV/c2 DM = 0 MeV/c2 6 2 0 4 0 p momentum [GeV/c] J-PARC seminar, K. Ozawa

  33. Emitted Neutron p- Bound w p0g decay Invariant mass in medium Expected results Initial condition is measured by forward neutron. w can be bounded in nucleus. Expected Invariant mass spectrum DM=9% ΔＥ/E = 3 %/√E DM=0 DM=13% Dm Show mass shift at p=0. J-PARC seminar, K. Ozawa

  34. Related experiment @ J-PARC J-PARC seminar, K. Ozawa

  35. Chiral symmetry with Baryon LOI by K. Itahashiet. al hbound state • N*(1535) • KS-KL s-wave resonance (Chiral Unitary model) • Chiral partner of nucleon (Chiral Doublet model) How to study N* experimentally? Calc. by H. Nagahiro h – N is strongly coupled with N* hin nucleus makes N* and hole Generate slowly moving hin nucleus J-PARC seminar, K. Ozawa

  36. Experiment for h Calc. by H. Nagahiro, D. Jido, S. Hirenzakiet. al LOI by K. Itahashiet. al Forward neutron is detected. missing mass distribution is measured. Simulation In addition, measurements of invariant mass of N* decay J-PARC seminar, K. Ozawa

  37. s s Φ K+ s u u s u u p Λ d d f bound state? Experiment 1: bg<1.25 (Slow) fp -> K+L Cu Experiment 2: Bound? pp -> ff See details in Dr. Ohnishi’s LOI J-PARC seminar, K. Ozawa

  38. Summary • According to the theory, Hadron mass is generated as a results of spontaneous breaking of chiral symmetry. • An experimental efforts are underway to investigate this mechanism. Some results are already reported. • Still, there are problems to extract physics information. • New experiments for obtaining further physics information are proposed. • Explore large kinematics region • Measurements with stopped mesons • Measurements of bound states J-PARC seminar, K. Ozawa

  39. Back up

  40. 質量の起源 Ｈｉｇｇｓ ＱＣＤ J-PARC seminar, K. Ozawa

  41. Chiral symmetry Dividewith chirality Gluon quark Neglect (if m ~0) mass V(q) Symmetric in rotation The lagrangian does not change under the transformation below . This symmetry is called as Chiral symmetry. q J-PARC seminar, K. Ozawa

  42. Breaking of symmetry When the potential is like V(f) = f4, Potential is symmetric and Ground state (vacuum) is at symmetric position If the interaction generate additional potential automatically, V’(f) = -a*f2 Potential is still symmetric, however, Ground state (vacuum) is at non-symmetric position This phenomenon is called spontaneous symmetry breaking dV ~ self energy of ground state ~ mass J-PARC seminar, K. Ozawa

  43. 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) J-PARC seminar, K. Ozawa

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

  45. Experimentalists face to reality - E325 simulation- e+e- 1g/cm2 1g/cm2 C Cu J-PARC seminar, K. Ozawa

  46. Issue: Final state interaction J.G.Messchendorp et al., Eur. Phys. J. A 11 (2001) 95 gA   + X p g p0g g simulation  w p0 g g disadvantage: • p0-rescattering no distortion by pion rescattering expected in mass range of interest; further reduced by requiring T>150 MeV J-PARC seminar, K. Ozawa

  47. Yield Estimation Summary plot of p-p  wn for backward w(G. Penner and U. Mosel, nucl-th/0111024, J. Keyne et al., Phys. Rev. D 14, 28 (1976)) • 0.14 mb/sr @ s = 1.8 GeV • same cross section is assumed. • Beam intensity • 107 / spill, 3 sec spill length) • Neutron Detector acceptance • Dq = 1°(30 cm x 30 cm @ 7m • Gamma Detector acceptance • 75 % for single, 42% for triple • Branching Ratio: 8.9% Optimistic obtained yield is 31650 J-PARC seminar, K. Ozawa

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