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J-PARC におけるハドロン質量起源の探索実験

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  1. J-PARCにおけるハドロン質量起源の探索実験 小沢 恭一郎(東京大学) Contents: Physics motivation Current results Future Experiments Summary

  2. 原子核反応による発光 安定な物質を作るための核力コア クォークの閉じ込めによるハドロンの形成 超新星爆発を起こす核反応 太陽 Big Bang W Z ν 超新星爆発 Higgs相転移 ハドロンの世界 中性子星の構造を支えるクォーク 原子核の世界 クォーク・グルオンの世界 原子核物理学の挑戦 中性子星 反クォーク・クォーク対凝縮によるカイラル対称性の自発的破れと質量の獲得 時間 J-PARC seminar, K. Ozawa

  3. ハドロン質量起源 High Temperature High Density • Quark is not confined. • Mass ~ 0 (Higgs only) • It looks real “vacuum”. q When T and r are 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 • Shifman et al., 1979 • Colangelo and Khodjamirian, 2001 • Hatsuda and Lee, 1992 • Lattice QCD • Wilson, 1974 • Karsch, 2002 • Empirical models • Potential model (De Rujula et al., 1975), Bag model (Chdos et 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. Measurements in 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 9 • Stable system • No (small) need for time development • Saturated density ECT*-WS, K. Ozawa J-PARC seminar, K. Ozawa Target

  10. p bound state p as 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

  11. 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) 11 • 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

  12. 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

  13. 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

  14. 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

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

  16. 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

  17. 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

  18. 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

  19. 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. J-PARC seminar, K. Ozawa

  20. 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

  21. NEXT STEP@ J-PARC J-PARC seminar, K. Ozawa

  22. 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

  23. 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. Beyond comparisons with models High statics Clear initial condition Experimental requirements J-PARC seminar, K. Ozawa

  24. 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

  25. 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

  26. 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

  27. Emitted Neutron p- Bound w p0g decay 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. Invariant mass in medium J-PARC seminar, K. Ozawa

  28. Chiral symmetry with Baryon LOI by K. Itahashi et. al h bound 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* h in nucleus makes N* and hole Generate slowly moving h in nucleus J-PARC seminar, K. Ozawa

  29. Experiment for h LOI by Dr. K. Itahashi’s Calc. by H. Nagahiro, D. Jido, S. Hirenzaki et. 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

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

  31. GEM DEVELOPMENT J-PARC seminar, K. Ozawa

  32. ED=500V/cm QIN EI=1000V/cm QOUT GAIN = QOUT / QIN 10~30 per foil GEM • High Field in hole induces avalanche Multiplication TYPICAL GEM: 50 µm Kapton 5 µm Copper 70 µm holes at 140 µm pitch F. Sauli, Nucl. Instr. and Meth. A386(1997)531 J-PARC seminar, K. Ozawa

  33. Ar(90%)-CH4(10%) Gain 3-GEM 104 2-GEM ・CERN-GEM Ar(70%)-CO2(30%) Gain 104 2-GEM 3-GEM 300 [V] 400 Effective Gain mesasured w X-ray Gain Typically, 3 layers are used. 55Fe X-ray 5.9 keV J-PARC seminar, K. Ozawa

  34. Japanese GEM • Dry etching method is applied. • Hole shape is improved and cylindrical hole GEM has better Gain stability. CERN-GEM SciEnergy GEM Etching method wet etching dry etching The cross section of a hole A hole with cylindrical shape A hole with double-conical shape Cost \60k per foil \80k per foil *CERN-like GEM can be produced in Japan (Ray-Tech Co.) also. J-PARC seminar, K. Ozawa

  35. Another advantages in Japan • 100mm thickness GEM is successfully developed by Dry etching method and LCP base material. • Higher gain is expected with thicker GEM • 150mm-GEM VGEM=750V • 100mm-GEM VGEM=500V • Standard-GEM (50mm) VGEM=250V • 150mm-GEM • 100mm-GEM • Standard-GEM (50mm) Electric field along the center of a GEM hole J-PARC seminar, K. Ozawa

  36. Prof. S. Uno @ MPGD WS Signal from GEM foil Signal from Readout pad 150mV 80ns Easy signal handling • GEM Response function No magnetic Field/ No Drift region σ=181.2±0.3 μm σ=359.7±0.4 μm Pulse shape P10 Ar-CO2 (70/30) Response function • Width of signal spread is consistent with transverse diffusion in GEM (along 3layers ). • It can be reduced by magnetic field. • Time constant is from the drift time in the last gap. (No ion tail) • It can be reduced to ~20ns. Intrinsic multi-track resolution DV ~ 1 mm3 (Standard MWPC TPC ~ 1 cm3) J-PARC seminar, K. Ozawa

  37. Good @ high rate counting • MWPC limitation • Wire spacing: 1~2 mm • Gain dropping @ high rate • Micro strip gas chamber • Discharge problem • Micromegas • Another candidate • GEM • Flat gain over 105 Hz/mm2 • I like flexibility of configuration • Good characteristics of signal • Signal is generated by electron • Not by ion • No ion tail and pole cancellation electronics MWPC 104 105 GEM I took these ideas and figures from F. Sauli’s presentation at XIV GIORNATE DI STUDIO SUI RIVELATORI Villa Gualino 10-13 Febbraio 2004 J-PARC seminar, K. Ozawa

  38. Beam Line tracker Collaboration with KEK J-PARC seminar, K. Ozawa

  39. Hadron Blind Detector CsI光電面を用いた光検出器の開発 電子 チェレンコフ光 • 紫外域に感度を持つ光検出器を開発する。 • 実験では、Cherenkov光検出器として電子識別に用いられる。 • 電子は、ガス中で光を出す。 • p中間子は、出さない。 • 具体的には、 • GEM上面にCsI光電面を蒸着 • GEM3層を電子増幅に使用 • 読み出しにStripやPadを用いることで位置情報も得られる • References • 1. NIM A523, 345, 2004 • 2. NIM A546, 466, 2005 J-PARC seminar, K. Ozawa

  40. R&D @ RIKEN • Beam Test @ LNS Tohoku Univ. • 100 um thick CsI coated GEM as a photo cathode • Reverse bias btw mesh and CsI GEM to suppress ionization electrons dE/dx (Blind ON) dE/dx + Light (Blind OFF) 1~2 photo electrons J-PARC seminar, K. Ozawa

  41. 10cm 10cm GEM TPC Use GEM for signal avalanche • Low ion feed back • No Gate operation • Easy signal handling • Small time constant • Narrow signal distribution • Flexible readout configuration • No wire • Resolution • Diffusion • Pad configuration GEM TPC @ CNS J-PARC seminar, K. Ozawa

  42. 1st ResX 2nd 3rd Pad-row direction Drift direction GEN TPC R&D @CNS 1. Hit positions in pad-row direction (X) and drift direction (Z) are determined by simple weighted mean of charge. 2. Spatial resolution is estimated from a residual between the position of the middle pad row and the interpolated position. Result • Best resolution was 80mm (X-direction) and 310mm(Z-direction) with Ar-C2H6 gas, with rectangular pad, for drift length of 13mm. • Zigzag pad and rectangular pad have similar spatial resolution. Large offset due to GEM and electronics J-PARC seminar, K. Ozawa

  43. 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

  44. Back up

  45. 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

  46. Chiral symmetry Dividewith chirality Neglect (if m ~0) Gluon quark 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

  47. 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

  48. 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

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

  50. 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