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Measurements of meson mass at J-PARC

Measurements of meson mass at J-PARC. K. Ozawa (KEK ). Contents: Physics motivation Current results Experiments @ J-PARC Summary. Origin of Hadron mass. Current quark masses generated by spontaneous symmetry breaking (Higgs field). Constituent quark masses should be generated by

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Measurements of meson mass at J-PARC

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  1. Measurements of meson mass at J-PARC K. Ozawa (KEK) Contents: Physics motivation Current results Experiments @ J-PARC Summary

  2. Origin of Hadronmass 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. Zimanyi school 2011, 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. Zimanyi school 2011, 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+) Best 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 measure mass modification of narrow resonance. Zimanyi school 2011, K. Ozawa

  5. Mass shift and Condensate In fact, Mass modification of a vector meson can be connected to quark condensates. • Average of Imaginary part of P(w2) • vector meson spectral function q Vacuum Vacuum QCD sum rule q Example: Theoretical Assumption Prediction mV T.Hatsuda and S.H. Lee, PRC 46 (1992) R34 Spectrum Measurements of mass related information in hot/dense matter is essential! Zimanyi school 2011, K. Ozawa

  6. Predicted “spectra” In addition, several models predict mass spectra of mesons and it can be compared with experimental results directly. • Predicted mass 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 Zimanyi school 2011, K. Ozawa R. Rapp and J. Wambach, EPJA 6 (1999) 415

  7. Current Experiments Zimanyi school 2011, K. Ozawa

  8. Generate hot/dense media • Measurements of Vector Meson mass spectra in hot/dense medium will provide QCD medium 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. 8 Zimanyi school 2011, K. Ozawa

  9. SPS-CERES results D. Miskowiec, QM05 talk PLB663, 43 (2008) Zimanyi school 2011, K. Ozawa Existing of Mass modification is established.

  10. 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, Let’s go to RHIC! Zimanyi school 2011, K. Ozawa 10

  11. Results @ RHIC • Electron pair invariant mass in Au-Au at sNN=200 GeV Excess from known hadronic sources is also observed. However, it looks different. PRC81(2010) 034911 No concluding remarks at this moment. New data with New detector (HBD) can answer it. Zimanyi school 2011, 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! Zimanyi school 2011, K. Ozawa

  13. Then, 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 Zimanyi school 2011, K. Ozawa

  14. Nucleon Hole Emitted Proton Neutron p, p, g Meson Decay Target Two Experimental methods • Meson bound state spectroscopy • Direct measurements of mass spectra Zimanyi school 2011, K. Ozawa

  15. Results with Bound states p bound state 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. Y. Umemoto et al., Phys. Rev. C62(2004) 024606 Zimanyi school 2011, K. Ozawa

  16. Direct Measurements of Mass KEK-PS E325: 12 GeV proton induced. p+A r, w, f+ X Electron decays are detected. Zimanyi school 2011, K. Ozawa

  17. E325 Spectrometer Zimanyi school 2011, K. Ozawa

  18. E325 Results I 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 Zimanyi school 2011, K. Ozawa

  19. w/r/f g Note: 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 Zimanyi school 2011, K. Ozawa

  20. E325 Result II: 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. Zimanyi school 2011, 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 Zimanyi school 2011, K. Ozawa

  22. New EXPERIMENTs@ J-PARC Zimanyi school 2011, K. Ozawa

  23. Performance of the 50-GeV PS Numbers in parentheses are ones for the Phase 1. • Beam Energy： 50ＧｅＶ (Currently, 30GeV) • 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) Zimanyi school 2011, 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 Zimanyi school 2011, K. Ozawa

  25. NP-HALL 56m(L)×60m(W) Hadron Hall Stopped w for Clear mass modification Upgrade of E325 Large statistics Zimanyi school 2011, K. Ozawa

  26. Exp1: 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!! Zimanyi school 2011, 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 Zimanyi school 2011, K. Ozawa Kinematic dependence

  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 Zimanyi school 2011, 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 Zimanyi school 2011, K. Ozawa

  30. 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. 0.4 If p momentum is chosen carefully, momentum transfer will be ~ 0. Beam momentum is ~ 1.8 GeV/c. As a result of KEK-E325, 9% mass decreasing (70 MeV/c2) can be expected. w momentum [GeV/c] 0.2 4 2 0 0 p momentum [GeV/c] Zimanyi school 2011, K. Ozawa

  31. Experimental setup • p-p  wn @ 1.8 GeV/c •  p0g gg • Target: Carbon 6cm • Small radiation loss • Clear calculation of w bound state • Also, Ca, Nb, LH2 • Neutron Detector • Flight length 7m • 60cm x 60 cm (~2°) • Gamma Detector • Good resolution • 75% of 4p Neutron Beam Gamma Detector Zimanyi school 2011, K. Ozawa

  32. 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. Zimanyi school 2011, K. Ozawa

  33. 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 Zimanyi school 2011, K. Ozawa

  34. Exp 3: Study of Baryon sector 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 Zimanyi school 2011, K. Ozawa

  35. 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 Zimanyi school 2011, K. Ozawa

  36. s s Φ K+ s u u s u u p Λ d d Exp 4: fbound state? bg<1.25 (Slow) Generation: Cu Detection: Bound? pp -> ff fp -> K+L Zimanyi school 2011, K. Ozawa

  37. Exp 5: h’ @ J-PARC It’s under discussion with Prof. T. Csorgo. Please join us and come to Japan! Zimanyi school 2011, 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. • New experiments for obtaining further physics information are proposed. • Explore large kinematics region • Measurements with stopped mesons Zimanyi school 2011, K. Ozawa

  39. Back up

  40. 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 Zimanyi school 2011, K. Ozawa

  41. 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 Zimanyi school 2011, K. Ozawa

  42. Theoretical efforts Connect hadron properties and chiral properties using QCD and/or phenomenology. • Nambu-Jona-Lasino model • Nambu and Jona-Lasino, 1961 • Vogl and Wise, 1991 • Hatsuda and Kunihiro, 1994 • Chiral Perturbation theory • Weinberg 1979 • QCD sum rule • Shifmanet al., 1979 • Hatsuda and Lee, 1992 • Lattice QCD • Wilson, 1974 • Empirical models • Potential model (De Rujulaet al., 1975), Bag model (Chdoset al., 1974) • In addition, Collisional broadening, nuclear mean field … Vector meson mass G.E.Brown and M. Rho, PRL 66 (1991) 2720 ‘ T.Hatsuda and S. Lee, PRC 46 (1992) R34 Zimanyi school 2011, K. Ozawa

  43. RHIC&PHENIX Zimanyi school 2011, K. Ozawa

  44. Not only mass spectra, p bound state K. Suzuki et al., Phys. Rev. Let., 92(2004) 072302 • bound state is observed in • Sn(d, 3He) pion transfer reaction. Y. Umemoto et al., Phys. Rev. C62(2004) 024606 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 New exp. will be done at RIKEN Zimanyi school 2011, K. Ozawa

  45. Mass spectra measurements Note Obtained spectra is combination of two spectra, such as decayed in nucleus and free space. Expected mass spectra 45 • Following four experiments, • TAGX experiments @ INS-Japan • CBELSA/TAPS experiments • KEK-E325 @KEK-PS-Japan • CLAS g7 experiment @ J-Lab-USA • Use heavy and light nucleus and extract mass modification Zimanyi school 2011, K. Ozawa

  46. 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,… Zimanyi school 2011, K. Ozawa

  47. 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 Zimanyi school 2011, K. Ozawa

  48. Experimentalists face to reality - E325 simulation- e+e- 1g/cm2 1g/cm2 C Cu Zimanyi school 2011, K. Ozawa

  49. Condensates and Spectrum How to access quark condensate experimentally? Unfortunately, quark condensates is not an observable. We can link condensates and vector meson spectrum. q • Average of Imaginary part of P(w2) • vector meson spectral function Vacuum Vacuum q QCD sum rule The relation is established by Prof. Lee and Prof. Hatsuda. Assume Prediction mV T.Hatsuda and S. Lee, PRC 46 (1992) R34 Spectrum Zimanyi school 2011, K. Ozawa

  50. Next step Evaluate quark condensate directly. Not comparison btw predictions and measurements. Replace by average of measured spectra Average of Imaginary part of P(w2) Assumed Spectrum p Then, calculate quark condensate using QCD sum rule. High statics Clear initial condition Experimental requirements Zimanyi school 2011, K. Ozawa

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