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北沢 正清

KEK, Aug. 8, 2008. 高温・高密度 QCD の相構造と物性現象. 北沢 正清. T. Quark-Gluon Plasma. ?. Hadrons. Color SC. 0. m. success of ideal hydro models early thermalization. RHIC. strongly coupled QGP near T c. success of recombination model. existence of quark quasi-particles even near T c. m.

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北沢 正清

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  1. KEK, Aug. 8, 2008 高温・高密度QCDの相構造と物性現象 北沢 正清 T Quark-Gluon Plasma ? Hadrons Color SC 0 m

  2. success of ideal hydro models • early thermalization RHIC strongly coupled QGP near Tc • success of recombination model existence of quark quasi-particles even near Tc m PRL98,162301 Phase Diagram of QCD T 0

  3. Saito, Nakamura, 2004 Gluons • Screening masses of gluons • quenched Saito,Nakamura,2004. • full(Nf=2) WHOT-Collab.2008. Quasi-Particles on the Lattice Lattice correlator for T =3Tc Quarks Karsch,MK, 2007 • Quenched correlator is reproduced • by a pole ansatz for r (w,p). quark quasi-particles do exist even under a non-perturbative thermal gluon field tT • light quarks has a thermal mass mT ~ 0.8T

  4. hadronic modes above Tc • charmonium on the lattice / chiral soft modes Compact stars Phase Diagram 0th approximation: (quasi-)fermions + interaction (gluon-ex.) analogy to cold atomic gas • crossover transition T • quarkyonic state ? McLerran, Pisarski, 2007 • chirally restored but confined 0 m

  5. Color Superconductivity T Quark-Gluon Plasma Hadrons Color SC 0 m

  6. d s Dud u Dus Dds Color Superconductivity At extremely dense matter, quark (fermion) system attractive channel in one-gluon exchange interaction. [３]c×[３]c＝[３]c＋[６]c Cooper instability at sufficiently low T SU(3)c color-gauge symmetry is broken! • pairing in scalar (JP=0+) channel color,flavor anti-symmetric T m

  7. d d s s Dud u Dus Dds Various Phases of Color Superconductivity T m Dud u Dus Dds 2-flavor SuperCondoctor (2SC) Color-Flavor Locking (CFL) analogy with B-phase in 3He superfluid

  8. d s Color Superconductivity in Compact Stars Dud u • effect of strange quark mass ms • neutrality and b-equilibrium conditions Dus Dds Mismatch of densities (1) strong coupling! (2) mismatched Fermi surfaces (1) weak coupling (2) common Fermi surface T m

  9. d s Various Phases of Color Superconductivity Dud 3 order parameters Dud, Dus, Dds  2*2*2=8 possibilities of distinct phases u Dus Dds cf.) Neumann, Buballa, Oertel ’03 Abuki, Kunihiro ’05 + chiral symmetry restoration many phases at intermediate densities T Abuki, Kunihiro, 2005; Ruster et al.,2005 m

  10. d s Various Phases of Color Superconductivity Dud 3 order parameters Dud, Dus, Dds  2*2*2=8 possibilities of distinct phases u Dus Dds cf.) Neumann, Buballa, Oertel ’03 Abuki, Kunihiro ’05 + chiral symmetry restoration many phases at intermediate densities T Abuki, Kunihiro, 2005; Ruster et al.,2005 m

  11. However, gapless phases at T=0 have imaginary color Meissner masses mM2<0. gapless Chromo-magnetic instability BCS There is more stable state. Gapless Superconductivity G. Sarma, 1963 fermion dispersion: normal gapless Huang, Shovkovy,2003

  12. Instability in Phase Diagram The instability is limited in a rather narrow region at finite T. T m Fukushima, hep-ph/0510299

  13. 2q k -k k+q -k+q What is the True Ground State? Various candidates: LOFF gluonic phases crystalline CSC spin-one superconductivity CSC + Kaon condensation

  14. Diquark excitations at finite temperature T Quark-Gluon Plasma Hadrons Color SC 0 m

  15. D ~ 100MeV in electric SC D / EF ~ 0.1 D / EF ~ 0.0001 x / d diquarks in hadrons? m[MeV] x – coherence length d – interquark distance Structual Change of Cooper Pairs T m Matsuzaki, 2000 Abuki, Hatsuda, Itakura, 2002

  16. BCS-BEC Crossover Nozieres, Schmitt-Rink, 1985 phase diagram of cold atom for fixed r : Tdiss BEC BCS strong unitarity limit weak non-rela.: m < 0 m ~ 0 m > 0 m < m m ~ m m > m relativistic: in the relativistic system, modifications at strong coupling regionNishida, Abuki,2005

  17. bound diquarks for us, ds pairs 3-flavor NJL model w/ standard diquark coupling GD/GS=0.75 Bound Diquarks mu,d=5MeV ms = 80MeV MK, Rischke, Shovokovy,2008 • m > m superfluidity • m < m vacuum: No BEC region. • Nevertheless, bound diquarks exist in the phase diagram.

  18. Phase Diagram strong diquark coupling GD/GS=1.1 BEC • BEC manifests itself. • Bound diquarks would exist in the deconfined phase. • The existence can be checked by lattice QCD.

  19. Conceptual Phase Diagram T Tdiss preformed stable bosons Tc superfluidity BEC BCS strong coupling lower r large m m=m weak coupling higher r m~0

  20. Pseudogap in HTSC The large fluctuations modifies the properties of quarks. Pseudogap

  21. 2-flavor NJL; GD/GS = 0.61 Pseudogap Region pseudogap region The pseudogap survives up to e =0.05~0.1 ( 5~10% above TC ).

  22. RHIC; hadronization, etc. measurement on lattice QCD Bound diquark would exist in sQGP. Large fluctuations affect various observables. Pseudogap (pre-critical) region T* FAIR@GSI? Diquarks in the Phase Diagram Conceptual phase diagram T Tdiss preformed stable bosons Tc superfluidity BEC BCS m=m weak coupling higher r strong coupling lower r large m

  23. Recombination Yasui, et al., 2007 How to measure Diquarks? m = 400MeV Dilepton production rate dRee/dM2 [fm-4GeV-2] -per invariant mass invariant mass M [MeV] Prominent enhancement at M<150MeV. The peak becomes sharp as e 0.

  24. QCD Critical End Point T Quark-Gluon Plasma Hadrons Color SC 0 m

  25. Critical End Point(s) T Quark-Gluon Plasma possible 2nd CEP Hadrons Color SC 0 m Two scenarios: • non-linear competition b/w chiral and diquark condensates • MK,Koide,Kunihiro,Nemoto,2002 • axial anomaly • Yamamoto,Hatsuda,Tachibana,Baym,2007

  26. Fast (anti-)proton is emitted earlier. • momentum profile of p/p ratio • focusing of hydro path • Behavior of m/T on each line • is quite different! Can we find CEP experimentally? • fluctuations enhanced around the critical point • modification of hydro. path Asakawa,Bass,Muller,Nonaka,2008

  27. Can we find CEP experimentally? • fluctuations enhanced around the critical point • modification of hydro. path Asakawa,Bass,Muller,Nonaka,2008 NA49, Phys. Rev. C 73, 044910 (2006) • focusing of hydro path • Behavior of m/T on each line • is quite different!

  28. Summary Rich physics in hot and dense QCD! T • hadronic modes • bound diquarks sQGP CEP Pseudogap Hadrons Extremely rich phases of color superconductor Color SC 0 m BEC crossover? 2nd CEP

  29. pseudogap region T* Diquarks in the Phase Diagram Conceptual phase diagram T Tdiss preformed stable bosons Tc superfluidity BEC BCS m=m weak coupling higher r strong coupling lower r large m

  30. 祝！稼働 LHC • success of ideal hydro models • early thermalization RHIC strongly coupled QGP near Tc • success of recombination model existence of quark quasi-particles even near Tc m PRL98,162301 Phase Diagram of QCD T 0

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