Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session DB: Mini-Symposium on Mapping the QCD Phase Diagrams I |
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Chair: Akira Ohnishi, Yukawa Institute for Theoretical Physics Room: Kona 4 |
Thursday, October 15, 2009 7:00PM - 7:30PM |
DB.00001: The QCD Phase Diagram from Lattice Regularized QCD Invited Speaker: We will discuss the status of studies of the QCD phase diagram through lattice QCD calculations at non-zero temperature and density. We will report on the calculations of the QCD transition temperature at vanishing chemical potential, on attempts to establish the universal structure of the chiral transition in the limit of vanishing quark mass and on the QCD equation of state with physical light and strange quark masses. At non-zero baryon chemical potential we will report on attempts to establish the existence of a critical point and comment on studies of higher moments of charge fluctuations that may serve as signatures for the QCD critical points. [Preview Abstract] |
Thursday, October 15, 2009 7:30PM - 7:45PM |
DB.00002: Importance of imaginary chemical potential for determination of QCD phase diagram Kouji Kashiwa, Hiroaki Kouno, Yuji Sakai, Masanobu Yahiro Lattice QCD (LQCD) calculations have the well-known sign problem at finite real chemical potential. One approach to circumvent the problem is the analytic continuation of LQCD data to real chemical potential from imaginary one. This approach, however, has some problems in moderate real chemical potential region. Therefore, we propose the new approach, {\it Imaginary chemical potential matching approach}, to quantitatively determine the QCD phase diagram by using a phenomenological model that reproduce LQCD data at imaginary chemical potential. In this approach, we fit the model parameter by LQCD data at imaginary chemical potential. At the imaginary chemical potential, the QCD partition function has the special periodicity called Roberge-Weiss (RW) periodicity. Therefore, an adopted model must have the RW periodicity. We reveal the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model has the RW periodicity. Moreover, we investigate the meson mass behavior and show that meson mass is useful for fitting the model parameters at imaginary chemical potential. [Preview Abstract] |
Thursday, October 15, 2009 7:45PM - 8:00PM |
DB.00003: Determination of QCD phase diagram from the imaginary chemical potential Sakai Yuji, Kashiwa Kouji, Kouno Hiroaki, Yahiro Masanobu Lattice QCD has the well-known sign problem at real chemical potential. An approach to circumvent the problem is the analytic continuation to real chemical potential from imaginary one. We propose a new analytic continuation by using the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. This work is published in our papers of Phys. Rev. D77, 051901 (2008), Phys. Rev. D78, 036001 (2008), Phys. Rev. D78 076007 (2008), Phys. Rev. D 79, 076008 (2009), Phys. Rev. D 79, 096001 (2009). This talk presents the latest result of these studies. The partition function of QCD has the Roberge-Weiss (RW) periodicity in the imaginary chemical potential region. We revealed that the PNJL model has the RW periodicity. Strength parameters of the vector-type four-quark and scalar-type eight- quark interactions are determined so as to reproduce lattice data on pseudocritical temperatures of the deconfinement and chiral phase transitions in the imaginary chemical potential region. The QCD phase diagram in the real chemical potential region is predicted by the PNJL model. The critical endpoint survives, even if the vector-type four-quark interaction is taken into account. [Preview Abstract] |
Thursday, October 15, 2009 8:00PM - 8:15PM |
DB.00004: Quark number density in the phase with unbroken center Z2 symmetry in two-flavor QCD Shinpei Takemoto, Masayasu Harada, Chihiro Sasaki We study the phase structure of two-flavor QCD including the 2-quark and 4-quark states. Using the Ginzburg-Landau type approach, we show a possible existence of the phase in which the chiral SU(2)L x SU(2)R symmetry is spontaneously broken to SU(2)V x Z2 symmetry, i.e., the center Z2 symmetry is left unbroken. In this Z2 symmetric phase, the chiral symmetry is broken by the 4-quark condensate although the 2-quark condensate vanishes. We find that it appears a new tricritical point between the Z2 symmetric phase and the Z2 broken phase. It is shown that the quark number susceptibility is strongly enhanced at the restoration point of the center Z2 symmetry rather than that of the chiral symmetry. [Preview Abstract] |
Thursday, October 15, 2009 8:15PM - 8:30PM |
DB.00005: Next-to-Next-to-Leading Order Evaluation of Effective Potential in the Strong Coupling Lattice QCD Takashi Nakano, Akira Ohnishi, Kohtaroh Miura Strong Coupling Lattice QCD (SC-LQCD) is a method directly based on QCD, and has been applied to investigate the properties of QCD phase diagram in the finite chemical potential region. The previous studies in next-to-leading order (NLO) evaluation assert that the effect of NLO in the effective potential are renormalized in modification of the quark mass and chemical potential in the strong coupling limit (SCL), and two order parameters (the chiral condensate and the density) are found to appear. These studies indicate the possibility of the partially chiral restored phase as well. In this study, we evaluate the effective potential in the next-to-next-to-leading order of SC-LQCD. We also discuss the properties of QCD phase diagram from the effective potential, including the position of the critical point which will be searched for in the low energy RHIC program. [Preview Abstract] |
Thursday, October 15, 2009 8:30PM - 8:45PM |
DB.00006: Deconfined phase transition in dense and hot QCD at large N Ariel Zhitnitsky We conjecture that the confinement- deconfinement phase transition in QCD at large number of colors $N$ and $N_f\ll N$ at $T\neq 0$ and $\mu\neq 0$ is triggered by the drastic change in $\theta$ behavior. The conjecture is motivated by the holographic model of QCD. The conjecture is also supported by a number of numerical lattice results. Based on papers: Phys.Rev.D78:125002,2008, Nucl.Phys.A813:279-292,2008. [Preview Abstract] |
Thursday, October 15, 2009 8:45PM - 9:00PM |
DB.00007: 2+1 flavor QCD phase structure at finite temperature and density in chiral random matrix models Takashi Sano, Hirotsugu Fujii The conventional chiral random matrix models are known to predict a second-order phase transition at finite temperature irrespective of the number of flavors. Here we propose a random matrix model which properly contains the UA(1) breaking term and as a result predicts a first-order transition for the three- flavor case. This is the first chiral random matrix model which allows us to investigate the effects of the strange quark degree on the QCD phase diagram, especially on the QCD critical point, at finite temperature and density. We will discuss the shape of the critical surface by varying the strength of the UA (1) anomaly. [Preview Abstract] |
Thursday, October 15, 2009 9:00PM - 9:15PM |
DB.00008: Analysis of the phase structure of graphene using lattice gauge theory Yasufumi Araki, Tetsuo Hatsuda The electrons in graphene can be described as the (2+1)- dimensional Dirac particles interacting with (3+1)-dimensional Abelian gauge field. It is suggested that the emergence of the spectral gap of graphene has intimate relation to the dynamical chiral symmetry breaking in gauge theories. We have studied the phase structure of monolayer graphene by employing the techniques of lattice gauge theory. We report our recent studies on the exciton condensate in graphene for variable temperature and coupling constant. [Preview Abstract] |
Thursday, October 15, 2009 9:15PM - 9:30PM |
DB.00009: Non-Gaussian fluctuations and the search for the QCD critical point Mikhail Stephanov We study the effect of the QCD critical point on non-Gaussianity of the fluctuations of experimental observables in heavy-ion collisions. We find that non-Gaussian moments are very sensitive to the proximity of the critical point, as measured by the magnitude of the correlation length~$\xi$. For example, the cubic central moment of multiplicity grows as $\xi^{4.5}$ and the quartic cumulant -- as $\xi^7$. We estimate the magnitude of the critical point effects and conclude that non-monotonic variation of non-Gaussian moments with the collision energy can serve as a very sensitive signature of the QCD critical point. [Preview Abstract] |
Thursday, October 15, 2009 9:30PM - 9:45PM |
DB.00010: Exploring QCD phase diagram with third moments of conserved charges Masakiyo Kitazawa, Masayuki Asakawa, Shinji Ejiri We point out that the third moments of conserved charges, the baryon and electric charge numbers, and energy, as well as their mixed moments, change their signs around the QCD phase boundary in the temperature and baryon chemical potential plane. These signs can be measured in relativistic heavy ion collisions, and will give clear information on the phase structure of QCD and the state of the system in the early stage of relativistic heavy ion collisions. The behaviors of these moments on the temperature axis and at small quark chemical potential can be analyzed in lattice QCD simulations. We emphasize that the third moments obtained on the lattice, together with the experimental results, will provide a deep understanding about the QCD phase diagram and the location of the state created in heavy ion collisions. [Preview Abstract] |
Thursday, October 15, 2009 9:45PM - 10:00PM |
DB.00011: Chiral phase transition with the functional renormalization group equation Kazuhiko Kamikado, Kenji Fukushima It has been conjectured by the perturbative renormalization group technique (epsilon-expansion) that, if interaction induced by the axial anomaly is suppressed at high temperature, the chiral phase transition of two-flavor quark matter is of fluctuation-induced first order transition. We discuss the shape of the effective potential using the linear sigma model and the functional renormalization group method and confirm that the shape change leads to the first-order phase transition. That is, the effective potential has a double-well structure in a certain parameter region. We also clarify the relation between the perturbative renormalization group (epsilon-expansion) and the functional renormalization group equations. [Preview Abstract] |
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