Nanjing, China
Nanjing, China

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Cao J.,Nanjing University | Jiang Y.,Zhejiang Normal University | Sun W.-M.,Nanjing University | Sun W.-M.,Joint Center for Particle | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

In this Letter, an improved quasi-particle model is presented. Unlike the previous approach of establishing quasi-particle model, we introduce a classical background field (it is allowed to depend on the temperature) to deal with the infinity of thermal vacuum energy which exists in previous quasi-particle models. After taking into account the effect of this classical background field, the partition function of quasi-particle system can be made well-defined. Based on this and following the standard ensemble theory, we construct a thermodynamically consistent quasi-particle model without the need of any reformulation of statistical mechanics or thermodynamical consistency relation. As an application of our model, we employ it to the case of (2. +. 1) flavor QGP at zero chemical potential and finite temperature and obtain a good fit to the recent lattice simulation results of Borsányi et al. A comparison of the result of our model with early calculations using other models is also presented. It is shown that our method is general and can be generalized to the case where the effective mass depends not only on the temperature but also on the chemical potential. © 2012 Elsevier B.V.


Shi C.,Nanjing University | Chang L.,University of Adelaide | Roberts C.D.,Argonne National Laboratory | Schmidt S.M.,Jülich Research Center | And 4 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We compute the kaon's valence-quark (twist-two parton) distribution amplitude (PDA) by projecting its Poincaré-covariant Bethe-Salpeter wave-function onto the light-front. At a scale ζ=2GeV, the PDA is a broad, concave and asymmetric function, whose peak is shifted 12-16% away from its position in QCD's conformal limit. These features are a clear expression of SU(3)-flavour-symmetry breaking. They show that the heavier quark in the kaon carries more of the bound-state's momentum than the lighter quark and also that emergent phenomena in QCD modulate the magnitude of flavour-symmetry breaking: it is markedly smaller than one might expect based on the difference between light-quark current masses. Our results add to a body of evidence which indicates that at any energy scale accessible with existing or foreseeable facilities, a reliable guide to the interpretation of experiment requires the use of such nonperturbatively broadened PDAs in leading-order, leading-twist formulae for hard exclusive processes instead of the asymptotic PDA associated with QCD's conformal limit. We illustrate this via the ratio of kaon and pion electromagnetic form factors: using our nonperturbative PDAs in the appropriate formulae, FK/Fπ=1.23 at spacelike-Q2=17GeV2, which compares satisfactorily with the value of 0.92(5) inferred in e+e- annihilation at s=17GeV2. © 2014 Argonne National Laboratory and the authors.


Segovia J.,Argonne National Laboratory | Chang L.,University of Adelaide | Cloet I.C.,Argonne National Laboratory | Roberts C.D.,Argonne National Laboratory | And 4 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We exploit a method introduced recently to determine parton distribution amplitudes (PDAs) from minimal information in order to obtain light-quark pseudoscalar and vector meson PDAs from the limited number of moments produced by numerical simulations of lattice-regularised QCD. Within errors, the PDAs of pseudoscalar and vector mesons constituted from the same valence quarks are identical; they are concave functions, whose dilation expresses the strength of dynamical chiral symmetry breaking; and SU(3)-flavour symmetry is broken nonperturbatively at the level of 10%. Notably, the appearance of precision in the lattice moments is misleading. The moments also exhibit material dependence on lattice volume, especially for the pion. Improvements need therefore be made before an accurate, unified picture of the light-front structure of light-quark pseudoscalar and vector mesons is revealed. © 2014.


Yang Y.,Anyang University, China | Yang Y.,Joint Center for Particle
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Dark matter (DM) annihilation or decay can affect the anisotropy of the cosmic microwave background (CMB). Therefore, the CMB data can be used to constrain the properties of a dark matter particle. In this work, we use the new CMB data obtained by the Planck satellite to investigate the limits on the basic parameters of a dark matter particle. The parameters are the dark matter mass (mχ) and the thermally averaged cross section (σv) for dark matter annihilation and the decay rate (Γ) (or lifetime τ=1/Γ) for dark matter decay. For dark matter annihilation, we also consider the impact of the structure formation process which is neglected by the recent work. We find that for DM annihilation, the constraints on the parameters are fann= σv/mχ<0.16×10-26cm3s-1GeV-1(or fann<0.89×10-6m3s-1kg-1, 95% C.L.). For DM decay, the constraints on the decay rate are Γ<0.28×10-25s-1(95% C.L.). © 2015 American Physical Society.


Feng H.,Nanjing Southeast University | Shi S.,Nanjing University | Yin P.,Nanjing University | Zong H.,Nanjing University | Zong H.,Joint Center for Particle
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In the framework of the truncated Dyson-Schwinger equation for the fermion propagator, we investigate the chiral and fermion number susceptibility at finite temperature and chemical potential in quantum electrodynamics in (2+1) dimensions (QED 3). The critical end point in the phase diagram of QED 3 is identified, and the behavior of these two susceptibilities around the critical end point is highlighted. © 2012 American Physical Society.


Zhao T.,Nanjing University | Yan Y.,Nanjing University | Luo X.-L.,Nanjing University | Zong H.-S.,Nanjing University | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In this paper we utilize our improved quasiparticle model to obtain the equation of state (EOS) and use it as an input to the Tolman-Oppenheimer-Volkoff (TOV) equation to get the mass-radii relation of a pure quark star. We discuss the relation between structures of quark stars and the parameters in the EOS and get a maximum mass of quark star over two solar mass. To compare the result with recent observation, we also calculate the structure of a hybrid star and consider the influence of rotation. Finally, the hadron-quark phase transition in the interior of neutron stars and how much energy will be released when a neutron star bursts into a quark star are discussed. © 2015 American Physical Society.


Zhang S.,Chinese Academy of Sciences | Zhang S.,Joint Center for Particle
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

In this Letter, we have studied the shock wave and discontinuity propagation for relativistic superfluid with spontaneous U(1) symmetry breaking in the framework of hydrodynamics. General features of shock waves are provided, the propagation of discontinuity and the sound modes of shock waves are also presented. The first sound and the second sound are identified as the propagation of discontinuity, and the results are in agreement with earlier theoretical studies. Moreover, a differential equation, called the growth equation, is obtained to describe the decay and growth of the discontinuity propagating along its normal trajectory. The solution is in an integral form and special cases of diverging waves are also discussed. © 2014 The Author.


Zeng H.-B.,Nanjing University | Fan Z.-Y.,Nanjing University | Zong H.-S.,Nanjing University | Zong H.-S.,Joint Center for Particle
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

A d-wave holographic superconductor in the presence of a constant magnetic field is studied by the perturbation method. We obtain both droplet and triangular vortex lattice solutions. The results are the same as that of an s-wave holographic superconductor. The non-Abelian holographic superconductor with p+ip-wave background in the presence of a magnetic field is also studied. Unlike the d-wave and s-wave models, it is found that the non-Abelian model has only a droplet solution. © 2010 The American Physical Society.


Zeng H.-B.,Nanjing University | Fan Z.-Y.,Nanjing University | Zong H.-S.,Nanjing University | Zong H.-S.,Joint Center for Particle
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

A classical SU(2) Einstein-Yang-Mills theory in (3+1)-dimensional anti-de Sitter spacetime is believed to be dual to a p-wave superconductor in (2+1)-dimensional flat spacetime. In order to calculate the superconducting coherence length ξ of the holographic superconductor near the superconducting phase transition point, we make a perturbative study of the gravity theory analytically. The superconducting coherence length ξ is found to be proportional to (1-T/Tc)-1/2 near the critical temperature Tc. We also obtain the magnetic penetration depth λ(Tc-T)1/2 by adding a small external homogeneous magnetic field. The results agree with the Ginzburg-Landau theory. © 2010 The American Physical Society.


Li H.,Nanjing University | Luo X.-L.,Nanjing University | Jiang Y.,Nanjing University | Zong H.-S.,Nanjing University | Zong H.-S.,Joint Center for Particle
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In this paper we apply the equation of state (EOS) of QCD at finite chemical potential and zero temperature proposed in H.S. Zong and W.M. Sun to the study of properties of quark star. This EOS contains only one adjustable parameter mD which sets the scale of chiral symmetry breaking (in our calculation we have chosen two values of mD: mD=244MeV and mD=239MeV, which is fitted from the value of fπ and determined by e⊃+e⊃- annihilation experiment, respectively). From this EOS a model of quark star is established by applying the Tolman-Oppenheimer- Volkoff equation under two conditions: with the P(μ=0) term and without the P(μ=0) term. Our results show clearly that the P(μ=0) term is an important quantity in the study of quark star. A comparison between our model and other models of quark star is made. In particular, we have compared our results with the most recent observational data measured using Shapiro delay reported in P.B. Demorest. © 2011 The American Physical Society.

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