The chiral order-parameter $σ$ field and its higher-order cumulants of fluctuations are calculated within the functional renormalization group approach. The influence of the glue dynamics on the fluctuations of $σ$ field is investigated, and we find that the $σ$-field fluctuations are weakly affected by the glue dynamics. This is in sharp contrast to the baryon number fluctuations, which are sensitive to the glue dynamics and involve information of the color confinement. Implications of our calculated results on theoretical and experimental efforts to search for the QCD critical ending point are discussed.
A chiral field theory of $0^{-+}$ glueball is presented. By adding a $0^{-+}$ glueball field to a successful Lagrangian of chiral field theory of pseudoscalar, vector, and axial-vector mesons, the Lagrangian of this theory is constructed. The couplings between the pseodoscalar glueball field and mesons are via U(1) anomaly revealed. Qualitative study of the physical processes of the $0^{-+}$ glueball of $m=1.405\textrm{GeV}$ is presented. The theoretical predictions can be used to identify the $0^{-+}$ glueball.
A chiral field theory of $0^{-+}$ glueball is presented. The coupling between the quark operator and the $0^{-+}$ glueball field is revealed from the U(1) anomaly. The Lagrangian of this theory is constructed by adding a $0^{-+}$ glueball field to a successful Lagrangian of chiral field theory of pseudoscalar, vector, and axial-vector mesons. Quantitative study of the physical processes of the $0^{-+}$ glueball of $m=1.405\textrm{GeV}$ is presented. The theoretical predictions can be used to identify the $0^{-+}$ glueball.
We discuss the critical properties of net-baryon-number fluctuations at the chiral restoration transition in matter at nonzero temperature and net-baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polykov-loop extended Quark-Meson Lagrangian, that includes the coupling of quarks to temporal gauge fields. The Functional Renormalization Group is employed to account for the criticality at the phase boundary. We focus on the ratios of the net-baryon-number cumulants, $χ_B^n$, for $1\leq n\leq 4$. The results are confronted with recent experimental data on fluctu…
We explore fluctuations of the net-baryon number density in hadronic matter at vanishing chemical potential. We discuss the interplay between chiral dynamics and repulsive interactions and their influence on the properties of these fluctuations near the chiral crossover in the parity doublet model. We find that the characteristic properties of cumulants are entirely linked to the critical chiral dynamics and cannot be reproduced in phenomenological models, which account only for repulsive interactions. Consequently, a description of the higher-order cumulants of the net-baryon density requires…
We investigate the Fourier coefficients $b_k(T)$ of the net--baryon number density in strongly interacting matter at nonzero temperature and density. The asymptotic behavior of the coefficients at large $k$ is determined by the singularities of the partition function in the complex chemical potential plane. Within a QCD-like effective chiral model, we show that the chiral and deconfinement properties at nonzero baryon chemical potential are reflected in characteristic $k$-- and $T$-- dependences of the Fourier coefficients. We also discuss the influence of the Roberge-Weiss transition on these…
We explore the critical fluctuations near the chiral critical endpoint (CEP) in a chiral effective model and discuss possible signals of the CEP, recently explored experimentally in nuclear collision. Particular attention is paid to the dependence of such signals on the location of the phase boundary and the CEP relative to the chemical freeze-out conditions in nuclear collisions. We argue that in effective models, standard freeze-out fits to heavy-ion data should not be used directly. Instead, the relevant quantities should be examined on lines in the phase diagram that are defined self-consi…
We investigate the impact of the matter and glue dynamics on baryon number fluctuations and the kurtosis of baryon number distribution. This is done within the framework of QCD-improved low energy effective models. In particular we include the momentum scale dependence of the quark-meson scattering and the non-trivial dispersions of both, quarks and mesons. On the gluonic side we take into account the backreaction of the matter sector on the glue dynamics. It is shown that the above fluctuations lead to a more rapid change of the baryon number fluctuations as well as the kurtosis of with the c…
Thermodynamics of strongly interacting matter near critical end point are investigated in a holographic QCD model, which could describe the QCD phase diagram in $T-μ$ plane qualitatively. Critical exponents along different axis ($α,β,γ,δ$) are extracted numerically. It is given that $α\approx 0, β\approx 0.54, γ\approx 1.04, δ\approx 3.0$, the same as 3D Ising mean-field approximation and previous holographic QCD model calculations. We also discuss the possibilities to go beyond mean field approximation by including the full back-reaction of chiral dynamics in the holographic framework.
eta and eta' hadronic decays in U_L(3)xU_R(3) Chiral Perturbation Theory
在U_L（3）xU_R（3）手征微扰理论的框架下，研究了衰变eta/eta' -> pi pi pi和eta' -> eta pi pi的首序和次首序.分析中考虑了η-η系统的重要特征，如轴向异常和η_0/η_8混合所引起的胶球α GG的贡献。单回路校正，这是三阶的贡献，根据合并的手征和1/Nc展开，不包括在内。在大多数情况下，都能得到相当好的结果。
In this work, we offer a dynamical soft-wall model to describe the gluodynamics and chiral dynamics in one systematical framework. We firstly construct a quenched dynamical holographic QCD (hQCD) model in the graviton-dilaton framework for the pure gluon system, then develop a dynamical hQCD model for the two flavor system in the graviton-dilaton-scalar framework by adding light flavors on the gluodynamical background. For two forms of dilaton background field $Φ=μ_G^2z^2$ and $Φ=μ_G^2z^2\tanh(μ_{G^2}^4z^2/μ_G^2)$, the quadratic correction to dilaton background field at infrared encodes import…
We compute the probability distribution $P(N)$ of the net-baryon number at finite temperature and quark-chemical potential, $μ$, at a physical value of the pion mass in the quark-meson model within the functional renormalization group scheme. For $μ/T<1$, the model exhibits the chiral crossover transition which belongs to the universality class of the $O(4)$ spin system in three dimensions. We explore the influence of the chiral crossover transition on the properties of the net baryon number probability distribution, $P(N)$. By considering ratios of $P(N)$ to the Skellam function, with the sam…
We discuss the violation of quark-flavor symmetry at high temperatures, induced from nonperturbative thermal loop corrections and axial anomaly, based on a three-flavor linear-sigma model including an axial-anomaly induced-flavor breaking term. We employ a nonperturbative analysis following the Cornwall-Jackiw-Tomboulis formalism, and show that the model undergoes a chiral crossover with a pseudo-critical temperature, consistently with lattice observations. We find following features regarding the flavor breaking eminent around and above the pseudo-critical temperature: i) up-and down-quark co…
We discuss the properties of fluctuations of the electric charge in the vicinity of the chiral crossover transition within effective chiral models at finite temperature and vanishing net baryon density. The calculation includes non-perturbative dynamics implemented within the functional renormalization group approach. We study the temperature dependence of the electric charge susceptibilities in the linear sigma model and explore the role of quantum statistics. Within the Polyakov loop extended quark-meson model, we study the influence of the coupling of quarks to mesons and to an effective gl…
We study quantum criticality of the magnetic field induced charge density wave (CDW) order in correlated spinless Dirac fermions on the $π$-flux square lattice at zero temperature as a prototypical example of the magnetic catalysis, by using the infinite density matrix renormalization group. It is found that the CDW order parameter $M(B)$ exhibits an anomalous magnetic field $(B)$ scaling behavior characteristic of the $(2+1)$-dimensional chiral Ising universality class near the quantum critical point, which leads to a strong enhancement of $M(B)$ compared with a mean field result. We also est…
We study the effect of quantum and thermal fluctuations as well as the mass dependence of the phase structure of QCD at finite temperature and density within a dynamical Polyakov-loop--extended quark-meson model. The glue dynamics is simulated by the Polyakov-loop potential, also including the back-coupling of the matter sector to the glue dynamics. In the chiral limit, the chiral phase transition at large chemical potential and low temperature splits into two transition branches. For non-vanishing pion masses the chiral transition at small chemical potential changes from a phase transition to…
Thermal fluctuations and correlations between the light and heavy-light mesons are explored within a chiral effective theory implementing heavy quark symmetry. We show, that various heavy-light flavor correlations indicate a remnant of the chiral criticality in a narrow range of temperature where the chiral susceptibility exhibits a peak structure. The onset of the chiral crossover, in the heavy-light flavor correlations, is therefore independent from the light flavors. This indicates that the fluctuations carried by strange charmed mesons can also be used to identify the chiral crossover, whi…
We study the signs of criticality in conserved charge fluctuations and related observables of finite temperature QCD at vanishing chemical potential, as we approach the chiral limit of two light quarks. Our calculations have been performed on gauge ensembles generated using Highly Improved Staggered Quark (HISQ) fermion action, with pion masses ranging from 140 MeV to 55 MeV.
We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polykov-loop extended Quark-Meson Lagrangian, that includes the coupling of quarks to vector meson and temporal gauge fields. The Functional Renormalization Group is employed to properly account for the $O(4)$ criticality at the phase boundary. We focus on the properties and systematics of ratios of the net-baryon-number cumulants $χ_B^n$, for ${1\leq n\leq 6}$, nea…
