Probing the QCD Critical Point with Higher Moments of Net-proton Multiplicity Distributions

Higher moments of event-by-event net-proton multiplicity distributions are applied to search for the QCD critical point in the heavy ion collisions. It has been demonstrated that higher moments as well as moment products are sensitive to the correlation length and directly connected to the thermodynamic susceptibilities computed in the Lattice QCD and Hadron Resonance Gas (HRG) model. In this paper, we will present measurements for kurtosis ($\kappa$), skewness ($S$) and variance ($\sigma^{2}$) of net-proton multiplicity distributions at the mid-rapidity ($|y|<0.5$) and $0.4<p_{T}<0.8$ GeV/$c$ for Au+Au collisions at $\sqrt{s_{NN}}$=19.6, 39, 62.4, 130 and 200 GeV, Cu+Cu collisions at $\sqrt{s_{NN}}$=22.4, 62.4 and 200 GeV, d+Au collisions at $\sqrt{s_{NN}}$=200 GeV and p+p collisions at $\sqrt{s_{NN}}$=62.4 and 200 GeV. The moment products $\kappa \sigma^{2}$ and $S \sigma$ of net-proton distributions, which are related to volume independent baryon number susceptibility ratio, are compared to the Lattice QCD and HRG model calculations. The $\kappa \sigma^{2}$ and $S \sigma$ of net-proton distributions are consistent with Lattice QCD and HRG model calculations at high energy, which support the thermalization of the colliding system. Deviations of $\kappa \sigma^{2}$ and $S \sigma$ for the Au+Au collisions at low energies from HRG model calculations are also observed.Comment: 10 pages, 8 figures, Proceedings of 27th Winter Workshon on Nuclear Dynamics. Feb. 6-13 (2011

Thermodynamical quantities of lattice full QCD from an efficient method

I extend to QCD an efficient method for lattice gauge theory with dynamical fermions. Once the eigenvalues of the Dirac operator and the density of states of pure gluonic configurations at a set of plaquette energies (proportional to the gauge action) are computed, thermodynamical quantities deriving from the partition function can be obtained for arbitrary flavor number, quark masses and wide range of coupling constants, without additional computational cost. Results for the chiral condensate and gauge action are presented on the $10^4$ lattice at flavor number $N_f=0$, 1, 2, 3, 4 and many quark masses and coupling constants. New results in the chiral limit for the gauge action and its correlation with the chiral condensate, which are useful for analyzing the QCD chiral phase structure, are also provided.Comment: Latex, 11 figures, version accepted for publicatio

Improved lattice QCD with quarks: the 2 dimensional case

QCD in two dimensions is investigated using the improved fermionic lattice Hamiltonian proposed by Luo, Chen, Xu, and Jiang. We show that the improved theory leads to a significant reduction of the finite lattice spacing errors. The quark condensate and the mass of lightest quark and anti-quark bound state in the strong coupling phase (different from t'Hooft phase) are computed. We find agreement between our results and the analytical ones in the continuum.Comment: LaTeX file (including text + 10 figures

Threshold-cusp explanation for XX and ZcsZ_{cs} in B+→J/ψϕK+B^+\to J/\psi\phi K^+

Several $X$ and $Z_{cs}$ exotic hadrons were claimed in the LHCb's amplitude analysis on $B^+\to J/\psi \phi K^+$. The data shows that all the peaks and also dips in the spectra are located at thresholds of seemingly relevant meson-meson channels. While the LHCb analysis fitted the peaks with Breit-Wigner resonances, threshold kinematical cusps might be the cause of such structures. We thus analyze the LHCb data considering the threshold cusps. Our model is simultaneously fitted to $J/\psi \phi$, $J/\psi K^+$, and $K^+\phi$ invariant mass distributions. The threshold cusps fit well all the $X$, $Z_{cs}$, and dip structures. Our analysis indicates that spin-parity of the $X(4274)$ and $X(4500)$ structures are $0^-$ and $1^-$, respectively. This is different from the LHCb's spin-parity assignments ($1^+$ and $0^+$). The number of fitting parameters can be significantly reduced by considering the relevant threshold cusps. Our analysis shows that $D_s^{(*)}\bar{D}^{*}$ scattering lengths are consistent with zero. This disfavors an explanation of $Z_{cs}(4000)$ and $Z_{cs}(4220)$ as $D_s^{(*)}\bar{D}^{*}$ molecules, which is consistent with lattice QCD via the SU(3) relation.Comment: 5 pages, 2 figures, Contribution to the Proceedings for 20th International Conference on Hadron Spectroscopy and Structure (HADRON 2023), June 5 -9 2023, Genova, Ital

Bound States and Critical Behavior of the Yukawa Potential

We investigate the bound states of the Yukawa potential $V(r)=-\lambda \exp(-\alpha r)/ r$, using different algorithms: solving the Schr\"odinger equation numerically and our Monte Carlo Hamiltonian approach. There is a critical $\alpha=\alpha_C$, above which no bound state exists. We study the relation between $\alpha_C$ and $\lambda$ for various angular momentum quantum number $l$, and find in atomic units, $\alpha_{C}(l)= \lambda [A_{1} \exp(-l/ B_{1})+ A_{2} \exp(-l/ B_{2})]$, with $A_1=1.020(18)$, $B_1=0.443(14)$, $A_2=0.170(17)$, and $B_2=2.490(180)$.Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in China

Are Proactive Employees Proactive Performers? The Moderating Role of Supervisor-Subordinate Marital Status Similarity

In accordance with the similarity attraction paradigm, this paper investigates when and how proactive employees can be rated as proactive performers by proposing supervisor-subordinate marital status similarity as a relational moderator and leader-member exchange as the mediator. It therefore advances understanding of performance evaluation of proactive employees. Data from a sample of 471 Chinese employees and their 161 supervisors are used to examine the models hypothesized. The results show that LMX mediates the interaction effect between a proactive personality and supervisor-subordinate marital status similarity on supervisors’ evaluations of proactive performance. When proactive employees and their supervisors have similar (dissimilar) marital status, the indirect relationship between proactive personality and supervisor-rated proactive performance via LMX is stronger (weaker). Theoretical and practical implications are discussed