arXiv subjects

Liang-Kai Wu

Publications and source records attributed to Liang-Kai Wu.

9 recordsLinked to original sources

arXiv2026

Masses of the conjectured H-dibaryon for different channels at different temperatures

We present a lattice QCD spectroscopy study of the conjectured H dibaryon for 5 different channels at nine different temperatures. The H dibaryon operator is constructed with five different channels which are flavor singlet, flavor 27-plet, $ΛΛ$, $N Ξ$ and $ΣΣ$. The nine different temperatures range from $T/T_c =0.24$ to $T/T_c = 1.90$. The simulations are performed on anisotropic lattice with $N_f=2+1$ flavours of clover fermion at quark mass which corresponds to $m_π=384(4) {\rm MeV} $. The thermal ensembles were provided by the FASTSUM collaboration and the zero temperature ensembles by the Hadspec collaboration. The simulations show that the mass of H-dibaryon for 27-plet channel is the largest at different temperatures, while the mass for $ΣΣ$ channel is the lightest. We also calculate the spectral function of the correlation function of H dibaryon for five channels. The spectral density distributions exhibit similar behavior for the five channels. The mass differences $Δm = m_H - 2\,m_Λ $ of H-dibaryon and $Λ$ pair at $T/T_c =0.24 $ for five channels are also estimated. The results show that $Δm = m_H - 2\,m_Λ $ for channels of 27-plet and $ΛΛ$ is positive, while $Δm = m_H - 2\,m_Λ $ for channels of singlet, $N Ξ$ and $ΣΣ$ is negative.

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arXiv2025

The curvature of the pseudo-critical line in the QCD phase diagram from mesonic lattice correlation functions

In the QCD phase diagram, the dependence of the pseudo-critical temperature, $T_{\rm{pc}}$, on the baryon chemical potential, $μ_B$, is of fundamental interest. The variation of $T_{\rm{pc}}$ with $μ_B$ is normally captured by $κ$, the coefficient of the leading (quadratic) term of the polynomial expansion of $T_{\rm{pc}}$ with $μ_B$. In this work, we present the first calculation of $κ$ using hadronic quantities. Simulating $N_f=2+1$ flavours of Wilson fermions on {\sc Fastsum} ensembles, we calculate the ${\cal O}(μ_B^2)$ correction to mesonic correlation functions. By demanding degeneracy in the vector and axial-vector channels we obtain $T_{\rm{pc}}(μ_B)$ and hence $κ$. While lacking a continuum extrapolation and being away from the physical point, our results are consistent with previous works using thermodynamic observables (renormalised chiral condensate, strange quark number susceptibility) from lattice QCD simulations with staggered fermions.

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arXiv2024

Masses of the conjectured H-dibaryon at different temperatures

We present a lattice QCD determination of masses of the conjectured H-dibaryon $m_H$ at nine different temperatures $T/T_c =0.24, 0.63, 0.76, 0.84, 0.95, 1.09, 1.27, 1.52, 1.90$. In the meantime, the masses of baryon $N$, $Σ$, $Ξ$ and $Λ$ at different temperatures are also computed. The simulation is performed on anisotropic lattice with $N_f=2+1$ flavours of clover fermion at quark mass which corresponds to $m_π=384(4) {\rm MeV} $. The thermal ensembles were provided by the FASTSUM collaboration and the zero temperature ensembles by the Hadspec collaboration. We also calculate the spectral density of the correlation function of those particles. The spectral density distributions show rich peak structure at the lowest temperature, while at intermediate temperatures, the mass values of those particles obtained by extrapolation method reflect a two-peak structure. While the spectral density for octet baryon becomes smooth at $T/T_c = 1.27, 1.52, 1.90$, the spectral density for H-dibaryon becoms smooth at $T/T_c = 1.90$. At $T/T_c =0.24 $, the mass difference of H-dibaryon and $Λ$ pair $Δm = m_H - 2\,m_Λ $ is estimated to be $Δm = -14.6(6.2) {\rm MeV}$ which suggests there exists a bound H-dibaryon state.

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arXiv2019

Spectral quantities in thermal QCD: a progress report from the FASTSUM collaboration

In order to study spectral quantities in thermal QCD, the FASTSUM collaboration employs anisotropic lattice simulations with N_f=2+1 flavours of Wilson fermions. Here we discuss our Generation 2 and Generation 2L ensembles, which differ in the pion mass. The focus is on observables related to the light quarks and chiral symmetry restoration.

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arXiv2018

Nature of the chiral phase transition of two flavour QCD from imaginary chemical potential with HISQ fermions

The nature of the thermal phase transition of two flavor QCD in the chiral limit has an important implication for the QCD phase diagram. We carry out lattice QCD simulations in an attempt to address this problem. Simulations are conducted with a Symanzik-improved gauge action and the HISQ fermion action. Within the imaginary chemical potential formulation, five different quark masses, $am=0.020,\, 0.018, \, 0.015, \, 0.013,\, 0.010$, and four different lattice volumes $N_s=8, \, 12,\, 16, \, 20$ with temporal extent $N_t=4$ are used to explore the scaling behavior. At each of the quark masses, the Binder cumulants of the chiral condensate on different lattice volumes approximately intersect at one point. We find that at the intersection point, the Binder cumulant $B_4(am,aμ_c) $ is around $3$ which deviates from the $Z(2)$ universality class value 1.604. However, based on the expectations of $Z(2)$ criticality, the fitting result only with the data from the largest lattice volume $N_s=20$ agrees well with earlier result [ Phys. Rev., D90, 074030(2014) ]\cite{Bonati:2014kpa}. This fact implies that, although the finite cut-off effects could be reduced with HISQ fermions even on $N_t=4$ lattices, larger lattices with spatial extent $N_s>=20$ for such studies are needed to control finite volume effects.

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arXiv2016

Locations of Roberge-Weiss transition endpoints in lattice QCD with $N_f=2$ improved KS quarks

Result on the locations of the tricritical points of $N_f=2$ lattice QCD with imaginary chemical potential is presented. Simulations are carried out with Symanzik improved gauge action and Asqtad fermion action. With imaginary chemical potential $iμ_I=iπT$, previous studies show that the Roberge-Weiss (RW) transition endpoints are triple points at both large and small quark masses, and second order transition points at intermediate quark masses. The triple and second order endpoints are separated by two tricritical ones. Our simulations are carried out at 7 values of quark mass $am$ ranging from 0.024 to 0.070 on lattice volume $12^3\times 4, 16^3\times 4,\, 20^3\times4$. The susceptibility and Binder cumulant of the imaginary part of Polyakov loop are employed to determine the nature of RW transition endpoints. The simulations suggest that the two tricritical points are within the range $0.024-0.026$ and $0.040-0.050$, respectively.

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arXiv2014

Nature of Roberge-Weiss transition end points for heavy quarks in $N_f=2$ lattice QCD with Wilson fermions

The phase structure of QCD with imaginary chemical potential provides information on the phase diagram of QCD with real chemical potential. With imaginary chemical potential $iμ_I=iπT$, previous studies show that the Roberge-Weiss (RW) transition end points are triple points at both large and small quark masses, and second order transition points at intermediate quark masses. The triple and second order end points are separated by two tricritical ones. We present simulations with $ N_f=2 $ Wilson fermions to investigate the nature of RW transition end points. The simulations are carried out at 8 values of the hopping parameter $κ$ ranging from 0.020 to 0.140 on different lattice volumes. The Binder cumulant, susceptibility and reweighted distribution of the imaginary part of Polyakov loop are employed to determine the nature of RW transition end points. The simulations show that the two tricritical points are within the range $0.070-0.080$ and $0.120-0.140$, respectively.

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arXiv2013

Nature of the Roberge-Weiss transition end points in two-flavor lattice QCD with Wilson quarks

We make simulations with 2 flavor Wilson fermions to investigate the nature of the end points of Roberge-Weiss (RW) first order phase transition lines. The simulations are carried out at 9 values of the hopping parameter $κ$ ranging from 0.155 to 0.198 on different lattice spatial volume. The Binder cumulants, susceptibilities and reweighted distributions of the imaginary part of Polyakov loop are employed to determine the nature of the end points of RW transition lines. The simulations show that the RW end points are of first order at the values of $κ$ in our simulations.

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arXiv2007

Phase structure of lattice QCD with two flavors of Wilson quarks at finite temperature and chemical potential

We present results for phase structure of lattice QCD with two degenerate flavors ($N_f=2$) of Wilson quarks at finite temperature $T$ and small baryon chemical potential $μ_B$. Using the imaginary chemical potential for which the fermion determinant is positive, we perform simulations at points where the ratios of pseudo-scalar meson mass to the vector meson mass $m_π/m_ρ$ are between $0.943(3)$ and $0.899(4)$ as well as in the quenched limit. By analytic continuation to real quark chemical potential $μ$, we obtain the transition temperature as a function of small $μ_B$. We attempt to determine the nature of transition at imaginary chemical potential by histogram, MC history, and finite size scaling. In the infinite heavy quark limit, the transition is of first order. At intermediate values of quark mass $m_q$ corresponding to the ratio of $m_π/m_ρ$ in the range from $0.943(3)$ to $0.899(4)$ at $aμ_I=0.24$, the MC simulations show absence of phase transition.

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