Scale Setting and Strong Coupling Determination in the Gradient Flow Scheme for 2+1 Flavor Lattice QCD
Fakultät für Physik, Universität Bielefeld（比勒费尔德大学物理学院）；Physics Department, Brookhaven National Laboratory（布鲁克海文国家实验室物理系）；Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University（华中师范大学夸克与轻子物理教育部重点实验室及粒子物理研究所）；Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin（柏林洪堡大学物理学院及IRIS阿德勒斯霍夫研究所）；Institut für Kernphysik, Technische Universität Darmstadt（达姆施塔特工业大学核物理研究所）
Rasmus Larsen, Swagato Mukherjee, Peter Petreczky, Hai-Tao Shu, Johannes Heinrich Weber
We report on the determination of the gradient flow scales in $N_f=2+1$ QCD using highly improved staggered quark (HISQ) ensembles generated by the HotQCD Collaboration for bare gauge couplings ranging from $β= 6.423$ to $8.400$. Using bottomonium splittings, kaon decay constant, the decay constant of unmixed $η_s$ meson and the $ϕ$ meson mass we obtained the values of the gradient flow scales in physical units, $\sqrt{t_0} = 0.14446 (76)$ fm and $w_0 = 0.17429 (83)$ fm. Using the same physical inputs we revisit the determination of the potential $r_1$ scale and find $r_1 = 0.3118(26)$~fm. As a byproduct of our study we obtain the running of the gauge coupling in the gradient flow scheme. We find that within the uncertainties the running of the gradient flow coupling obtained on the lattice is compatible with the perturbative results up to flow radius $\sqrt{8 τ_F}=0.15$ fm.
Common lore suggests that $N$-color QCD with massive quarks has no useful order parameters which can be non-trivial at zero baryon density. However, such order parameters do exist when there are $n_f$ quark flavors with a common mass and $d\equiv\gcd(n_f,N) > 1$. These theories have a $\mathbb Z_d$ color-flavor center symmetry arising from intertwined color center transformations and cyclic flavor permutations. The symmetry realization depends on the temperature, baryon chemical potential and value of $n_f/N$, with implications for conformal window studies and dense quark matter.
A review of QCD-based theory approaches to study the heavy-flavor and exotic hadrons is given. The focus is on the results from lattice QCD and from lattice QCD complemented by effective field theories. Both approaches are first briefly introduced and applied in few examples. Then the status of various hadrons sectors is presented.
We report on preliminary results from the calculations of the QCD equation of state for 2+1+1 flavors using HISQ action. The calculations are performed on lattices with temporal extents $N_τ=6,~8,~10$, and $12$ and aspect ratio $N_σ/N_τ=4$. We find that there is a significant contribution to the pressure from charm quarks at temperatures $T> 300$ MeV.
We review highlights of recent results on the hadron spectrum and flavor physics from lattice QCD. We also discuss recent rapid progress on the muon anomalous magnetic moment.
We discuss the QCD critical point at finite density through the study of many flavor QCD, in which two light flavors and Nf massive flavors exist. Performing simulations of QCD with two flavors of improved Wilson fermions, we calculate probability distribution functions of many flavor QCD at finite temperature and density. The dynamical effects of massive flavors and the chemical potential are added using the reweighting technique. From the shape of the distribution functions, we determine the critical surface separating the first order transition and crossover regions in the parameter space o…
We perform lattice numerical simulations to study the phase transition of QCD at finite temperature to clarify the nature of the transition of massless two flavor QCD. We investigate QCD with two light and Nf heavy quarks instead of two-flavor QCD, and focus on the light quark mass dependence of the critical heavy mass, below which the transition is of first order. The heavy quarks are incorporated into two flavor configurations in the form of the hopping parameter expansion through the reweighting technique. The nature of the transition is identified by the shape of the constraint effective p…
We demonstrate that the QCD topological susceptibility nonperturbatively gets a significant contribution signaled by flavor-nonuniversal quark condensates at around the pseudo-critical temperature of the chiral crossover. It implies a remarkable flavor breaking in the axial anomaly as well as the QCD theta vacuum in high temperature QCD, which are almost flavor universal in the vacuum. A nontrivial flavor breaking is triggered by nonperturbative thermal loop corrections at around the chiral crossover, which is different from the trivial flavor violation just scaled by the quark mass ratio, obs…
We present the first calculation within lattice QCD of excited light meson resonances with $J^{PC} = 1^{--}$, $2^{--}$ and $3^{--}$. Working with an exact SU(3) flavor symmetry, for the singlet representation of pseudoscalar-vector scattering, we find two $1^{--}$ resonances, a lighter broad state and a heavier narrow state, a broad $2^{--}$ resonance decaying in both $P$- and $F$-waves, and a narrow $3^{--}$ state. We present connections to experimental $ω^\star_J, ϕ^\star_J$ resonances decaying into $πρ$, $K\bar{K}^*$, $ηω$ and other final states.
