Light quark masses in N_f = 2+1 lattice QCD with Wilson fermions
Mattia Bruno, Isabel Campos, Patrick Fritzsch, Jonna Koponen, Carlos Pena, David Preti, Alberto Ramos, Anastassios Vladikas
备注：
27 pages, 5 figures. Published version of the paper. The present version contains additions and improvements proposed by the referee; the results remain unchanged
We present a lattice QCD determination of light quark masses with three sea-quark flavours ($N_f = 2+1$). Bare quark masses are known from PCAC relations in the framework of CLS lattice computations with a non-perturbatively improved Wilson-Clover action and a tree-level Symanzik improved gauge action. They are fully non-perturbatively improved, including the recently computed Symanzik counter-term $b_{\rm A} - b_{\rm P}$. The mass renormalisation at hadronic scales and the renormalisation group running over a wide range of scales are known non-perturbatively in the Schrödinger functional scheme. In the present paper we perform detailed extrapolations to the physical point, obtaining (for the four-flavour theory) $m_{u/d}(2{\rm GeV}) = 3.54(12)(9)$ MeV and $m_s(2{\rm GeV}) = 95.7(2.5)(2.4)$ MeV in the $\bar{MS}$ scheme. For the mass ratio we have $m_s/m_{u/d} = 27.0(1.0)(0.4)$. The RGI values in the three-flavour theory are $M_{u/d} = 4.70(15)(12)$ MeV and $M_s = 127.0(3.1)(3.2)$ MeV.
Stabilized Wilson fermions are a reformulation of Wilson clover fermions that incorporates several numerical stabilizing techniques, but also a local change of the fermion action - the original clover term being replaced with an exponentiated version of it. We intend to apply the stabilized Wilson fermions toolbox to the thermodynamics of QCD, starting on the $N_f=3$ symmetric line on the Columbia plot, and to compare the results with those obtained with other fermion discretizations.
In the simulation of QCD with 2+1 flavors of Wilson fermions, the positivity of the fermion determinant is generally assumed. We present evidence that this assumption is in general not justified and discuss the consequences of this finding.
We analyse the leading logarithmic corrections to the $a^2$ scaling of lattice artefacts in QCD, following the seminal work of Balog, Niedermayer and Weisz in the O(n) non-linear sigma model. Limiting the discussion to contributions from the action, the leading logarithmic corrections can be determined by the anomalous dimensions of mass-dimension 6 operators. These operators form a minimal on-shell basis of the Symanzik Effective Theory. We present results for non-perturbatively O($a$) improved Wilson and Ginsparg-Wilson quarks.
In this work we present a calculation of the Wilson Coefficients $C_1$ and $C_2$ of the Effective Weak Hamiltonian to all-orders in $α_s$, using lattice simulations. Given the current availability of lattice spacings we restrict our calculation to unphysically light $W$ bosons around 2 GeV and we study the systematic uncertainties of the two Wilson Coefficients.
We discuss color screening in 2+1 flavor QCD in terms of free energies of a static quark-antiquark pair. Thermal modifications of long distance correlations in quark-antiquark systems are studied in terms of static meson correlators. We calculate the Polyakov loop correlator, the color-singlet Wilson line correlator in Coulomb gauge and the cyclic Wilson loop on lattices using the HISQ/Tree action and almost physical quark mases with $N_τ= 4, 6, 8, 10, 12$. We present results in the continuum limit for temperatures up to $T \lesssim 650$ MeV and discuss the linear divergence of the cyclic Wils…
We show how the hopping parameter expansion at order $κ^2$ and $κ^4$ can be exploited in the simulation of lattice QCD with two flavours of degenerate Wilson fermions. A natural extension of this idea is a "UV-filtering" by using rooted polynomials. These approaches can be easily combined with, for example, mass preconditioning. First numerical tests are performed for the Wilson gauge action at $β=5.6$ and $κ=0.156$ and $0.1575$.
