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In quenched lattice QCD with standard Wilson fermions the quark propagator is computed very close to the chiral limit in the zero-temperature case. Starting from our experience with lattice QED we employ a modified statistical method in…

High Energy Physics - Lattice · Physics 2009-10-30 A. Hoferichter , E. Laermann , V. K. Mitrjushkin , M. Müller-Preussker , P. Schmidt

We present numerical simulation of QCD with two dynamical quark flavors described by the overlap fermion action on a $16^3\times 32\times (0.12 {\rm fm})^4$ lattice. We calculate pseudo-scalar masses and decay constants and investigate…

High Energy Physics - Lattice · Physics 2009-04-14 J. Noaki , S. Aoki , H. Fukaya , S. Hashimoto , T. Kaneko , H. Matsufuru , T. Onogi , E. Shintani , N. Yamada

We study the change of the QCD spectrum of low-lying mesons in the presence of an external magnetic field using Wilson fermions in the quenched approximation. Motivated by qualitative differences observed in the spectra of overlap and…

High Energy Physics - Lattice · Physics 2015-10-15 Gunnar Bali , Bastian B. Brandt , Gergely Endrodi , Benjamin Glaessle

Values for the strange quark mass and average up/down mass have been obtained from quenched lattice QCD simulations using the domain wall fermion action. This discretization preserves the properties of flavor and chiral symmetry at nonzero…

High Energy Physics - Lattice · Physics 2009-10-31 Matthew Wingate

We calculate the vacuum polarization functions on the lattice using the overlap fermion formulation.By matching the lattice data at large momentum scales with the perturbative expansion supplemented by Operator Product Expansion (OPE), we…

High Energy Physics - Lattice · Physics 2019-08-13 E. Shintani , S. Aoki , T. W. Chiu , S. Hashimoto , T. H. Hsieh , T. Kaneko , H. Matsufuru , J. Noaki , T. Onogi , N. Yamada

Complete two-loop calculation of a dimensionally regularized Wilson loop with light-like segments is performed in the light-like axial gauge with the Mandelstam-Leibbrandt prescription for the gluon propagator. We find an expression which…

High Energy Physics - Phenomenology · Physics 2009-10-22 A. Bassetto , I. A. Korchemskaya , G. P. Korchemsky , G. Nardelli

We determine the scale setting function and the pseudo-critical temperature on the lattice in $N_f=2$ two-color QCD using the Iwasaki gauge and Wilson fermion actions. Although two-color QCD does not correspond to the real world, it is very…

High Energy Physics - Lattice · Physics 2020-08-17 Kei Iida , Etsuko Itou , Tong-Gyu Lee

We report a calculation of all two-loop QED corrections with closed fermion loops for the n=1 and n=2 states of H-like ions and for a wide range of the nuclear charge numbers Z=1-100. The calculation is performed to all orders in the…

Atomic Physics · Physics 2009-11-13 V. A. Yerokhin , P. Indelicato , V. M. Shabaev

The two-loop QCD corrections to vector boson pair production at hadron colliders involve a new class of Feynman integrals: two-loop four-point functions with two off-shell external legs. We describe their reduction to a small set of master…

High Energy Physics - Phenomenology · Physics 2013-08-26 Thomas Gehrmann , Lorenzo Tancredi , Erich Weihs

The chromoelectric and chromomagnetic fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a $24^3\times 48$ lattice at $\beta=6.2$ and $a=0.07261(85) fm$. We compute the hybrid Wilson…

High Energy Physics - Lattice · Physics 2010-04-06 M. Cardoso , N. Cardoso , P. Bicudo

We present results of lattice QCD simulations with mass-degenerate up and down and mass-split strange and charm (Nf=2+1+1) dynamical quarks using Wilson twisted mass fermions at maximal twist. The tuning of the strange and charm quark…

The computational effort in the calculation of Wilson fermion quark propagators in Lattice Quantum Chromodynamics can be considerably reduced by exploiting the Wilson fermion matrix structure in inversion algorithms based on the…

High Energy Physics - Lattice · Physics 2015-06-25 Andreas Frommer , Stephan Güsken , Thomas Lippert , Bertold Nöckel , Klaus Schilling

We present a lattice QCD calculation of the scattering phase shift for the I=2 $S$-wave two-pion system using the finite size method proposed by L\"uscher. We work in the quenched approximation employing the standard plaquette action at…

We describe in detail the calculation of the two-loop corrections to the QED Bhabha scattering cross section due to the vacuum polarization by heavy fermions. Our approach eliminates one mass scale from the most challenging part of the…

High Energy Physics - Phenomenology · Physics 2008-11-26 R. Bonciani , A. Ferroglia , A. A. Penin

We test the nonrelativistic QCD factorization conjecture for inclusive quarkonium production at two loops by carrying out a covariant calculation of the nonrelativistic quantum chromodynamics (NRQCD) long-distance matrix element (LDME) for…

High Energy Physics - Phenomenology · Physics 2020-05-27 Geoffrey T. Bodwin , Hee Sok Chung , June-Haak Ee , U-Rae Kim , Jungil Lee

Lattice QCD calculations using gauge smearing for fermion kernels are computationally efficient. Hypercubic blocking (nHYP smearing) has been shown to reduce scaling errors. In this work we use an improved action for $N_f=2$ QCD, based on…

High Energy Physics - Lattice · Physics 2020-11-18 Hossein Niyazi , Andrei Alexandru , Frank X. Lee , Ruairí Brett

Parity and flavor symmetry is not broken in QCD. Using this fact, we propose a new method to measure the chiral condensate in lattice QCD using Wilson fermions with an operator that breaks parity and flavor in addition to the chiral…

High Energy Physics - Theory · Physics 2009-10-30 Khalil M. Bitar , Urs M. Heller , Rajamani Narayanan

As computing resources are limited, choosing the parameters for a full Lattice QCD simulation always amounts to a compromise between the competing objectives of a lattice spacing as small, quarks as light, and a volume as large as possible.…

High Energy Physics - Lattice · Physics 2009-11-11 B. Orth , Th. Lippert , K. Schilling

The calculation of force is most difficult part in lattice Quantum Chromodynamics (QCD). This lecture gives the details of the force calculation in one-loop Symanzik improved action, Wilson fermion with clover term, asqtad fermion, HISQ…

High Energy Physics - Lattice · Physics 2021-12-14 Daming Li

We present the current status of our computation of quark bilinear renormalization constants for Wilson fermions and Symanzik improved gauge action. Computations are performed in Numerical Stochastic Perturbation Theory. Volumes range from…

High Energy Physics - Lattice · Physics 2010-02-03 M. Brambilla , F. Di Renzo , L. Scorzato