SEARCH · Searcharxiv

Results for “hep-lat”

Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources

arXiv2009

Baryon-baryon potentials in the flavor SU(3) limit from lattice QCD

We investigate baryon-baryon (BB) interactions in the flavor SU(3) symmetric world, by using the 3-flavor full QCD simulations. In the SU(3) limit, six independent two-baryon states exist for a given orbital angular momentum. We forcus on S-wave states and extract BB potentials using the method recently developed. We discuss the flavor dependence of the potentials, in particular, the strength of the repulsion at short distance. We find that the SU(3) flavor structure of the repulsive core is compatible with that expected from the Pauli principle for the quarks.

hep-lat↗

arXiv2010

Form factors for rare B decays: strategy, methodology, and numerical study

We investigate the combined use of moving NRQCD and stochastic sources in lattice calculations of form factors describing rare B and B_s decays. Moving NRQCD leads to a reduction of discretisation errors compared to standard NRQCD. Stochastic sources are tested for reduction of statistical errors.

hep-lat↗

arXiv2009

Strangeness and charm content of the nucleon

We present results on the scalar strangeness and charm contents of the nucleon and of the disconnected contributions to the nucleon spin. These are obtained on two flavour non-perturbatively improved Sheikholeslami-Wilson configurations at a pseudoscalar mass of 290 MeV. We quote f_{T_s} = m_s /m_N< = 0.070(22) as our preliminary value for the strange quark fraction of the nucleon mass and a modified minimal subtraction scheme value Delta s = -0.015(10), with as yet unknown systematics, for the strangeness contribution to the spin.

hep-lat↗

arXiv2009

Chiral symmetry breaking in nearly conformal gauge theories

We present new results on chiral symmetry breaking in nearly conformal gauge theories with fermions in the fundamental representation of the SU(3) color gauge group. The number of fermion flavors is varied in an extended range below the conformal window with chiral symmetry breaking ($χ{\rm SB}$) for all flavors between $N_f=4$ and $N_f=12$. To identify $χ{\rm SB}$ we apply several methods which include, within the framework of chiral perturbation theory, the analysis of the Goldstone spectrum in the p-regime and the spectrum of the fermion Dirac operator with eigenvalue distributions of random matrix theory in the $\eps$-regime. Chiral condensate enhancement is observed with increasing $N_f$ when the electroweak symmetry breaking scale $F$ is held fixed in technicolor language. Important finite-volume consistency checks from the theoretical understanding of the $SU(N_f)$ rotator spectrum of the $δ$-regime are discussed. We also consider these gauge theories at $N_f=16$ inside the conformal window. The importance of understanding finite volume, zero momentum gauge field dynamics inside the conformal window is pointed out. Staggered lattice fermions with supressed taste breaking are used throughout the simulations.

hep-lat↗

arXiv2009

Neutron electric polarizability

We use the background field method to extract the "connected" piece of the neutron electric polarizability. We present results for quenched simulations using both clover and Wilson fermions and discuss our experience in extracting the mass shifts and the challenges we encountered when we lowered the quark mass. For the neutron we find that as the pion mass is lowered below $500\MeV$, the polarizability starts rising in agreement with predictions from chiral perturbation theory. For our lowest pion mass, $m_π=320\MeV$, we find that $α_n = 3.8(1.3)\times 10^{-4}\fm^3$, which is still only one third of the experimental value. We also present results for the neutral pion; we find that its polarizability turns negative for pion masses smaller than $500\MeV$ which is puzzling.

hep-lat↗

arXiv2009

Two-flavor lattice QCD study of $Λ$(1405)

Low-lying $Λ$ baryons with spin 1/2 are analyzed in two-flavor unquenched lattice QCD. We construct $2 \times 2$ cross correlators from flavor SU(3) ``octet'' and ``singlet'' baryon operators, and diagonalize them so that we can extract two low-lying states for each parity. The two-flavor CP-PACS gauge configurations are employed, which are generated in the renormalization-group improved gauge action and the ${\mathcal O}(a)$-improved quark action. Simulation are performed at three different $β$'s, $β= 1.80$, 1.95 and 2.10, whose corresponding lattice spacings are $a = 0.2150$, 0.1555 and 0.1076 fm. For each cutoff, we adopt four different hopping parameters, ($κ_{\rm val}, κ_{\rm sea}$). The corresponding pion masses range about from 500 MeV to 1.1 GeV. Results indicate that there are two negative-parity $Λ$ states nearly degenerate at around 1.6 GeV, while no state as low as $Λ(1405)$ is observed. By decomposing the flavor components of each state, we find that the lowest (1st-excited) negative-parity state is dominated by flavor-singlet (flavor-octet) component.

hep-lat↗

arXiv2009

Coulomb gauge gluon propagator on anisotropic lattices

We calculate the transverse and the time-time components of the Coulomb-gauge gluon propagator in SU(3) lattice Yang-Mills theory both on isotropic and anisotropic lattices. The problem of scaling violation observed on the isotropic lattice is drastically reduced as the anisotropy increases; namely, the system approaches the Hamiltonian limit. In the infrared region, the transverse gluon propagator exhibits a turnover and the temporal gluon propagator shows divergent behavior.

hep-lat↗

arXiv2009

Entanglement entropy of SU(3) Yang-Mills theory

We calculate the entanglement entropy using a SU(3) quenched lattice gauge simulation. We find that the entanglement entropy scales as $1/l^2$ at small $l$ as in the conformal field theory. Here $l$ is the size of the system, whose degrees of freedom is left after the other part are traced out. The derivative of the entanglement entropy with respect to $l$ hits zero at about $l^{\ast} = 0.6 \sim 0.7$ [fm] and vanishes above the length. It may imply that the Yang-Mills theory has the mass gap of the order of $1/l^{\ast}$. Within our statistical errors, no discontinuous change can be seen in the entanglement entropy. We discuss also a subtle point appearing in gauge systems when we divide a system with cuts.

hep-lat↗

arXiv2009

Soft dynamics in heavy-light mesons

We compute the radial distributions of the scalar, vector and axial charge density in the heavy-light mesons. We present the results obtained for both the lowest lying static heavy-light mesons as well as for their nearest excitations, with $N_f=2$ dynamical quarks of Wilson (Clover) type. We used various improvements of the static heavy-quark actions. From these distributions we were able to compute the corresponding charges and their radii $< r^2>$, the results of which are also presented.

hep-lat↗

arXiv2009

Calculating the running coupling in strong electroweak models

One possibility for Beyond Standard Model physics is a new strongly-interacting gauge theory. One way to determine if a non-abelian gauge theory is QCD-like or conformal is to measure the running of the renormalized gauge coupling. We define the renormalized coupling from Wilson loop ratios, and measure these ratios via lattice simulations. We test this method in SU(3) pure gauge theory and show some first results for simulations with dynamical fermions in the fundamental representation.

hep-lat↗

arXiv2009

The CKM matrix and flavor physics from lattice QCD

I discuss the role of lattice QCD in testing the Standard Model and searching for physics beyond the Standard Model in the quark flavor sector. I first review the Standard Model CKM framework. I then present the current status of the CKM matrix, focusing on determinations of CKM matrix elements and constraints on the CKM unitarity triangle that rely on lattice QCD calculations of weak matrix elements. I also show the potential impact of improved lattice QCD calculations on the global CKM unitarity triangle fit. I then describe several hints of new physics in the quark flavor sector that rely on lattice QCD calculations of weak matrix elements, such as evidence of a ~2-3 sigma tension in the CKM unitarity triangle and the "f_{D_s} puzzle". I finish with a discussion of lattice QCD calculations of rare B- and K-decays needed to probe physics beyond the Standard Model at future experiments.

hep-lat↗

arXiv2009

Scaling study of the relativistic corrections to the static potential

The relativistic corrections to the static potential, i.e. the O(1/m) correction, the O(1/m^2) spin-dependent and momentum-dependent corrections are investigated in SU(3) lattice gauge theory. These corrections are relevant ingredients of an effective field theory for heavy quarkonium called potential nonrelativistic QCD. Utilizing the multilevel algorithm for the field strength correlator on the quark-antiquark source, these corrections are determined at the distances ranged from 0.25 to 1.2 fm. A reasonable scaling behavior and long-range nonperturbative contributions are observed.

hep-lat↗

arXiv2009

A Stochastic Method for Semileptonic Form Factor Calculations on the Lattice

We investigate an alternative to the Sequential Propagator Method used in Lattice QCD calculations of semileptonic form factors. We replace the sequential propagator with a stochastic propagator so that, in principle, all momentum and sink smearing combinations are available with only a single spin-color inversion. Practically, the stochastic noise is significant and must be reduced at the cost of more inversions. We study the behavior of the stochastic noise and compare the computational costs of this stochastic technique and the Sequential Propagator Method. We also present preliminary semileptonic form factor results using the stochastic technique on N_f=2 configurations with a non-perturbatively improved Sheikoleslami-Wohlert action generated by the QCDSF collaboration. At a fixed cost, measured in terms of the number of heavy-quark inversions, the method provides more correlators for the extraction of the form factors at various q^2's than the Sequential Propagator Method. These additional correlators reduce the total statistical errors of certain kinematic points, although the stochastic error is still comparable to the gauge error at other points.

hep-lat↗

arXiv2009

Excited-Nucleon Spectroscopy with 2+1 Fermion Flavors

We present progress made by the Hadron Spectrum Collaboration (HSC) in determining the tower of excited nucleon states using 2+1-flavor anisotropic clover lattices. The HSC has been investigating interpolating operators projected into irreducible representations of the cubic group in order to better calculate two-point correlators for nucleon spectroscopy; results are published for quenched and 2-flavor anisotropic Wilson lattices. In this work, we present the latest results using a new technique, distillation, which allows us to reach higher statistics than before. Future directions will be outlined at the end.

hep-lat↗

arXiv2009

Dimensional reduction and the phase diagram of 5d Yang-Mills theory

We present a non-perturbative study of the phase diagram of 5d SU(2) Yang-Mills theory with one compact extra dimension on the lattice. Assuming at least a modest scale separation between the cutoff and the compactification scales leads to an exponential separation between the compactification scale and the four-dimensional correlation length. While we demonstrate that it is not possible to take a full five-dimensional continuum limit, this dynamical generation of scale hierarchy opens up the possibility for us to make limited, but non-perturbative, predictions about continuum theories whose low-energy sector is described by an effective 5d Yang-Mills theory.

hep-lat↗

arXiv2009

Mixed action computations on fine dynamical lattices

We report on our first experiences in simulating Neuberger valence fermions on CLS $N_f=2$ configurations with light sea quark masses and small lattice spacings. Valence quark masses are considered that allow to explore the matching to (partially quenched) chiral perturbation theory both in the $ε$- and $p$-regimes. The setup is discussed, and first results are presented for spectral observables.

hep-lat↗

arXiv2009

Simulating Wilson fermions without critical slowing down

We present a simulation algorithm for Wilson fermions based on the exact hopping expansion of the fermion action. The algorithm essentially eliminates critical slowing down by sampling the fermionic two-point correlation function and it allows simulations directly in the massless limit. As illustrative examples, the algorithm is applied to the Gross-Neveu and the Schwinger model, the latter in the strong coupling limit.

hep-lat↗

arXiv2009

Wilson fermions with imaginary chemical potential

We study the phase structure of imaginary chemical potential. We calculate the Polyakov loop using clover-improved Wilson action and renormalization improved gauge action. We obtain a two-state signals indicating the first order phase transition for $β= 1.9, μ_I = 0.2618, κ=0.1388$ on $8^3\times 4$ lattice volume We also present a result of the matrix reduction formula for the Wilson fermion.

hep-lat↗