76 research outputs found
Future trends in lattice QCD simulations
No full textThis proceeding gives a short overview on current trends for Markov chain Monte Carlo simulations of lattice QCD on supercomputers. State-of-the-art lattice QCD calculations are becoming more and more essential in the search for new physics at the precision (intensity) frontier. Within this proceeding a briefdiscussion on methods is given for the generation of ensembles at larger lattice sizes and finerlattice spacings as well as methods to reach higher statical accuracy
Probing the energy-smeared R-ratio on the lattice
No full textWe present a first-principles lattice QCD investigation of the -ratio
between the cross-section into hadrons and that into muons. By using
the method of Ref.[1], that allows to extract smeared spectral densities from
Euclidean correlators, we compute the -ratio convoluted with Gaussian
smearing kernels of widths of about MeV and central energies from
MeV up to GeV. Our theoretical results are compared with the
corresponding quantities obtained by smearing the KNT19 compilation [2] of
-ratio experimental measurements with the same kernels and, by centring the
Gaussians in the region around the -resonance peak, a tension of about
three standard deviations is observed. From the phenomenological perspective,
we have not included yet in our calculation QED and strong isospin-breaking
corrections and this might affect the observed tension. From the methodological
perspective, our calculation demonstrates that it is possible to study the
-ratio in Gaussian energy bins on the lattice at the level of accuracy
required in order to perform precision tests of the Standard Model.Comment: Version accepted for publication on PRL. Results unchange
Quark masses and decay constants in Nf=2+1+1 isoQCD with Wilson clover twisted mass fermions
No full textWe present a preliminary study of the pion, kaon and D-meson masses and decay constants in isosymmetric QCD, as well as a preliminary result for the light-quark renormalized mass. The analysis is based on the gauge ensembles produced by ETMC with N f = 2 + 1 + 1 flavours of Wilson-clover twisted mass quarks, spanning a range of lattice spacings from ∼ 0.10 to 0.07 fm and include configurations at the physical pion point on lattices with linear size up to L ∼ 5.6 fm
Nucleon axial and pseudoscalar form factors using twisted-mass fermion ensembles at the physical point
No full textWe compute the nucleon axial and pseudoscalar form factors using three
2+1+1 twisted mass fermion ensembles with all quark masses tuned to
approximately their physical values. The values of the lattice spacings of
these three physical point ensembles are 0.080 fm, 0.068 fm, and 0.057 fm, and
spatial sizes 5.1 fm, 5.44 fm, and 5.47 fm, respectively, yielding >3.6. Convergence to the ground state matrix elements is assessed using
multi-state fits. We study the momentum dependence of the three form factors
and check the partially conserved axial-vector current (PCAC) hypothesis and
the pion pole dominance (PPD). We show that in the continuum limit, the PCAC
and PPD relations are satisfied. We also show that the Goldberger-Treimann
relation is approximately fulfilled and determine the Goldberger-Treiman
discrepancy. We find for the nucleon axial charge =1.245(28)(14), for the
axial radius =0.339(48)(06) fm, for the pion-nucleon
coupling constant =13.25(67)(69) and for =8.99(39)(49)
Simulation of an ensemble of Nf = 2 + 1 + 1 twisted mass cloverimproved fermions at physical quark masses
No full textWe present a general strategy aimed at generating Nf = 2+1+1 configurations with quarks at their physical mass using maximally twisted mass fermions to ensure automatic O(a) improvement, in the presence of a clover term tuned to reduce the charged to neutral pion mass difference. The target system, for the moment, is a lattice of size 643 × 128 with a lattice spacing a ~ 0:08 fm. We show preliminary results on the pion and kaon mass and decay constants
Lattice calculation of the R-ratio smeared with Gaussian kernels
No full textThe ratio R(E) of the cross-sections for e+e−→ hadrons and e+e−→μ+μ− is a valuable energy-dependent probe of the hadronic sector of the Standard Model. Moreover, the experimental measurements of R(E) are the inputs of the dispersive calculations of the leading hadronic vacuum polarization contribution to the muon g−2 and these are in significant tension with direct lattice calculations and with the muon g−2 experiment. In this talk we discuss the results of our first-principles lattice study of R(E). By using a recently proposed method for extracting smeared spectral densities from Euclidean lattice correlators, we have calculated R(E) convoluted with Gaussian kernels of different widths σ and central energies up to 2.5 GeV. Our theoretical results have been compared with the KNT19 [1] compilation of experimental results smeared with the same Gaussian kernels and a tension (about three standard deviations) has been observed for σ∼600 MeV and central energies around the ρ-resonance peak
Deflation and polynomial preconditioning in the application of the overlap operator at nonzero chemical potential
No full textWhen solving linear systems with the overlap operator at nonzero chemical potential in lattice QCD one needs, at every iteration of the iterative solver, to apply the sign function evaluated on a non-Hermitian operator times a vector, i.e., . In this work we describe how deflation and (the more recently proposed) polynomial preconditioning can be applied to this problem, in particular in the context of lattice QCD. Furthermore, we describe how both methods can be combined, we compare them in numerical experiments and explore whether there might be any synergy between both that can be exploited
Inclusive Hadronic Decay Rate of the τ Lepton from Lattice QCD: The u[over ¯]s Flavor Channel and the Cabibbo Angle.
No full textWe present a lattice determination of the inclusive decay rate of the process τ↦X_{us}ν_{τ} in which the τ lepton decays into a generic hadronic state X_{us} with u[over ¯]s flavor quantum numbers. Our results have been obtained in n_{f}=2+1+1 isosymmetric QCD with full nonperturbative accuracy, without any operator product expansion approximation and, except for the presently missing long-distance isospin-breaking corrections, include a solid estimate of all sources of theoretical uncertainties. This has been possible by using the Hansen-Lupo-Tantalo method [M. Hansen et al., Phys. Rev. D 99, 094508 (2019)PRVDAQ2470-001010.1103/PhysRevD.99.094508] that we have already successfully applied [A. Evangelista et al., Phys. Rev. D 108, 074513 (2023)PRVDAQ2470-001010.1103/PhysRevD.108.074513] to compute the inclusive decay rate of the process τ↦X_{ud}ν_{τ} in the u[over ¯]d flavor channel. By combining our first-principles theoretical results with the presently available experimental data, we extract the Cabibbo-Kobayashi-Maskawa matrix element |V_{us}|, the Cabibbo angle, with a 0.9% accuracy, dominated by the experimental error
Corrigendum to “One flavor mass reweighting in lattice QCD” [Nucl. Phys. B 877 (2) (2013) 441–456]
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