Search results for "lattice QCD"
showing 10 items of 241 documents
Determination of the pole position of the lightest hybrid meson candidate
2019
Mapping states with explicit gluonic degrees of freedom in the light sector is a challenge, and has led to controversies in the past. In particular, the experiments have reported two different hybrid candidates with spin-exotic signature, pi1(1400) and pi1(1600), which couple separately to eta pi and eta' pi. This picture is not compatible with recent Lattice QCD estimates for hybrid states, nor with most phenomenological models. We consider the recent partial wave analysis of the eta(') pi system by the COMPASS collaboration. We fit the extracted intensities and phases with a coupled-channel amplitude that enforces the unitarity and analyticity of the S-matrix. We provide a robust extracti…
Developments in the position-space approach to the HLbL contribution to the muon $g-2$ on the lattice
2019
The measurement of the anomalous magnetic moment of the muon and its prediction allow for a high-precision test of the Standard Model (SM). In this proceedings article we present ongoing work combining lattice QCD and continuum QED in order to determine an important SM contribution to the magnetic moment, the hadronic light-by-light contribution. We compute the quark-connected contribution in the Mainz position-space approach and investigate the long-distance part of our data using calculations of the $\pi^0$-pole and charged pion loop contributions.
Recent results on the meson and baryon spectrum from lattice QCD
2017
Recent lattice results on the meson and baryon spectrum with a focus on the determination of hadronic resonance masses and widths using a combined basis of single-hadron and hadron-hadron interpolating fields are reviewed. These mostly exploratory calculations differ from traditional lattice QCD spectrum calculations for states stable under QCD, where calculations with a full uncertainty estimate are already routinely performed. Progress and challenges in these calculations are highlighted.
Hadronic light-by-light scattering contribution to the muon $g-2$ on the lattice
2018
International Workshop on “Flavour Changing and Conserving Processes, FCCP2017, Anacapri, Italy, 7 Sep 2017 - 9 Sep 2017; The European physical journal / Web of Conferences 179, 01017 (2018). doi:10.1051/epjconf/201817901017
Lorentz-covariant coordinate-space representation of the leading hadronic contribution to the anomalous magnetic moment of the muon
2017
We present a Lorentz-covariant, Euclidean coordinate-space expression for the hadronic vacuum polarisation, the Adler function and the leading hadronic contribution to the anomalous magnetic moment of the muon. The representation offers a lot of flexibility for an implementation in lattice QCD. We expect it to be particularly helpful for the quark-line disconnected contributions.
Model-independent determination of the nucleon charge radius from lattice QCD
2020
Lattice QCD calculations of nucleon form factors are restricted to discrete values of the Euclidean four-momentum transfer. Therefore, the extraction of radii typically relies on parametrizing and fitting the lattice QCD data to obtain its slope close to zero momentum transfer. We investigate a new method, which allows to compute the nucleon radius directly from existing lattice QCD data, without assuming a functional form for the momentum dependence of the underlying form factor. The method is illustrated for the case of the isovector mean square charge radius of the nucleon $\langle r^2_\mathrm{isov} \rangle$ and the quark-connected contributions to $\langle r^2_p\rangle$ and $\langle r^2…
Isospin breaking in the nucleon mass and the sensitivity of β decays to new physics.
2013
We discuss the consequences of the approximate conservation of the vector and axial currents for the hadronic matrix elements appearing in beta decay if non-standard interactions are present. In particular the isovector (pseudo)scalar charge g_S(P) of the nucleon can be related to the difference (sum) of the nucleon masses in the absence of electromagnetic effects. Using recent determinations of these quantities from phenomenological and lattice QCD studies we obtain the accurate values g_S=1.02(11) and g_P=349(9) in the MS-bar scheme at mu=2 GeV. The consequences for searches of non-standard scalar interactions in nuclear beta decays are studied, finding epsilon_S=0.0012(24) at 90%CL, whic…
Hadronic light-by-light contribution to $(g-2)_\mu $ from lattice QCD: a complete calculation
2021
The European physical journal / C 81(7), 651 (2021). doi:10.1140/epjc/s10052-021-09455-4
Lattice QCD study of the $H$ dibaryon using hexaquark and two-baryon interpolators
2019
Physical review / D 99(7), 074505 (2019). doi:10.1103/PhysRevD.99.074505
Density distributions in the $B$ meson
2016
We report on a two-flavor lattice QCD study of the axial, charge and matter distributions of the $B$ meson and its first radial excitation. As our framework is the static limit of Heavy Quark Effective Theory (HQET), taking their Fourier transform gives access to several form factors at the kinematical point $q^2=0$. Moreover they provide some useful information on the nature of an excited state, i.e. a radial excitation of a quark-antiquark bound state or a multihadron state.