相关论文: Disconnected contributions to hadronic structure
The magnetic polarisability of the neutral pion has been calculated using the background field method in lattice QCD. These early results do not consider the effect of the disconnected loop contractions arising from the breaking of charge…
The alternative to the standard formulation of the quark-parton model is proposed. Our relativistically covariant approach is based on the solution of the master equations relating the structure and distribution functions, which…
The contributions of strange quarks to the nucleon mass and the nucleon spin are investigated in a mixed action scheme employing domain wall valence quarks and quark loops on MILC asqtad dynamical fermion ensembles. Results are presented…
We report our (HPQCD) progress on the calculation of the Hadronic Vacuum Polarisation contribution to the anomalous magnetic moment of muon. In this article we discuss the calculations for the light (up/down) quark connected contribution…
We calculate the spin density matrix of the hadron $h$ created via quark fragmentation in the process $e^-e^+ \to q\bar q \to h + X$. In the case of $h=\Lambda$ the experimental data could possibly elucidate the problem of $s$-quark…
Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The…
Sea quark contributions to the scalar density and the axial current matrix elements of the nucleon are studied in lattice qcd with two flavours of dynamical wilson fermions. the results are compared to trends in heavy quark mass expansions,…
By introducing an additional operator into the action and using the Feynman-Hellmann theorem we describe a method to determine both the quark line connected and disconnected terms of matrix elements. As an illustration of the method we…
A few chosen nucleon properties are described from a lattice QCD perspective: the nucleon sigma term and the scalar strangeness in the nucleon; the vector form factors in the nucleon, including the vector strangeness contribution, as well…
Hadron spin physics is now one of the most active fields of physics. Especially in the last ten years, great progress has been made both theoretically and experimentally that has considerably improved our knowledge of the spin structure of…
We perform a Nf = 2 + 1 lattice QCD simulation to determine the quark spin fractions of hadrons using the Feynman-Hellmann theorem. By introducing an external spin operator to the fermion action, the matrix elements relevant for quark spin…
Contributions of hadronic effects to the muonium physics and anomalous magnetic moment of muon are considered. Special attention is paid to higher-order effects and the uncertainty related to the hadronic contribution to the hyperfine…
Quark-hadron duality is studied in a systematic way for polarized and unpolarized structure functions, by taking into account all the available data in the resonance region. In both cases, a precise perturbative QCD based analysis of the…
We check the $u$ and $d$ quark contributions to the spin content of the $\Lambda$ by means of the $q\to\Lambda$ fragmentation and find that the $u$ and $d$ quarks of the $\Lambda$ are likely positively polarized. The parton distributions in…
The alternative to the standard formulation of the quark-parton model is proposed. Our relativistically covariant approach is based on the solution of the master equations relating the structure and distribution functions, which…
Within the framework of the so-called "valon" model, we argue that a substantial part of the nucleon spin, about 40%, is carried by the polarized valence quarks. The remaining is the result of cancellations between gluon polarization and…
The present contribution continues and extends foregoing work on the calculation of electroweak form factors of hadrons using the point-form of relativistic quantum mechanics. Here we are particularly interested in studying pionic effects…
We present a quark-parton model to describe polarized and unpolarized nucleon structure functions. The twist-two matrix elements for the QCD evolution analysis of lepton-hadron scattering are calculated within a light-front covariant quark…
The quark spin densities related to generalized parton distributions in impact-parameter space and to transverse-momentum dependent parton distributions are reviewed within a light-cone quark model, with focus on the role of the different…
Gluon topology makes a potentially important contribution to the spin of the constituent quark.