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We evaluate the strange nucleon electromagnetic form factors using an ensemble of gauge configurations generated with two degenerate maximally twisted mass clover-improved fermions with mass tuned to approximately reproduce the physical…

High Energy Physics - Lattice · Physics 2018-05-23 C. Alexandrou , M. Constantinou , K. Hadjiyiannakou , K. Jansen , C. Kallidonis , G. Koutsou , A. Vaquero Aviles-Casco

We calculate the spin dependent structure functions g_{1}(x) and g_{2}(x) of the proton and neutron. Our calculation uses the meson cloud model of nucleon structure, which has previously given a good description of the HERMES data on…

High Energy Physics - Phenomenology · Physics 2008-11-26 F. Bissey , F. G. Cao , A. I. Signal

We present results on the spin and quark content of the nucleon using $N_f=2$ twisted mass clover-improved fermion simulations with a pion mass close to its physical value. We use recently developed methods to obtain accurate results for…

High Energy Physics - Lattice · Physics 2016-11-29 C. Alexandrou , M. Constantinou , K. Hadjiyiannakou , Ch. Kallidonis , G. Koutsou , K. Jansen , Ch. Wiese , A. Vaquero Avilés-Casco

We investigate contributions of excited states to nucleon matrix elements by studying the two- and three-point functions using nucleon and pion-nucleon interpolating fields. This study is carried out using twisted mass fermion ensembles…

High Energy Physics - Lattice · Physics 2024-01-02 Constantia Alexandrou , Giannis Koutsou , Yan Li , Marcus Petschlies , Ferenc Pittler

We report on recent progress of our analysis of the nucleon sigma terms, as well as the singlet scalar, axial and tensor nucleon charges. These are determined employing the CLS gauge ensembles, which are generated using the L\"uscher-Weisz…

High Energy Physics - Lattice · Physics 2021-11-29 Daniel Jenkins , Sara Collins , Gunnar Bali

I present a preliminary determination of the Fragmentation Functions (FFs) of unidentified charged hadrons at next-to-leading order in quantum chromodynamics. The analysis is based on hadron production cross section data in single-inclusive…

High Energy Physics - Phenomenology · Physics 2017-09-12 Emanuele R. Nocera

There are generally two types of Wick contractions in lattice QCD calculations of a correlation function --- connected and disconnected ones. The disconnected contribution is difficult to calculate and noisy, thus it is often neglected. In…

High Energy Physics - Lattice · Physics 2013-10-29 Feng-Kun Guo , Liuming Liu , Ulf-G. Meißner , Ping Wang

This is a review of progress in hadron structure physics from lattice QCD. Recent results on the structure of the nucleon and the pion in terms of (transition) form factors, moments of distribution amplitudes and (generalized) parton…

High Energy Physics - Lattice · Physics 2008-11-26 Philipp Hägler

We present new sets of fragmentation functions for charged pions and kaons, both at leading and next-to-leading order. They are fitted to TPC data taken at energy $\sqrt s=29$~GeV and describe excellently a wealth of other $e^+e^-$ data on…

High Energy Physics - Phenomenology · Physics 2009-10-28 J. Binnewies , B. A. Kniehl , G. Kramer

We calculate the disconnected contribution to isoscalar nucleon charges for scalar, axial and tensor channels of light and strange quarks. The calculation has been done with the Clover valence quarks on the MILC $N_f=2+1+1$ HISQ lattices…

High Energy Physics - Lattice · Physics 2015-03-23 Tanmoy Bhattacharya , Rajan Gupta , Boram Yoon

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…

High Energy Physics - Phenomenology · Physics 2011-04-15 Marco Traini , Pietro Faccioli , Vicente Vento

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…

High Energy Physics - Lattice · Physics 2014-07-30 A. J. Chambers , R. Horsley , Y. Nakamura , H. Perlt , D. Pleiter , P. E. L. Rakow , G. Schierholz , A. Schiller , H. Stüben , R. D. Young , J. M. Zanotti

Nucleon sigma terms are quantities that play an important role in various areas: among others, they connect the pion-nucleon and the kaon-nucleon amplitudes to the hadron spectrum and they are also relevant for the direct detection of Dark…

High Energy Physics - Lattice · Physics 2019-08-14 Christian Torrero

In this thesis we explore a diverse array of issues that strike at the inherently nonperturbative structure of hadrons at momenta below the QCD confinement scale. In so doing, we mainly seek a better control over the partonic substructure…

High Energy Physics - Phenomenology · Physics 2014-08-26 T. J. Hobbs

This snapshot of recent progress in hadron physics made in connection with QCD's Dyson-Schwinger equations includes: a perspective on confinement and dynamical chiral symmetry breaking (DCSB); a pre'cis on the physics of in-hadron…

Nuclear Theory · Physics 2017-08-23 H. L. L. Roberts , L. Chang , I. C. Cloet , C. D. Roberts

We present results for the nucleon electromagnetic form factors using an ensemble of maximally twisted mass clover-improved fermions with pion mass of about 130 MeV. We use multiple sink-source separations and three analysis methods to…

We present results on the nucleon form factors, momentum fraction and helicity moment for $N_f=2$ and $N_f=2+1+1$ twisted mass fermions for a number of lattice volumes and lattice spacings. First results for a new $N_f=2$ ensemble at the…

High Energy Physics - Lattice · Physics 2013-12-11 C. Alexandrou , M. Constantinou , V. Drach , K. Jansen , Ch. Kallidonis , G. Koutsou

This is a review of recent developments in hadron structure within the framework of Lattice QCD. The main focus is on recent achievements in the evaluation of nucleon quantities, such as the axial charge, electromagnetic form factors, the…

High Energy Physics - Lattice · Physics 2014-11-04 Martha Constantinou

We calculate both connected and disconnected contribution to the $\pi$-$N$ $\sigma$-term in quenched lattice QCD with Wilson quark action on a $12^3\times 20$ lattice at $\beta=5.7$. The latter is evaluated with the aid of the variant wall…

High Energy Physics - Lattice · Physics 2009-10-22 M. Fukugita , Y. Kuramashi , M. Okawa , A. Ukawa

We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is…