Browsing by Author "Jansen, K."

Article

Axial nucleon form factors from lattice QCD

Alexandrou, Constantia; Brinet, M.; Carbonell, J.; Constantinou, Martha; Harraud, P. A.; Guichon, P.; Jansen, K.; Korzec, T.; Papinutto, M. (2011)

We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1fm and ...

Article

Baryon spectrum with Nf=2+1+1 twisted mass fermions

Alexandrou, Constantia; Drach, V.; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis (2014)

The masses of the low-lying baryons are evaluated using a total of ten ensembles of dynamical twisted mass fermion gauge configurations. The simulations are performed using two degenerate flavors of light quarks, and a ...

Article

BK-parameter from Nf=2 twisted mass lattice QCD

Constantinou, Martha G.; Dimopoulos, Petros; Frezzotti, R.; Jansen, K.; Gimenez, V.; Lubicz, V.; Mescia, F.; Panagopoulos, Haralambos G.; Papinutto, M.; Rossi, G. C.; Simula, S.; Skouroupathis, A.; Stylianou, Fotos S.; Vladikas, A. (2011)

We present an unquenched Nf=2 lattice computation of the B K parameter which controls K0-K̄0 oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence ...

Article

A complete non-perturbative renormalization prescription for quasi-PDFs

Alexandrou, Constantia; Cichy, K.; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Panagopoulos, Haralambos G.; Steffens, F. (2017)

In this work we present, for the first time, the non-perturbative renormalization for the unpolarized, helicity and transversity quasi-PDFs, in an RI′ scheme. The proposed prescription addresses simultaneously all aspects ...

Conference Object

Computation of disconnected contributions to nucleon observables

Alexandrou, Constantia; Drach, V.; Jansen, K.; Koutsou, Giannis; Avilés-Casco, A. V. (Proceedings of Science (PoS), 2013)

We compare several methods for computing disconnected fermion loops contributing to nucleon three-point functions. The comparison is carried out using one ensemble of Nf =2+1+1 twisted mass fermions with pion mass of 373 ...

Article

Direct Evaluation of the Quark Content of Nucleons from Lattice QCD at the Physical Point

Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, A. V. (2016)

We evaluate the light, strange, and charm scalar content of the nucleon using one lattice QCD ensemble generated with two degenerate light quarks with mass fixed to their physical value. We use improved techniques to ...

Conference Object

Disconnected diagrams with twisted-mass fermions

Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Finkenrath, J.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, A. V.; Volmer, J. (Proceedings of Science (PoS), 2016)

The latest results from the Twisted-Mass collaboration on disconnected diagrams at the physical value of the pion mass are presented. In particular, we focus on the sigma terms, the axial charges and the momentum fraction, ...

Article

Disconnected quark loop contributions to nucleon observables in lattice QCD

Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Vaquero, A. (2014)

We perform a high statistics calculation of disconnected fermion loops on graphics processing units for a range of nucleon matrix elements extracted using lattice QCD. The isoscalar electromagnetic and axial vector form ...

Conference Object

Disconnected quark loop contributions to nucleon observables using Nf = 2 twisted clover fermions at the physical value of the light quark mass

Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, A. V. (Proceedings of Science (PoS), 2015)

We compute the disconnected quark loops contributions entering the determination of nucleon observables, by using a Nf = 2 ensemble of twisted mass fermions with a clover term at a pION mass mπ = 133 MeV. We employ exact ...

Conference Object

The electric dipole moment of the neutron from Nf = 2+1+1 twisted mass fermions

Petschlies, Marcus; Alexandrou, Constantia; Athenodorou, A.; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Ottnad, K. (Proceedings of Science (PoS), 2015)

We extract the neutron electric dipole moment (nEDM) dn on configurations produced with Nf = 2+1+1 twisted mass fermions with lattice spacing of a ≃ 0.082fm and a light quark mass that correpsonds to Mπ ≃ 373 MeV. We do ...

Article

Erratum: Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass (Physical Review D - Particles, Fields, Gravitation and Cosmology (2015) 92 (114513))

Abdel-Rehim, A.; Alexandrou, Constantia; Constantinou, Martha; Dimopoulos, Petros; Frezzotti, R.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kallidonis, Christos; Kostrzewa, B.; Koutsou, Giannis; Mangin-Brinet, M.; Oehm, M.; Rossi, G. C.; Urbach, C.; Wenger, U. (2016)

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 ...

Article

Evaluation of disconnected quark loops for hadron structure using GPUs

Alexandrou, Constantia; Constantinou, Martha; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Strelchenko, A.; Vaquero, A. (2014)

A number of stochastic methods developed for the calculation of fermion loops are investigated and compared, in particular with respect to their efficiency when implemented on Graphics Processing Units (GPUs). We assess ...

Article

First moment of the flavour octet nucleon parton distribution function using lattice QCD

Alexandrou, Constantia; Constantinou, Martha; Dinter, S.; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Koutsou, Giannis; Vaquero, A. (2015)

Abstract: We perform a lattice computation of the flavour octet contribution to the average quark momentum in the nucleon, (Formula presented.). In particular, we fully take the disconnected contributions into account in ...

Article

First physics results at the physical pion mass from Nf=2 Wilson twisted mass fermions at maximal twist

Petschlies, Marcus; Abdel-Rehim, A.; Alexandrou, Constantia; Burger, F.; Constantinou, Martha; Dimopoulos, Petros; Frezzotti, R.; Hadjiyiannakou, Kyriakos; Helmes, C.; Jansen, K.; Jost, C.; Kallidonis, Christos; Knippschild, B.; Kostrzewa, B.; Koutsou, Giannis; Liu, L.; Mangin-Brinet, M.; Ottnad, K.; Pientka, G.; Rossi, G. C.; Urbach, C.; Wenger, U.; Werner, M. (2017)

We present physics results from simulations of QCD using Nf=2 dynamical Wilson twisted mass fermions at the physical value of the pion mass. These simulations are enabled by the addition of the clover term to the twisted ...

Article

Hadron structure from lattice QCD

Alexandrou, Constantia; Jansen, K. (2015)

We review results for hadron masses and hadron structure using maximally twisted mass fermions for our non-perturbative studies of lattice QCD. We demonstrate that hadron masses can be computed reliably in this setup and ...

Conference Object

A lattice calculation of parton distributions

Alexandrou, Constantia; Cichy, K.; Hadjiyiannakou, Kyriakos; Jansen, K.; Steffens, F.; Wiese, C. (Proceedings of Science (PoS), 2016)

We present results for the x dependence of the unpolarized, helicity, and transversity isovector quark distributions in the proton using lattice QCD, employing the method of quasi-distributions proposed by Ji in 2013. ...

Article

Lattice calculation of parton distributions

Alexandrou, Constantia; Cichy, K.; Drach, V.; Garcia-Ramos, E.; Hadjiyiannakou, Kyriakos; Jansen, K.; Steffens, F.; Wiese, C. (2015)

We report on our exploratory study for the direct evaluation of the parton distribution functions from lattice QCD, based on a recently proposed new approach. We present encouraging results using N f = 2 + 1 + 1 twisted ...

Article

Light baryon masses with dynamical twisted mass fermions

Alexandrou, Constantia; Baron, R.; Blossier, B.; Brinet, M.; Carbonell, J.; Dimopoulos, Petros; Drach, V.; Farchioni, F.; Frezzotti, R.; Guichon, P.; Herdoiza, G.; Jansen, K.; Korzec, T.; Koutsou, Giannis; Liu, Z.; Michael, C.; Pène, O.; Shindler, A.; Urbach, C.; Wenger, U. (2008)

We present results on the mass of the nucleon and the Δ using two dynamical degenerate twisted mass quarks and the tree-level Symanzik improved gauge action. The evaluation is performed at four quark masses corresponding ...

Conference Object

Looking at the gluon moment of the nucleon with dynamical twisted mass fermions

Alexandrou, Constantia; Drach, V.; Hadjiyiannakou, Kyriakos; Jansen, K.; Kostrzewa, B.; Wiese, C. (Proceedings of Science (PoS), 2013)

To understand the structure of hadrons it is important to know the PDF of their constituents, the quarks and gluons. In our work we aim to compute the first moment of the gluon PDF h(x)ig for the nucleon. We follow two ...

Article

Low-lying baryon spectrum with two dynamical twisted mass fermions

Alexandrou, Constantia; Baron, R.; Carbonell, J.; Drach, V.; Guichon, P.; Jansen, K.; Korzec, T.; Pène, O. (2009)

The masses of the low-lying baryons are evaluated using two degenerate flavors of twisted mass sea quarks corresponding to pseudoscalar masses in the range of about 270-500 MeV. The strange valence quark mass is tuned to ...