arXiv subjects

Y. Proestos

Publications and source records attributed to Y. Proestos.

6 recordsLinked to original sources

arXiv2010

Nucleon to Delta transition form factors with $N_F=2+1$ domain wall fermions

We calculate the electromagnetic, axial and pseudo-scalar form factors of the Nucleon to $Δ(1232)$ transition using two dynamical light degenerate quarks and a dynamical strange quark simulated with the domain wall fermion action. Results are obtained at lattice spacings $a = 0.114$ fm and $a=0.084$ fm, with corresponding pion masses of $330$ MeV and $297$ MeV, respectively. High statistics measurements are achieved by utilizing the coherent sink technique. The dominant electromagnetic dipole form factor, the axial form factors and the pseudo-scalar coupling are extracted to a good accuracy. This allows the investigation of the non-diagonal Goldberger-Treiman relation. Particular emphasis is given on the extraction of the sub-dominant electromagnetic quadrupole form factors and their ratio to the dominant dipole form factor, $R_{EM}$ and $R_{SM}$, measured in experiment.

hep-lat↗

arXiv2010

The electromagnetic form factors of the Omega in lattice QCD

We present results on the Omega baryon electromagnetic form factors using $N_f=2+1$ domain-wall fermion configurations for three pion masses in the range of about 350 to 300 MeV. We compare results obtained using domain wall fermions with those of a mixed-action (hybrid) approach, which combine domain wall valence quarks on staggered sea quarks, for a pion mass of about 350 MeV. We pay particular attention in the evaluation of the subdominant electric quadrupole form factor to sufficient accuracy to exclude a zero value, by constructing a sequential source that isolates it from the dominant form factors. The $Ω^-$ magnetic moment, $μ_{Ω^{-}}$, the electric charge and magnetic radius, $\langle r^{2}_{E0/M1} \rangle$, are extracted for these pion masses. The electric quadrupole moment is determined for the first time using dynamical quarks.

hep-lat↗

arXiv2009

N to Delta transition form factors with Nf=2+1 domain wall fermions

The electromagnetic, axial and pseudoscalar nucleon to Delta form factors are calculated using dynamical domain wall fermions at a lattice spacing of a = 0.114 fm on a lattice of spatial size 2.74 fm and pion mass of 331 MeV. Pion pole dominance and the Goldberger-Treiman relations are examined.

hep-lat↗

arXiv2009

Omega baryon electromagnetic form factors from lattice QCD

We present results on the Omega baryon electromagnetic form factors using N_f= 2 + 1 dynamical domain-wall fermion configurations corresponding to a pion mass of about 330 MeV. We construct appropriate sequential sources for the determination of the two dominant form factors GE0 and GM1 as well as a sequential source that isolates the subdominant electric quadrupole form factor GE2. We calculate the Omega baryon magnetic moment, mu_omega, and electric charge radius, ^2, and compare to experiment, for the case of mu_omega, and to other lattice calculations.

hep-lat↗

arXiv2001

The Critical Hopping Parameter in O(a) improved Lattice QCD

We calculate the critical value of the hopping parameter, $κ_c$, in O(a) improved Lattice QCD, to two loops in perturbation theory. We employ the Sheikholeslami-Wohlert (clover) improved action for Wilson fermions. The quantity which we study is a typical case of a vacuum expectation value resulting in an additive renormalization; as such, it is characterized by a power (linear) divergence in the lattice spacing, and its calculation lies at the limits of applicability of perturbation theory. The dependence of our results on the number of colors $N$, the number of fermionic flavors $N_f$, and the clover parameter $c_{SW}$, is shown explicitly. We compare our results to non perturbative evaluations of $κ_c$ coming from Monte Carlo simulations.

hep-lat↗

arXiv2001

O(a) improved QCD: The 3-loop beta-function, and the critical hopping parameter

We calculate the 3-loop bare $β$-function of QCD, formulated on the lattice with the clover fermionic action. The dependence of our result on the number of colors $N$, the number of fermionic flavors $N_f$, and the clover parameter $c_{SW}$, is shown explicitly. A direct outcome of our calculation is the two-loop relation between the bare coupling constant $g_0$ and the one renormalized in the MS-bar scheme. Further, we can immediately derive the three-loop correction to the relation between the lattice $Λ$-parameter and $g_0$, which turns out to be very pronounced. We also calculate the critical value of the hopping parameter, $κ_c$, in the clover action, to two loops in perturbation theory. This quantity is an additive renormalization; as such, it exhibits a linear divergence in the lattice spacing. We compare our results to non perturbative evaluations of $κ_c$ coming from MC simulations.

hep-lat↗