Martha Constantinou

Non-perturbative renormalization of quark bilinear operators with N f = 2 (tmQCD) Wilson fermions and the tree-level improved gauge action

We present results for the renormalization constants of bilinear quark operators obtained by using the tree-level Symanzik improved gauge action and the Nf = 2 twisted mass fermion action at maximal twist, which guarantees automatic

Disconnected quark loop contributions to nucleon observables in lattice QCD

\mathcal{O}

Nucleon form factors and moments of generalized parton distributions using

(a)-improvement. Our results are also relevant for the corresponding standard (un-twisted) Wilson fermionic action since the two actions only differ, in the massless limit, by a chiral rotation of the quark fields. The scale-independent renormalization constants ZV, ZA and the ratio ZP/ZS have been computed using the RI-MOMapproach, as well as other alternative methods. For ZA and ZP/ZS, the latter are based on both standard twisted mass and Osterwalder-Seiler fermions, while for ZV a Ward Identity has been used. The quark field renormalization constant Zq and the scale dependent renormalization constants ZS, ZP and ZT are determined in the RI-MOM scheme. Leading discretization effects of

twisted mass fermions

\mathcal{O}\left( {{g^2}{a^2}} \right)

Moments of nucleon generalized parton distributions from lattice QCD

, evaluated in one-loop perturbation theory, are explicitly subtracted from the RI-MOM estimates.

Magnetic susceptibility of QCD at zero and at finite temperature from the lattice

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=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.