[Jlab-seminars] Theory Center Seminar

[Mary Fox]

Theory Center Seminar Wed., Nov. 30, 2016 2:00 p.m. (coffee at 1:45 
p.m.) CEBAF Center, Room L102 Fernanda Steffens DESY *Direct Calculation 
of PDFs in Lattice QCD* Parton distributions are usually defined as 
light-cone correlations in the nucleon. Until recently, however, it was 
not possible to calculate the distributions in lattice QCD because, 
unlike spatial correlations, one cannot simulate light-cone correlations 
in a Euclidian lattice. In 2013, Ji proposed a way to circumvent this 
restriction, through the use of quark quasi-distributions which are 
defined as purely spatial correlations. Although they are not the 
physical distributions, the quark quasi-distributions are related to the 
quark distributions through a perturbative calculation. Within this 
procedure, a direct calculation of the distributions in lattice QCD 
became a possibility, and we present here a high statistics analysis of 
the x-dependence of the bare unpolarized, helicity and transversity 
iso-vector parton distribution functions (PDFs) from lattice 
calculations employing (maximally) twistedmass fermions. The 
x-dependence of the calculated PDFs resembles those of the 
phenomenological parameterizations, a feature that makes this approach 
promising despite the lack of a full renormalization program for them.

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