Parton Distribution Functions with Twisted Mass Fermions

TL;DR

This paper reports on a lattice QCD calculation of the pion's parton distribution function moment using twisted mass fermions, demonstrating reliable results at small meson masses and confirming expected scaling behavior.

Contribution

It introduces a novel lattice calculation of < x > for pions with twisted mass fermions at small masses, enabling continuum extrapolation and improved understanding of parton distributions.

Findings

< x > can be computed at pseudoscalar masses as low as 250 MeV

Scaling behavior consistent with O(a^2) expectations

Reliable continuum results obtained at small meson masses

Abstract

We present a first Wilson twisted mass fermion calculation of the matrix element between pion states of the twist-2 operator, which is related to the the lowest moment < x > of the valence quark parton distribution function in a pion. Using Wilson twisted mass fermions in the quenched approximation we demonstrate that < x > can be computed at small pseudoscalar meson masses down to values of order 250 MeV. We investigate the scaling behaviour of this physically important quantity by applying two definitions of the critical mass and observe a scaling compatible with the expected O(a^2) behaviour in both cases. A combined continuum extrapolation allows to obtain reliable results for < x > at very small pseudoscalar meson masses, which previously could not be explored by lattice QCD simulations.