Improved determination of (d)over-bar(x) - (u)over-bar(x) flavor asymmetry in the proton by data from the BONuS experiment at JLAB and using an approach by Brodsky, Hoyer, Peterson, and Sakai

摘要

The experimental data taken from both Drell- Yan and deep- inelastic scattering experiments suggest a sign change in (d) over bar (x) - (u) over bar (x) flavor asymmetry in the proton at large values of momentum fraction x. In this work, we present a phenomenological study of (d) over bar (x) - (u) over bar (x) flavor asymmetry. First, we extract the (d) over bar (x) -(u) over bar (x) distribution using the more recent data from the BONuS experiment at Jefferson Lab on the ratio of neutron to proton structure functions, F-2(n)/F-2(p), and show that it undergoes a sign change and becomes negative at large values of momentum fraction x, as expected. The stability and reliability of our obtained results are examined by including target mass corrections as well as higher twist terms which are particularly important in the large-x region at low Q(2). Then, we calculate the (d) over bar (x)-(u) over bar (x) distribution using the Brodsky-Hoyer-Peterson-Sakai model and show that if one chooses a mass for the down quark smaller than the one for the up quark it leads to a better description for the Fermilab E866 data. To prove this claim, we determine the masses of down and up sea quarks by fitting to the available and up-to-date experimental data for the (d) over bar (x)-(u) over bar (x)distribution. In this respect, unlike the previous theoretical studies, we have shown that this distribution has a sign change at x 0.3 after evolution to the scale of available experimental data.