“School of Particles”
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Paper IPM / Particles / 15098  


Abstract:  
The experimental data taken from both DrellYan and deepinelastic scattering (DIS) experiments
suggest a signchange in ―d(x) − ―u(x) flavor asymmetry in the proton at large values of momentum fraction x.
In this work, we present a phenomenological study of ―d(x) − ―u(x) flavor asymmetry.
First, we extract the ―d(x)−―u(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 singchange and becomes negative at large values of momentum fraction x, as expected.
The stability and reliability of our obtained results have been examined by including target mass corrections (TMCs) as well as higher twist (HT) terms which are particularly important
at the largex region at low Q^{2}.
Then, we calculate the ―d(x) − ―u(x) distribution
using the Brodsky, Hoyer, Peterson, and Sakai (BHPS) 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. In order to prove this claim, we determine the masses of down and up sea quarks by fitting to the available and uptodate experimental data for the ―d(x)−―u(x) distribution. In this respect, unlike the previous performed theoretical studies, we have shown that this distribution has a signchange at x > 0.3 after evolution to the scale of available experimental data.
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