# Physics at the LHC and beyond

from September 29, 2015 to October 2, 2015
DESY Hamburg
Europe/Berlin timezone
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# Contribution

DESY Hamburg - Seminar room 4a

# Quark isospin asymmetry at small and large x

## Speakers

• Sergey ALEKHIN

## Abstract content

We discuss an improved determination of the up- and down-quark distributions in the proton using recent data on charged lepton asymmetries from $W^\pm$ gauge-boson production at the LHC and Tevatron. The analysis is performed in the framework of a global fit of parton distribution functions. The results are consistent with a non-zero iso-spin asymmetry of the sea, $x(\bar d - \bar u)$, at small values of Bjorken $x\sim 10^{-3}$ indicating a delayed onset of the Regge asymptotics of a vanishing $(\bar d - \bar u)$-asymmetry at small-$x$.