Measurement of the forward-backward asymmetry of $Λ$ and $\barΛ$ production in $p \bar{p}$ collisions

Abstract

We study $Λ$ and $\barΛ$ production asymmetries in $p \bar{p} \rightarrow Λ(\barΛ) X$, $p \bar{p} \rightarrow J/ψΛ(\barΛ) X$, and $p \bar{p} \rightarrow μ^\pm Λ(\barΛ) X$ events recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV. We find an excess of $Λ$'s ($\barΛ$'s) produced in the proton (antiproton) direction. This forward-backward asymmetry is measured as a function of rapidity. We confirm that the $\barΛ/Λ$ production ratio, measured by several experiments with various targets and a wide range of energies, is a universal function of "rapidity loss", i.e., the rapidity difference of the beam proton and the lambda.