Midrapidity antiproton-to-proton ratio in pp collisions at $\sqrt{s} = 0.9$ and $7$ TeV measured by the ALICE experiment

TL;DR

This paper reports measurements of the antiproton-to-proton ratio in proton-proton collisions at 0.9 and 7 TeV, showing the ratio approaches unity at higher energy and constrains models of baryon-number transfer.

Contribution

First measurement of the antiproton-to-proton ratio at these energies in the specified kinematic range, providing new data to test baryon-number transport models.

Findings

Ratio increases from 0.957 at 0.9 TeV to 0.991 at 7 TeV

Ratio is independent of rapidity and transverse momentum

Results support conventional baryon-number transport models

Abstract

The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at $\sqrt{s} = 0.9$ and $7$ TeV during the initial running periods of the Large Hadron Collider(LHC). The measurement covers the transverse momentum interval $0.45 < p_{\rm{t}} < 1.05$ GeV/$c$ and rapidity $|y| < 0.5$. The ratio is measured to be $R_{|y| < 0.5} = 0.957 \pm 0.006 (stat.) \pm 0.014 (syst.)$ at $0.9$ TeV and $R_{|y| < 0.5} = 0.991 \pm 0.005 (stat.) \pm 0.014 (syst.)$ at $7$ TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.