Measurement of prompt hadron production ratios in $pp$ collisions at $\sqrt{s} = $ 0.9 and 7 TeV

TL;DR

This paper measures various charged-particle production ratios in proton-proton collisions at different energies using the LHCb detector, comparing results to Monte Carlo predictions and exploring baryon transport models.

Contribution

It provides new measurements of hadron production ratios at 0.9 and 7 TeV, testing and constraining theoretical models and Monte Carlo generators.

Findings

None of the Monte Carlo models fully describe the data.

The $ar{p}/p$ ratio as a function of rapidity loss constrains baryon transport models.

Production ratios vary with transverse momentum and pseudorapidity.

Abstract

The charged-particle production ratios $\bar{p}/p$, $K^-/K^+$, $\pi^-/\pi^+$, $(p + \bar{p})/(\pi^+ + \pi^-)$, $(K^+ + K^-)/(\pi^+ + \pi^-)$ and $(p + \bar{p})/(K^+ + K^-)$ are measured with the LHCb detector using $0.3 {\rm nb^{-1}}$ of $pp$ collisions delivered by the LHC at $\sqrt{s} = 0.9$ TeV and $1.8 {\rm nb^{-1}}$ at $\sqrt{s} = 7$ TeV. The measurements are performed as a function of transverse momentum $p_{\rm T}$ and pseudorapidity $\eta$. The production ratios are compared to the predictions of several Monte Carlo generator settings, none of which are able to describe adequately all observables. The ratio $\bar{p}/p$ is also considered as a function of rapidity loss, $\Delta y \equiv y_{\rm beam} - y$, and is used to constrain models of baryon transport.