A Comprehensive Study of Energy Dependence of Particle Ratios in $pp$ Collisions from SPS to LHC Energies

TL;DR

This study analyzes the energy dependence of kaon to pion yield ratios in proton-proton collisions across a wide energy range, comparing experimental data with multiple models to understand underlying physics mechanisms.

Contribution

It provides a comprehensive comparison of model predictions with experimental data on particle ratios over a broad energy spectrum, highlighting the presence of a horn structure at lower energies.

Findings

Horn-like structure in $K/\pi$ ratio at SPS energies

Models predict saturation of yield ratios at high energies

EPOS-LHC and HIJING models align well with experimental data

Abstract

A comprehensive study has been performed to estimate the kaon to pion ($K^\pm$/$\pi^\pm$) yield ratio and total kaon to total pion ($K$/$\pi$) yield ratio as a function of centre of mass energy in $pp$ collisions at different energies i.e., \sqrts~= 6.3, 17.3, 62.4, 200, 900 GeV, 2.76 TeV, 7 TeV, 13 TeV and 14 TeV using EPOS1.99, EPOS-LHC, HIJING, QGSJETII-03 and Sibyll2.3d model simulations. NA61/SHINE experiment reported that $K^+/\pi^+$ yield ratio exhibits rapid changes at the SPS energy range. A horn like structure appears in $K/\pi$ yield ratio as a function of collision energy. Significant presence of horn in $K^+$/$\pi^+$ and $K^-$/$\pi^-$ yield ratio is suggested by experimental data at lower energies, which is confirmed by HIJING and EPOS-LHC models. A smooth increase in $K/\pi$ yield ratio is also seen at higher energies. The model simulations predict similar increase in yield ratio with increasing energies. On the basis of previous available measurements, we also study model predictions of these yield ratios at \sqrts~= 13 and 14 TeV where no data is available. Almost all models suggest a saturation in the yield ratio within statistical fluctuations at these energies except EPOS1.99 and QGSJETII-03 which slightly over predict the yield ratio. These systematic comparisons are helpful to apply possible constraints on various hadronic event generators to significantly improve the predictions of Standard Model physics as well as for the understanding of underlying physics mechanisms in high energy collisions.