Mean transverse mass of hadrons in proton-proton reactions

TL;DR

This study uses the UrQMD model to predict a nonmonotonous energy dependence of the mean transverse mass for certain hadrons in proton-proton collisions, highlighting the roles of baryonic resonances and strings.

Contribution

It introduces a novel prediction of nonmonotonous $ angle m_T angle$ dependence in $p+p$ reactions, linking it to baryonic resonance and string dynamics, awaiting experimental verification.

Findings

Predicted maximum of $ angle m_T angle$ at 5-8 GeV for $ ext{π}^+$, $p$, $K^+$, and $ ext{Λ}$.

No nonmonotonous dependence for $ ext{π}^-$, $K^-$, and antiprotons.

Results suggest specific hadron production mechanisms influence transverse mass energy dependence.

Abstract

An energy dependence of the mean transverse mass $\langle m_T\rangle$ at mid-rapidity in proton-proton ($p+p$) reactions is studied within the ultra-relativistic quantum molecular dynamics (UrQMD). The UrQMD model predicts a nonmonotonous dependence of $\langle m_T\rangle$ on collision energy for several hadron species: for $\pi^+$, $p$, $K^+$, and $\Lambda$ the mean transverse mass has a maximum at the center of mass energy region $5\le \sqrt{s}\le 8$ GeV. These results are a consequence of an interplay of two contributions: 1) excitations and decays of the baryonic resonances $N^*$ and $\Delta$; 2) excitations and decays of the baryonic strings. The UrQMD results do not show any nonmonotonous dependence of $\langle m_T\rangle$ on $\sqrt{s}$ for $\pi^-$, $K^{-}$, and antiprotons. Whether a nonmonotonous dependence of $\langle m_T\rangle$ at mid-rapidity on the collision energy for $\pi^+$, $p$, $K^+$, and $\Lambda$ is relevant for real $p+p$ interactions will be soon checked experimentally by the NA61/SHINE Collaboration.