Insight into particle production mechanisms via angular correlations of identified particles measured with ALICE in pp collisions at $\mathbf{\sqrt{{\textit s}}}=7$ TeV

TL;DR

This study analyzes two-particle angular correlations of identified particles in proton-proton collisions at 7 TeV to explore particle production mechanisms, revealing differences between baryons and mesons and challenging existing models.

Contribution

It provides new measurements of identified particle correlations at low transverse momentum in pp collisions, highlighting discrepancies with current Monte Carlo models.

Findings

Meson correlations show a peak consistent with jet fragmentation.

Baryon pairs with same baryon number exhibit near-side anti-correlation.

Current models do not reproduce the observed baryon correlation structures.

Abstract

Two-particle correlations as a function of $\Delta\eta$ and $\Delta\varphi$ are used in all collision systems to study a wide range of physical phenomena. Examples include the collective behavior of the quark-gluon plasma medium, jets, quantum statistics or Coulomb effects, conservation laws, and resonance decays. In this work, measurements of the correlations of identified particles and their antiparticles (for $\pi$, K, p, $\Lambda$) are reported in pp collisions at $\sqrt{s}=7$ TeV at low transverse momenta. The analysis reveals differences in particle production between baryons and mesons. The correlation functions for mesons exhibit the expected peak dominated by effects of mini-jet fragmentation and are reproduced well by general purpose Monte Carlo generators. For baryon pairs where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak; our experimental observation present a challenge to the contemporary models (PYTHIA, PHOJET). This effect is further interpreted in the context of baryon production mechanisms in the fragmentation processes.