A two-component model of hadron production applied to $\bf p_t$ spectra from 5 TeV and 13 TeV $\bf p$-$\bf p$ collisions at the large hadron collider

TL;DR

This study applies a two-component model to high-statistics $p_t$ spectra from 5 TeV and 13 TeV proton-proton collisions at the LHC, clarifying jet contributions and questioning the link to collective phenomena.

Contribution

It demonstrates the effectiveness of the two-component model in separating jet and nonjet contributions in $p$-$p$ spectra across different event selections and energies.

Findings

Jet contributions are accurately separated from nonjet components.

Spherocity has little relation to jet production.

Data are consistent with conventional QCD jet production expectations.

Abstract

The ALICE collaboration at the large hadron collider (LHC) recently reported high-statistics $p_t$ spectrum data from 5 TeV and 13 TeV $p$-$p$ collisions. Particle data for each energy were partitioned into event classes based on the total yields within two disjoint pseudorapidity $\eta$ intervals denoted by acronyms V0M and SPD. For each energy the spectra resulting from the two selection methods were then compared to a minimum-bias INEL $> 0$ average over the entire event population. The nominal goal was determination of the role of jets in high-multiplicity $p$-$p$ collisions and especially the jet contribution to the low-$p_t$ parts of spectra. A related motivation was response to recent claims of "collective" behavior and other nominal indicators of quark-gluon plasma (QGP) formation in small collision systems. In the present study a two-component (soft + hard) model (TCM) of hadron production in $p$-$p$ collisions is applied to the ALICE spectrum data. As in previous TCM studies of a variety of A-B collision systems the jet and nonjet contributions to $p$-$p$ spectra are accurately separated over the entire $p_t$ acceptance. Distinction is maintained among spectrum normalizations, jet contributions to spectra and systematic biases resulting from V0M and SPD event selection. The statistical significance of data-model differences is established. The effect of {\em spherocity} (azimuthal asymmetry measure nominally sensitive to jet production) on ensemble-mean $p_t$ vs event multiplicity $n_{ch}$ is investigated and found to have little relation to jet production. The general results of the TCM analysis are as expected from a conventional QCD description of jet production in $p$-$p$ collisions.