Triple parton scatterings in proton-nucleus collisions at high energies

TL;DR

This paper derives a general formula for triple parton scattering cross sections in high-energy proton-nucleus collisions, estimates their magnitudes at LHC and FCC energies, and highlights their significance in cosmic-ray interactions.

Contribution

It introduces a generic expression for TPS cross sections in pA collisions, incorporating the proton's transverse parton profile, and provides quantitative estimates for heavy quark production at collider energies.

Findings

TPS cross sections are enhanced by a factor of about 2000 in pPb compared to proton-nucleon collisions.

Approximately 10% of pPb events at 8.8 TeV produce three charm pairs in separate interactions.

TPS cross sections for triple-J/ψ and triple-bb are on the order of 1-10 mb at 63 TeV.

Abstract

A generic expression to compute triple parton scattering (TPS) cross sections in high-energy proton-nucleus (pA) collisions is derived as a function of the corresponding single-parton cross sections and an effective parameter encoding the transverse parton profile of the proton. The TPS cross sections are enhanced by a factor of $9\,A\approx 2000$ in pPb compared to those in proton-nucleon collisions at the same center-of-mass energy. Estimates for triple charm ($c\overline{c}$) and bottom ($b\overline{b}$) production in pPb collisions at LHC and FCC energies are presented based on next-to-next-to-leading order (NNLO) calculations for $c\overline{c}, b\overline{b}$ single-parton cross sections. At $\sqrt{s_{NN}} = 8.8$ TeV, about 10% of the pPb events have three $c\overline{c}$ pairs produced in separate partonic interactions. At $\sqrt{s_{NN}} = 63$ TeV, the pPb cross sections for triple-J$/\psi$ and triple-$b\overline{b}$ are ${\cal O}$(1--10 mb). In the most energetic cosmic-ray collisions observed on earth, TPS $c\overline{c}$-pair cross sections equal the total p-Air inelastic cross section.