Hadron multiplicity fluctuations in perturbative QCD

TL;DR

This paper investigates hadron multiplicity fluctuations in high-energy processes, comparing QCD predictions with experimental data from $e^+e^-$ annihilation and LHC jets, focusing on high-multiplicity events and related puzzles.

Contribution

It provides a detailed analysis of multiplicity fluctuations in perturbative QCD and explores the common origins of high-multiplicity puzzles in different high-energy processes.

Findings

QCD predictions align with observed multiplicity fluctuation patterns

Identification of common origins for high-multiplicity puzzles

Insights into fluctuations in high-$p_t$ jets and $e^+e^-$ annihilation

Abstract

We examine hadron multiplicity fluctuations in hard processes and confront analytic QCD predictions with the pattern of multiplicity fluctuations observed in $e^+e^-$ annihilation and high-$p_t$ jets produced in $pp$ collisions at the LHC. Special emphasis is placed on high-multiplicity fluctuations in jets. Selecting events with hadronic multiplicity exceeding the average value by a factor of 3 or more in various processes has been a source of conundrums for many years. We discuss two recent high-multiplicity puzzles and attempt to reveal their common origin.