# Correlations, multiplicity distributions, and the ridge in pp and p-Pb collisions

## TL;DR

This paper presents measurements of particle multiplicity and correlations in high-energy pp and p-Pb collisions, revealing long-range structures similar to those in heavy-ion collisions, aiding model tuning and baseline establishment.

## Contribution

It provides detailed experimental data on multiplicity distributions and two-particle correlations in small collision systems at 13 TeV, highlighting phenomena akin to heavy-ion collisions.

## Key findings

- Charged-particle multiplicity densities measured at 13 TeV
- Observation of long-range pseudorapidity correlations in p-Pb
- Baseline data for heavy-ion collision studies

## Abstract

Measurements made by the ALICE Collaboration of single- and two-particle distributions in high-energy pp and p-Pb collisions are used to characterize the interactions in small collision systems, tune models of particle production in QCD, and serve as a baseline for heavy-ion observables. The measurements of charged-particle multiplicity density, $\langle dN_{ch}/d\eta\rangle$, and multiplicity distributions are shown in pp and p-Pb collisions, including data from the top center-of-mass energy achieved at the Large Hadron Collider (LHC), $\sqrt{s}$ = 13 TeV. Two-particle angular correlations in p-Pb collisions are studied in detail to investigate long-range correlations in pseudorapidity which are reminiscent of structures previously thought unique to heavy-ion collisions.