# Collectivity in pp from resummed interference effects?

## TL;DR

This paper presents a resummed theoretical model showing that azimuthal asymmetries in hadronic collisions can produce persistent higher order flow cumulants through quantum interference effects, without requiring final state interactions.

## Contribution

It introduces the first resummed calculation of all powers of interference effects in multi-particle production, revealing the potential for sustained higher order flow signals in simple quantum interference models.

## Key findings

- Higher order flow cumulants decrease very mildly with increasing order.
- Non-vanishing higher order cumulants can exist without final state interactions.
- Quantum interference effects alone can generate persistent azimuthal asymmetries.

## Abstract

Azimuthal asymmetries $v_n$ in the soft transverse momentum spectra of hadronic collisions can result as a consequence of quantum interference and color flow which translates spatial anisotropies into momentum anisotropies via multipole radiation patterns. Here, we analyze to what extent these effects result in signal strengths $v_n\lbrace 2s\rbrace$ that can persist in higher order $(2s)$ cumulants. In a simple model of soft multi-particle production with quantum interference effects in which $m$ particles are emitted from $N$ sources and in which interference contributions appear naturally ordered in inverse powers of the adjoint color trace, $1/(N_c^2-1)$, we provide the first resummed calculation of all powers of $m^2/(N_c^2-1)$. This allows one to determine all higher order flow cumulants $v_n\lbrace 2s\rbrace$ with the same parametric accuracy. For a phenomenologically relevant range of $N$ sources emitting $m$ particles, we find that the even flow coefficients $v_n\lbrace 2s\rbrace$ decrease very mildly with increasing cumulants. This provides a proof of principle that non-vanishing higher order cumulants $v_n\lbrace 2s\rbrace$ can persist in systems that exhibit neither final state interactions nor phenomena related to high (saturated) initial parton densities.