ALPtraum: ALP production in proton beam dump experiments

TL;DR

This paper develops a method to accurately calculate axion-like particle production in proton beam dump experiments and reanalyzes past data to set new constraints, highlighting future experimental opportunities.

Contribution

It introduces a simplified yet precise approach for ALP production calculations in proton beam dumps and derives novel constraints from existing experiments.

Findings

Reanalysis of past experiments yields new ALP constraints.

NA62 could explore previously inaccessible parameter space.

Future experiments like SHiP have promising detection prospects.

Abstract

With their high beam energy and intensity, existing and near-future proton beam dumps provide an excellent opportunity to search for new very weakly coupled particles in the MeV to GeV mass range. One particularly interesting example is a so-called axion-like particle (ALP), i.e. a pseudoscalar coupled to two photons. The challenge in proton beam dumps is to reliably calculate the production of the new particles from the interactions of two composite objects, the proton and the target atoms. In this work we argue that Primakoff production of ALPs proceeds in a momentum range where production rates and angular distributions can be determined to sufficient precision using simple electromagnetic form factors. Reanalysing past proton beam dump experiments for this production channel, we derive novel constraints on the parameter space for ALPs. We show that the NA62 experiment at CERN could probe unexplored parameter space by running in 'dump mode' for a few days and discuss opportunities for future experiments such as SHiP.