Light in the beam dump. Axion-Like Particle production from decay photons in proton beam-dumps

Abstract

The exploration of long-lived particles in the MeV-GeV region is a formidable task but it may provide us a unique access to dark sectors. Fixed-target facilities with sufficiently energetic and intense proton beams are an ideal tool for this challenge. In this work we show that the production rate of Axion-Like-Particles (ALPs) coupled pre-dominantly to photons receives a significant contribution from daughter-photons of secondary π 0 and η mesons created in the proton shower. We carefully compare the PYTHIA simulated spectra of such secondaries to experimental literature, compute the ALP flux from the Primakoff conversion of these photons, and finally revisit existing limits on ALPs and update the prospects for a set of existing and future searches. Our results show that taking this production mechanism into account significantly enhances the sensitivity compared to previous studies based on coherent ALP production in primary proton-nucleus interactions.

ALP inflation and Big Bang on Earth

“…First, the ALP decays perturbatively into photons with the rate (29), and the produced photons form thermal plasma. The photons in thermal plasma acquire a thermal mass of order eT , and once it exceeds half the ALP mass, the perturbative decay becomes kinematically forbidden.…”

“…The gray region is excluded by experiments and SN1987A. Both the sensitivity reach and excluded regions are adopted from Ref [29]…”

Implications of the dark axion portal for SHiP and FASER and the advantages of monophoton signals

“…NA62 [21,60,61] is a charged kaon decay experiment using the 400 GeV proton beam at the CERN SPS. We take the decay volume to be a 135 meter long cylinder beginning 82 meters downstream of the target with a 1 meter radius.…”

Nonresonant Searches for Axionlike Particles at the LHC

“…ALPs are being searched at high-energy colliders [27][28][29][30][31][32][33][34][35][36][37], beam dump experiments [38,39], via their effects in flavor physics [40][41][42][43][44][45], and through their astrophysical signatures [46][47][48][49] (see Ref. [50] for a review).…”