Search for an axion-like particle with forward proton scattering in association with photon pairs at ATLAS

Abstract

A search for forward proton scattering in association with light-by-light scattering mediated by an axion-like particle is presented, using the ATLAS Forward Proton spectrometer to detect scattered protons and the central ATLAS detector to detect pairs of outgoing photons. Proton-proton collision data recorded in 2017 at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV were analysed, corresponding to an integrated luminosity of 14.6 fb−1. A total of 441 candidate events were selected. A search was made for a narrow resonance in the diphoton mass distribution, corresponding to an axion-like particle (ALP) with mass in the range 150–1600 GeV. No excess is observed above a smooth background. Upper limits on the production cross section of a narrow resonance are set as a function of the mass, and are interpreted as upper limits on the ALP production coupling constant, assuming 100% decay branching ratio into a photon pair. The inferred upper limit on the coupling constant is in the range 0.04–0.09 TeV−1 at 95% confidence level.

Overview of ATLAS forward proton detectors: status, performance, and new physics results

“…ToF performance in high-⟨𝜇⟩ runs and over time is under study. A recent search for axion-like particles was performed in the diphoton mass spectrum in conjunction with a forward proton tag in AFP [18]. Results were consistent with the background-only hypothesis and used to set 95 % confidence level limits on the ALP to diphoton cross-section and coupling constant.…”

“…Some extensions to the Standard Model predict the possibility of heavy axion-like particles (ALPs), so-called in that they are pseudo-scalars that couple to two photons. A narrow resonance search in the diphoton mass spectrum in conjunction with a single or double proton tag measured in AFP was recently performed in the 2017 high-pileup proton-proton dataset at centre-of-mass energy of 13 TeV [18]. The available luminosity was 14.6 fb −1 after ATLAS and AFP quality requirements were applied.…”

Overview of searches, prospects, what are we missing?

“…One of the searches for ALPs is through their interactions with photons. Recently ATLAS and CMS have measured the light by light scattering that can be interpreted in terms of an ALP mediator [12,13]. Their results allow to constrain the axion coupling constant to be 𝑓 −1 < 10 −1 TeV −1 in a range of axion masses 200 GeV < 𝑚 ALP < 1600 GeV.…”

ATLAS Forward Proton Time-of-Flight detectors: status, performance and new physics results

“…[4] about the exclusive dilepton measurement) and beyond SM processes (see Ref. [5] about the axion-like particle searches in exclusive diphoton measurement). Potential to measure other (semi)exclusive final states is large, see Ref [6][7][8][9][10][11][12].…”