Measurement of light-by-light scattering and search for axion-like particles with 2.2 nb−1 of Pb+Pb data with the ATLAS detector

Abstract

This paper describes a measurement of light-by-light scattering based on Pb+Pb collision data recorded by the ATLAS experiment during Run 2 of the LHC. The study uses 2.2 nb−1 of integrated luminosity collected in 2015 and 2018 at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy $$ {E}_{\mathrm{T}}^{\gamma } $$ E T γ > 2.5 GeV, pseudorapidity |ηγ| < 2.37, diphoton invariant mass mγγ> 5 GeV, and with small diphoton transverse momentum and diphoton acoplanarity. The integrated and differential fiducial cross sections are measured and compared with theoretical predictions. The diphoton invariant mass distribution is used to set limits on the production of axion-like particles. This result provides the most stringent limits to date on axion-like particle production for masses in the range 6–100 GeV. Cross sections above 2 to 70 nb are excluded at the 95% CL in that mass interval.

Elastic photon-initiated production at the LHC: the role of hadron-hadron interactions

“…The magnitude of this in particular becomes larger than the original N is some regions of Q 2 , in particular in the lead case. This effect is due to the modulating sign in the Fourier transform (21) and the equivalent expression without the b i⊥ < R A cut, which corresponds to the full N case. This may appear at first to be counterintuitive, given we are explicitly removing a contribution from the b i⊥ < R A region, but the only requirement this gives is that cross section integrated over b i⊥ , or equivalently q ⊥ in transverse momentum space, is reduced after we impose this cut.…”

“…In heavy ion collisions, the flux of photons emitted by the colliding hadrons is enhanced by ∼ Z 2 for each beam in comparison to the proton case and hence the rate for PI production of lower mass objects can be enhanced. In PbPb collisions, data on light-by-light scattering, as well as corresponding constraints on axion-like particles (ALPs), have been presented by both ATLAS [20,21] and CMS [22], while measurements of dilepton production in the continuum region have been presented at the LHC by ALICE [23] and ATLAS [24].…”

Leading logs in QCD axion effective field theory

“…Importantly, these light axions may constitute a fraction or the totality of the dark matter of the Universe [16][17][18], in which case a plethora of direct [9,[19][20][21][22][23][24][25][26][27][28][29] (see [30] for a recent overview) and indirect [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] detection experiments could be able to detect them. Axions at the heavier end 2 of the currently accessible mass range are best studied at the LHC [50][51][52][53][54][55][56][57][58] and B-factories [59][60][61][62][63][64][65]. For the intermediate regime between the MeV and the GeV scales, reactors [66], ra...…”

Axion-Like Particles at the ILC Giga-Z

“…The presence of an ALP which couples to photons would enhance the light by light scattering (γγ → γγ) cross section. Measurements of this cross section at CMS and ATLAS place constraints on Axion-Like Particles coupling to photons from 5 to 100 GeV down to a few ×10 −4 GeV [15,16,18], competitive with LEP and other LHC searches over this mass range.…”