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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

The collaboration
JHEP 03 (2021) 243, 2021.

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 $\sqrt{s_\mathrm{NN}}=5.02$ TeV. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy $E_{\mathrm{T}}^{\gamma} > 2.5$ GeV, pseudorapidity $|\eta_{\gamma}| < 2.37$, diphoton invariant mass $m_{\gamma\gamma} > 5$ 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.

• #### Differential diphoton invariant mass

Data from arXiv:2008.05355 Figure 8

10.17182/hepdata.95747.v1/t1

Measured differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for diphoton...

• #### Differential normalised diphoton invariant mass

Data from arXiv:2008.05355 Figure 11

10.17182/hepdata.95747.v1/t2

Measured normalised differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for...

• #### Differential diphoton $|cos(\theta*)|$

Data from arXiv:2008.05355 Figure 8

10.17182/hepdata.95747.v1/t3

Measured differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for diphoton...

• #### Differential normalised diphoton $|cos(\theta*)|$

Data from arXiv:2008.05355 Figure 11

10.17182/hepdata.95747.v1/t4

Measured normalised differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for...

• #### Differential average photon transverse momentum

Data from arXiv:2008.05355 Figure 8

10.17182/hepdata.95747.v1/t5

Measured normalised differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for...

• #### Differential normalised average photon transverse momentum

Data from arXiv:2008.05355 Figure 11

10.17182/hepdata.95747.v1/t6

Measured normalised differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for...

• #### Differential diphoton rapidity

Data from arXiv:2008.05355 Figure 8

10.17182/hepdata.95747.v1/t7

Measured differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for diphoton...

• #### Differential normalised diphoton rapidity

Data from arXiv:2008.05355 Figure 11

10.17182/hepdata.95747.v1/t8

Measured normalised differential fiducial cross sections of $\gamma\gamma \rightarrow \gamma\gamma$ production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for...

• #### The 95% CL upper limit on the ALP cross section

Data from arXiv:2008.05355 Figure 9

10.17182/hepdata.95747.v1/t9

The 95% CL upper limit on the ALP cross section $\sigma_{\gamma\gamma\rightarrow a \rightarrow\gamma\gamma}$ for the $\gamma\gamma\rightarrow a \rightarrow \gamma\gamma$ process...

• #### The 95% CL upper limit on the ALP coupling $1/\Lambda_{a}$

Data from arXiv:2008.05355 Figure 9

10.17182/hepdata.95747.v1/t10

The 95% CL upper limit on the ALP coupling $1/\Lambda_{a}$ for the $\gamma\gamma\rightarrow a \rightarrow \gamma\gamma$ process as a function...

• #### crossection

Data from arXiv:2008.05355

10.17182/hepdata.95747.v1/t11

Fiducial cross section for light-by-light scattering