Speaker
Description
The very strong electromagnetic fields found in PbPb collisions at the LHC make it effectively a photon-photon collider. Observation of the light-by-light scattering process, $\gamma\gamma \to \gamma\gamma$, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV recorded in 2018 by the CMS experiment is reported. The exclusive production of dielectrons is used as a process of similar production mechanism and experimental signature to control both the theoretical modeling and the reconstruction of low energy electromagnetic objects in the detector. Differential distributions in diphoton p$_{T}$, rapidity, mass, and acoplanarity are reported. The m$_{\gamma\gamma}$ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the $\gamma\gamma \to a \to \gamma\gamma$ process, down to 5 GeV.
| Contribution type | Contributed Talk |
|---|---|
| Track | Electroweak Probes |
| Collaboration (if applicable) | CMS |
