# paper review

## Lazy photons at the LHC

Title: “Search for long-lived particles using delayed photons in proton-proton collisions at $\sqrt{s}$ = 13 TeV” Author: CMS Collaboration Reference: https://arxiv.org/abs/1909.06166 (submitted to Phys. Rev. D) (Originally published on Particle Bites) An interesting group of searches for new physics at the LHC that has been gaining more attention in recent years relies on reconstructing and identifying physics objects that are displaced from the original proton-proton collision point. Several theoretical models predict such signatures due to the decay of long-lived particles (LLPs) that are produced in these collisions.

## When light and light collide

Title: “Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC” Author: ATLAS Collaboration Reference: doi:10.1038/nphys4208 (Originally published on Particle Bites) According to classical wave theory, two electromagnetic waves that happen to cross each other in space will not interfere. In fact, this is a crucial feature of the conventional definition of a wave, in contrast to a corpuscle or particle: when two waves meet, they briefly occupy the same space at the same time, each without “knowing” about the other’s existence.