Search for non-resonant new physics in high-mass diphoton events from pp collisions at $\sqrt{s}$ = 13 TeV with the CMS detector and highlights from HCAL upgrades

Results are presented from a search for non-resonant or broad signatures of beyond the standard model physics in the high-mass diphoton spectrum from proton-proton collisions at $\sqrt{s}$ = 13 TeV. The analysis uses data collected in 2016–2018 with the CMS detector at the LHC and corresponds to 138 fb$^{-1}$. Events with a diphoton invariant mass above 500 GeV are considered. A first-principles calculation of the standard model diphoton spectrum at next- to-next-to-leading order in perturbative quantum chromodynamics calculations was used to estimate the irreducible standard model background. The full data are used to constrain the large extra dimensions model of Arkani–Hamed, Dimopoulos, and Dvali, and the continuum clockwork mechanism. Preliminary studies and limits on the scenario of Unparticles decaying into two photons are also presented. Additionally, work on various hardware and software upgrades are discussed. Software support for improved timing information from the CMS Hadron Calorimeter Barrel for the creation of a Level-1 trigger for Long-Lived Particles are highlighted