In the quest for new physics beyond the Standard Model, decay channels in leptons or photons are particularly interesting, since they arise in clean final states, allowing quick and well defined strategy of analysis.
Resonances in the dielectron and dimuon decay channels arise in many well established theories beyond the standard model, like grand unified theories (GUT) or models proposing extra spatial dimension(s). The first part of the talk presents the search of heavy neutral resonances decaying in di-electron or di-muon pairs, where up to 2.8/fb of proton-proton (pp) collision data with √s = 13 TeV collected by the CMS experiment at the LHC were analyzed. In absence of a significant deviation from the standard model predictions, 95% confidence level limits are calculated.
The second part of the talk is focused on the search for heavy neutral resonances decaying in di-photon pairs, whose existence is predicted in two classes of models: ADD (Arkani-Hamed, Dimopoulos e Dvali) and Randall-Sundrum (RS) models. The search employs 3.3/fb of pp collision data collected by the CMS experiment in 2015 at a center-of-mass energy of 13 TeV. It is aimed at spin-0 and spin-2 resonances of mass between 500 and 4500 GeV and relative width up to 5.6 × 10−2 . The results of the search are combined with those obtained by the CMS collaboration in similar searches at √s = 8 TeV. The observed mass distribution was found to be consistent with the expectations from the SM. The largest excess in the combined analysis (13 TeV + 8 TeV) is observed for m = 750 GeV and relative width = 1.4 × 10−4 . The local p-value corresponds to approximately 3.4 standard deviations, which are reduced to approximately 1.6 standard deviations after taking into account the effect of searching for several signal hypotheses.