Search for narrow resonances in dilepton mass spectra in proton-proton collisions at sqrt(s) = 13 TeV and combination with 8 TeV data

TL;DR

This paper reports a search for narrow dilepton resonances in proton-proton collisions at 13 TeV, combining new data with previous 8 TeV results, setting new mass limits on potential new particles without finding evidence of new physics.

Contribution

The study combines 13 TeV and 8 TeV data to improve sensitivity in searching for narrow dilepton resonances, establishing more stringent mass limits on hypothetical particles.

Findings

No evidence for non-standard-model resonances was observed.

Set 95% CL lower mass limits for Z' and Kaluza-Klein gravitons.

Limits exceed previous 8 TeV results.

Abstract

A search for narrow resonances in dielectron and dimuon invariant mass spectra has been performed using data obtained from proton-proton collisions at sqrt(s) = 13 TeV collected with the CMS detector. The integrated luminosity for the dielectron sample is 2.7 inverse femtobarns and for the dimuon sample 2.9 inverse femtobarns. The sensitivity of the search is increased by combining these data with a previously analysed set of data obtained at sqrt(s) = 8 TeV and corresponding to a luminosity of 20 inverse femtobarns. No evidence for non-standard-model physics is found, either in the 13 TeV data set alone, or in the combined data set. Upper limits on the product of production cross section and branching fraction have also been calculated in a model-independent manner to enable interpretation in models predicting a narrow dielectron or dimuon resonance structure. Limits are set on the masses of hypothetical particles that could appear in new-physics scenarios. For the Z'[SSM] particle, which arises in the sequential standard model, and for the superstring inspired Z'[psi] particle, 95% confidence level lower mass limits for the combined data sets and combined channels are found to be 3.37 and 2.82 TeV, respectively. The corresponding limits for Kaluza-Klein gravitons arising in the Randall-Sundrum model of extra dimensions with coupling parameters 0.01 and 0.10 are 1.46 and 3.11 TeV, respectively. These results significantly exceed the limits based on the 8 TeV LHC data.