Abstract

A search for nonresonant excesses in the invariant mass spectra of electron and muon pairs is presented. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment in 2016, corresponding to a total integrated luminosity of 36 fb−1. No significant deviation from the standard model is observed. Limits are set at 95% confidence level on energy scales for two general classes of nonresonant models. For a class of fermion contact interaction models, lower limits ranging from 20 to 32 TeV are set on the characteristic compositeness scale Λ. For the Arkani-Hamed, Dimopoulos, and Dvali model of large extra dimensions, the first results in the dilepton final state at 13 TeV are reported, and values of the ultraviolet cutoff parameter ΛT below 6.9 TeV are excluded. A combination with recent CMS diphoton results improves this exclusion to ΛT below 7.7 TeV, providing the most sensitive limits to date in nonhadronic final states.

Highlights

  • Background and signal estimationThe primary SM production channel for lepton pairs in this analysis is the DY process

  • The level-1 (L1) trigger, composed of custom hardware processors, selects events of interest using information from the calorimeters and muon detectors; the software based high-level trigger (HLT) uses the full event information, including that from the inner tracker, to select the events that are recorded for analysis

  • It is simulated with powheg v2 [19,20,21,22,23,24] at next-to-leading-order (NLO) in perturbative QCD, using the nnpdf 3.0 [25] set of parton distribution functions (PDFs) and pythia 8.205 [26] for parton showering and hadronization

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Summary

The CMS detector

The central feature of the CMS detector is a superconducting solenoid providing an axial magnetic field of 3.8 T and enclosing a silicon strip and pixel tracker, an electromagnetic calorimeter (ECAL), and a hadron calorimeter (HCAL). The silicon tracker measures charged particles within the pseudorapidity range |η| < 2.5. The ECAL and HCAL, each composed of a barrel and two endcap sections, extend over the range |η| < 3, while a forward calorimeter encompasses 3 < |η| < 5. The level-1 (L1) trigger, composed of custom hardware processors, selects events of interest using information from the calorimeters and muon detectors; the software based high-level trigger (HLT) uses the full event information, including that from the inner tracker, to select the events that are recorded for analysis

Lepton reconstruction and event selection
Background and signal estimation
Systematic uncertainties
Mass spectra and statistical analysis
15 LL Const
Summary
Findings
14 Leading order
Full Text
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