CMS: Search for lepton flavour violating decays of heavy resonances and quantum black holes to an eμ pair in proton–proton collisions at √s = 8 TeV

Authors

S. Chatrchyan
Ekaterina Avdeeva, University of Nebraska-LincolnFollow
Kenneth Bloom, University of Nebraska-LincolnFollow
S. Bose, University of Nebraska - LincolnFollow
Jamila Butt, University of Nebraska - Lincoln
Daniel R. Claes, University of Nebraska-LincolnFollow
Aaron Dominguez, University of Nebraska-LincolnFollow
M. Eads, University of Nebraska-Lincoln, Lincoln,Follow
R. Gonzalez Suarez, University of Nebraska - Lincoln
P. Jindal, University of Nebraska - Lincoln
J. Keller, University of Nebraska - LincolnFollow
D. Knowlton, University of Nebraska-LincolnFollow
Ilya Kravchenko, University of Nebraska-LincolnFollow
Jose Lazo-Flores, University of Nebraska-LincolnFollow
Helena Malbouisson, University of Nebraska - Lincoln
Sudhir Malik, University of Nebraska - LincolnFollow
F. Meier, University of Nebraska-Lincoln, Lincoln,Follow
Gregory Snow, University of Nebraska - LincolnFollow

Date of this Version

2017

Citation

Eur. Phys. J. C (2016) 76:317

Comments

© CERN for the benefit of the CMS collaboration 2016.

Open access

DOI 10.1140/epjc/s10052-016-4149-y

Abstract

A search for narrow resonances decaying to an electron and a muon is presented. The eμ mass spectrum is also investigated for non-resonant contributions from the production of quantum black holes (QBHs). The analysis is performed using data corresponding to an integrated luminosity of 19.7 fb⁻¹ collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. With no evidence for physics beyond the standard model in the invariant mass spectrum of selected eμ pairs, upper limits are set at 95% confidence level on the product of cross section and branching fraction for signals arising in theories with charged lepton flavour violation. In the search for narrow resonances, the resonant production of a τ sneutrino in R-parity violating supersymmetry is considered. The τ sneutrino is excluded for masses below 1.28 TeV for couplings λ₁₃₂ = λ₂₃₁ = λ'₃₁₁ = 0.01, and below 2.30 TeV for λ₁₃₂ = λ₂₃₁ = 0.07 and λ'₃₁₁ = 0.11. These are the most stringent limits to date from direct searches at high-energy colliders. In addition, the resonance searches are interpreted in terms of a model with heavy partners of the Z boson and the photon. In a framework of TeV-scale quantum gravity based on a renormalization of Newton’s constant, the search for non-resonant contributions to the eμmass spectrum excludes QBH production below a threshold mass M_th of 1.99 TeV. In models that invoke extra dimensions, the bounds range from 2.36 TeV for one extra dimension to 3.63 TeV for six extra dimensions. This is the first search for QBHs decaying into the eμ final state.