Abstract
A search for a doubly-charged Higgs boson in pp collisions at $\sqrt{s} = 7 \ \mbox{TeV}$ is presented. The data correspond to an integrated luminosity of 4.9 fb−1, collected by the CMS experiment at the LHC. The search is performed using events with three or more isolated charged leptons of any flavor, giving sensitivity to the decays of pair-produced triplet components Φ ++ Φ −−, and Φ ++ Φ − from associated production. No excess is observed compared to the background prediction, and upper limits at the 95 % confidence level are set on the Φ ++ production cross section, under specific assumptions on its branching fractions. Lower bounds on the Φ ++ mass are reported, providing significantly more stringent constraints than previously published limits.
Highlights
The existence of non-zero neutrino masses may represent a signal of physics beyond the standard model (SM) [1]
The multi-purpose Monte Carlo (MC) event generator PYTHIA 6.4.24 [35] is used for the simulation of signal and background processes, either to generate a given hard interaction at leading order (LO), or for the simulation of showering and hadronization in cases where the hard processes are generated at next-to-leading order (NLO) outside PYTHIA, as in the case of top quark related backgrounds
The predicted background contribution in the signal region is given by: NBGSR = α · NSDBata + 1, with a relative uncertainty of 1/ NSDBata + 1, where NBGSR is the number of background events in the signal region estimated from the data, and NSDBata is the total number of data events in the sidebands after applying the preselection requirements
Summary
The existence of non-zero neutrino masses may represent a signal of physics beyond the standard model (SM) [1]. ++ αβ branching fractions would allow the neutrino mass generation mechanism to be tested [7] In this scenario, measurements at the Large Hadron Collider (LHC) could shed light [8,9,10,11] on the absolute neutrino mass scale, the mass hierarchy, and the Majorana CP-violating phases. In addition to a model-independent search in each final state, where the Φ++ is assumed to decay in 100 % of the cases in turn in each of the possible lepton combinations (ee, μμ, τ τ, eμ, eτ, μτ ), the type II seesaw model is tested, following [9], at four benchmark points (BP), that probe different neutrino mass matrix structures. The fourth benchmark point BP4 represents the case in which the Φ++ has an equal branching fraction to each lepton generation This corresponds to the following values of the Majorana phases: α1 = 0, α2 = 1.7. The addition of associated production and all possible final states significantly improves the sensitivity and reach of this analysis
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