Pair Production of Doubly-Charged Scalars: Neutrino Mass Constraints and Signals at the LHC

TL;DR

This paper investigates the production and detection of doubly charged Higgs bosons at the LHC, highlighting the significance of two-photon processes and decay modes for observing these particles up to 1 TeV.

Contribution

It introduces the role of two-photon processes in pair production of doubly charged scalars and analyzes decay channels to optimize detection strategies at the LHC.

Findings

Doubly charged scalars observable up to 1 TeV in the ll channel.

Two-photon processes contribute significantly to H++H++ production.

Detection feasible with 300 fb^-1 luminosity, even with 60% branching ratio.

Abstract

We study the pair production of doubly charged Higgs bosons at the Large Hadron Collider (LHC), assuming the doubly charged Higgs to be part of an SU(2)_L triplet which generates Majorana masses for left-handed neutrinos. Such pair-production has the advantage that it is not constrained by the triplet vacuum expectation value, which tends to make the single production rate rather small. We point out that, in addition to the Drell-Yan (DY) production mechanism, two-photon processes also contribute to H++H++ production at a level comparable to the QCD corrections to the DY channel. Decays of the doubly charged Higgs into both the l+l+ and W+W+ modes are studied in detail to optimize the signal observation over the backgrounds. Doubly charged scalars should be observable at the LHC with 300 fb^-1 integrated luminosity in the ll channel upto the mass range of 1 TeV even with a branching fraction of about 60 %, and in the WW channel upto a mass of 700 GeV. Such a doubly charged Higgs, if it is a member of a triplet generating neutrino masses,cannot be long-lived on the scale of collider detectors although it might lead to a displaced secondary vertex during its decay if it is lighter than about 250 GeV.