Search for doubly and singly charged Higgs bosons decaying into vector bosons in multi-lepton final states with the ATLAS detector using proton-proton collisions at $$ \sqrt{\mathrm{s}} $$ = 13 TeV

Abstract

A search for charged Higgs bosons decaying into W±W± or W±Z bosons is performed, involving experimental signatures with two leptons of the same charge, or three or four leptons with a variety of charge combinations, missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb−1. The search is guided by a type-II seesaw model that extends the scalar sector of the Standard Model with a scalar triplet, leading to a phenomenology that includes doubly and singly charged Higgs bosons. Two scenarios are explored, corresponding to the pair production of doubly charged H±± bosons, or the associated production of a doubly charged H±± boson and a singly charged H± boson. No significant deviations from the Standard Model predictions are observed. H±± bosons are excluded at 95% confidence level up to 350 GeV and 230 GeV for the pair and associated production modes, respectively.

Searches for additional Higgs bosons at the LHC

“…ATLAS performed the doubly charged Higgs search in the pair production of doubly charged H ±± bosons, or the associated production of a doubly charged H ±± boson and a singly charged H ± boson using 139 fb −1 data [25]. The search is guided by a type-II seesaw model that extends the scalar sector of SM with a scalar triplet [26].…”

Revisiting Type-II see-saw: Present Limits and Future Prospects at LHC

“…A wealth of BSM models such as the present model [1][2][3][4][5][6], left-right symmetric models [48][49][50] Higgs triplet models [51,52], little Higgs model [53][54][55], Georgi-Machacek model [56,57], Zee-Babu model [58,59] and other extensions of SM [60][61][62][63][64][65] envisage presence of doubly charged scalar bosons and their illustrious signatures. This is why, a number of collider searches have been carried out at the LHC by CMS and ATLAS [66][67][68][69][70][71][72][73][74][75] to look for the same. In view of the observations being consistent with the SM background expectations, these analyses derived stringent limits with 95% confidence level (CL) on the mass of the doubly charged scalar in the context of a simplified model.…”

“…Another search in multilepton final states with an integrated luminosity of 36.1 fb −1 of pp collisions at √ s = 13 TeV LHC by the ATLAS collaboration [72] has set a limit of 770-870 GeV and 450 GeV for H ±± decaying, respectively, 100% and 10% into same-sign light lepton (e, µ) pair. A recent search in multilepton final states, optimised for H ±± decaying exclusively into same-sign W -boson pair, with an integrated luminosity of 139 fb −1 of pp collisions at √ s = 13 TeV LHC by the ATLAS collaboration [75] has excluded them with masses up to 350 GeV and 230 GeV, respectively, for the pair and associated production modes assuming v t = 0.1 GeV and the mixing between the CP-even scalars to be 10 −4 . Patently, the above-cited limits are not befitting to the entire parameter space, rather valid only for a constrained parameter space of the model.…”

“…Patently, the above-cited limits are not befitting to the entire parameter space, rather valid only for a constrained parameter space of the model. For instance, the CMS search in [71] is only valid for ∆m = 0 and v t < 10 −4 GeV, whereas the ATLAS search in ref [75] is only valid for ∆m = 0 and v t > 10 −4 GeV. Though in a realistic type-II see-saw scenario, the branching fractions of the triplet-like scalars into different lepton flavours are dictated by the neutrino oscillation parameters, most of the aforecited limits are derived in the context of simplified scenarios without reckoning the footprints of the low-energy neutrino parameters.…”

“…Furthermore, these limits are often conservative as these searches do not incorporate all the production channels for the triplet-like scalars. For instance, the ATLAS search in [75] considered either pair or associated production modes for the doubly charged scalars, but not both at once. As argued in Section III, all the channels entail to be incorporated in the analyses.…”