Search for doubly charged Higgs boson production in multi-lepton final states with the ATLAS detector using proton–proton collisions at $$\sqrt{s}=13\,\text {TeV}$$ s = 13 TeV

Abstract

A search for doubly charged Higgs bosons with pairs of prompt, isolated, highly energetic leptons with the same electric charge is presented. The search uses a protonproton collision data sample at a centre-of-mass energy of 13 TeV corresponding to 36.1 fb −1 of integrated luminosity recorded in 2015 and 2016 by the ATLAS detector at the LHC. This analysis focuses on the decays H ±± → e ± e ± , H ±± → e ± μ ± and H ±± → μ ± μ ± , fitting the dilepton mass spectra in several exclusive signal regions. No significant evidence of a signal is observed and corresponding limits on the production cross-section and consequently a lower limit on m(H ±± ) are derived at 95% confidence level. With ± ± = e ± e ± /μ ± μ ± /e ± μ ± , the observed lower limit on the mass of a doubly charged Higgs boson only coupling to left-handed leptons varies from 770 to 870 GeV (850 GeV expected) for B(H ±± → ± ± ) = 100% and both the expected and observed mass limits are above 450 GeV for B(H ±± → ± ± ) = 10% and any combination of partial branching ratios. IntroductionEvents with two prompt, isolated, highly energetic leptons with the same electric charge (same-charge leptons) are produced very rarely in a proton-proton collision according to the predictions of the standard model (SM), but may occur with higher rate in various theories beyond the standard model (BSM). This analysis focuses on BSM theories that contain a doubly charged Higgs particle H ±± using the observed invariant mass of same-charge lepton pairs. In the absence of evidence for a signal, lower limits on the mass of the H ±± particle are set at the 95% confidence level.Doubly charged Higgs bosons can arise in a large variety of BSM theories, namely in left-right symmetric (LRS) e-mail: atlas.publications@cern.ch models [1][2][3][4][5], Higgs triplet models [6,7], the little Higgs model [8], type-II see-saw models [9][10][11][12][13], the GeorgiMachacek model [14], scalar singlet dark matter [15], and the Zee-Babu neutrino mass model [16][17][18]. Theoretical studies [19][20][21] [22]. Besides the leptonic decay, the H ±± particle can decay into a pair of W bosons as well. For low values of the Higgs triplet vacuum expectation value v , it decays almost exclusively to leptons while for high values of v the decay is mostly to a pair of W bosons [9,12]. In this analysis, the coupling to W bosons is assumed to be negligible and only pair production via the Drell-Yan process is considered. The Feynman diagram of the production mechanism is presented in Fig. 1.The analysis targets only decays of the H ±± particle into electrons and muons, denoted by . Other final states X that are not directly selected in this analysis are taken into account by reducing the lepton multiplicity of the final state. These states X would include, for instance, τ leptons or W bosons, as well as particles which escape detection. The total assumed branching ratio of H ±± is therefore B(Moreover, the decay width is assumed to be negligible compared to the detector resolution, which is compa...

Scalar dark matter, type II seesaw and the DAMPE cosmic ray e++e− excess

“…3 TeV satisfies the current lower bound [23], M ∆ 770-870 GeV, from the search for doubly charged Higgs bosons at the Large Hadron Collider. To account for the DAMPE excess, the DM annihilation cross section is found to be much larger than the thermal cross section [5], and some enhancement mechanism is necessary.…”

“…σv rel ∆ ±± / σv rel = 1 in Eq. (23). In this case the local density is required to be ρ s ≈ 100 GeV/cm 3 to fit the DAMPE excess for m D − M ∆ ±± = 3 GeV.…”

Zee-Babu type model with U(1)Lμ−LτNomura1, Okada2 2018Phys. Rev. D273120View full textAdd to dashboardCite

“…In Fig. 2, we show the cross section for the 13 TeV LHC, which is compared with the current LHC limit obtained from data of ∼36 fb −1 integrated luminosity [15]. Then, the doubly charged scalar should be larger than ∼650 GeV.…”

“…[2,3], considering lepton-flavor violations (LFVs). 1 Also, one could find new signals of new bosons; especially, the mass of k AEAE and its related interacting couplings can be constrained by the LEP experiment [13] and can be well measured by current LHC experiments [14,15] and by future International Linear Collider (ILC) experiments [16,17] applying the chiral polarizations of the beam, which might be distinguished from those in the other models [18].…”

Phenomenological study of texture zeros in lepton mass matrices of minimal left-right symmetric model

“…It is worth noting that the chosen doubly charged scalar masses respect the latest bounds from collider experiment. On the basis of the results of the ATLAS searches for same-sign dileptonic new physics signals [113], there is a lower bound on the masses of the doublycharged scalars ∆ ±± L and ∆ ±± R . Assuming that the branching ratios into electronic and muonic final states are both equal to 50%, the SU (2) L and SU (2) R doubly-charged Higgsboson masses have to be larger than 785 GeV and 675 GeV respectively.…”