New Light H± Discovery Channels at the LHC

A light charged Higgs boson has been searched for at the Large Hadron Collider (LHC) via top (anti)quark decay, i.e., t→bH+, if kinematically allowed. In this contribution, we propose new channels for light charged Higgs boson searches via the pair productions pp→H±h/A and pp→H+H− at the LHC in the context of the Two-Higgs Doublet Model (2HDM) Type-I. By focusing on a case where the heavy H state is the Standard Model (SM)-like one already observed, we investigate the production of the aforementioned charged Higgs bosons and their bosonic decay channels, namely, H±→W±h and/or H±→W±A. We demonstrate that such production and decay channels can yield substantial alternative discovery channels for H± bosons at the LHC. Finally, we propose eight benchmark points (BPs) to motivate the search for such signatures.

Analysis of W± + 4γ in the 2HDM Type-I at the LHC

We analyse a light charged Higgs boson in the 2-Higgs Doublet Model (2HDM) Type-I, when its mass satisfies the condition MH±< Mt + Mb and the parameter space is consistent with theoretical requirements of self-consistency as well as the latest experimental constraints from Large Hadron Collider (LHC) and other data. Over such a parameter space, wherein the Standard Model (SM)-like state discovered at the LHC in 2012 is the heaviest CP-even state of the 2HDM, it is found that the decay modes of the charged Higgs boson are dominated by H±→ W±(∗)h. Furthermore, the light neutral Higgs boson h dominantly decays into two photons. Under these conditions, we find that the production and decay process pp → H±h → W±(∗)hh → ℓνℓ + 4γ (ℓ = e, μ) is essentially background free. However, since the W±(∗) could be largely off-shell and the h state is very light, so that both the lepton coming from the former and the photons coming from the latter could be rather soft, we perform here a full Monte Carlo (MC) analysis at the detector level demonstrating that such a W± + 4γ signal is very promising, as it would be yielding significant excesses at the LHC with an integrated luminosity of L = 300 fb−1 at both $$ \sqrt{s} $$ s = 13 and 14 TeV.

New discovery modes for a light charged Higgs boson at the LHC

At the Large Hadron Collider (LHC), both the ATLAS and CMS Collaborations have been searching for light charged Higgs bosons via top (anti)quark production and decays channels, like pp → t$$ \overline{t} $$ t ¯ with one top (anti)quark decaying into a charged Higgs boson and a b (anti)quark, when the decay is kinematically open (i.e., when $$ {m}_{H^{\pm }} $$ m H ± ≲ mt). In this paper, we propose new searches at the LHC involving light charged Higgs bosons via their pair production channels like pp → H±h/A and pp → H+H− in the 2-Higgs Doublet Model (2HDM) Type-I and -X scenarios. By focusing on the case where the heavy H state plays the role of the Standard Model (SM)-like Higgs boson with a mass near 125 GeV, we study the aforementioned Higgs boson pair production channels and investigate their bosonic decays, such as H± → W±h and/or H± → W±A. We demonstrate that for a light charged Higgs boson state, with $$ {m}_{H^{\pm }} $$ m H ± ≲ mt, at the LHC, such di-Higgs production and decay channels can give rise to signatures with event rates much larger than those emerging from pp → t$$ \overline{t} $$ t ¯ → t$$ \overline{b} $$ b ¯ H− + c.c. We specifically study h/A → b$$ \overline{b} $$ b ¯ and τ+τ− decays. We, therefore, claim that the discussed combination of new production and decay modes can result in an alternative discovery channel for charged Higgs bosons lighter than the top (anti)quark at the LHC within the above two 2HDM Types. Finally, in order to motivate experimentalists in ATLAS and CMS to search for such signatures, we propose 16 Benchmark Points (BPs) which are compatible with both theoretical and experimental constraints.

Production of the Doubly Charged Higgs Boson in Association with the SM Gauge Bosons and/or Other HTM Scalars at Hadron Colliders

We investigate an extension of the Standard Model with one additional triplet of scalar bosons. Altogether, the model contains four Higgs bosons. We analyze the associated production of the doubly charged scalar with the Standard Model gauge bosons and the remaining Higgs bosons of the model, which are: the light (SM) and heavy neutral scalars and a singly charged scalar. We estimate, in the context of the present (HL–LHC) and future (FCC–hh) hadron colliders, the most promising processes in which a single produced doubly charged Higgs boson is involved.

The forgotten channels: charged Higgs boson decays to a W± and a non-SM-like Higgs boson

The presence of charged Higgs bosons is a generic prediction of multiplet extensions of the Standard Model (SM) Higgs sector. Focusing on the Two-Higgs-Doublet-Model (2HDM) with type I and lepton-specific Yukawa sectors, we discuss the charged Higgs boson collider phenomenology in the theoretically and experimentally viable parameter space. While almost all existing experimental searches at the LHC target the fermionic decays of charged Higgs bosons, we point out that the bosonic decay channels — especially the decay into a non-SM-like Higgs boson and a W boson — often dominate over the fermionic channels. Moreover, we revisit two genuine BSM effects on the properties of the discovered Higgs boson — the charged Higgs contribution to the diphoton rate and the Higgs decay to two light Higgs bosons — and their implication for the charged Higgs boson phenomenology. As main result of the present paper, we propose five two-dimensional benchmark scenarios with distinct phenomenological features in order to facilitate the design of dedicated LHC searches for charged Higgs bosons decaying into a W boson and a light, non-SM-like Higgs boson.

Search for charged Higgs bosons decaying into a top quark and a bottom quark at $$ \sqrt{\mathrm{s}} $$ = 13 TeV with the ATLAS detector

A search for charged Higgs bosons decaying into a top quark and a bottom quark is presented. The data analysed correspond to 139 fb−1 of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV, recorded with the ATLAS detector at the LHC. The production of a heavy charged Higgs boson in association with a top quark and a bottom quark, pp → tbH+ → tbtb, is explored in the H+ mass range from 200 to 2000 GeV using final states with jets and one electron or muon. Events are categorised according to the multiplicity of jets and b-tagged jets, and multivariate analysis techniques are used to discriminate between signal and background events. No significant excess above the background-only hypothesis is observed and exclusion limits are derived for the production cross-section times branching ratio of a charged Higgs boson as a function of its mass; they range from 3.6 pb at 200 GeV to 0.036 pb at 2000 GeV at 95% confidence level. The results are interpreted in the hMSSM and $$ {M}_h^{125} $$ M h 125 scenarios.

Probing top changing neutral Higgs couplings at colliders

The [Formula: see text] boson, discovered only in 2012, is lower than the top quark in mass, hence [Formula: see text] search commenced immediately thereafter, with current limits at the per mille level and improving. As the [Formula: see text] rate vanishes with the [Formula: see text]-[Formula: see text] mixing angle [Formula: see text], we briefly review the collider probes of the top changing [Formula: see text] coupling [Formula: see text] of the exotic [Formula: see text]-even/odd Higgs bosons [Formula: see text]. Together with an extra top conserving [Formula: see text] coupling [Formula: see text], one has an enhanced [Formula: see text] coupling alongside the familiar [Formula: see text] coupling, where [Formula: see text] is the charged Higgs boson. The main processes we advocate are [Formula: see text], [Formula: see text] (same-sign top and triple-top), and [Formula: see text]. We also discuss some related processes such as [Formula: see text], [Formula: see text] that depend on [Formula: see text] being nonzero, comment briefly on [Formula: see text] resonant production and touch upon the [Formula: see text] coupling.