New strategies for Heavy Charged Higgs Boson Searches at the Large Hadron Collider

• Adil Jueid (Konkuk University)

The current bounds on the Charged Higgs boson, either from low energy or high energy experiments, are pushing its mass to regions that are very hard to probe due to: (i) relatively small production cross sections and (ii) large associated backgrounds. However, due to the fact that the charged Higgs Boson couplings to SM particles (in particular the top quark) is very unique, it is always possible to find alternatives that would increase the signal-to-background ratios at future luminosities. First, I will talk about the particular features of the top quark-Charged Higgs Boson and then discuss its implications on the differential distributions that are not blind to the top quark polarization. Finally, I discuss the possibility to implement these features in relatively new search strategies for the charged Higgs bosons.

The analysis of W+4\gamma in the 2HDM type-I at the LHC

• Yan Wang

We analyze a light charged Higgs boson in the 2-Higgs Doublet Model (2HDM) Type-I, when its mass satisfies the condition $M_{H^{\pm}} < M_{t}+M_{b}$  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 $H^\pm \rightarrow {W^\pm}^{(*)} h$.  Furthermore, the light neutral Higgs boson $h$ dominantly decays into two photons. Under these conditions, we find that the production and decay process  $ p p \to H^\pm h \to {W^\pm}^{(*)} h h \to \ell \nu_{\ell} + 4 \gamma$ ($\ell=e,\mu$) is essentially background free. However, since the $W^{\pm(*)}$ 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 $W^{\pm} + 4\gamma$  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 $\sqrt{s}= 13$ and  $14 ~\text{TeV}$.

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

• Henning Bahl (Deutsches Elektronen-Synchrotron DESY)

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 the 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.

Unusual signals of charged scalars

• Rafael Boto (Instituto Superior Técnico)

We consider models with two charged scalars. In a Z3 3HDM, both charged scalars come from doublet components; in the Zee model, the two come from a doublet component mixing with a singlet component. In the former, we found situations where the charged scalars would be hidden through cancellations in $h \to \gamma\gamma$ and $h \to X_s \gamma$, but could be found in $H_2^+ \rightarrow H_1^+ h_j$. In contrast, the Zee model allows the unusual signal $H_2^+ \rightarrow H_1^+  Z$, which should be sought at LHC.

Higgs Pair Production in Extended Higgs Models

• Milada Margarete Mühlleitner

We present our results for Higgs pair production in extended Higgs models, namely the R2HDM, C2HDM, N2HDM, and NMSSM. All shown points take into account theoretical and experimental constraints. We identify distinguishing features of the models and discuss the impact of the various parameters of the models on the size of Higgs pair production.

Higgs pair-production via mass-degenerate heavy scalars in the N2HDM

• Shoaib Munir (ICTP-EAIFR, Kigali)

A large variety of data from the Large Hadron Collider (LHC) points to new physics beyond the Standard Model, with a Higgs sector containing more than one state. In these extended Higgs sectors, it is possible that the mass-difference between two (or more) of the Higgs bosons is comparable to the sum of their decay widths, resulting in quantum  interference between their propagators. We investigate such interference between the heavier two Higgs bosons of the next-to-two-Higgs-doublet model (N2HDM), produced in gluon fusion at  the 14 TeV LHC. We found that its effects can be quite sizeable in certain parameter space regions, which invalidates the narrow-width approximation for estimating the pair-production cross sections of the 125 GeV SM-like Higgs boson in them.

Unexplored signatures in the IDM and TRSM

• Tania Natalie Robens (Rudjer Boskovic Institute (HR))

I will briefly discuss unexplored signatures in the IDM, a Two Higgs Doublet Model with a dark matter candidate, as well as the TRSM, a new physics model featuring 2 additional real scalars.

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

• Mohamed Krab

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 → tt¯ 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 mH± < ∼ mt). In this talk, 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 mH± < ∼ 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 → tt¯→ t ¯bH− + c.c. We specifically study h/A → 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.

CP-violation in the dark sector

• Venus Keus (University of Helsinki)

Extended scalar sectors are a common feature of almost all beyond Standard Model (SM) scenarios which, in fact, can address many of the SM shortcomings solely on their own. While many beyond SM scenarios have lost their appeal due to the non-observation of their predicted particles or are experimentally inaccessible, scalar extensions are well within the reach of many current and upcoming experiments. Moreover, they allow for the novel phenomenon of dark CP-violation which was introduced for the first time in the context of non-minimal Higgs frameworks with an extended dark sector. In this talk, I will discuss CP-violation in non-minimal Higgs frameworks and the exotic possibilities arising therein, such as CP-violating Dark Matter and CP-violating inflation. I will point out their implications for cosmology and collider searches.

Benchmark Points for Two-Higgs-doublet Models with Soft CP-violation

• Mao Ying-nan

We analyzed the CP-violated 2HDM in our current paper (2003.04178). For some special scenario in which some cancellation appears in electron EDM, the CP-violation angle can still reach as large as 0.3, which will be tested by future high and low energy experiments. The future neutron EDM experiments will be sensitive to such a scenario, while LHC experiments will also provide necessary and direct cross checks.

Impact of NLO corrections to the Higgs boson invisible decay in N2HDM

• Kodai Sakurai (Tohoku University)

The invisible decay of the discovered Higgs boson is one of the crucial process in testing dark matter.  While the upper bounds from the current LHC experiments is approximately 10%, the sensitivity will be improved in the future collider experiments. In this study, we calculated 1-loop corrections to the Higgs boson decay into a pair of dark matter in the next-to two Higgs doublet model (N2HDM), which involves a candidate of dark matter.  We discuss whether or not the loop corrections can affect the constraint from the Higgs invisible decay in the N2HDM.

Searches for a light pseudoscalar in L2HDM

• Tanmoy Mondal (Korea Institute for Advanced Study)

Leptophilic 2HDM can allow a light pseudoscalar (A) which can explain the muon g-2 at large tanbeta. Such a particle is being, or could be searched for through h -> AA\to 2 mu 2 tau,  or Z->H^\pm (H) A\to 3 (4) \tau and perhaps Z->tau tau A->4 tau. It would be worthwhile to make more dedicated studies for these channels considering the limited parameter space favoured by the muon g-2 data.

Light Higgs searches in $t\bar{t}\phi$ production at the LHC

• Rodrigo Capucha (Centro de Física Teórica e Computacional, FCUL)

A new reconstruction method to explore the low mass region in the associated production of top-quark pairs ($t\bar{t}$) with a generic scalar boson ($\phi$) at the LHC is proposed, using dileptonic final states of the $t\bar{t}\phi$ system with $\phi \to b\bar{b}$. The new method of mass reconstruction shows an improved resolution of at least a factor of two in the low mass region when compared to previous methods, without the loss of sensitivity of previous analyses. It turns out that it also leads to an improvement of the mass reconstruction of the 125 GeV Higgs for the same production process. We use an effective Lagrangian to describe a scalar with a generic Yukawa coupling to the top quarks. A full phenomenological analysis was performed, using Standard Model background and signal events generated with MadGraph5_aMC@NLO and reconstructed using a kinematic fit. The use of CP-sensitive variables allows then to maximize the distinction between CP-even and CP-odd components of the Yukawa couplings. Confidence Levels (CLs) for the exclusion of $\phi$ bosons with mixed CP (both CP-even and CP-odd components) were determined as a function of the top Yukawa couplings to the $\phi$ boson. The mass range analysed starts slightly above the $\Upsilon$ mass up to 40 GeV, although the analysis can be used for an arbitrary mass. If no new light scalar is found, exclusion limits at 95% CL for the absolute value of the CP-even and CP-odd Yukawa are derived.

Light-scalar phenomenology in Flavour Aligned 2-Higgs Doublet Model

• Luigi Delle Rose (University of Florence)

We discuss a flavour aligned realisation of the 2-Higgs Doublet Model with right-handed neutrinos. In the region of the parameter space that explains the anomalous magnetic moments of the leptons, we predict an almost background-free signature, consisting of the production of the charged and pseudo-scalar states, followed by their decays into multi-tau final states, that can be pursued at the Large Hadron Collider.

A Three-Higgs Doublet Model with Symmetry-constrained Flavour Changing Neutral Currents

• Pedro Rodrigues

In this talk a Three-Higgs Doublet Model (3HDM) with a flavour-violating continuous symmetry is presented and its phenomenology discussed. It is shown that the model has scalar-mediated  Flavour Changing Neutral Currents (FCNC) which are naturally suppressed by off-diagonal CKM matrix elements - a generalization, for the 3HDM, of the successful BGL model. It is shown that the model has vast regions of parameter space conforming with all known experimental constraints, both from the flavour sector and LHC direct searches. The model can accommodate extra scalars with relatively low masses, and their possible discovery in ditau decay channels is discussed.

Search for a Heavy Neutral CP-even Higgs Bosons at the LHC

• Mustafa Ashry

A search for a CP-even heavy Higgs boson at the LHC is analysed in a Left-Right model with a minimal Higgs sector. We report our results for potential signatures for heavy a neutral Higgs decaying into two SM-like Higgs bosons via the channel H>hh>bbγγ for a center-of-mass energy sqrt(s)s = 14 TeV and integrated luminosity L_int = 300, 3000 fb^-1.

Interference and finite width effects in BSM searches

• Tania Natalie Robens (Rudjer Boskovic Institute (HR))

Width and interference effects can have an important impact in new physics searches. For some processes, these are well-known, while for others such effects are often neglected. This contribution is tailored as an open discussion session regarding such effects in new physics searches, both regarding current practice in experimental searches as well as theoretical prescriptions.