Department of Physics
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24 results
Search Results
Item Electroweak multi-higgs production: a smoking gun for the type-I two-higgs-doublet model(AIP, 2023-12) Mondal, TanmoyExtending the Higgs sector of the standard model (SM) by just one additional Higgs doublet field leads to the two-Higgs-doublet model (2HDM). In the type-I 𝑍2-symmetric limit of the 2HDM, all the five new physical Higgs states can be fairly light, 𝒪(100) GeV or less, without being in conflict with current data from the direct Higgs boson searches and the 𝐵-physics measurements. In this Letter, we establish that the new neutral as well as the charged Higgs bosons in this model can all be simultaneously observable in the multi-𝑏 final state. The statistical significance of the signature for each of these Higgs states, resulting from the electroweak (EW) production of their pairs, can exceed 5𝜎 at the 13 TeV high-luminosity Large Hadron collider (HL-LHC). Since the parameter space configurations where this is achievable are precluded in the other, more extensively pursued, 2HDM types, an experimental validation of our findings would be a clear indication that the true underlying Higgs sector in nature is the type-I 2HDM.Item Multiphoton signatures as a probe of violation in extended Higgs sectors(APS, 2024-02) Mondal, TanmoyWe propose a novel signature with four-photon final states to probe 𝐶𝑃-violating (CPV) extended Higgs sectors via 𝑓 ¯ 𝑓 →𝑍*→𝐻1𝐻2→4𝛾 processes with 𝐻1,2 being additional neutral Higgs bosons. We focus on the nearly Higgs alignment scenario, in which the discovered Higgs boson almost corresponds to a neutral scalar state belonging to the isospin doublet field with the vacuum expectation value 𝑣≃246 GeV. We show that the branching ratios of 𝐻1,2 →𝛾𝛾 can simultaneously be sizable when CPV phases in the Higgs potential are of order one due to the enhancement of charged-Higgs boson loops. Such branching ratios can be especially significant when the fermiophobic scenario is taken into account. As a simple example, we consider the general two Higgs doublet model, and demonstrate that the cross section for the four-photon process can be 0.1 fb at LHC with the masses of 𝐻1,2 to be a few 100 GeV in the Higgs alignment limit under the constraints from electric dipole moments (EDMs) and LHC Run-II data. We also illustrate that the searches for EDMs and diphoton resonances at high-luminosity LHC play complementary roles to explore CPV extended Higgs sectors.Item Implications of unitarity and charge breaking minima in a left-right symmetric model(APS, 2015-11) Mondal, TanmoyWe examine the usefulness of the unitarity conditions in a left-right symmetric model which can translate into giving a stronger constraint on the model parameters together with the criteria derived from vacuum stability and perturbativity. In this light, we demonstrate the bounds on the masses of the physical scalars present in the model and find the scenario where multiple scalar modes are in the reach of the Large Hadron Collider. We also analyze the additional conditions that can come from charge breaking minima in this context.Item Gamma-ray signals from multicomponent scalar dark matter decays(IOP, 2020-01) Mondal, TanmoyWithin a multicomponent dark matter scenario, novel gamma-ray signals may arise from the decay of the heavier dark matter component into the lighter. For a scalar dark sector of this kind, the decay ϕ2→ϕ1 γ is forbidden by the conservation of angular momentum, but the decay ϕ2 → ϕ1 γγ can have a sizable or even dominant branching ratio. In this paper we present a detailed study of this decay channel. We determine the width and photon energy spectrum generated in the decay, employing an effective theory approach, and in UV complete models where the scalar dark matter components interact with heavy or light fermions. We also calculate limits on the inverse width from current data of the isotropic diffuse photon flux, both for a hierarchical and a degenerate dark matter spectrum. Finally, we briefly comment on the prospects of observing the diphoton signal from sneutrino decay in the minimal supersymmetric standard model extended with right-handed neutrino superfields (tilde nuMSSM) .Item Right sneutrino with Δ𝐿��=2 masses as nonthermal dark matter(APS, 2019-02) Mondal, TanmoyWe consider the minimal supersymmetric standard model (MSSM) with right-chiral neutrino superfields with Majorana masses, where the lightest right-handed sneutrino dominated scalars constitutes nonthermal dark matter (DM). The Δ𝐿=2 masses are subject to severe constraints coming from freeze-in relic density of such DM candidates as well as from sterile neutrino freeze-in. In addition, big bang nucleosynthesis and freeze-out of the next-to-lightest superparticle shrink the viable parameter space of such a scenario. We examine various Δ𝐿=2 mass terms for families other than that corresponding to the LSP sneutrino. Δ𝐿=2 masses are difficult to reconcile with a right-sneutrino DM, unless there is either (a) a hierarchy of about 3 orders of magnitudes among various supersymmetry-breaking mass parameters, or, (b) strong cancellation between the Higgsino mass and the trilinear supersymmetry breaking mass parameter for sneutrinos.Item Nonstandard signatures of vectorlike quarks in a leptophobic 221 model(APS, 2019-06) Mondal, TanmoyWe consider vectorlike quarks in a leptophobic 221 model characterized by the gauge group 𝑆𝑈(2)𝐿×𝑆𝑈(2)2×𝑈(1)𝑋, where the 𝑆𝑈(2)2 is leptophobic in nature. We discuss the pattern of mixing between Standard Model quarks and vectorlike quarks and how we prevent tree level flavor-changing interactions in the model. The model also predicts tauphilic scalars decaying mostly to tau leptons. We consider a typical signal of the model in the form of pair production of top-type vectorlike quarks which decays to the tauphilic scalars and a third generation quark. We analyze the resulting final state signal for the 13 TeV LHC, containing ≥3𝑗(1𝑏)+≥2𝜏+≥1𝑙 and discuss the discovery prospects of such vectorlike quarks with nonstandard decay modes.Item Demystifying the compressed top squark region with kinematic variables(APS, 2017-11) Mondal, TanmoyThe ongoing perplexing scenario with no hints of new physics at the Large Hadron Collider can be elucidated amicably if the exotic particle spectrum in many of the well-motivated theoretical models possesses degenerate mass. We investigate the usefulness of different kinematic variables sensitive to the compressed mass region, and propose a search strategy considering a phenomenological supersymmetric scenario where the top squark undergoes a four-body decay due to its extremely narrow mass difference with the lightest supersymmetric particle. Considering a challenging but relatively clean dileptonic decay channel, we demonstrate that one can effectively restrain the significant background from the top quark, which provides a complementary approach to the present CMS analysis. With the new strategic approach the current limit can be extended to a phase-space region that was not explored beforeItem Higgs vacuum stability and inflationary dynamics after BICEP2 and PLANCK dust polarisation data(IOP, 2014-12) Mondal, TanmoyIf the recent detection of B-mode polarization of the Cosmic Microwave Background by BICEP2 observations, withstand the test of time after the release of recent PLANCK dust polarisation data, then it would surprisingly put the inflationary scale near Grand Unification scale if one considers single-field inflationary models. On the other hand, Large Hadron Collider has observed the elusive Higgs particle whose presently observed mass can lead to electroweak vacuum instability at high scale (∼ Script O(1010) GeV). In this article, we seek for a simple particle physics model which can simultaneously keep the vacuum of the theory stable and yield high-scale inflation successfully. To serve our purpose, we extend the Standard Model of particle physics with a U(1)B-L gauged symmetry which spontaneously breaks down just above the inflationary scale. Such a scenario provides a constrained parameter space where both the issues of vacuum stability and high-scale inflation can be successfully accommodated. The threshold effect on the Higgs quartic coupling due to the presence of the heavy inflaton field plays an important role in keeping the electroweak vacuum stable. Furthermore, this scenario is also capable of reheating the universe at the end of inflation. Though the issues of Dark Matter and Dark Energy, which dominate the late-time evolution of our universe, cannot be addressed within this framework, this model successfully describes the early universe dynamics according to the Big Bang model.Item Reconstructing a light pseudoscalar in the Type-X two Higgs doublet model(Elsevier, 2017-11) Mondal, TanmoyWe investigate the detectability as well as reconstructibility of a light pseudoscalar particle A, of mass in the 50–60 GeV range, which is still allowed in a Type-X (lepton-specific) two-Higgs doublet scenario. Such a pseudoscalar can be pair-produced in the decay of the 125 GeV scalar h. The light pseudoscalar in the aforementioned range, helpful in explaining the muon anomalous magnetic moment, has not only substantial branching ratio in the channel but also one of about in the final state. We show how to faithfully reconstruct the A mass using the mode, and establish the existence of a pseudoscalar around 50–60 GeV, using the process . This is the most reliable way of reconstructing the light A mass, with a statistical significance that amounts to discovery, with a few hundred (or less) of integrated luminosity.Item Reconstructing heavy Higgs boson masses in a type X two-Higgs-doublet model with a light pseudoscalar particle(APS, 2018) Mondal, TanmoyWe analyze the prospects of reconstructing the mass of a heavy charged Higgs boson in the context of a type X two-Higgs-doublet model where a light pseudoscalar 𝐴 in the mass range 40–60 GeV is phenomenologically allowed, and is in fact favored if one wants to explain the muon anomalous magnetic moment. The associated production of charged Higgs bosons with the pseudoscalar 𝐴 and subsequent decay of the charged Higgs boson into a 𝑊 and 𝐴 is found to be our relevant channel. The branching ratio for 𝐻+→𝑊+𝐴 with 𝑀𝐻+∼200 GeV is close to 50%. The hadronic decay of the 𝑊 boson, coupled with the leptonic decays of 𝐴 into a tau and muon pair, help in identifying the charged Higgs bosons. The neutral heavy Higgs boson, being degenerate with the charged Higgs boson for most of the allowed parameter space of the model, also contributes to similar final states. Thus, both the charged and neutral 𝐶𝑃-even heavy Higgs bosons are reconstructed within a band of about 10 GeV.
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