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Gautam Bhattacharyya

Publications and source records attributed to Gautam Bhattacharyya.

At least 37 records · Page 2Linked to original sources
arXiv2013

A practical GMSB model for explaining the muon (g-2) with gauge coupling unification

We present a gauge mediated supersymmetry breaking model having weak SU(2) triplet, color SU(3) octet and SU(5) 5-plet messengers, that can simultaneously explain the muon $(g-2)$ data within 1$σ$ and the observed Higgs boson mass of 125 GeV. Gauge coupling unification is nontrivially maintained. Most of the parameter space satisfying both is accessible to the 14 TeV LHC. The lighter of the two staus weighs around (100-200) GeV, which can be a potential target of the ILC.

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arXiv2013

Scalar sector properties of two-Higgs-doublet models with a global U(1) symmetry

We analyze the scalar sector properties of a general class of two-Higgs-doublet models which has a global U(1) symmetry in the quartic terms. We find constraints on the parameters of the potential from the considerations of unitarity of scattering amplitudes, the global stability of the potential and the $ρ$-parameter. We concentrate on the spectrum of the non-standard scalar masses in the decoupling limit which is preferred by the Higgs data at the LHC. We exhibit charged-Higgs induced contributions to the diphoton decay width of the 125\,GeV Higgs boson and its correlation with the corresponding $Zγ$ width.

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arXiv2013

A natural scenario for heavy colored and light uncolored superpartners

Influenced by the current trend of experimental data, especially from the LHC, we construct a supersymmetric scenario where a natural dynamics makes the squarks and gluino super-heavy (order 10 TeV) while keeping the sleptons and the weak gauginos light (100-500 GeV). The dynamics relies on the interfusion of two underlying ideas: ($i$) gauge mediation of supersymmetry breaking with two messenger multiplets, one transforming as a triplet of weak SU(2) and the other as an octet of color SU(3); ($ii$) perturbative gauge coupling unification at the string scale even with these incomplete SU(5) multiplets. Interestingly, the relative magnitude of the triplet and octet messenger scales that ensures gauge unification at the two-loop level also helps to naturally keep the uncolored superpartners light while making the colored ones heavy.

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arXiv2013

Modified Higgs couplings and unitarity violation

Prompted by the recent observation of a Higgs-like particle at the CERN Large Hadron Collider (LHC), we investigate a quantitative correlation between possible departures of the gauge and Yukawa couplings of this particle from their Standard Model expectations and the scale of unitarity violation in the processes $WW \to WW$ and $t\bar t \to WW$.

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arXiv2013

Pushing the SUSY Higgs mass towards 125 GeV with a color adjoint

We show that inclusion of a TeV scale chiral superfield transforming in the adjoint representation of the color SU(3) to the MSSM particle content modifies the renormalization group running of some parameters in such a way that a 125 GeV mass of the light Higgs boson is accommodated more comfortably than in cMSSM / mSUGRA. Put differently, the introduction of a color adjoint TeV scale superfield helps resurrecting lighter choices for the stop and gluino which are otherwise disfavored in cMSSM / mSUGRA.

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arXiv2012

Novel signatures of the Higgs sector from S3 flavor symmetry

In an earlier work we analyzed the CP-even scalar sector of an S3 flavor model, where we identified some novel decay signatures of an exotic scalar. In this work we extend our analysis by including the complete set of scalars/pseudoscalars, revisiting the potential minimization conditions in a more general setup, setting the spectrum in conformity with the current LHC limits on the scalar mass, and identifying yet another spectacularly novel decay channel which might be revealed from an intense study of rare top decays at the LHC into modes containing multileptons of different flavors.

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arXiv2012

Naturally split supersymmetry

Nonobservation of superparticles till date, new Higgs mass limits from the CMS and ATLAS experiments, WMAP constraints on relic density, various other low energy data, and the naturalness consideration, all considered simultaneously imply a paradigm shift of supersymmetric model building. In this paper we perform, for the first time, a detailed numerical study of brane-world induced supersymmetry breaking for both minimal and next-to-minimal scenarios. We observe that a naturally hierarchical spectrum emerges through an interplay of bulk, brane-localized and quasi-localized fields, which can gain more relevance in the subsequent phases of the LHC run.

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arXiv2012

Proceedings of the first workshop on Flavor Symmetries and consequences in Accelerators and Cosmology (FLASY2011)

The main goals of the first "Workshop on FLAvor SYmmetries and consequences in accelerators and cosmology" (FLASY) was to summarize the theoretical status of flavor symmetries, bringing together young researchers in the field to stimulate discussions and new collaborations, with the aim of investigating possible new physics scenarios to be tested at the LHC, as well as in future neutrino, cosmology experiments and dark matter searches.

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arXiv2012

Electroweak Symmetry Breaking Beyond the Standard Model

In this talk, I shall address two key issues related to electroweak symmetry breaking. First, how fine-tuned different models are that trigger this phenomenon? Second, even if a light Higgs boson exists, does it have to be necessarily elementary? After a brief introduction, I shall first review the fine-tuning aspects of the MSSM, NMSSM, generalized NMSSM and GMSB scenarios. I shall then compare and contrast the little Higgs, composite Higgs and the Higgsless models. Finally, I shall summarize by giving a broad overview on where we stand at the end of 2011.

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arXiv2011

R-Parity violating flavor symmetries, recent neutrino data and absolute neutrino mass scale

We study the role of a very general type of flavor symmetry in controlling the strength of R-parity violation in supersymmetric models. We assume that only leptons are charged under a global symmetry whose breaking induces lepton number (and, hence, R-parity) violation. The charge assignments of leptons under this symmetry are such that the total number of independent lepton number violating couplings is reduced from 39 to 6. The most severe constraints on these flavor-correlated couplings arise from neutrino masses and mixing as well as from the non-observation of K_L -> eμ. We find that such a scenario predicts an almost vanishing smallest neutrino mass eigenvalue, allowing the upcoming generation of neutrinoless double beta decay experiments to shed light on the hierarchy.

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arXiv2011

Can Flavor Physics Hint at Distinctive Signals for R-parity Violation at the LHC?

Observation of some low-energy processes in the flavor physics regime may require the existence of supersymmetry with two relatively large R-parity-violating couplings of the LQD-type, together with reasonably light superparticles. At the LHC, such interactions would be expected to give rise to clear signals with convenient leptonic triggers, including some multileptons of the same sign. We undertake a detailed investigation of these signals taking care to correlate with low-energy requirements and taking proper account of the Standard Model backgrounds as well as the R-parity-conserving sector of the supersymmetric model. We find clear indications that R-parity violation as envisaged in this scenario can be detected at the LHC - even, perhaps, in the early runs.

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arXiv2011

A possible connection between neutrino mass generation and the lightness of a NMSSM pseudoscalar

One of the interesting properties of the NMSSM is that it can accommodate a light pseudoscalar of order 10 GeV. However, such scenarios are challenged by several experimental constraints, especially those related to the fermionic decays of the pseudoscalar. In this Letter, we extend the NMSSM field content by two gauge singlets, with lepton numbers +1 and -1. This serves the twin purpose of generating neutrino masses via the inverse see-saw mechanism and keeping the option of a very light pseudoscalar experimentally viable by opening dominant invisible decay channels of the pseudoscalar which help it evade the existing bounds.

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arXiv2011

Exotic Higgs boson decay modes as a harbinger of $S_3$ flavor symmetry

Discrete symmetries employed to explain flavor mixing and mass hierarchies can be associated with an enlarged scalar sector which might lead to exotic Higgs decay modes. In this paper, we explore such a possibility in a scenario with $S_3$ flavor symmetry which requires three scalar SU(2) doublets. The spectrum is fixed by minimizing the scalar potential, and we observe that the symmetry of the model leads to tantalizing Higgs decay modes potentially observable at the CERN Large Hadron Collider (LHC).

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arXiv2010

A Pedagogical Review of Electroweak Symmetry Breaking Scenarios

We review different avenues of electroweak symmetry breaking explored over the years. This constitutes a timely exercise as the world's largest and the highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at CERN near Geneva, has started running whose primary mission is to find the Higgs or some phenomena that mimic the effects of the Higgs, i.e. to unravel the mysteries of electroweak phase transition. In the beginning, we discuss the Standard Model Higgs mechanism. After that we review the Higgs sector of the Minimal Supersymmetric Standard Model. Then we take up three relatively recent ideas: Little Higgs, Gauge-Higgs Unification, and Higgsless scenarios. For the latter three cases, we first present the basic ideas and restrict our illustration to some instructive toy models to provide an intuitive feel of the underlying dynamics, and then discuss, for each of the three cases, how more realistic scenarios are constructed and how to decipher their experimental signatures. Wherever possible, we provide enough pedagogical details, which the beginners might find useful.

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arXiv2010

A reappraisal of spontaneous R-parity violation

In this short reappraisal of spontaneous lepton number violation in a supersymmetric scenario implemented through singlet sneutrino vacuum expectation value (VEV), we contribute with two new things in the context where the lepton number symmetry is global: (i) provide explicit expressions of $R$-parity violating couplings in terms of the neutrino Yukawa couplings and the singlet sneutrino VEV, and (ii) estimate the limit on this VEV using the current knowledge of the light neutrino mass and the astrophysical constraint on the Majoron-electron coupling. Besides, we put updated constraints on the VEV and Yukawa coupling of the singlet superfield when lepton number is gauged.

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arXiv2010

A phenomenological study of 5d supersymmetry

Supersymmetry and extra dimension need not be mutually exclusive options of physics for the TeV scale and beyond. In this paper, we envisage a phenomenological scenario by embedding the 4d constrained minimal supersymmetric standard model in a flat 5d $S_1 /Z_2$ orbifold, with the inverse radius of compactification at the TeV scale. The gauge, Higgs and the third generation matter multiplets are placed in the bulk. From a 4d perspective, the bulk has N=2 supersymmetry which entails a special non-renormalization theorem giving rise to a significant numerical impact on the renormalization group running of various parameters. The brane supersymmetry corresponds to N=1 which we assume to be broken in an unspecified but phenomenologically acceptable way. Given this set-up, we study how the gauge and Yukawa couplings and the N=1 brane supersymmetry breaking soft masses run through the energy scale exciting the Kaluza-Klein states at regular interval. We present our results by showing the allowed/disallowed zone in the plane of the common scalar mass ($m_0$) and common gaugino mass ($M_{1/2}$). Our plots are the first 5d versions of the often displayed 4d $m_0$--$M_{1/2}$ plots, and we provide reasons behind the differences between the 4d and 5d plots.

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arXiv2010

Correlated enhancements in $D_s \to \ellν$, $(g-2)$ of muon, and lepton flavor violating $τ$ decays with two R-parity violating couplings

With just two R-parity violating couplings, $λ'_{223}$ and $λ'_{323}$, we correlate several channels, namely, $D_s \to \ell ν$ ($\ell = μ, τ$), $(g-2)_μ$, and some lepton flavor violating $τ$ decays. For $λ'_{223} = λ'_{323} \sim 0.3$ and for a common superpartner mass of 300 GeV, which explain the recently observed excesses in the above $D_s$ decay channels, we predict the following R-parity violating contributions: ${\rm Br} (τ\to μγ) \sim 4.5 \cdot 10^{-8}$, ${\rm Br} (τ\to μμμ) \sim 1.2 \cdot 10^{-8}$, ${\rm Br} (τ\to μη/η') \sim 4 \cdot 10^{-10}$, and $(g_μ-2)/2 \sim 4 \cdot 10^{-11}$. We exhibit our results through observable versus observable correlation plots.

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