arXiv subjects

Debottam Das

Publications and source records attributed to Debottam Das.

At least 37 records · Page 2Linked to original sources

arXiv2020

Probing Doubly and Singly Charged Higgs at $pp$ Collider HE-LHC

We analyse the signal sensitivity of multi-lepton final states at collider that can arise from doubly and singly charged Higgs decay in a type-II seesaw framework. We assume triplet vev to be very small and degenerate masses for both the charged Higgs states. The leptonic branching ratio of doubly and singly charged Higgs states have a large dependency on the neutrino oscillation parameters, lightest neutrino mass scale, as well as neutrino mass hierarchy. We explore this as well as the relation between the leptonic branching ratios of the singly and doubly charged Higgs states in detail. We evaluate the effect of these uncertainties on the production cross-section. Finally, we present a detailed analysis of multi-lepton final states for a future hadron collider HE-LHC, that can operate with center of mass energy $\sqrt{s}=27$ TeV.

hep-ph↗

arXiv2020

A Minimal Model of Torsion Mediated Dark Matter

We present a minimal model of fermionic dark matter (DM), where a singlet Dirac fermion can interact with the Standard Model (SM) particles via the torsion field of gravitational origin. In general, torsion can be realized as an antisymmetric part of the affine connection associated with the spacetime diffeomorphism symmetry and thus can be thought of as a massive axial vector field. Because of its gravitational origin, the torsion field couples to all the fermion fields including the DM with equal strength, which makes the model quite predictive. The DM is naturally stable without any imposition of ad-hoc symmetry {\it e.g.,} $\mathcal{Z}_2$. Apart from producing the correct thermal abundance, singlet fermion can easily evade the stringent bounds on the spin-independent DM-nucleon direct detection cross-section due to its axial nature. However, in the allowed parameter space, strong bounds can be placed on the torsion mass and its couplings to fermions from the recent LHC searches. Assuming a non universal torsion-DM and torsion-SM coupling, smaller values of torsion masses may become allowed. In both cases we also study the reach of spin-dependent direct detection searches of the DM.

hep-ph↗

arXiv2019

Dominant production of heavier Higgs bosons through vector boson fusion in NMSSM

We study the features of the additional Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model where the lightest beyond Standard Model Higgs boson does not dominantly couple to up-type quarks. The new state is dominantly singlet-like while it can also accommodate a small down-type Higgs component. The gluon-gluon fusion cannot be adequate enough for such a Higgs production. We show that the vector-boson fusion may become the leading production mechanism to probe this new scalar at the LHC. Using the existing 13 TeV LHC data for an integrated luminosity $36.1~fb^{-1}$, we show the LHC constraints on the parameter space. Finally, we also study the reach of the planned high luminosity LHC (${\mathcal L}=3~{\rm ab}^{-1}$ at $\sqrt s=$~14 TeV) and the proposed high energy upgrade of the LHC (${\mathcal L}=15~{\rm ab}^{-1}$ at $\sqrt s=$~27 TeV) to probe this singlet-like Higgs scalar.

hep-ph↗

arXiv2018

Exploring Non-Holomorphic Soft Terms in the Framework of Gauge Mediated Supersymmetry Breaking

It is known that in the absence of a gauge singlet field, a specific class of supersymmetry (SUSY) breaking non-holomorphic (NH) terms can be soft breaking in nature so that they may be considered along with the Minimal Supersymmetric Standard Model (MSSM) and beyond. There have been studies related to these terms in minimal supergravity based models. Consideration of an F-type SUSY breaking scenario in the hidden sector with two chiral superfields however showed Planck scale suppression of such terms. In an unbiased point of view for the sources of SUSY breaking, the NH terms in a phenomenological MSSM (pMSSM) type of analysis showed a possibility of a large SUSY contribution to muon $g-2$, a reasonable amount of corrections to the Higgs boson mass and a drastic reduction of the electroweak fine-tuning for a higgsino dominated $\widetildeχ^0_1$ in some regions of parameter space. We first investigate here the effects of the NH terms in a low scale SUSY breaking scenario. In our analysis with minimal gauge mediated supersymmetry breaking (mGMSB) we probe how far the results can be compared with the previous pMSSM plus NH terms based study. We particularly analyze the Higgs, stop and the electroweakino sectors focusing on a higgsino dominated $\widetildeχ^0_1$ and $\widetildeχ^{\pm}_1$, a feature typically different from what appears in mGMSB. The effect of a limited degree of RG evolutions and vanishing of the trilinear coupling terms at the messenger scale can be overcome by choosing a non-minimal GMSB scenario, such as one with a matter-messenger interaction.

hep-ph↗

arXiv2018

Probing sterile neutrinos in the framework of inverse seesaw mechanism through leptoquark productions

We consider an extension of the Standard Model (SM) augmented by two neutral singlet fermions per generation and a leptoquark. In order to generate the light neutrino masses and mixing, we incorporate inverse seesaw mechanism. The right handed neutrino production in this model is significantly larger than the conventional inverse seesaw scenario. We analyze the different collider signatures of this model and find that the final states associated with three or more leptons, multi jet and at least one b-tagged and (or) $τ$-tagged jet can probe larger RH neutrino mass scale. We have also proposed a same-sign dilepton signal region associated with multiple jets and missing energy that can be used to distinguish the the present scenario from the usual inverse seesaw extended SM.

hep-ph↗

arXiv2014

Discovery of Charged Higgs through γγ final states

Extending the Higgs sector by an additional $SU(2)_L$ doublet Higgs boson implies the existence of a charged Higgs boson $H^+$. The LHC experiments search for such particle focusing on it decays into leptonic and quark decay final states, namely $τν$,$cs$ and $tb$. However, if the Higgs sector if further extended, e.g. by a gauge singlet as in the NMSSM, the charged Higgs boson can also decay into a light scalar or pseudoscalar Higgs boson which itself decays further into a two photon final state. We present here scenarios where $H^+$ is produced in top-quark decays with a sizable cross-section such the corresponding signal is well above the Standard Model background at the 13 TeV run of Large Hadron Collider (LHC) with an integrated luminosity 100 fb$^{-1}$.

hep-ph↗

arXiv2014

Right Sneutrino Dark Matter and a Monochromatic Photon Line

The inclusion of right-chiral sneutrino superfields is a rather straightforward addition to a supersymmetric scenario. A neutral scalar with a substantial right sneutrino component is often a favoured dark matter candidate in such cases. In this context, we focus on the tentative signal in the form of a monochromatic photon, which may arise from dark matter annihilation and has drawn some attention in recent times. We study the prospect of such a right sneutrino dark matter candidate in the contexts of both MSSM and NMSSM extended with right sneutrino superfields, with special reference to the Fermi-LAT data.

hep-ph↗

arXiv2013

LHC constraints on M_1/2 and m_0 in the semi-constrained NMSSM

Constraints from searches for squarks and gluinos at the LHC at sqrt{s}=8 TeV are applied to the parameter space of the NMSSM with universal squark/slepton and gaugino masses at the GUT scale, but allowing for non-universal soft Higgs mass parameters (the sNMSSM). We confine ourselves to regions of the parameter space compatible with a 125 GeV Higgs boson with diphoton signal rates at least as large as the Standard Model ones, and a dark matter candidate compatible with WMAP and XENON100 constraints. Following the simulation of numerous points in the m_0-M_{1/2} plane, we compare the constraints on the sNMSSM from 3-5 jets + missing E_T channels as well as from multijet + missing E_T channels with the corresponding cMSSM constraints. Due to the longer squark decay cascades, lower bounds on M_{1/2} are alleviated by up to 50 GeV. For heavy squarks at large m_0, the dominant constraints originate from multijet + missing E_T channels due to gluino decays via stop pairs.

hep-ph↗

arXiv2013

Implications of 98 GeV and 125 GeV Higgs scenario in non-decoupling SUSY with updated ATLAS, CMS and PLANCK data

We discuss both MSSM and NMSSM scenarios in which the lightest Higgs boson with $m_h=98$~GeV is consistent with the small excess ($\sim 2.3 σ$) observed at the LEP in $e^+ e^-\rightarrow Zh$, with $h \rightarrow b {\bar b}$ process and the heavier Higgs boson of mass close to 125~GeV as the observed candidate of the SM Higgs like particle at the LHC. We show the allowed regions in the non-decoupling Higgs zone of MSSM parameter space which are consistent with several low energy constraints coming from heavy flavour physics, latest experimental data on Higgs signals and lower limit on superparticle masses from 7~TeV and 8~TeV LHC run. We also implement the constraints from the relic density of the cold dark matter as obtained from the recent PLANCK data. Additionally, we discuss the possibility of observing the light Higgs boson of mass 98~GeV at the 14~TeV LHC run via $pp \rightarrow V h$, with $h \rightarrow b \bar b$ using the technique of jet substructure. Our analysis shows that at 14~TeV LHC run with 300 ${\rm fb}^{-1}$ luminosity the signal efficiency of such a light Higgs boson is at most 2.5$σ$. Finally, we make a comment on the prospect of proposed $e^+ e^-$ ILC to discover/exclude this light Higgs boson.

hep-ph↗

arXiv2012

Enhancing lepton flavour violation in the supersymmetric inverse seesaw beyond the dipole contribution

In minimal supersymmetric models the $Z$-penguin usually provides sub-dominant contributions to charged lepton flavour violating observables. In this study, we consider the supersymmetric inverse seesaw in which the non-minimal particle content allows for dominant contributions of the $Z$-penguin to several lepton flavour violating observables. In particular, and due to the low-scale (TeV) seesaw, the penguin contribution to, for instance, $\Br(μ\to 3e)$ and $μ-e$ conversion in nuclei, allows to render some of these observables within future sensitivity reach. Moreover, we show that in this framework, the $Z$-penguin exhibits the same non-decoupling behaviour which had previously been identified in flavour violating Higgs decays in the Minimal Supersymmetric Standard Model.

hep-ph↗

arXiv2012

A 130 GeV photon line from dark matter annihilation in the NMSSM

In the Next-to-Minimal Supersymmetric Standard Model, neutralino dark matter can annihilate into a pair of photons through the exchange of a CP-odd Higgs boson in the s-channel. The CP-odd Higgs boson couples to two photons through a loop of dominantly higgsino-like charginos. We show that the parameter space of the NMSSM can accommodate simultaneously i) neutralino-like dark matter of a mass of about 130 GeV giving rise to a 130 GeV photon line; ii) an annihilation cross section of or larger than 10^{-27}cm^3s^{-1}; iii) a relic density in agreement with WMAP constraints; iv) a direct detection cross section compatible with bounds from XENON100, and v) a Standard Model like Higgs mass of about 125 GeV. However, the CP-odd Higgs mass has to lie accidentally close to 260 GeV.

hep-ph↗

arXiv2012

Modified Signals for Supersymmetry in the NMSSM with a Singlino-like LSP

In the framework of the NMSSM with a singlino-like LSP, we study quantitatively the impact of the additional bino -> singlino cascade on the efficiencies in several search channels for supersymmetry of the ATLAS and CMS collaborations. Compared to the MSSM, the additional cascade reduces the missing transverse energy, but leads to additional jets or leptons. For the NMSSM benchmark lines which generalize cMSSM benchmark points, the efficiencies in the most relevant 2/3 jet + missing energy search channels can drop by factors ~1/3 to ~1/7, and can reduce the present lower bounds on M_{1/2} by as much as ~0.9 - 0.75 in the NMSSM for large bino-singlino mass differences. The larger efficiencies in multijet or multilepton search channels are not strong enough to affect this conclusion. In the fully constrained cNMSSM, sparticle decay cascades via the lightest stau can lead to signal cross sections in multilepton and 2tau search channels which are potentially visible at the LHC with 7 TeV center of mass energy.

hep-ph↗

arXiv2012

Enhanced Higgs Mediated Lepton Flavour Violating Processes in the Supersymmetric Inverse Seesaw Model

We study the impact of the inverse seesaw mechanism on several low-energy flavour violating observables such as tau decaying to three muons in the context of the Minimal Supersymmetric Standard Model. As a consequence of the inverse seesaw, the contributions of the right-handed sneutrinos significantly enhance the Higgs-mediated penguin diagrams. We find that different flavour violating branching ratios can be enhanced by as much as two orders of magnitude. We also comment on the impact of the Higgs-mediated processes on the leptonic B-meson decays and on the Higgs flavour violating decays.

hep-ph↗

arXiv2011

Soft supersymmetry breaking with tiny cosmological constant in flux compactified N=1 Supergravity

Using the flux compactification scenario in a generic supergravity model we construct a set of conditions which are necessary to generate de-Sitter or anti de-Sitter vacua for appropriate choices of the parameters in superpotential. It is shown that a mass spectrum consistent with softly broken TeV scale supersymmetry in a minimal supersymmetric standard model at the observable sector can be obtained along with a tiny cosmological constant when the Kahler and superpotential of the hidden sector satisfy a set of general constraints. Constructing a specific model with Kahler and superpotentials which satisfy the above constraints, it is demonstrated that all the hidden sector fields have vacuum expectation values close to Planck scale and the resulting low energy potential does not have any flat direction.

hep-th↗

arXiv2011

NMSDECAY: A Fortran Code for Supersymmetric Particle Decays in the Next-to-Minimal Supersymmetric Standard Model

The code NMSDECAY allows to compute widths and branching ratios of sparticle decays in the Next-to-Minimal Supersymmetric Standard Model. It is based on a generalization of SDECAY, to include the extended Higgs and neutralino sectors of the NMSSM. Slepton 3-body decays, possibly relevant in the case of a singlino-like lightest supersymmetric particle, have been added. NMSDECAY will be part of the NMSSMTools package, which computes Higgs, sparticle masses and Higgs decays in the NMSSM.

hep-ph↗

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.

hep-ph↗

arXiv2010

Exploring SUSY light Higgs boson scenarios via dark matter experiments

We examine the dark matter phenomenology in supersymmetric light higgs boson scenarios, adapting nonuniversal Higgs masses at the gauge coupling unification scale. The correct relic density is obtained mostly through the annihilation into a pseudoscalar $A$, which gives high values for the self-annihilation cross-section at present times. Our analysis shows that most part of the $A$ pole region can produce detectable gamma-rays and antiproton signals, and still be compatible with with recent direct detection data from XENON100 and CDMS-II.

hep-ph↗

arXiv2010

Probing the light Higgs pole resonance annihilation of dark matter in the light of XENON100 and CDMS-II observations

We consider the prospect of lightest neutralino (${\tilde χ}_1^0$) as a dark matter candidate in the light of recent interesting observations from the XENON100 and CDMS-II experiments in minimal supergravity framework with large $\tanβ$ and non-vanishing $A_0$. Within the WMAP satisfied zone, there is a large direct detection reach of lighter ${\tilde χ}_1^0$ in the lighter Higgs boson mediated resonance annihilation domain of the above scenario. It is seen that the heavier Higgs boson plays a dominating role in the ${\tilde χ}_1^0-p$ cross-section in the associated zone of parameter space in spite of having a larger mass. Possible LHC signatures are discussed.

hep-ph↗