arXiv subjects

Purusottam Ghosh

Publications and source records attributed to Purusottam Ghosh.

28 records · Page 2Linked to original sources

arXiv2021

Singlet-Doublet Majorana Dark Matter and Neutrino Mass in a minimal Type-I Seesaw Scenario

In a bid to simultaneous explanation of dark matter (DM) and tiny but non-zero masses of left-handed neutrinos, we propose a minimal extension of the Standard Model (SM) by a vector-like fermion doublet and three right handed (RH) singlet neutrinos. The DM arises as a mixture of the neutral component of the fermion doublet and one of the RH neutrinos, both assumed to be odd under an additional $\mathcal{Z}_2$ symmetry. As a result, the DM emerges to be a dominantly Majorana particle and escapes from $Z$-mediated direct search constraints to mark a significant difference from singlet-doublet Dirac DM. The other two $\mathcal{Z}_2$ even heavy RH neutrinos give rise masses and mixing of light neutrinos via Type-I Seesaw mechanism. The particle content automatically allows us to extend the model by a gauged $U(1)_{B-L}$ symmetry, which is anomaly free and brings an additional portal between DM and SM particles. Relic density and direct search allowed parameter space for both the cases are investigated through detailed numerical scan, while collider search strategies are also indicated.

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arXiv2020

Two component dark matter with inert Higgs doublet: neutrino mass, high scale validity and collider searches

The idea of this work is to investigate the constraints on the dark matter (DM) allowed parameter space from high scale validity (absolute stability of Higgs vacuum and perturbativity) in presence of multi particle dark sector and heavy right handed neutrinos to address correct neutrino mass. We illustrate a simple two component DM model, consisting of one inert $SU(2)_L$ scalar doublet and a scalar singlet, both stabilised by additional $\mathcal{Z}_2 \times \mathcal{Z}^{'}_2$ symmetry, which also aid to vacuum stability. We demonstrate DM-DM interaction helps achieving a large allowed parameter space for both the DM components by evading direct search bound. High scale validity puts further constraints on the model, for example, on the mass splitting between the charged and neutral component of inert doublet, which has important implication to its leptonic signature(s) at the Large Hadron Collider (LHC).

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arXiv2020

SIMPler realisation of Scalar Dark Matter

With growing agony of not finding a dark matter (DM) particle in direct search experiments so far (for example in XENON1T), frameworks where the freeze-out of DM is driven by number changing processes within the dark sector itself and do not contribute to direct search, like Strongly Interacting Massive Particle (SIMP) are gaining more attention. In this analysis, we ideate a simple scalar DM framework stabilised by $Z_3$ symmetry to serve with a SIMP-like DM ($χ$) with additional light scalar mediation ($ϕ$) to enhance DM self interaction. We identify that a large parameter space for such DM is available from correct relic density and self interaction constraints coming from Bullet or Abell cluster data. We derive an approximate analytic solution for freeze-out of the SIMP like DM in Boltzmann Equation describing $3 \to 2$ number changing process within the dark sector. We also provide a comparative analysis of the SIMP like solution with the Weakly Interacting Massive Particle (WIMP) realisation of the same model framework here.

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arXiv2019

Flavoured gauge extension of singlet-doublet fermionic dark matter: neutrino mass, high scale validity and collider signatures

We propose an Abelian gauged version of the singlet-doublet fermionic dark matter (DM) model where DM, combination of a vector like fermion doublet and a fermion singlet, is naturally stabilised by the gauge symmetry without requiring any ad-hoc discrete symmetries. In order to have good detection prospects at collider experiments like the large hadron collider (LHC) and enlarged parameter space for low mass DM, we consider the additional gauge symmetry to be based on the quantum $B-3L_τ$ where the restriction to third generation of leptons is chosen to have weaker bounds from the LHC on the corresponding gauge boson. The triangle anomalies arising in this model can be cancelled by including a right handed neutrino which takes part in generating light neutrino masses through type I seesaw mechanism. Apart from DM, collider prospects and light neutrino masses, the model also offers high scale validity giving rise to a stable electroweak vacuum and perturbative couplings all the way up to the Planck scale. We constrain our model parameters from these requirements as well as existing relevant constraints related to DM and colliders.

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arXiv2019

Fermion Dark Matter with Scalar Triplet at Direct and Collider Searches

Fermion dark matter (DM) as an admixture of additional singlet and doublet vector like fermions provides an attractive and allowed framework by relic density and direct search constraints within TeV scale, although limited by its discovery potential at the Large Hadron Collider (LHC). An extension of the model with scalar triplet can yield neutrino masses and provide some cushion to the direct search constraint of the DM through pseudo-Dirac mass splitting. This in turn, allow the model to live in a larger region of the parameter space and open the door for detection at LHC, even if slightly. The model however can see an early discovery at International Linear Collider (ILC) without too much of fine-tuning. The complementarity of LHC, ILC and direct search prospect of this framework is studied in this paper.

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arXiv2019

A Mini-review on Vector-like Leptonic Dark Matter, Neutrino Mass and Collider Signatures

We review a class of models in which the Standard Model (SM) is augmented by vector-like leptons: one doublet and a singlet, which are odd under an unbroken discrete $Z_2$ symmetry. As a result, the neutral component of these additional vector-like leptons are stable and behave as dark matter. We study the phenomenological constraints on the model parameters and elucidate the parameter space for relic density, direct detection and collider signatures of dark matter. In such models, we further add a scalar triplet of hypercharge two and study the consequences. In particular, after electro weak symmetry breaking (EWSB), the triplet scalar gets an induced vacuum expectation value (vev), which yield Majorana masses not only to the light neutrinos but also to vector-like leptonic doublet DM. Due to the Majorana mass of DM, the $Z$ mediated elastic scattering with nucleon is forbidden and hence allowing the model to survive from stringent direct search bound. The DM without scalar triplet lives in a small singlet-doublet leptonic mixing region ($\sinθ\le 0.1$) due to large contribution from singlet component and have small mass difference ($Δm \sim 10$ GeV) with charged companion, the NLSP (next to lightest stable particle), to aid co-annihilation for yielding correct relic density. Both these observations change to certain extent in presence of scalar triplet to aid observability of hadronically quiet leptonic final states at LHC, while one may also confirm/rule-out the model through displaced vertex signal of NLSP, a characteristic signature of the model in relic density and direct search allowed parameter space.

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arXiv2019

Multipartite Dark Matter with Scalars, Fermions and signatures at LHC

Basic idea of this analysis is to achieve a two-component dark matter (DM) framework composed of a scalar and a fermion, with non-negligible DM-DM interaction contributing to thermal freeze out (hence relic density), but hiding them from direct detection bounds. We therefore augment the Standard Model (SM) with a scalar singlet ($S$) and three vectorlike fermions: two singlets ($χ_1,χ_2$) and a doublet ($N$). Stability of the two DM components is achieved by a discrete $\mathcal{Z}_2 \times {\mathcal{Z}^\prime}_2$ symmetry, under which the additional fields transform suitably. Fermion fields having same $\mathcal{Z}_2 \times {\mathcal{Z}^\prime}_2$ charge ($N,χ_1$ in the model) mix after electroweak symmetry breaking (EWSB) and the lightest component becomes one of the DM candidates, while scalar singlet $S$ is the other DM component connected to visible sector by Higgs portal coupling. The heavy fermion ($χ_2$) plays the role of mediator to connect the two DM candidates through Yukawa interaction. This opens up a large parameter space for the heavier DM component through DM-DM conversion. Hadronically quiet dilepton signature, arising from the fermion dark sector, can be observed at Large Hadron Collider (LHC) aided by the presence of a lighter scalar DM component, satisfying relic density and direct search bounds through DM-DM conversion.

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arXiv2018

Study of Electroweak Vacuum Stability from Extended Higgs Portal of Dark Matter and Neutrinos

We investigate the electroweak vacuum stability in an extended version of the Standard Model which incorporates two additional singlet scalar fields and three right handed neutrinos. One of these extra scalars plays the role of dark matter while the other scalar not only helps in making the electroweak vacuum stable but also opens up the low mass window of the scalar singlet dark matter (< 500 GeV). We consider the effect of large neutrino Yukawa coupling on the running of Higgs quartic coupling. We have analyzed the constraints on the model and identify the range of parameter space which is consistent with neutrino mass, appropriate relic density and direct search limits from the latest XENON 1T preliminary result as well as in realizing the stability of the electroweak vacuum upto the Planck scale.

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arXiv2017

Mitigating Direct Detection Bounds in Non-minimal Higgs Portal Scalar Dark Matter Models

Minimal scalar Higgs portal dark matter model is increasingly in tension with recent results form direct detection experiments like LUX and XENON. In this paper we make a systematic study of minimal extension of the $ \mathbb{Z}_2$ stabilised singlet scalar Higgs portal scenario in terms of their prospects at direct detection experiments. We consider both enlarging the stabilising symmetry to $\mathbb{Z}_3$ and incorporating multipartite features in the dark sector. We demonstrate that in these non-minimal models the interplay of annihilation, co-annihilation and semi-annihilation processes considerably relax constraints from present and proposed direct detection experiments while simultaneously saturating observed dark matter relic density. We explore in particular the resonant semi-annihilation channel within the multipartite $\mathbb{Z}_3$ framework which results in new unexplored regions of parameter space that would be difficult to constrain by direct detection experiments in the near future. The role of dark matter exchange processes within multi-component $\mathbb{Z}_3 \times \mathbb{Z}_3'$ framework is illustrated. We make quantitative estimates to elucidate the role of the various annihilation processes in the different allowed regions of parameter space of these models.

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arXiv2017

Multipartite Interacting Scalar Dark Matter in the light of updated LUX data

We explore constraints on multipartite dark matter (DM) framework composed of singlet scalar DM interacting with the Standard Model (SM) through Higgs portal coupling. We compute relic density and direct search constraints including the updated LUX bound for two component scenario with non-zero interactions between two DM components in $\mathcal{Z}_2\times \mathcal{Z}_2^{'}$ framework in comparison with the one having $\mathcal{O}(2)$ symmetry. We point out availability of a significantly large region of parameter space of such a multipartite model with DM-DM interactions.

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