arXiv subjects

Vandana Sahdev

Publications and source records attributed to Vandana Sahdev.

5 recordsLinked to original sources

arXiv2025

Search for Quadruplet Scalars using Boosted Decision Trees at the LHC

Beyond the Standard Model scenarios introduce additional scalar and fermion multiplets, which influence neutrino mass generation mechanisms and yield distinctive collider signatures. This work focuses on a particular scenario involving a fermion quintuplet and a scalar quadruplet. The study examines the production and decay of the scalar quadruplet components at the Large Hadron Collider (LHC), emphasizing how their decay patterns, fermiophobic versus fermiophilic, depend on mass differences and Yukawa couplings with the fermion multiplets. This study provides an overview of possible signals at the LHC, along with a detailed collider analysis focused on final states containing at least four leptons and two jets, in which the masses of the scalars and fermions are reconstructed successfully. Standard Model backgrounds are also incorporated in the study, with multivariate techniques leveraged via Boosted Decision Trees. Results indicate discovery potential for scalar masses around 600-700 GeV and exclusion sensitivity extending beyond 1 TeV, highlighting the promising experimental signatures of the model and its role in probing new physics at colliders.

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arXiv2025

Exotic Decays and Collider Signatures of pNGB Scalars in the $SU(5)/SO(5)$ Composite Higgs Model

The nature of the Higgs boson, whether it is elementary or composite, will be investigated through precision measurements at the collider experiments. In composite Higgs scenarios, the Higgs may manifest as a pseudo Nambu-Goldstone boson (pNGB) arising from a strongly interacting sector. The $SU(5)/SO(5)$ Composite Higgs Model features a rich scalar sector, with the decay patterns of the scalars being heavily influenced by the way fermions are embedded in various representations of $SU(5)$. We discuss how masses of the pNGB scalars and their couplings depend functionally on the compositeness scale and the parameters of the strong sector. Unique decay modes of the scalars emerge from the model when the mixing among the various pNGB scalars is non-negligible. We present a comprehensive and thorough analysis of the fermiophilic and fermiophobic decay modes of the pNGB scalars. Significant differences are observed in the decay patterns of the two singly charged scalars. Further, the decay of one pNGB to another on-shell pNGB when masses exceed about $1$ TeV presents a rich phenomenology, leading to distinctive signatures at the colliders. In this context, the future muon collider offers a promising avenue for detecting pNGB scalars with masses larger than $1$ TeV, especially in final states involving $W/Z$ fatjets.

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arXiv2024

Neutrino masses, anomalous magnetic moments and dark matter with vector-like fermions and an inert scalar doublet

The beyond-the-standard-model scenario in this work is motivated from the observations of neutrino masses, anomalous magnetic moments of electron and muon, and dark matter in the Universe. We explain these observations by extending the standard model with two generations of vector-like fermions and an inert scalar doublet, all odd under a $Z_2$ symmetry. The light neutrino masses and mixings are generated radiatively while maintaining consistency with bounds on lepton flavor violation. Loop diagrams with the very same fields also serve to explain the anomalous magnetic moments. Similarly, the correct dark matter relic abundance is reproduced without coming into conflict with direct detection constraints, or those from big bang nucleosynthesis or the cosmic microwave observations. Finally, prospective signatures at the LHC are discussed.

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arXiv2021

Alternative signatures of the quintuplet fermions at the LHC and future linear colliders

Large fermionic multiplets appear in different extensions of the Standard Model (SM), which are essential to predict small neutrino masses, relic abundance of the dark matter (DM) and the measured value of muon anomalous magnetic moment (muon (g-2)). Models containing quintuplet of fermions ($\Sigma$), along with other scalar multiplets, can address recent anomalies in the flavor sector while satisfying the constraints from the electroweak physics. In standard scenarios, the exotic fermions couple with the SM particles directly and there exists a strong limit on their masses from collider experiments such as the Large Hadron Collider (LHC). In this paper, we choose a particular scenario where the quintuplet fermions are heavier than the scalars, which is naturally motivated from the muon (g-2) data. A unique nature of these models is that they predict non-standard signatures at the colliders as the quintuplet fermions decay via the scalars once produced at the colliders. We study these non-standard interactions and provide alternative search strategies for these exotic fermions at the LHC and future linear colliders (such as $e^+e^-$ colliders). We also discuss their exclusion and discovery limits. For the doubly charged quintuplet fermion ($\Sigma^{\pm\pm}$), discovery is possible with 5$\sigma$ significance at integrated luminosity of 3000 fb$^{-1}$ at 14 TeV LHC if $M_\Sigma\leq 980$ GeV. For the singly charged quintuplet fermion ($\Sigma^\pm$), the discovery is challenging at LHC but there might be a possibility of 5 $\sigma$ discovery with 1000 fb$^{-1}$ luminosity at $e^+e^-$ collider for $M_\Sigma\leq 700$ GeV.

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arXiv2020

Dark Matter, Muon Anomalous Magnetic Moment and the XENON1T Excess

A very economic scenario with just three extra scalar fields beyond the Standard Model is invoked to explain the muon anomalous magnetic moment, the requisite relic abundance of dark matter as well as the Xenon-1T excess through the inelastic down-scattering of the dark scalar.

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