arXiv subjects

Tirtha Sankar Ray

Publications and source records attributed to Tirtha Sankar Ray.

At least 19 recordsLinked to original sources

arXiv2026

Probing Axion Dark Matter via the Chiral Magnetic Effect in Zero-Bias Weyl Semimetals

Sub-eV axion dark matter behaves as a coherent classical field that can induce macroscopic current in quantum materials. We explore the possibility of axion detection via the chiral magnetic effect in zero-bias Weyl semimetals under a static external magnetic field. We demonstrate that for a $1 \, {\rm cm^2}$ sample in a realistic $10 \, {\rm T}$ magnetic field, the signal remains in the observable femto-ampere range. Utilizing state-of-the-art SQUID-based current readout, the setup can probe axion-electron couplings below existing stellar cooling bounds across a broad range of axion masses.

hep-ph↗

arXiv2025

Constraints on dark matter self-interaction from velocity distribution function in isolated halos

Self-interactions facilitate inter-particle redistribution of energy within the dense regions of galactic halos, implying modifications in the density and velocity distribution of dark matter. Simulating dark-matter only isolated halos for a wide range of mass and specific self-scattering cross-sections, we make a systematic study of the impact of self-scattering on the velocity distribution profiles. We report a conservative bound on $\sigma/m$ $\leq 2.7 \rm cm^2/gm$ at $95\%$ C.L. from observations of rotation curves in Milky-Way size galaxies. Sub-leading bounds from LSB galaxy and clusters are also presented.

hep-ph↗

arXiv2024

Cogenesis of visible and dark matter in a scotogenic model

Within a scotogenic neutrino mass model we explore the cogenesis of matter from the CP violating decay of a heavy $\mathbb{Z}_2$-odd right handed neutrino that simultaneously populates the visible and a multipartite dark sector. The relic density of a sub-GeV scale freeze-in dark matter is generated by the late time decay of the next-to-lightest dark particle dynamically regulated by an interplay with the thermal scattering processes. We show that this model can simultaneously explain visible matter asymmetry and provide a cosmologically viable sub-GeV dark matter while remaining in consonance with the neutrino parameters and flavour observables.

hep-ph↗

arXiv2024

Neutrinos from captured dark matter in galactic stars

Sub-GeV neutrinos produced in a stellar core may emerge from main sequence stars, white dwarfs and brown dwarfs producing possible observable signals of dark matter capture. A distribution of these stars near the Milky Way galactic center will produce a neutrino flux that can be probed at Earth based neutrino observatories like Super-Kamiokande and Hyper-Kamiokande. We demonstrate that this can provide a handle to probe dark matter masses in the $200\,$MeV\,$-$\,$2\,$GeV mass scales that compares favourably with present day direct detection bounds.

hep-ph↗

arXiv2024

Towards a more complete description of hybrid leptogenesis

Hybrid leptogenesis framework combining type I and type II seesaw mechanism for neutrino mass necessarily include scattering topologies involving both the scalar triplet and the right handed neutrino. We demonstrate that a systematic inclusion of these mixed scatterings can significantly alter the evolution of the number densities exhibiting up to a factor ten deviation in the predicted asymmetry as demonstrated by our benchmark scenarios. We provide quantitative constraints on the degeneracy of the seesaw scales where the complete analysis becomes numerically significant, limiting the validity of leptogenesis being dominated by the lightest seesaw species only.

hep-ph↗

arXiv2023

Troubles mounting for multipolar dark matter

In this paper, we revisit the experimental constraints on the multipolar dark matter that has derivative coupling to the visible sector mediated by the Standard Model photon. The momentum dependent interaction enables them to be captured efficiently within massive celestial bodies boosted by their steep gravitational potential. This phenomena makes compact celestial bodies as an efficient target to probe such type of dark matter candidates. We demonstrate that a synergy of the updated direct detection results from DarkSide-50 and LUX-ZEPLIN together with IceCube bounds on high energy solar neutrinos from dark matter capture disfavour the viable parameter space of the dipolar dark matter scenario. Whereas, for the anapole dark matter scenario, a narrow window survives that lies within the reach of prospective heating signals due to the capture of dark matter at cold neutron stars.

hep-ph↗

arXiv2022

Neutrino mass and leptogenesis in a hybrid seesaw model with a spontaneously broken CP

We introduce a novel hybrid framework combining type I and type II seesaw models for neutrino mass where a complex vacuum expectation value of a singlet scalar field breaks CP spontaneously. Using pragmatic organizing symmetries we demonstrate that such a model can simultaneously explain the neutrino oscillation data and generate observed baryon asymmetry through leptogenesis. Interestingly, natural choice of parameters leads to a mixed leptogenesis scenario driven by nearly degenerate scalar triplet and right handed singlet neutrino fields for which we present a detailed quantitative analysis.

hep-ph↗

arXiv2022

Constraints on dark matter self-interaction from galactic core size

Self-interaction of particulate dark matter may help thermalising the central region of the galactic halo and driving core formation. The core radius is expectedly sensitive to the self-interaction strength of dark matter (DM). In this paper we study the feasibility of constraining dark matter self-interaction from the distribution of the core radius in isolated haloes. We perform systematic DM only $N$-body simulations of spherically symmetric isolated galactic haloes in the mass range of $10^{10} $-$10^{15}M_{\odot}$, incorporating the impact of isotropic DM self-interaction. Comparing the simulated profiles with the observational data, we provide a conservative upper limit on the self-interaction cross-section, $ \sigma/m < $ $ 9.8 $ $\ \rm cm^2 /\rm gm $ at $ 95 \% $ confidence level. We report significant dependence of the derived bounds on the galactic density distribution models assumed for the analysis.

astro-ph.GA↗

arXiv2022

Reappraisal of the minimal flavoured $Z^{\prime}$ scenario

Recent results from the intensity frontier indicate the tantalizing possibility of violation in lepton flavour universality. In light of this we revisit the minimal phenomenological $Z'$ model taking in account both vectorial and axial-vectorial flavour violating couplings to the charged leptons. We make a systematic study to identify the minimal framework that can simultaneously explain the recent results on anomalous magnetic moment of muon and electron while remaining in consonance with $R_{K^{(*)}}$, $B^0_s-\bar{B^0_s}$ mixing and angular observables in the $B^+\to K^{+*} \mu^+\mu^-$ channel reported by the LHCb collaboration. We demonstrate that the neutrino trident data imply a further ${\rm SU(2)}_L$ violation in the leptonic couplings of the exotic $Z'$.

hep-ph↗

arXiv2021

Solar constraints on captured electrophilic dark matter

Dark matter captured by interaction with electrons inside the Sun may annihilate via long-lived mediator to produce observable gamma ray signals. We utilize solar gamma ray flux measurements from the Fermi Large Area Telescope and High Altitude Water Cherenkov observatory to put bounds on the dark matter electron scattering cross-section. We find that our limits are four to six orders of magnitude stronger than the existing limits for dark matter masses ranging between GeV to PeV scale.

hep-ph↗

arXiv2021

Broad toplike vector quarks at LHC and HL-LHC

Top like vector quarks arising from underlying strong sectors are expected to have large decay widths pushing them beyond the narrow width approximation. In this paper we consider a broad colored vector quark that strongly couples to an exotic pseudoscalar. We use the full 1PI resummed propagator for the exotic quark to recast the present LHC constraints ruling out masses below $\sim1.2~(1.1)$ TeV for width to mass ratio of $0.1~(0.6)$. We utilize machine learning techniques that are demonstratively more efficient than traditional cut based searches to present the reach of HL-LHC on the parameter space of this broad resonance. We find that at $3~ab^{-1}$ the HL-LHC has a discovery potential up to $1.6$ TeV dominated by the pair production channel. We study the feasibility of using machine learning techniques to analyze the broad resonance peaks expected from these exotic quarks at collider experiments like the LHC.

hep-ph↗

arXiv2021

Neutrinos from captured dark matter annihilation in a galactic population of neutron stars

Particulate dark matter captured by a population of neutron stars distributed around the galactic center while annihilating through long-lived mediators can give rise to an observable neutrino flux. We examine the prospect of an idealised gigaton detector like IceCube/KM3NeT in probing such scenarios. Within this framework, we report an improved reach in spin-dependent and spin-independent dark matter nucleon cross-section below the current limits for dark matter masses in the TeV-PeV range.

hep-ph↗

arXiv2021

Probing composite Higgs boson substructure at the HL-LHC

The Higgs boson may well be a composite scalar with a finite extension in space. Owing to the momentum dependence of its couplings the imprints of such a composite pseudo Goldstone Higgs may show up in the tails of various kinematic distributions at the LHC, distinguishing it from an elementary state. From the bottom up we construct the momentum dependent form factors to capture the interactions of the composite Higgs with the weak gauge bosons. We demonstrate their impact in the differential distributions of various kinematic parameters for the $pp\rightarrow Z^*H\rightarrow l^+l^-b\bar{b}$ channel. We show that this channel can provide an important handle to probe the Higgs' substructure at the HL-LHC.

hep-ph↗

arXiv2020

Halo uncertainties in electron recoil events at direct detection experiments

The dark matter direct detection rates are highly correlated with the phase space distribution of dark matter particles in our galactic neighbourhood. In this paper, we make a systematic study of the impact of astrophysical uncertainties on electron recoil events at the direct detection experiments with Xenon and semiconductor detectors. We find that within the standard halo model there can be up to $ \sim 50\%$ deviation from the fiducial choice in the exclusion bounds from these observational uncertainties. For non-standard halo models, we report a similar deviation from the fiducial standard halo model when fitted with recent cosmological $N$-body simulations while even larger deviations are obtained in case of the observational uncertainties.

hep-ph↗

arXiv2020

Prospects of Migdal Effect in the Explanation of XENON1T Electron Recoil Excess

The XENON1T experiment has recently announced the observation of an excess in electron recoil events at energy range of $1-7$ keV with a $3.5~\sigma$ signal significance over the Standard Model prediction. In this letter we sketch the prospects of explaining such an excess from Migdal ionization events with below threshold nuclear recoil energies. Interestingly, these are expected to show signal events in the ballpark energy scale of the observed excess. We demonstrate that the observed signal can be reproduced through the Migdal effect by an $\mathcal{O}(1)$ GeV neutron-philic dark matter having a spin-dependent coupling with the nucleus. A more optimistic scenario is explored where the Migdal ionization is driven by MeV scale boosted dark matter.

hep-ph↗

arXiv2019

Impact of a colored vector resonance on the collider constraints for top-like top partner

In this work we reappraise the collider constraints from leptonic final states on the vectorlike colored top partners taking into account the impact of exotic colored vector resonances. These colored states are intrinsic to a broad class of models that employ a strongly interacting sector to drive electroweak symmetry breaking. We translate the recent results in the {\sl monolepton + jets} channel as reported by CMS with an integrated luminosity of 35.8 fb$^{-1}$, and {\sl dilepton + jets} and {\sl trilepton + jets} channels as reported by ATLAS with an integrated luminosity of 36.1 fb$^{-1}$ to constrain the parameter space of these class of models. We also comment on the impact and modification of the derived constraints due to the expected fatness of the colored vector resonance, when accounted for beyond the narrow-width approximation by simulating the full one-particle irreducible resummed propagator.

hep-ph↗

arXiv2019

Exchange driven freeze out of dark matter

We introduce a novel mechanism where processes that preserve the number density of the dark sector set the relic density of a thermal particulate dark matter. In a relatively degenerate multipartite dark sector if there is a considerable time lapse between the freeze out of various species then a process like exchange between dark sector constituents can play the pivotal role of driving freeze out and setting dark matter relic density. As a proof of principle, we present simple scalar models with viable dark matter in the GeV scale to demonstrate this phenomenon.

hep-ph↗

arXiv2019

Resonant Assisted Annihilation

Assisted annihilation is a novel mechanism to generate viable sub-GeV thermal dark matter, where a pair of stable dark matter annihilates with an assister to Standard Model states. Typically such $3 \to 2$ annihilation topologies are flux suppressed compared to $2 \to 2$ processes. In this paper, we explore the possibility of a resonant $3 \to 2$ assisted annihilation dominantly driving the freeze-out of dark matter. We demonstrate that in a simple multipartite scalar extension of the Standard Model this can be realized in certain regions of parameter space to provide viable dark matter relic density, in agreement with observation. We demonstrate that for photophilic assisters parts of the parameter space are already constrained by indirect detection experiments and the measurements of CMB anisotropies while substantial regions remain beyond the present limit.

hep-ph↗