arXiv subjects

Partha Kumar Paul

Publications and source records attributed to Partha Kumar Paul.

26 records · Page 2Linked to original sources

arXiv2025

Lepton parity dark matter and naturally unstable domain walls

We propose a simple and predictive setup that connects neutrino masses, dark matter (DM), and gravitational waves. A minimal lepton parity DM scenario is considered where the residual symmetry $(-1)^L$ from the type I seesaw acts as the dark parity $D=(-1)^{L+2j}$, ensuring DM stability without imposing any new symmetry. A singlet Majorana fermion $S$ with even lepton parity serves as the DM candidate, interacting via a real scalar $σ$ which is also even lepton parity. The scalar potential possesses an accidental $\mathcal{Z}_2$ symmetry, whose spontaneous breaking gives rise to unstable domain walls (DW) in the presence of explicit $\mathcal{Z}_2$ breaking terms allowed by the lepton parity. The subsequent DW annihilation generates a stochastic gravitational wave (GW) background potentially observable at different GW experiments.

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arXiv2025

Anatomy of singlet-doublet dark matter relic: annihilation, co-annihilation, co-scattering, and freeze-in

The singlet-doublet vector-like fermion dark matter model has been extensively studied in the literature over the past decade. An important parameter in this model is the singlet-doublet mixing angle ($\sinθ$). All the previous studies have primarily focused on annihilation and co-annihilation processes for obtaining the correct dark matter relic density, assuming that the singlet and doublet components decouple at the same epoch. In this work, we demonstrate that this assumption holds only for larger mixing angles with a dependency on the mass of the dark matter. However, it badly fails for the mixing angle $\sinθ<0.05$. We present a systematic study of the parameter space of the singlet-doublet dark matter relic, incorporating annihilation, co-annihilation, and, for the first time, co-scattering processes. Additionally, non-thermal productions via the freeze-in and SuperWIMP mechanism are also explored. We found that due to the inclusion of co-scattering processes, the correct relic density parameter space is shifted towards the detection sensitivity range of the LHC and MATHUSLA via displaced vertex signatures.

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arXiv2025

Super heavy dark matter origin of the PeV neutrino event: KM3-230213A

The recent observation of the ultrahigh-energy neutrino event KM3-230213A by the KM3NeT experiment offers a compelling avenue to explore physics beyond the Standard Model (SM). In this paper, we explore a simplest possibility that this event originates from the decay of a super-heavy dark matter (SHDM). We consider a minimal scenario where the SHDM decays to neutrino and SM Higgs. We derive constraints on the DM lifetime as a function of DM mass, ensuring consistency with IceCube, Auger upper limits, and the observed KM3-230213A event, along with the gamma-ray constraints. We find that KM3-230213A gives stringent constraint on the DM mass ranging from $1.5\times10^8$ GeV to $5.2\times10^9$ GeV with lifetime in the range: $1.42\times10^{30}$ s to $5.4\times10^{29}$ s. Remarkably, in our SHDM scenario, the apparent tension between the KM3NeT observation and the nonobservation of this event by IceCube and Auger can be reduced to below $1.2σ$. Our results are applicable to any neutrinophilic SHDM models while evading gamma-ray constraints.

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arXiv2025

Thermal leptogenesis, dark matter, and gravitational waves from an extended canonical seesaw scenario

In a canonical type-I seesaw scenario, the Standard Model is extended with three singlet right-handed neutrinos (RHNs) $N_i, i=1,2,3$ with masses $M_i, i=1,2,3$ to simultaneously explain sub-eV masses of light neutrinos and baryon asymmetry of the Universe at high scales. In this paper, we show that a relatively low-scale thermal leptogenesis accompanied by gravitational wave signatures is possible when the type-I seesaw is extended with a singlet fermion ($S$) and a singlet scalar ($ρ$), where $S$ and $ρ$ are odd under a discrete $Z_2$ symmetry. We also add a vectorlike fermion doublet $Ψ$ and impose a $Z^\prime_2$ symmetry under which both $N_1$ and $Ψ$ are odd while all other particles are even. This gives rise to a singlet-doublet Majorana fermion dark matter in our setup. At a high scale, the $Z_2$ symmetry is broken spontaneously by the vacuum expectation value of $ρ$ and leads to (i) mixing between RHNs ($N_2, N_3$) and $S$, and (ii) formation of Domain walls (DWs). In the former case, the final lepton asymmetry is generated by the out-of-equilibrium decay of $S$, which dominantly mixes with $N_2$. We show that the scale of thermal leptogenesis can be lowered to $M_S \sim 2 \times 10^6$ GeV, which is \textit{3} orders of magnitude lower than the thermal leptogenesis in canonical type-I seesaw. In the latter case, the disappearance of the DWs gives observable gravitational wave signatures, which can be probed at LISA, DECIGO, ${\rm μARES}$ etc.

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arXiv2025

Asymmetric long-lived dark matter and leptogenesis from type-III seesaw framework

We propose a simple model in the type-III seesaw framework to explain the neutrino mass, asymmetric dark matter (ADM), and baryon asymmetry of the Universe. We extend the standard model with a vector-like singlet lepton ($χ$) and a hypercharge zero scalar triplet ($Δ$) in addition to three hypercharge zero triplet fermions($Σ_i~,i=1,2,3$). A $Z_2$ symmetry is imposed under which $χ$ and $Δ$ are odd, while all other particles are even. As a result, the lightest $Z_2$ odd particle $χ$ behaves as a candidate of DM. In the early Universe, the $CP$-violating out-of-equilibrium decay of heavy triplet fermions to the Standard Model lepton ($L$) and Higgs ($H$) generate a net lepton asymmetry, while that of triplet fermions to $χ$ and $Δ$ generate a net asymmetric DM. The lepton asymmetry is converted to the required baryon asymmetry of the Universe via the electroweak sphalerons, while the asymmetry in $χ$ remains as a DM relic that we observe today. We introduce a singlet scalar $Φ$, with mass $M_ϕ< M_χ$, which not only assists to deplete the symmetric component of $χ$ through the annihilation process: $\barχ χ\to ΦΦ$ but also paves a path to detect DM $χ$ at direct search experiments through $Φ-H$ mixing. The electro-weak symmetry breaking induces a non-zero vacuum expectation value to $Δ$, which leads to an unstable asymmetric DM ranging from a few MeV to hundreds of GeV. We then explore the displaced vertex signatures of the charged components of the scalar triplet $Δ$ at colliders.

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arXiv2024

Asymmetric self-interacting dark matter with a canonical seesaw model

We study the possibility of generating dark matter (DM) and baryon asymmetry of the Universe (BAU) simultaneously in an asymmetric DM framework, which also alleviates the small-scale structure issues of cold DM. While the thermal relic of such self-interacting DM remains under-abundant due to efficient annihilation into light mediators, a nonzero asymmetry in the dark sector can lead to the survival of the required DM in the Universe. The existence of a light mediator leads to the required self-interactions of DM at small scales while keeping DM properties similar to cold DM at large scales. It also ensures that the symmetric DM component annihilates away, leaving the asymmetric part in the spirit of cogenesis. The particle physics implementation is done in canonical seesaw models of light neutrino mass, connecting it to the origin of DM and BAU. In particular, we consider type-I and type-III seesaw origin of neutrino mass for simplicity and minimality of the field content. We show that the desired self-interactions and relic of DM together with BAU while satisfying relevant constraints lead to strict limits on DM mass $\mathcal{O}({\rm GeV}) \lesssim M_{\rm DM} \lesssim460 $ GeV. In spite of being a high-scale seesaw, the models remain verifiable in different experiments, including direct and indirect DM searches as well as colliders.

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arXiv2024

Scotogenic $U(1)_{L_μ-L_τ}$ origin of $(g-2)_μ$, W-mass anomaly and 95 GeV excess

We study a scotogenic extension of the minimal gauged $L_μ-L_τ$ model, including three right-handed singlet fermions and a scalar doublet all odd under an in-built $Z_2$ symmetry to explain the anomalous magnetic moments of the muon, CDF-II W-mass anomaly, and the 95 GeV excess reported by the CMS collaboration. While the minimal model can successfully explain the muon $(g-2)$ and CDF-II W-mass anomalies, the required diphoton signal strength for the 95 GeV scalar, together with that of the SM Higgs, can not be obtained in the minimal model. The same can, however, be explained by incorporating one additional scalar doublet whose only role is to contribute radiatively to diphoton decay modes of the light, neutral scalars. Due to the scotogenic extension, the model remains consistent with the observed properties of light neutrinos and dark matter in the Universe.

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arXiv2023

Connecting dark matter, baryogenesis and neutrinoless double beta decay in a $A_{4}\otimes Z_{8}$ based $ν$2HDM

In this paper, we discuss the impact of neutrino phenomenology and related cosmology on an $A_{4}\otimes Z_{8}$ symmetric $ν$2HDM along with an addition of a new particle, i.e. a gauge singlet(S). The additional particle is a sterile neutrino which is considered to be a probable dark matter candidate in our work. With the choice of sterile neutrino mass in keV range we evaluate the active-DM mixing angle, decay rate and relic abundance considering various cosmological constraints. Simultaneously, a detailed analysis on baryogenesis and neutrinoless double beta decay is also carried out for low scale right-handed neutrino masses. We have considered various bounds from experiments such as Lyman-$α$, X-ray observation, Planck data and KamLAND-Zen limit to validate the model w.r.t the phenomena studied in it.

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