arXiv subjects

Shivam Gola

Publications and source records attributed to Shivam Gola.

6 recordsLinked to original sources

arXiv2026

Hunting Sterile Neutrino Dark Matter in the MeV Gap

We investigate the sensitivities of upcoming MeV gamma-ray telescopes to sterile neutrino dark matter in the mass range $(0.2-100)\,{\rm MeV}$. Sterile neutrinos in this regime can produce observable photon signals through radiative two-body decays and three-body decays with final-state radiation. We perform a Fisher forecasting analysis incorporating realistic astrophysical background modeling and detector response to derive projected constraints on the sterile neutrino decay rate. We find that future MeV instruments can improve existing limits by several orders of magnitude across a wide region of parameter space. Our results highlight the discovery potential of next-generation MeV telescopes in probing sterile neutrino dark matter.

hep-ph↗

arXiv2025

Dark matter from axion and small neutrino mass

We explore a KSVZ-like extension of the Standard Model with a Dirac fermion and three right-handed neutrinos. PQ symmetry allows the Dirac mass for neutrinos and prevents the Majorana mass. A $\mathcal{Z}_2$ symmetry guarantees the stability of Dirac fermion dark matter. The breakdown of PQ symmetry generates the QCD axion at a high scale. The fermion dark matter relic abundance arises from the UV-freeze-in mechanism through the axion portal. We determine the fermion DM relic by solving the coupled Boltzmann equations and finding the allowed parameter space using the relic density constraints. Having determined the allowed parameter space for fermion DM, we also look for non-thermal axion production schemes to seek the two DM possibility. We find that FIMP alone is a suitable dark matter that is not excluded while considering several current bounds and future sensitivities on axion and dark matter. Our study highlights the interlinking of dark matter, axion, and neutrinos while addressing the strong CP problem and small neutrino masses.

hep-ph↗

arXiv2024

A Phenomenological Study of WIMP Models

In this thesis, we investigate various possibilities of Weakly Interacting Massive Particle (WIMP) dark matter (DM) and their implications. These possibilities are important because they challenge the viability of WIMP DM in light of tight constraints from experiments such as direct detection. We begin by analyzing a fermion dark matter possibility with an axion-like particle (ALP) portal. We consider theoretical and experimental limits related to neutrino and ALP data within a certain mass range, and we find the allowed parameter space. This possibility resolves the problem of the lack of direct detection of WIMP DM through the ALP portal. Furthermore, we examine the limits on photon signals from HESS and Fermi-LAT data. Next, we look at a two-component scalar and fermion dark matter possibility, following a similar approach to our previous work. This simple possibility requires only a few additional fields and symmetries to explain neutrino mass and dark matter candidates. By finding parameter space that satisfies various bounds, such as relic density, direct detection, and invisible Higgs width, we show that both scalar and fermion particles can serve as DM. This possibility is consistent and offers a rich spectrum of phenomenology that can be tested through collider-based experiments. In our final work, we removie the extra Z2 symmetry and added a new pseudoscalar particle in our two compoent model. We test this pseudoscalar particle against multiple DM and non-DM related bounds, including DM lifetime bound, Planck bound, direct-detection limits from various target materials, and invisible Higgs width. The possibility exhibits a significant parameter space for our pseudoscalar DM while being in agreement with theoretical and experimental limits.

hep-ph↗

arXiv2023

Pseudo scalar dark matter in a generic U$(1)_X$ model

We consider a $U(1)_X$ extension of the Standard Model~(SM), where the spontaneous breaking of $U(1)_X$ gauge group results in a pseudo scalar particle which is the proposed candidate for dark matter. In the model, we introduce three right-handed neutrinos~(RHNs) $N_R^i$ and two extra scalars $Φ$, $χ$, which are SM gauge singlets but charged under $U(1)_X$ gauge group. Right-handed neutrinos are required to have the model anomaly free and explain the neutrino oscillation data. The heaviest scalar breaks the $U(1)_X$ gauge symmetry and the other extra scalar gives a pseudo scalar DM candidate. A pseudo scalar dark matter~(DM) is an interesting candidate as it naturally evades the stringent direct detection bounds due to its coupling structure. We study the phenomenology of this pseudo-scalar DM while considering several theoretical and experimental constraints. We find that in our model, there is a feasible parameter space, which satisfies by the DM lifetime bound, relic and direct detection constraints while respecting the colliders and other bounds.

hep-ph↗

arXiv2022

ALP-portal majorana dark matter

Axion like particles(ALPs) and right handed neutrinos~(RHNs) are two well-motivated dark matter(DM) candidates. However, these two particles have a completely different origin. Axion was proposed to solve the Strong CP problem, whereas RHNs were introduced to explain light neutrino masses through seesaw mechanisms. We study the case of ALP portal RHN DM taking into account existing constraints on ALPs. We consider the leading effective operators mediating interactions between the ALP and SM particles and three RHNs to generate light neutrino masses through type-I seesaw. Further, ALP-RHN neutrino coupling is introduced to generalize the model which is restricted by the relic density and indirect detection constraint.

hep-ph↗

arXiv2022

Two-component scalar and fermionic dark matter candidates in a generic U$(1)_X$ model

We consider a $U(1)_X\otimes \mathbb{Z}_2\otimes \mathbb{Z}'_2$ extension of the Standard Model (SM), where the $U(1)_X$ charge of an SM field is given by a linear combination of its hypercharge and B$-$L number. Apart from the SM particle content, the model contains three right-handed neutrinos (RHNs) $N_R^i$ and two scalars $Φ$, $χ$, all singlets under the SM gauge group but charged under $U(1)_X$ gauge group. Two of these additional fields, fermion $N_R^3$ is odd under $\mathbb{Z}_2$ and scalar $χ$ is odd under $\mathbb{Z}'_2$ symmetry. Thus both $χ$ and $N_R^3$ contribute to the observed dark matter relic density, leading to two-component dark matter candidates. We study in detail its dark matter properties such as relic density and direct detection taking into account the constraints coming from collider studies. We find that in our model, there can be possible annihilation of one Dark Matter (DM) into the other, which may potentially alter the relic density in a significant way.

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