arXiv subjects

Dipankar Pradhan

Publications and source records attributed to Dipankar Pradhan.

15 recordsLinked to original sources

arXiv2026

Complex Scalar Dark Matter with a Vector-Like Quark and Lepton: Precision, Flavor, and HL-LHC

We investigate a minimal extension of the SM consisting of a $\mathbb{Z}_3$-stabilized complex scalar dark matter (CSDM) candidate, a down-type vector-like quark (VLQ), and a charged vector-like lepton (VLL). The additional vector-like fermions not only enable the CSDM to reproduce the observed relic abundance beyond the Higgs-resonance region through semi-annihilation and co-annihilation processes, but also induce correlated signatures across flavor, electroweak precision, dark matter, and collider observables. We perform a comprehensive one-loop analysis of neutral meson mixing, rare meson decays, charged lepton flavor violation, anomalous magnetic moments of charged leptons, and $Z$-pole observables. We find that neutral meson mixing and rare meson decays provide the dominant constraints on the VLQ sector, while charged lepton flavor-violating processes strongly restrict the VLL Yukawa couplings. Current direct-detection limits require Higgs-DM coupling $\lambda_{\Phi H} \lesssim5\times10^{-3}$ and the VLQ Yukawa coupling $\mathtt{y}_d \lesssim 0.05$ for TeV-scale VLQ masses, whereas present indirect-detection searches impose no additional constraints. Combining all flavor, electroweak precision, dark matter, and collider constraints, we identify viable parameter regions with CSDM masses above approximately $1.0~\rm TeV$ and VLQ masses above about $1.5~\rm TeV$. We also find that the LHC can exclude VLQs (VLLs) with masses up to approximately $1.6~(0.38)$ TeV, depending on the CSDM mass, at the $2\sigma$ confidence level. The HL-LHC can further probe an extended region of the parameter space, with discovery prospects at the $3\sigma$ level. Finally, we demonstrate the complementarity of flavor, dark matter, and collider searches in probing this framework.

hep-ph↗

arXiv2026

From WIMP to FIMP during reheating: collider vs non-collider probes for p-wave annihilation

By examining the transition from freeze-out to freeze-in dark matter (DM) production within the framework of perturbative reheating, where DM interacts with the visible sector through effective operators of dimension six, we have investigated how a broad range of new physics probes can reveal the nature of the pre-BBN Universe. Incorporating constraints from direct and indirect DM searches, invisible decay measurements, collider experiments, and gravitational wave observations, our analysis demonstrates that both current and forthcoming experimental sensitivities can serve as powerful tools for probing as well as constraining the post-inflationary era, together with new physics beyond the SM. Our analysis demonstrates that collider experiments at both the intensity and energy frontiers can impose strong bounds on derivative operators whose interactions are typically {\it p-wave suppressed}, and therefore only weakly constrained by astrophysical observations. In particular, these complementary searches can significantly restrict the allowed reheating temperature, DM mass and effective interaction scale required to reproduce the observed DM abundance for DM produced during the epoch of reheating.

hep-ph↗

arXiv2025

Complex scalar dark matter with effective Higgs portals beyond radiation domination

The increasingly stringent bounds on the Higgs-portal coupling, arising from dark matter (DM) direct-detection searches, confront the minimal renormalizable complex scalar DM scenario with thermal production, where freeze-out occurs in the standard radiation-dominated era. This limitation can be alleviated by introducing a dimension-5 Higgs-portal operator in the minimal renormalizable complex scalar DM model and/or by modifying the standard cosmological history of the Universe. In this article, we analyze complex scalar DM production in both the reheating and radiation-dominated epochs within an effective field theory (EFT) framework. While both scenarios exhibit sizeable regions of parameter space consistent with existing constraints, freeze-out during reheating opens up additional viable regions that are otherwise ruled out by DM overabundance in the radiation-dominated scenario. Notably, the renormalizable Higgs-portal coupling is constrained by relic density, direct- and indirect-detection limits, whereas the EFT coupling associated with the dimension-5 operator is constrained by relic density and indirect-detection bounds arising from DM semi-annihilation. We further study the production cross section of complex scalar DM at hadron and lepton colliders.

hep-ph↗

arXiv2025

Multi-messenger FIMP

We propose a multi-messenger frontier probe of non-thermal or freeze-in massive particle (FIMP) dark matter (DM) by considering an effective field theory (EFT) setup. Assuming leptophilic operators connecting DM with the standard model (SM) bath, we consider DM mass ($m_{\rm DM}$) and the reheat temperature of the Universe ($T_{\rm rh}$) in a regime which prevents DM-SM thermalisation. Low $T_{\rm rh}$ allows sizeable DM-SM interactions even for non-thermal DM allowing the latter to be probed at direct, indirect detection frontiers as well as future electron-positron and muon colliders. An extended reheating period governed by monomial inflaton potential after its slow-roll phase not only generates the required abundance of non-thermal DM via ultraviolet (UV) freeze-in but also brings the scale-invariant primordial gravitational waves (GW) within reach of near future experiments across a wide range of frequencies. While particle physics experiments can probe $T_{\rm rh} \sim O(10)$ GeV and FIMP DM with mass $m_{\rm DM} \sim O(1)$ TeV, future GW detectors are sensitive to a much wider parameter space.

hep-ph↗

arXiv2025

Up-type FCNC in presence of Dark Matter

Dark Matter (DM) is a known unknown. Apart, current experimental constraints on flavor-changing neutral current (FCNC) processes involving up-type quarks also provide scope to explore physics beyond the Standard Model (SM). In this article, we establish a connection between the flavor sector and the DM sector with minimal extension of the SM. Here a singlet complex scalar field, stable under $\mathbb{Z}_3$ symmetry, acts as DM and couples to SM up-type quarks through a heavy Dirac vector-like quark (VLQ), which shares the same $\mathbb{Z}_3$ charge as of the DM. The model thus addresses the observed $D^0-\bar{D^0}$ mixing, top-FCNC interactions, and $D^0$ meson decays, together with DM relic density, while evading the direct and indirect DM search bounds. The model can be probed at the future high-energy muon collider, through distinctive signatures of VLQ production, where the VLQ decays into DM and SM particles, abiding by the existing bounds.

hep-ph↗

arXiv2025

Direct Search signal of two-component Dark Matter

How do we know if the dark sector consists of more than one dark matter (DM) component is an important question, for which the answer is not very definite. In this article we study such a possibility in context of direct DM search. It was pointed out earlier in a model independent analysis that a kink in the nuclear recoil energy spectrum may indicate to the presence of two DM components. However, realising one such model was difficult due to experimental constraints. Here we propose and study a model containing a vector boson DM and a scalar DM, aided by a light scalar mediator, where a kink in the nuclear recoil spectrum arises after addressing individual relic densities, direct search limits, collider constraints and theoretical limits. We find out the allowed parameter space of the model and those regions likely to show such distinctive signal.

hep-ph↗

arXiv2024

Two-component Dark Matter and low scale Thermal Leptogenesis

The observable cosmos exhibits sizable baryon asymmetry, small active neutrino masses, and the presence of dark matter (DM). To address these phenomena together, we propose a two component DM scenario in an extension of Scotogenic model, imposing $\mathbb{Z}_2 \otimes \mathbb{Z}_2^{\prime}$ symmetry. The electroweak sphaleron process converts the $\rm Y_{B-L}^{}$ yield, generated through the Leptogenesis mechanism, into the baryon asymmetry ($\rm Y_{\Delta B}^{}$) at $\rm T_{\rm sph}\sim 130$ GeV, the sphalerons decoupling temperature. In this framework, the CP asymmetry as well as the radiative neutrino mass generation explicitly involve the two DM particles, thus establishing a correlation between the baryon asymmetry, DM and observed active neutrino masses. We study in details the allowed parameter space available after considering all the constraints from the three phenomena as well as from the collider search limits, and outline the region which could potentially be tested in future DM detection experiments through direct or indirect detection searches, lepton flavor-violating decays, etc.

hep-ph↗

arXiv2024

Pseudo-FIMP dark matter in presence of a SIMP

Pseudo-feebly Interacting Massive Particle (pFIMP) has been postulated in two component dark matter (DM) scenarios, where it has feeble interaction with the visible sector, but sizeable one with a thermal bath partner. In this work, we study the possibility and dynamics of pFIMP in presence of a Strongly Interacting Massive Particle (SIMP), which is well known to solve too-big-to-fail and core-vs-cusp problems. Our analysis is primarily model-independent via solving coupled Boltzmann equations, with negligible DM-DM conversion adhering to pure SIMP-FIMP limit, and then with larger DM-DM conversion rate pertaining to SIMP-pFIMP limit. We also illustrate the simplest model yielding pFIMP-SIMP set-up having two scalars stabilised under $\mathbb{Z}_2\otimes \mathbb{Z}_3$ symmetry, and explore the accessible parameter space after addressing relic density, unitarity, self interaction constraints etc. pFIMP detectability is limited in such circumstances, but possible via a thermal DM loop when the SIMP has a visible sector interaction via light mediator.

hep-ph↗

arXiv2024

The Influence of Lepton Portal on the WIMP-pFIMP framework

The dynamics and detection possibility of a pseudo-FIMP (pFIMP) dark matter (DM) in the presence of a thermal DM have been studied in different contexts. The pFIMP phenomenology largely depends on the WIMP-like partner DM, as pFIMP interacts with the standard model (SM) particles only via the partner DM loop. Introducing a lepton portal interaction, which connects DM directly to the SM lepton sector, improves its detection prospects. However, such possibilities are constrained strongly by the non-observation of lepton flavor-violating decays. Interestingly, this also makes it possible to probe such models in future low-energy experiments. In this article, we have tried to establish such connections and find parameter space which respects the limits from DM relic, direct, indirect, and lepton flavor violation (LFV). We also recast the constraints from di-lepton/di-tau plus missing energy signal at the LHC on our model and provide projections for HL-LHC and future lepton colliders. Although the LFV and collider limits mainly concern WIMPs, the parameter space for pFIMPs is also constrained due to its strong connection to WIMPs through DM relic density and detection prospects.

hep-ph↗

arXiv2024

Lepton collider as a window to reheating via freezing in dark matter detection. Part II

Dark matter (DM) genesis via Ultraviolet (UV) freeze-in embeds the seed of reheating temperature and dynamics in its relic density. Thus, discovery of such a DM candidate can possibly open the window for post-inflationary dynamics. However, there are several challenges in this exercise, as freezing-in DM possesses feeble interaction with the visible sector and therefore very low production cross-section at the collider. We show that mono-photon (and dilepton) signal at the ILC, arising from DM effective operators connected to the SM field strength tensors, can still warrant a signal discovery. We study both the scalar and fermionic DM production during reheating via UV freeze-in, when the inflaton oscillates at the bottom of a general monomial potential. Interestingly, we see, right DM abundance can be achieved only in the case of bosonic reheating scenario, satisfying bounds from big bang nucleosynthesis (BBN). This provides a unique correlation between collider signal and the post-inflationary dynamics of the Universe within single-field inflationary models.

hep-ph↗

arXiv2024

Multiparticle scalar dark matter with $\mathbb{Z}_N$ symmetry

More than one dark sector particle transforming under the same symmetry provides one stable dark matter (DM) component which undergoes co-annihilation with the heavier particle(s) decaying to DM. Specific assumptions on the kinematics and on the coupling parameters may render the heavier component(s) stable and contribute as DM. The choices of the charges of the dark sector fields under transformation play a crucial role in the resultant phenomenology. In this paper, we systematically address the possibility of obtaining two scalar DM components under $\mathbb{Z}_N$ symmetry. We consider both the possibilities of DM being weakly interacting massive particle (WIMP) or pseudofeebly interacting massive particle (pFIMP). We elaborate upon $\mathbb{Z}_3$ symmetric model, confronting the relic density allowed parameter space with recent most direct and indirect search bounds and prospects. We also highlight the possible distinction of the allowed parameter space in single component and two component cases, as well as between WIMP-WIMP and WIMP-pFIMP scenarios.

hep-ph↗

arXiv2024

Lepton collider as a window to reheating via freezing in dark matter detection. Part I

We propose a methodology to infer the reheat temperature ($T_{\rm RH}$) of the Universe from the collider signal of freezing in dark matter (DM). We demonstrate it for the mono-$\gamma$ signal at the electron-positron colliders, which indicates to a low-scale $T_{\rm RH}$, after addressing observed DM abundance, BBN, and other relevant constraints. The method can be used to correlate different reheating dynamics, DM models, and collider signals.

hep-ph↗

arXiv2023

Dynamics of the pseudo-FIMP in presence of a thermal Dark Matter

We demonstrate that in a two component dark matter (DM) set up, when DM$_1$ is equilibrated with the thermal bath, the other DM$_2$, in spite of having feeble or negligible interaction with the SM particles, can be brought to equilibrium just by having sizeable interaction with DM$_1$. We propose that such DM candidates (DM$_2$) should be classified into a category called pseudo-FIMP (pFIMP) having unique freeze-out characteristics which depend on the thermal DM partner. The draft elaborates upon the pFIMP properties from a generic coupled Boltzmann Equations (cBEQ) in a model independent way, followed by a concrete model illustration.

hep-ph↗

arXiv2022

Detection possibility of a Pseudo-FIMP in presence of a thermal WIMP

A dark matter (DM) having feeble interaction with the visible sector can thermalise via substantial interaction with a Weakly Interacting Massive Particle (WIMP). Such DM candidates are categorised as pseudo-FIMP (pFIMP). pFIMP can provide both direct and indirect search prospects via WIMP loop. This work focuses into such possibilities. We provide all such one loop graphs involving scalar, fermion and vector boson particles via which pFIMP can interact with the Standard Model assuming both of them are stabilised via $\mathbb{Z}_2\otimes \mathbb{Z}_2^{\prime}$ symmetries. We elaborate upon a model where a fermion DM acts as WIMP and a scalar singlet acts as pFIMP having negligible Higgs portal interaction and substantial conversion via Yukawa interaction. We study in details the loop induced direct and indirect search prospects of the pFIMP in the relic density allowed region of the model.

hep-ph↗

arXiv2022

Electroweak Symmetry Breaking and WIMP-FIMP Dark Matter

Electroweak Symmetry Breaking (EWSB) is known to produce a massive universe that we live in. However, it may also provide an important boundary for freeze-in or freeze-out of dark matter (DM) connected to Standard Model via Higgs portal as processes contributing to DM relic differ across the boundary. We explore such possibilities in a two-component DM framework, where a massive $U(1)_X$ gauge boson DM freezes-in and a scalar singlet DM freezes-out, that inherits the effect of EWSB for both the cases in a correlated way. Amongst different possibilities, we study two sample cases; first when one DM component freezes in and the other freezes out from thermal bath both necessarily $before$ EWSB and the second, when both freeze-in and freeze-out occur $after$ EWSB. We find some prominent distinctive features in the available parameter space of the model for these two cases, after addressing relic density and the recent most direct search constraints from XENON1T, some of which can be borrowed in a model independent way.

hep-ph↗