arXiv subjects

Arindam Das

Publications and source records attributed to Arindam Das.

At least 19 recordsLinked to original sources

arXiv2026

Heavy neutral leptons from light scalar in fixed target and forward search experiments

The observation of neutrino masses strongly motivates $U(1)_{B-L}$ extensions of the Standard Model, in which heavy neutral leptons acquire Majorana masses through spontaneous $U(1)_{B-L}$ symmetry breaking and generate light neutrino masses via the seesaw mechanism. In this framework, the singlet scalar responsible for symmetry breaking mixes with the SM Higgs boson, allowing it to be produced in rare meson decays. We investigate a scenario in which this light scalar promptly decays into a pair of long-lived heavy neutrinos that subsequently decay into visible charged leptons and hadrons through light-heavy neutrino mixing inside the proposed Forward Physics Facility (FPF) at the FCC-hh and the SHiP beam-dump experiment. Taking into account realistic detector geometries, decay probabilities, and visible branching fractions, we estimate the projected sensitivities to the scalar-Higgs mixing angle as a function of the scalar mass and to the light-heavy neutrino mixing as a function of the heavy neutrino mass. We find that FPF and SHiP can significantly extend the discovery reach for both light scalars and long-lived heavy neutrinos beyond existing experimental limits, providing powerful and complementary probes of neutrino-mass generation and hidden-sector physics.

hep-ph↗

arXiv2026

Quantum spin correlations in $Z^\prime$-mediated $t\bar{t}$ production at future lepton colliders

We study quantum spin correlations in top-quark pair production at future lepton colliders in the presence of a neutral gauge boson from anomaly-free general $U(1)$ extensions of the Standard Model. The process $\ell^+\ell^-\to t\bar t$, with $\ell=e,\mu$, is analyzed through the spin-density matrix including $\gamma$, $Z$ and $Z^\prime$ exchange and their interference. We focus on quantum-information observables such as the sufficient entanglement marker $\mathcal{D}_{\min}$, concurrence, purity and the maximal Clauser-Horne-Shimony-Holt (CHSH) parameter, and compare their behavior with conventional rate information. Within the $U(1)_X$ framework, we consider several representative charge assignments to investigate how different chiral structures influence these observables, with particular emphasis on the $Z^\prime$ resonance region and polarized $e^-e^+$ collisions, where the two allowed initial-state helicity configurations can be selectively enhanced. We show that electron-beam polarization provides a direct handle on the left- and right-handed lepton charges of various $U(1)_X$ scenarios. These results demonstrate that quantum spin observables provide information complementary to cross sections and angular distributions in searches for chiral neutral gauge interactions.

hep-ph↗

arXiv2026

Leptonic CP asymmetry and heavy neutrino searches in seesaw scenario

We investigate the prospects for probing heavy Majorana neutrinos in the type-I seesaw framework at the 14 TeV LHC. In this scenario, the light-heavy neutrino mixing enables the production of heavy neutrinos in association with charged leptons, followed by decays into dilepton plus dijet final states. We perform a detector-level cut-based analysis of both same-sign (SS) and opposite-sign (OS) dilepton channels and investigate the sensitivity as a function of the ratio $R_{ll}$ of SS to OS events. We derive projected constraints on the light-heavy neutrino mixing as a function of the heavy-neutrino mass. For $R_{ll} \simeq 1$, the sensitivity at $140~\rm{fb}^{-1}$ improves upon current LHC bounds by about one order of magnitude for $M_N \simeq 60-80~\rm{GeV}$, with a further order of magnitude improvement expected at the HL-LHC with $3~\rm{ab}^{-1}$. The sensitivity decreases substantially for smaller $R_{ll}$. We show that, for $50~\text{GeV} \lesssim M_N \lesssim 100~\text{GeV}$, the collider reach is strongly correlated with $R_{ll}$ and the associated CP asymmetry, providing additional motivation for future measurements of $R_{ll}$ and heavy-neutrino oscillations at colliders.

hep-ph↗

arXiv2026

Forward Searches for Heavy Neutrinos and $Z'$ Bosons at FCC-hh

The discovery of neutrino masses strongly motivates extensions of the Standard Model containing heavy neutral leptons and additional gauge interactions. We investigate the prospects for probing these states at the proposed Forward Physics Facility (FPF) of the 100 TeV Future Circular Collider (FCC-hh) within a broad class of anomaly-free chiral $U(1)$ gauge extensions. These models predict a new neutral gauge boson, $Z'$, together with right-handed neutrinos responsible for generating light neutrino masses through the seesaw mechanism. We study long-lived particle signatures arising from both heavy neutrinos and the $Z'$ boson produced in the far-forward region. In particular, we analyze heavy neutrino production from meson decays, visible decays of long-lived $Z'$ bosons produced through meson decays and proton bremsstrahlung, long-lived $Z'$ bosons decaying into heavy-neutrino pairs, and prompt $Z'$ decays yielding long-lived heavy neutrinos. The expected event rates are evaluated for the proposed FPF detector configurations, taking into account realistic detector geometry, decay probabilities, and visible final states. We derive projected sensitivities to the heavy neutrino mass and active-sterile mixing as well as to the $Z'$ mass and gauge coupling for several representative $U(1)$ charge assignments. Our results demonstrate that the FPF at FCC-hh can substantially extend the discovery reach for light long-lived heavy neutrinos and light $Z'$ bosons beyond existing and proposed experiments, providing a powerful and complementary probe of neutrino-mass models and hidden gauge sectors. https://github.com/SouvikPhD/RHN-Detection-with-FASER-2-

hep-ph↗

arXiv2026

Dynamic Wettability Modulation of Textured, Soft and LIS Interfaces Using Electrowetting

Electrowetting on textured and lubricant infused surfaces is conventionally expected to promote enhanced droplet spreading by reducing apparent contact angles. Contrary to this intuition, we report rapid tangential droplet ejection at applied DC voltages on specific microtextured, lubricant infused surfaces. Using high speed imaging and a precisely controlled electrowetting setup, we reveal the dependence of droplet dynamics on surface topology, wetting state, and the presence of a lubricant. On densely textured thick PDMS substrates of post spacing 5 to 10 um in a low hysteresis non-wetting Cassie state, and on all lubricant infused textured surfaces, droplets experience sudden lateral motion and eventual detachment. We attribute this counterintuitive phenomenon to unbalanced electrocapillary forces at the contact line combined with minimal pinning, which allows asymmetries in electric stresses to translate directly into net lateral motion. In contrast, Wenzel state droplets or surfaces with larger texture spacing exhibit conventional spreading with strong adhesion. By capturing the fundamental interplay among electrostatic driving forces, contact line pinning, and interfacial mobility, our results provide a new paradigm for controlled droplet transport and ejection in electrowetting systems mediated by dense micro posts and lubricant induced interfaces.

cond-mat.soft↗

arXiv2025

Constraining Gravitational Dark Matter with LHAASO and Fermi-LAT

We use diffuse Galactic high energy gamma ray data from LHAASO and Fermi-LAT to constrain gravitationally produced decaying dark matter (DM). Focusing on four benchmark candidates: a dark photon, a heavy right-handed neutrino (RHN), a pseudo-Nambu-Goldstone boson (pNGB), and a non-minimally coupled scalar we derive bounds on the DM mass and its couplings to the visible sector. For dark photons, RHNs, and pNGBs, the combined data constrain the relevant interaction strength to $\lesssim\mathcal{O}(10^{-30})$ for DM masses $\gtrsim\mathcal{O}$(TeV), while the non-minimally coupled scalar is limited to $\lesssim\mathcal{O}(10^{-10})$. Moreover, photon-dark photon oscillations yield strong constraints for massive dark photon beyond 10 GeV, closing a region of parameter space previously left unconstrained.

hep-ph↗

arXiv2025

Lepton number violation from Higgs/$Z$ decays into a pair of right-handed neutrinos

We explore signatures of Lepton Number Violation (LNV) from decays of the discovered Higgs ($h$) and Z bosons into a pair of Right-Handed Neutrinos (RHNs). Due to the Majorana nature of RHNs, the final state can be the same-sign dilepton plus jets leading to 2 units of LNV. As a simple but plausible scenario, we investigate such a signal in models with a new $U(1)_X$ gauge symmetry which naturally introduces three RHNs for gauge anomaly cancellation, and is spontaneously broken down by a vacuum expectation value of an isospin singlet scalar field ($\phi$). In this scenario, $h$ and the Z boson can decay into a pair of RHNs via the $h$-$\phi$ mixing and the $Z$-$Z'$ mixing with $Z'$ being a new massive gauge boson, respectively. Estimating the LNV signal and corresponding backgrounds for the $\ell^{\pm} \ell^{\pm} 4j$ final states, we find bounds on the $h$-$\phi$ mixing and the $Z$-$Z^\prime$ mixing as a function of a mass of RHNs at Higgs factories, e.g., at High-Luminosity LHC with $\sqrt{s}=$ 14 TeV, future $e^-e^+$ colliders at $\sqrt{s}=$ 250 GeV, muon colliders at $\sqrt{s}=$ 125 GeV as well as at Z factories, e.g., CEPC and FCC-ee at $\sqrt{s}=$ 91.2 GeV. We also discuss limits on the scalar mixing at $e^-\mu^+$ and $\mu^+ \mu^+$ collisions ($\mu$TRISTAN) with $\sqrt{s}=$346 GeV/775 GeV and 2 TeV, respectively.

hep-ph↗

arXiv2025

High-Speed Imagery Analysis of Droplet Impact on Van der Waals and Non-Van der Waals Soft-Textured Oil-Infused Surfaces

This study investigates the impact of surface functionalization, oil coating, and oil absorption on droplet impact behavior on textured polydimethylsiloxane(PDMS) substrates. The textured surfaces were fabricated with square micro-posts having spacings of 5 and 20 microns. The PDMS samples were functionalized with octadecyltrichlorosilane (OTS) to improve water repellency. Following, the surfaces were either coated with or allowed to absorb two different lubricants, silicone oil (SO-5cSt) and hexadecane. We performed detailed wetting measurements on both untreated and OTS-functionalized substrates. These measurements provided useful insights into how water and lubricants were retained and distributed under static conditions. High-speed imaging was used to capture droplet impact across a range of Weber numbers. On SO-5cSt-absorbed substrates, droplets consistently showed complete rebound at all Weber numbers, regardless of post spacing. This robust rebound was attributed to the oil's ability to fill the gaps between the posts through capillary action, while also forming a stable lubricating layer above the texture. This thin oil film reduced friction between the droplet and the surface, enabling the droplet to retain sufficient energy for complete rebound. In contrast, hexadecane-absorbed substrates displayed different dynamics. At low Weber numbers, only partial rebound was observed, while at intermediate values, droplets rebounded completely. However, droplets no longer rebounded at higher Weber numbers and remained deposited. Repeated droplet impacts further demonstrated that hexadecane-infused surfaces gradually lost oil from the textured gaps, resulting in a decline in rebound performance over time. This effect was not observed with SO-5cSt, underscoring the importance of lubricant affinity and stability.

physics.flu-dyn↗

arXiv2025

New constraints on $Z^\prime$ from captured dark matter annihilation in astrophysical objects

Considering dark matter capture in astrophysical objects such as neutron stars and brown dwarfs, followed by their annihilation into two neutrino and four neutrino final states, we derive new constraints on the mass and coupling of a novel abelian gauge boson $Z^\prime$ arising from an anomaly-free $U(1)$ extension of the Standard Model. We further confront these astrophysical limits with complementary bounds from the Planck-observed relic abundance via the freeze-in mechanism, big bang nucleosynthesis (BBN), gravitational wave signatures from cosmic strings, and searches at energy and intensity frontier experiments.

hep-ph↗

arXiv2025

Indirect dark matter searches with neutrino telescopes via energetic cosmic showers

We explore the possibility that the high energy neutrino flux observed by terrestrial telescopes originates from dark matter (DM) annihilation. Specifically, we study a minimal, UV-complete $U(1)$ extension of the Standard Model with a Dirac DM candidate, whose annihilation into neutrinos proceeds exclusively through a $Z^\prime$ boson. By computing the annihilation cross section and comparing with the observed flux, we derive bounds on the model parameters. Additional constraints are obtained within the freeze-in framework, where the observed relic abundance is reproduced, leading to the strongest bounds. Considering cosmic string vibrations as a source of gravitational waves, we further constrain the vacuum expectation value of the $U(1)$ breaking. All results are contrasted with perturbativity limits and existing constraints from low- and high-energy experiments.

hep-ph↗

arXiv2025

Right handed neutrino production from $Z^\prime$ interactions in forward search experiments

We study two general $U(1)$ extensions of the Standard Model (SM) those generate tiny neutrino masses via the seesaw mechanism after general $U(1)$ breaking. These models predict a new neutral gauge boson ($Z'$) and right-handed neutrinos (RHNs), the latter introduced for anomaly cancellation and neutrino mass generation. In both scenarios, left- and right-handed fermions couple differently to the $Z'$, and RHNs mix with light neutrinos, enabling variety of decay modes. Focusing on the high-luminosity LHC (HL-LHC) and the future FASER2 experiment, we explore RHN pair production from $Z'$ decays in two cases: (i) long-lived $Z'$ decays to visible modes and long-lived RHNs, and (ii) short-lived $Z'$ decays to long-lived RHNs, which further decay visibly inside FASER2. We estimate projected limits on the general $U(1)$ gauge coupling, $Z'$ mass, RHN mass, and light-heavy neutrino mixing for various $U(1)$ charge assignments, and compare them with current experimental bounds.

hep-ph↗

arXiv2025

Water Entry Dynamics of Superhydrophobic and Lubricant-Impregnated Surfaces: A Theoretical and Experimental Perspective

In this current work, a comprehensive investigation into the impact dynamics of superhydrophobic and lubricant-impregnated aluminium sphere balls on liquid surfaces were carried out. The study delves into the hydrodynamic lubrication behavior and the resulting phenomena during impact. The Worthington jet and cavity associated give more insight into fundamental forces. The experimental analysis and theoretical modeling suggest potential applications in various fields such as fluid dynamics, tribology, and materials science. The stability investigation on an aluminum-textured sphere ball is carried out, and the evaluation of jet height and pinch-off phenomena is analyzed in detail. The experiment on entrapped air on a superhydrophobic surface and the oil inside the LIS for greater height was performed. The experimental setup involved a carefully designed apparatus for impact analysis by utilizing high-speed imaging techniques. Parameters such as impact velocity, Weber number, and sphere diameter were systematically varied to understand their influence on the observed dynamics. The lubricant viscosity is chosen such that it is comparable to water viscosity. Furthermore, the study on Lubricant Impregnated Surfaces (LIS) assessed frictional losses, i.e., drag reduction, compared to control and textured surfaces. In conclusion, the valuable insights into the impact dynamics advance our understanding of hydrodynamic lubrication and its applications. The findings presented here underscore the importance of further research in optimizing surface properties, selecting suitable lubricants, and exploring broader applications in the fields of fluid dynamics, surface engineering, and mechanical engineering.

physics.flu-dyn↗

arXiv2025

New Physics Search at the CEPC: a General Perspective

The Circular Electron-Positron Collider (CEPC), a proposed next-generation Higgs factory, provides new opportunities to explore physics beyond the Standard Model (SM). With its clean electron-positron collision environment and the ability to collect large samples of Higgs, W, and Z bosons, the CEPC enables precision measurements and searches for new physics. This white paper outlines the CEPC's discovery potential, including studies of exotic decays of the Higgs, Z, and top quarks, dark matter and dark sector phenomena, long-lived particles, supersymmetry, and neutrino-related signatures. Advanced detector technologies and reconstruction techniques, such as one-to-one correspondence reconstruction and jet origin identification, significantly improve sensitivity to rare and weakly interacting processes. The CEPC is particularly well suited to probe the electroweak phase transition and test models of electroweak baryogenesis and dark sector interactions. In addition, global fit analyses highlight the CEPC's complementary role in constraining a wide range of new physics scenarios. These features position the CEPC as a powerful tool for exploring the next frontier in fundamental particle physics in the post-Higgs discovery era.

hep-ex↗

arXiv2025

What KM3-230213A events may tell us about the neutrino mass and dark matter

Within the framework of general $U(1)$ scenario, we demonstrate that the ultra high energy neutrinos recently detected by KM3NeT could originate from a decaying right handed neutrino dark matter (DM), with a mass of 440 PeV. Considering DM production via freeze-in, we delineate the parameter space that satisfies the observed relic abundance and also lies within the reach of multiple gravitational wave detectors. Our study provides a testable new physics scenario, enabled by multi-messenger astronomy.

hep-ph↗

arXiv2025

Dewetting Dynamics of Unstable Lubricant Impregnated Surfaces in Liquid Environment

This article outlines a thorough stability analysis by means of both theoretical and experimental modeling for Omni-phobic Lubricant Impregnated Surfaces (LIS). The liquid-repellent properties, particularly with regard to water and oil, have gained substantial attention due to their numerous potential applications. The theoretical section of this study focuses on the validation of mathematical models to understand the underlying principles driving the stability of Omni-phobic LIS. Theoretical insights about the interaction of surface texture, chemical composition, impregnated, and ambient liquid properties contribute to a better understanding of the mechanisms that govern stability. A series of experiments were performed to understand better the stability of fabricated Omni-phobic LIS under cyclopentane and water environments, including viscosity and surface texture variations, especially post-spacing variation. The experimental results validate the theoretical predictions and provide valuable statistical information regarding possible model modification. The replaced oil or nucleation sites can be explained through CHNT. The analysis was further validated with experimentally observed nucleation sites. This confirms the accuracy of the nucleation predictions and supports the underlying theoretical model. According to the CLW model, the length of a liquid's penetration into a cylinder/square-shaped capillary is expressed as a square root of time. Our findings contribute to designing a stable LIS and then determining the model followed by an unstable one. The proposed MLW model validated the experimental results. In addition, these experimental data points fit the different capillary imbibition regimes such as inertial, early viscous etc. This contributes to the development of robust and durable solutions for practical applications.

cond-mat.soft↗

arXiv2025

BEVMOSNet: Multimodal Fusion for BEV Moving Object Segmentation

Accurate motion understanding of the dynamic objects within the scene in bird's-eye-view (BEV) is critical to ensure a reliable obstacle avoidance system and smooth path planning for autonomous vehicles. However, this task has received relatively limited exploration when compared to object detection and segmentation with only a few recent vision-based approaches presenting preliminary findings that significantly deteriorate in low-light, nighttime, and adverse weather conditions such as rain. Conversely, LiDAR and radar sensors remain almost unaffected in these scenarios, and radar provides key velocity information of the objects. Therefore, we introduce BEVMOSNet, to our knowledge, the first end-to-end multimodal fusion leveraging cameras, LiDAR, and radar to precisely predict the moving objects in BEV. In addition, we perform a deeper analysis to find out the optimal strategy for deformable cross-attention-guided sensor fusion for cross-sensor knowledge sharing in BEV. While evaluating BEVMOSNet on the nuScenes dataset, we show an overall improvement in IoU score of 36.59% compared to the vision-based unimodal baseline BEV-MoSeg (Sigatapu et al., 2023), and 2.35% compared to the multimodel SimpleBEV (Harley et al., 2022), extended for the motion segmentation task, establishing this method as the state-of-the-art in BEV motion segmentation.

cs.CV↗

arXiv2025

High Speed Imagery Analysis of Droplet Impact on Soft Oil Infused Surface

Droplet impact on solid liquid-infused surfaces (LIS) has been widely explored due to its significant scientific implications and industrial relevance. In most studies, the predominant impact behavior observed is complete droplet rebound. In This study we investigated the influence of octadecyltrichlorosilane (OTS) functionalization and oil coatings on the droplet impact dynamics of smooth polydimethylsiloxane (PDMS) surfaces. We conducted droplet impact experiments on smooth PDMS functionalized with OTS and subsequently coated or absorbed with two different oils, silicone oil (5cSt) and hexadecane, to create Van der Waals and non-Van der Waals SLIP surfaces. Contact angle measurements revealed that OTS functionalization reduced adhesion and increased water repellency, facilitating partial droplet rebound upon impact. Oil-coated surfaces exhibited reduced droplet spreading due to viscous resistance, while absorbed oils altered surface flexibility, influencing impact dynamics. PDMS samples absorbed with silicone oil demonstrated complete droplet rebound at all Weber numbers, whereas hexadecane-absorbed surfaces exhibited limited spreading and no rebound, highlighting the significance of oil-PDMS interactions. High-speed imaging and quantitative analysis confirmed that surface functionalization and oil interactions critically affect droplet spreading, recoil, and rebound behavior. These findings provide insights into optimizing liquid-repellent surfaces for applications such as self-cleaning coatings and droplet transport systems.

physics.flu-dyn↗

arXiv2025

Hunting for heavy $Z^\prime$ with IceCube neutrinos and gravitational waves

In the minimal gauged B-L extension of the Standard Model, we demonstrate that PeV-scale dark matter (DM) and the baryon asymmetry of the Universe (BAU) can be simultaneously explained through the three right-handed neutrinos (RHNs) present in the theory. The DM candidate undergoes decay into light neutrinos, providing an explanation for the observed IceCube events, while the other two RHNs generate the BAU via leptogenesis. The breaking of gauge symmetry gives rise to detectable gravitational waves (GWs) from decaying cosmic strings (CS), making this framework testable at several future GW detectors-despite being beyond the reach of conventional collider experiments due to the extremely weak coupling. The symmetry-breaking scale establishes a connection between particle masses, couplings, and the GW spectrum, offering a unified and predictive scenario.

hep-ph↗