arXiv subjects

Subhadeep Mondal

Publications and source records attributed to Subhadeep Mondal.

At least 19 recordsLinked to original sources

arXiv2026

Interfacial-Thermo-Fluid-Adhesion Dynamics of Evaporating Capillary Bridges between Curved Surfaces

We probe the evaporation mechanism, and the associated adhesion dynamics of liquid capillary bridges connecting two curved, solid substrates. The coupled thermo fluid species transport and the transient evolution of capillary adhesion during evaporation are systematically examined. An accurate, fully coupled transient numerical framework is developed, wherein the equilibrium capillary profiles are first determined from level set method. Next, the evaporation is simulated via Arbitrary Lagrangian Eulerian ALE framework to accurately track the moving liquid vapor interface. The combined influence of substrate curvature, surface wettability, and solid thermal conductivity on evaporation and capillary adhesion character is comprehensively analysed. The simulation methodology is robustly validated against published literature for capillary profiles, evaporation rates, and capillary forces, demonstrating good agreement. Our results reveal that the evaporation characteristics of both hydrophilic and superhydrophobic SH liquid bridges are strongly governed by substrate curvature and thermal conductivity, and increasing values pose favourable condition for augmented interfacial mass transfer rate. The innately non uniform vapour flux generates spatially varying evaporative cooling, producing surface tension gradients that drive internal thermo capillary circulation. A non dimensional scaling analysis shows that Marangoni flow dominates buoyancy induced flow throughout. Also, increasing substrate curvature decreases the overall capillary force, owing to the reduced curvatures of the liquid bridge, while the temporal evolution of the adhesion force is strongly influenced by both substrate curvature and wettability.

physics.flu-dyn↗

arXiv2025

CNN on `Top': In Search of Scalable & Lightweight Image-based Jet Taggers

While Transformer-based and standard Graph Neural Networks (GNNs) have proven to be the best performers in classifying different types of jets, they require substantial computational power. We explore the scope of using a lightweight and scalable version of EfficientNet architecture, along with global features of the jet. The end product is computationally inexpensive but is capable of competitive performance. We showcase the efficacy of our network in tagging top-quark jets in a sea of other light quark and gluon jets. The work also sheds light on the importance of global features for both the accuracy and the apparent redundancy of the network's complexity.

hep-ph↗

arXiv2025

Exploring the BSM parameter space with Neural Network aided Simulation-Based Inference

Some of the issues that make sampling parameter spaces of various beyond the Standard Model (BSM) scenarios computationally expensive are the high dimensionality of the input parameter space, complex likelihoods, and stringent experimental constraints. In this work, we explore likelihood-free approaches, leveraging neural network-aided Simulation-Based Inference (SBI) to alleviate this issue. We focus on three amortized SBI methods: Neural Posterior Estimation (NPE), Neural Likelihood Estimation (NLE), and Neural Ratio Estimation (NRE) and perform a comparative analysis through the validation test known as the \textit{ Test of Accuracy with Random Points} (TARP), as well as through posterior sample efficiency and computational time. As an example, we focus on the scalar sector of the phenomenological minimal supersymmetric SM (pMSSM) and observe that the NPE method outperforms the others and generates correct posterior distributions of the parameters with a minimal number of samples. The efficacy of this framework is tested on 5 parameter pMSSM with Higgs and flavor physics data and its performance is compared with the MCMC method. We further add dark matter (DM) observables to make the task more challenging and consider a 9 parameter pMSSM. We observe that even though the efficiency factor drops, the amortized SBI method still produces faithful posterior distributions. SBI predicted points satisfying DM constraints are mostly bino-dominated upto $\sim$ 1.5 TeV, and are mostly wino-dominated within the 1.5 - 2 TeV range.

hep-ph↗

arXiv2025

Normalizing Flow-Assisted Nested Sampling on Type-II Seesaw Model

We propose a novel technique for sampling particle physics model parameter space. The main sampling method applied is Nested Sampling (NS), which is boosted by the application of multiple Machine Learning (ML) networks, e.g., Self-Normalizing Network (SNN) and Normalizing Flow (specifically RealNVP). We apply this on Type-II Seesaw model to test the efficacy of the algorithm. We present the results of our detailed Bayesian exploration of the model parameter space subjected to theoretical constraints and experimental data corresponding to the 125 GeV Higgs boson, $\rho$-parameter, and the oblique parameters. All associated data, figures, and trained ML models can be found here: https://github.com/sunandopatra/MLNS-T2SS

hep-ph↗

arXiv2024

Probing sub-TeV Higgsinos aided by a ML-based top tagger in the context of Trilinear RPV SUSY

Probing higgsinos remains a challenge at the LHC owing to their small production cross-sections and the complexity of the decay modes of the nearly mass degenerate higgsino states. The existing limits on higgsino mass are much weaker compared to its bino and wino counterparts. This leaves a large chunk of sub-TeV supersymmetric parameter space unexplored so far. In this work, we explore the possibility of probing higgsino masses in the 400 - 1000 GeV range. We consider a simplified supersymmetric scenario where R-Parity is violated through a baryon number violating trilinear coupling. We adopt a machine learning-based top tagger to tag the boosted top jets originating from higgsinos, and for our collider analysis, we use a BDT classifier to discriminate signal over SM backgrounds. We construct two signal regions characterized by at least one top jet and different multiplicities of $b$-jets and light jets. Combining the statistical significance obtained from the two signal regions, we show that higgsino mass as high as 925 GeV can be probed at the high luminosity LHC.

hep-ph↗

arXiv2024

Markov Chain Monte Carlo analysis to probe trilinear $R$-parity violating SUSY scenarios and possible LHC signatures

In this article, we probe the trilinear $R$-parity violating (RPV) supersymmetric (SUSY) scenarios with specific nonzero interactions in the light of neutrino oscillation, Higgs, and flavor observables. We attempt to fit the set of observables using a state-of-the-art Markov Chain Monte Carlo (MCMC) setup and study its impact on the model parameter space. Our main objective is to constrain the trilinear couplings individually, along with some other SUSY parameters relevant to the observables. We present the constrained parameter regions in the form of marginalized posterior distributions on different two-dimensional parameter planes. We perform our analyses with two different scenarios characterized by our choices for the lightest SUSY particle (LSP), bino, and stop. Our results indicate that the lepton number violating trilinear couplings $\lambda_{i33}$ ($i$=1,2) and $\lambda_{j33}^{\prime}$ ($j$=1,2,3) can be at most of the order of $10^{-4}$ or even smaller while $\tan\beta$ is restricted to below 15 even when $3\sigma$ allowed regions are considered. We further comment on the possible LHC signatures of these LSPs focusing on and around the best-fit regions.

hep-ph↗

arXiv2024

On the family discrimination in 331-model

In the so-called 331-models the gauge anomalies cancel only if there are three generations of fermions. This requires one of the quark generations to be in a different representation than the other two. But which generation is treated differently? In this work we study how the choice of differently treated generation effects the quark flavour structure and how the discriminated generation can be deduced from experiments. We study a general model based on $\beta=-1/\sqrt{3}$, which contains exotic quarks with same electric charges as SM quarks. We take fully into account the effects from exotic quark mixing with the SM quarks, which is often omitted in literature. We will also pay particular attention to $125$ GeV Higgs, and show analytically why its flavour violating couplings between SM quarks are suppressed.

hep-ph↗

arXiv2024

Probing intractable beyond-standard-model parameter spaces armed with Machine Learning

This article attempts to summarize the effort by the particle physics community in addressing the tedious work of determining the parameter spaces of beyond-the-standard-model (BSM) scenarios, allowed by data. These spaces, typically associated with a large number of dimensions, especially in the presence of nuisance parameters, suffer from the curse of dimensionality and thus render naive sampling of any kind -- even the computationally inexpensive ones -- ineffective. Over the years, various new sampling (from variations of Markov Chain Monte Carlo (MCMC) to dynamic nested sampling) and machine learning (ML) algorithms have been adopted by the community to alleviate this issue. If not all, we discuss potentially the most important among them and the significance of their results, in detail.

hep-ph↗

arXiv2024

Status of R-parity violating SUSY

In this article, we discuss various phenomenological implications of possible R-parity violating (RPV) supersymmetric scenarios. In this context, the implications of both bilinear and trilinear RPV terms are reviewed from the viewpoint of neutrino physics, anomalous muon magnetic moment, different flavor observables, and collider physics. Apart from discussing the distinctive phenomenological implications of the RPV scenarios, we also survey the updated results from different studies to highlight the present status of the RPV couplings.

hep-ph↗

arXiv2023

Slepton searches in the trilinear RPV SUSY scenarios at the HL-LHC and HE-LHC

In this work we have studied a multi-lepton final state arising from sneutrino and left-handed slepton production at the high luminosity and high energy LHC in the context of R-parity violating supersymmetry when only the lepton number violating $\lambda_{121}$ and/or $\lambda_{122}$ couplings are non-zero. We have taken into account both pair production and associated production of the three generations of left-handed sleptons and sneutrinos, which are assumed to be mass degenerate. The lightest supersymmetric particle is assumed to be bino and it decays via the R-parity violating couplings into light leptons and neutrinos. Our final state has a large lepton multiplicity, $N_{l}\geq 4~(l=e,~\mu)$. We perform both cut-based and machine learning based analyses for comparison. We present our results in the bino-slepton/sneutrino mass plane in terms of exclusion and discovery reach at the LHC. Following our analysis, the slepton mass can be discovered upto $\sim$ 1.54 TeV and excluded upto $\sim$ 1.87 TeV at the high luminosity LHC while these ranges go upto $\sim$ 2.46 TeV and $\sim$ 3.06 TeV respectively at the high energy LHC.

hep-ph↗

arXiv2023

Improving sensitivity of trilinear RPV SUSY searches using machine learning at the LHC

In this work, we have explored the sensitivity of multilepton final states in probing the gaugino sector of R-parity violating supersymmetric scenario with specific lepton number violating trilinear couplings ($\lambda_{ijk}$) being non-zero. The gaugino spectrum is such that the charged leptons in the final state can arise from the R-parity violating decays of the lightest supersymmetric particle (LSP) as well as R-parity conserving decays of the next-to-LSP (NLSP). Apart from a detailed cut-based analysis, we have also performed a machine learning-based analysis using boosted decision tree algorithm which provides much better sensitivity. In the scenarios with non-zero $\lambda_{121}$ and/or $\lambda_{122}$ couplings, the LSP pair in the final states decays to $4l~(l = e, \mu) + \rm E{\!\!\!/}_T$ final states with $100\%$ branching ratio. We have shown that under this circumstance, a final state with $\ge 4l$ has the highest sensitivity in probing the gaugino masses. We also discuss how the sensitivity can change in the presence of $\tau$ lepton(s) in the final state due to other choices of trilinear couplings. We present our results through the estimation of the discovery and exclusion contours in the gaugino mass plane for both the HL-LHC and the HE-LHC. For $\lambda_{121}$ and/or $\lambda_{122}$ nonzero scenario, the projected 2$\sigma$ exclusion limit on NLSP masses reaches upto 2.37 TeV and 4 TeV for the HL-LHC and the HE-LHC respectively by using a machine learning based algorithm. We obtain an enhancement of $\sim$ 380 (190) GeV in the projected 2$\sigma$ exclusion limit on the NLSP masses at the 27 (14) TeV LHC. Considering the same final state ($N_l \geq 4$) for $\lambda_{133}$ and/or $\lambda_{233}$ non-zero scenario, we find that the corresponding 2$\sigma$ projected limits are $\sim$ 1.97 TeV and $\sim$ 3.25 TeV for the HL-LHC and HE-LHC respectively.

hep-ph↗

arXiv2023

Bilinear R-parity violating supersymmetry under the light of neutrino oscillation, higgs and flavor data

In this work, we explore a well motivated beyond the Standard Model scenario, namely, R-parity violating Supersymmetry, in the context of light neutrino masses and mixing. We assume that the R-parity is only broken by the lepton number violating bilinear term. We try to fit two non-zero neutrino mass square differences and three mixing angle values obtained from the global $\chi^2$ analysis of neutrino oscillation data. We have also taken into account the updated data of the standard model (SM) Higgs mass and its coupling strengths with other SM particles from LHC Run-II along with low energy flavor violating constraints like rare b-hadron decays. We have used a Markov Chain Monte Carlo (MCMC) analysis to constrain the new physics parameter space. While doing so, we ensure that all the existing collider constraints are duly taken into account. Through our analysis, we have derived the most stringent constraints possible to date with existing data on the 9 bilinear R-parity violating parameters along with $\mu$ and $\tan\beta$. We further explore the possibility of explaining the anomalous muon~(g~-~2) measurement staying within the parameter space allowed by neutrino, Higgs and flavor data while satisfying the collider constraints as well. We find that there still remains a small sub-TeV parameter space where the required excess can be obtained.

hep-ph↗

arXiv2022

Multi-phase critical Higgs boson at colliders

The recently proposed multi-phase criticality principle in Coleman-Weinberg models can provide a new explanation for the hierarchy between the electroweak and new physics scales. When applied to the Standard Model, a Higgs boson as light as the pseudo-Goldstone boson of broken scale invariance occurs. The suppressed mixing between the two light fields still carries information about the large scale of symmetry breaking, albeit up to logarithmic corrections. In this work we probe this scenario with the present LHC data and assess the impact of future lepton and hadron colliders. Our results show that the multi-phase criticality can easily explain the apparent absence of new physics at the energy scales tested in current experiments.

hep-ph↗

arXiv2021

Electron and muon magnetic moments and implications for dark matter and model characterisation in non-universal $U(1)^\prime$ supersymmetric models

We attribute deviations of the muon and electron magnetic moments from the theoretical predictions to the presence of an additional $U(1)^\prime$ supersymmetric model. We interpret the discrepancies between the muon and electron anomalous magnetic moments to be due to the presence of non-universal $U(1)^\prime$ charges. In a minimally extended model, we show that requiring both deviations to be satisfied imposes constraints on the spectrum of the model, in particular on dark matter candidates and slepton masses and ordering. Choosing three benchmarks with distinct dark matter features, we study implications of the model at colliders, concentrating on variables that can distinguish our non-universal scenario from other $U(1)^\prime$ implementations.

hep-ph↗

arXiv2020

Multi-Higgs Boson Probes of the Dark Sector

We consider dark sectors with spontaneously broken gauge symmetries, where cascade decays of the dark sector fields naturally produce multi-Higgs boson final states along with dark matter. Our study focuses on two and three Higgs boson final states with missing energy using a multivariate analysis with Boosted Decision Trees. We find that the di-Higgs boson channel is quite promising for the $\bar b b + γγ$ and $\bar b b + \bar \ell \ell$ decay modes. The tri-Higgs boson final state with missing energy, on the other hand, appears to be beyond the reach of the LHC in analogous channels. This may change when fully hadronic Higgs boson decays are considered.

hep-ph↗

arXiv2020

Probing heavy scalars with an effective $Hb\bar bg$ coupling at the LHC

We have explored the prospect of probing a neutral scalar ($H$) produced in association with one $b$-quark and decaying either invisibly or into a pair of $b$-quarks at the LHC with centre of mass energy $\sqrt s = 14$ TeV. In this regard, we adopt an effective theory approach to parameterize a $Hb\bar bg$ vertex arising from a dimension six operator that encompasses the effect of some new physics setting in at a high scale. We concentrate solely on the five-flavor scheme to ascertain the sensitivity of the 14 TeV LHC in probing such an effective coupling as a function of the scalar mass at the highest possible projected luminosity, $3000~{\rm fb}^{-1}$. Through our multivariate analysis using machine learning algorithm we show that staying within the perturbative limit of the Wilson coefficient of the effective interaction, evidence with statistical significance of $3σ$ can be obtained in two different signal regions for $m_H\lesssim 2$ TeV and the scale of new physics $Λ= 3$ TeV.

hep-ph↗

arXiv2020

The left-right supersymmetric option at a high-energy upgrade of the LHC

We investigate the possibility that a minimal realization of left-right supersymmetry can be reachable at a high-energy upgrade of the LHC, expected to operate at a center-of-mass energy of 27 TeV. This minimal scenario has a relatively light $SU(2)_R$ doubly-charged Higgs boson, which could decay dominantly into tau-lepton pairs. We explore the associated signals comprised of at least three hadronically-decaying taus, or with at least two hadronic taus and one same-sign-same-flavor charged lepton pair. Our analysis shows that the former signature is challenging to use for getting handles on the signal due to the large corresponding background, and that the latter one can lead to a handful of new physics events in an almost background-free environment. We however find that a signal comprised of three hadronically-decaying tau leptons is likely to be observed at a low luminosity of proton-proton collisions at a 27 TeV upgrade of the LHC.

hep-ph↗

arXiv2019

Dark matter and Collider signals in supersymmetric $U(1)^\prime$ models with non-universal $Z^\prime$ couplings

We analyse supersymmetric models augmented by an extra $U(1)$ gauge group. To avoid anomalies in these models without introducing exotics, we allow for family-dependent $U(1)^\prime$ charges, and choose a simple form for these, dependent on one $U(1)^\prime$ charge parameter only. With this choice, $Z^\prime$ decays into di-taus but not di-leptons, weakening considerably the constraints on its mass. In the supersymmetric sector, the effect is to lower the singlino mass, allowing it to be the dark matter candidate. We investigate the dark matter constraints and collider implications of such models, with mostly singlino, or mostly higgsinos, or a mixture of the two as lightest supersymmetric particles. In these scenarios, $Z^\prime$ decays significantly into chargino or neutralino pairs, and thus indirectly into final state leptons. We devise benchmarks which, with adequate cuts, can yield signals visible at the high-luminosity LHC.

hep-ph↗