arXiv subjects

Prasenjit Sanyal

Publications and source records attributed to Prasenjit Sanyal.

At least 19 recordsLinked to original sources

arXiv2026

Search for Light Scalars in the Two Real Singlet Model at the LHC

We investigate exotic scalar decays $h_2 \to h_1 h_1$ in the Two Real Singlet Model (TRSM), focusing on light CP-even scalars with $20 \le M_{1} \le 60$~GeV and $20 \le M_{2} \le 120$~GeV. Unlike previous studies focused on gluon--gluon fusion or vector-boson fusion production, we explore associated production with electroweak gauge bosons, $pp \to Vh_2$ {\sl($V = W,Z$)}, as a complementary and experimentally clean probe of light scalar cascades in the TRSM. The subsequent decay $h_1 \to b\bar{b}$ leads to final states containing four $b$-jets accompanied by a charged lepton and missing transverse energy. We evaluate the sensitivity of the $4b+\ellν_\ell$ channel at $\sqrt{s}=13.6$~\TeV for the LHC Run~3 and the HL-LHC. For an integrated luminosity of $300~\mathrm{fb}^{-1}$, the $W^+h_2$ channel provides the strongest sensitivity, reaching a significance of approximately $4σ$, while the $W^-h_2$ channel reaches approximately $3σ$. At the HL-LHC with $3000~\mathrm{fb}^{-1}$, the corresponding significances increase to approximately $12σ$ and $8σ$, respectively, highlighting the strong discovery potential of associated light-scalar production in the TRSM.

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arXiv2026

Dark Photon mediated Inelastic Dark Matter in Cosmology, Astrophysics and Colliders

We explore the phenomenology of Dark Photon iDM (A$^{\prime}$iDM) where the Standard Model (SM) is extended by a dark sector containing an additional $U(1)_D$ gauge symmetry under which all SM particles are neutral, and that couples to the SM hypercharge gauge boson through a kinetic mixing parameter $ε$. The model contains two Majorana states $χ_1$ and $χ_2$ with $δ=M_{χ_2}-M_{χ_1}>0$ and $χ_1$ the dark matter candidate, and a dark photon $A^{\prime}$ with mass $M_{A^{\prime}}$. Our analysis represents an integration of existing ones, where only specific benchmarks of the A$^{\prime}$iDM scenario have been discussed. In particular, we fix the $U(1)_D$ coupling $α_D$ equal to the electromagnetic one $α_{EM}$ and $ε$ to its experimental upper bound, and perform a complete scan of the remaining parameters $(M_{χ_1},δ, M_{A^{\prime}})$, discussing the $χ_1$ relic abundance, its direct and indirect searches, as well as potential signals from astrophysics and accelerators. Our scan shows that $α_D$ = $α_{EM}$ is not disfavored, as some previous analyses, limited to specific benchmarks, may suggest. We also find that when the $χ_1$ relic density matches observation direct and indirect searches are not kinematically accessible. On the other hand we find that the projected luminosity of FASER, a detector searching for Long Lived Particles (LLP) decay at the LHC, can probe or rule out the parameters space of the model for $M_{χ_1}\lesssim$ 7 GeV, 100 MeV $\lesssim δ\lesssim$ 300 MeV and $M_{A^{\prime}}\lesssim$ 25 GeV. This range of parameter could be significantly extended by the FASER 2 upgrade proposed for the High-Luminosity phase at the LHC. The parameter space probed by LLP seaches partially overlaps with that probed by $χ_1$ capture in neutron stars.

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arXiv2026

Signatures of Long-Lived Heavy Neutral Leptons from Neutrinophilic Charged Higgs Pair Production at the LHC

In the neutrinophilic Higgs doublet framework, the neutrino Dirac Yukawa couplings can be sizable because of the small vacuum expection value of the extra Higgs doublet, even for a low seesaw scale. Due to this structure, the neutrinophilic charged Higgs bosons, once created, decay dominantly into heavy neutral leptons (HNLs) and charged leptons. This is a new mechanism to produce a gauge singlet HNL without suppressed cross sections. In the standard seesaw, one HNL can be long-lived, when the lightest neutrino is sufficiently light. We investigate displaced vertex signatures of the long-lived HNLs produced from the decays of the charged Higgs pair at the high luminosity LHC. We consider one displaced vertex as well as two displaced vertices signatures and perform a dedicated simulation to identify the displaced leptons. We find that high statistical significance can be achieved for the observation of one displaced vertex for charged Higgs pair production cross section $>\mathcal{O}(1)$ fb. On the other hand, the observation of two displaced vertices is challenging even for charged Higgs pair production cross section of $\mathcal{O}(10)$ fb.

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arXiv2026

Search for Light Scalars in the TRSM at the LHC

We study the production of Beyond the Standard Model light scalar states in association with a vector boson ($Vh_2$, with $V = W^\pm, Z$) at the LHC. We consider the scenario where the Standard Model scalar sector is extended by two real scalar singlets, where these additional scalars have mass $ M_i \leq M_{h_{125}}$. In this work, the scalar boson $h_2$ decays via $h_2 \to h_1 h_1 \to 4b$, while the associated vector boson decays either into a pair of oppositely charged leptons or into a single charged lepton and a neutrino. We analyze the signal using LHC detector parameterizations and evaluate its statistical significance at a center-of-mass energy of 13.6~TeV for integrated luminosities of 300~fb$^{-1}$ and 3000~fb$^{-1}$ corresponding to the LHC Run 3 and High Luminosity LHC, respectively. Our preliminary results indicate promising discovery prospects for this channel serving as a complementary probe of extended scalar sectors.\\ RBI-ThPhys-2026-04, COMETA-2026-04

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arXiv2025

On the CP Nature of the `95 GeV' Anomalies

Under the assumption that the various evidences of a `95 GeV' excess, seen in data at the Large Electron Positron (LEP) collider as well as the Large Hadron Collider (LHC), correspond to actual signals of new physics Beyond the Standard Model (BSM), we characterise the underlying particle explaining these anomalies in terms of its Charge/Parity (CP) quantum numbers. In doing so, we use $χ^2$ fits to test the CP-even (scalar) and CP-odd (pseudoscalar) hypotheses and superpositions of these, thus under the assumption of a spin-0 resonance. This is done through the exploitation of $τ^+τ^-$ decays, in both their fully hadronic and semi-leptonic modes, in a model-independent way, so that our approach enables one to test a variety of BSM hypotheses, having proven here that the High-Luminosity LHC (HL-LHC) will be in a position to disentangle the CP nature of such a new particle within $\pm(0.27-0.47)$ radians of the true hypothesis at $90\%$ Confidence Level (CL), depending on the assumed background systematics.

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arXiv2025

Discovery Prospects for the Light Charged Higgs Boson Decay to an Off-Shell Top Quark and a Bottom Quark at Future High-Energy Colliders

The charged Higgs boson ($H^\pm$) with a mass below the top quark mass remains a viable possibility within the Type-I two-Higgs-doublet model under current constraints. While previous LHC searches have primarily focused on the $H^\pm\toτ^\pmν$ decay mode, the decay channel into an off-shell top quark and a bottom quark, $H^\pm \rightarrow t^*b$, is leading or subleading for $H^\pm$ masses between 130 and 170 GeV. This study investigates the discovery potential of future colliders for this off-shell decay mode through pair-produced charged Higgs bosons decaying via $H^+H^-\rightarrow t^*bτν\rightarrow bbjjτν$. We perform signal-to-background analyses at the HL-LHC and a prospective 100 TeV proton-proton collider, employing cut-flow strategies and the Boosted Decision Tree method. However, due to the softness of the $b$ jets, signal significances fall below detection thresholds at these facilities. Extending our study to a multi-TeV muon collider (MuC), we demonstrate that a 3 TeV MuC achieves high signal significance, surpassing the $5σ$ threshold with an integrated luminosity of 1 ab$^{-1}$ and a 10\% background uncertainty. Specifically, for $M_{H^\pm} = 130$, 150, and 170 GeV, the significances are 13.7, 13.5, and 6.06, respectively. In contrast, a 10 TeV MuC requires 10 ab$^{-1}$ to achieve similar results. Our findings highlight the critical role of the MuC in probing the new signal channel $H^\pm\rightarrow t^*b$, offering a promising avenue for future charged Higgs boson searches involving off-shell top quarks.

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arXiv2025

Probing a Heavy Dark $Z$ Boson at Multi-TeV Muon Colliders: Leveraging the Optimized Recoil Mass Technique

We investigate the discovery potential of multi-TeV muon colliders for a heavy dark $Z$ boson ($Z_{\rm D}$) with a mass above 1 TeV through the associated production channel $μ^+μ^- \to Z_{\rm D}γ$. This process enables precise $M_{Z_{\rm D}}$ reconstruction using the photon recoil mass ($m_{\rm recoil}$). Focusing on the $Z_{\rm D} \to jjX$ and $Z_{\rm D} \to e^+e^-$ decay modes, we present strategies for achieving high sensitivity to the kinetic mixing parameter $\varepsilon$ at 3, 6, and 10 TeV muon colliders with integrated luminosities of 1, 4, and 10 ab$^{-1}$ respectively, assuming $Z_{\rm D}$ decays exclusively into Standard Model particles. A key innovation is our optimized implementation of $M_{Z_{\rm D}}$-dependent cuts on $m_{\rm recoil}$, which accounts for the energy-dependent detector response. For heavier $Z_{\rm D}$, the associated photon becomes less energetic, leading to better photon energy resolution and thus enabling more stringent $m_{\rm recoil}$ cuts. This approach enhances $\varepsilon$ sensitivity for heavier $Z_{\rm D}$. Conversely, for lighter $Z_{\rm D}$, the lower-energy electron pair from $Z_{\rm D} \to e^+e^-$ enables tighter cuts on the invariant mass of the electron pair ($m_{ee}$), providing better sensitivity in the lighter mass regime. Combining these complementary $m_{\rm recoil}$- and $m_{ee}$-based selections with both $jjX$ and $e^+e^-$ channels, we achieve $\varepsilon$ sensitivity down to $O\left(10^{-3}\right)$ as $M_{Z_{\rm D}}$ approaches $\sqrt{s}$, substantially surpassing the reach of a 100 TeV proton-proton collider. Even if $Z_{\rm D}$ decays into dark-sector particles, the recoil mass method remains effective, establishing muon colliders as powerful facilities for exploring heavy dark sectors.

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arXiv2024

$4b + X$ via electroweak multi-Higgs production as smoking gun signals for Type-I 2HDM at the LHC

Extending the Standard Model (SM) by one additional Higgs doublet leads to the Two-Higgs Doublet Model (2HDM). A specific charge assignment of the SM fermions under the $\mathbb{Z}_2$ symmetry leads to the Type-I 2HDM. A key feature of the Type-I 2HDM is that all the additional Higgs bosons can be fermiophobic, when their couplings to the SM fermions are suppressed. As a result, all the new Higgs states can be fairly light, $\sim$100 GeV or less, without being in conflict with the current data from the direct Higgs boson searches and the $B$-physics measurements. In a recent study Ref.~\cite{Mondal:2023wib}, which this proceeding is based on, we established that the new neutral as well as the charged Higgs bosons in this model can all be simultaneously observable in the multi-$b$ final state. An experimental validation of our results would be a clear indication that the true underlying Higgs sector in nature is the Type-I 2HDM.

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arXiv2023

Electroweak Multi-Higgs Production: A Smoking Gun for the Type-I Two-Higgs-Doublet Model

Extending the Higgs sector of the Standard Model (SM) by just one additional Higgs doublet field leads to the two-Higgs-doublet model (2HDM). In the Type-I $Z_2$-symmetric limit of the 2HDM, all the five new physical Higgs states can be fairly light, $\mathcal{O}(100)$\,GeV or less, without being in conflict with current data from the direct Higgs boson searches and the $B$-physics measurements. In this article, we establish that the new neutral as well as the charged Higgs bosons in this model can all be simultaneously observable in the multi-$b$ final state. The statistical significance of the signature for each of these Higgs states, resulting from the electro-weak (EW) production of their pairs, can exceed 5$σ$ at the 13\,TeV High-Luminosity Large Hadron Collider (HL-LHC). Since the parameter space configurations where this is achievable are precluded in the other, more extensively pursued, 2HDM Types, an experimental validation of our findings would be a clear indication that the true underlying Higgs sector in nature is the Type-I 2HDM.

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arXiv2023

Probing Light Fermiophobic Higgs Boson via diphoton jets at the HL-LHC

In this study, we explore the phenomenological signatures associated with a light fermiophobic Higgs boson, $h_{\rm f}$, within the type-I two-Higgs-doublet model at the HL-LHC. Our meticulous parameter scan illuminates an intriguing mass range for $m_{h_{\rm f}}$, spanning $[1,10]{\;{\rm GeV}}$. This mass range owes its viability to substantial parameter points, largely due to the inherent challenges of detecting the soft decay products of $h_{\rm f}$ at contemporary high-energy colliders. Given that this light $h_{\rm f}$ ensures $Br(h_{\rm f}\toγγ)\simeq 1$, $Br(H^\pm \to h_{\rm f} W^\pm)\simeq 1$, and $M_{H^\pm}\lesssim 330{\;{\rm GeV}}$, we propose a golden discovery channel: $pp\to h_{\rm f}H^\pm\to γγγγ\,l^\pmν$, where $l^\pm$ includes $e^\pm$ and $μ^\pm$. However, a significant obstacle arises as the two photons from the $h_{\rm f}$ decay mostly merge into a single jet due to their proximity within $ΔR<0.4$. This results in a final state characterized by two jets, rather than four isolated photons, thus intensifying the QCD backgrounds. To tackle this, we devise a strategy within \textsc{Delphes} to identify jets with two leading subparticles as photons, termed diphoton jets. Our thorough detector-level simulations across 18 benchmark points predominantly show signal significances exceeding the $5σ$ threshold at an integrated luminosity of $3{\;{\rm ab}^{-1}}$. Furthermore, our approach facilitates accurate mass reconstructions for both $m_{h_{\rm f}}$ and $M_{H^\pm}$. Notably, in the intricate scenarios with heavy charged Higgs bosons, our application of machine learning techniques provides a significant boost in significance.

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arXiv2023

Probing the electroweak $4b + \ell + {\rlap{\,/}{E}_T}$ final state in type I 2HDM at the LHC

Most of the experimental searches of the non-Standard Model Higgs boson(s) at the LHC rely on the QCD induced production modes. However, in some beyond Standard Model frameworks, the additional Higgs bosons can have fermiophobic behaviour. The type I two Higgs doublet model considered here is a perfect example where all the additional Higgs bosons exhibit fermiophobic nature over a large region of parameter space. Thus the electroweak productions of these new Higgs bosons are more dominant over the QCD induced processes. In scenarios with light pseuodoscalar ($A$) which is bound to decay dominantly to $b\bar{b}$, even being fermiophobic, the $4b + W$ state via $p p \to H^\pm A \to (AW)A \to 4b + W$ and followed by the leptonic decay of $W$ boson can surpass the QCD initiated $4b$ final state. However, the signal gets overshadowed by large $t\bar{t}+$jets background and hence constructing a suitable discriminator based on the signal hypothesis and signal topology is necessary. We devised a $χ^2$ variable as the most suitable signal-background discrimintor to reduce the background by a sizable amount and showed the discovery reach ( $>3σ$) of the electroweak initiated $4b+ \ell + {\rlap{\,/}{E}_T}$ final state at the LHC.

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arXiv2023

Charged Higgs induced 5 and 6 lepton signatures from heavy neutrinos at the LHC

We propose an anomaly free gauged U$(1)$ extension of the SM where three right handed heavy neutrinos, being charged under the general U$(1)$ gauge group, are introduced to explain the origin of the tiny neutrino mass through the seesaw mechanism after the general U$(1)$ symmetry is broken. Due to the breaking of the general U$(1)$ symmetry a neutral beyond the standard model gauge boson $Z^\prime$ acquires mass. There are two Higgs doublets in this model where one interacts with the SM fermions and the other one interacts with the right handed heavy neutrinos and charged leptons. The charged multiplet of the second Higgs can completely decay into the heavy neutrinos and charged lepton in the neutrinophilic limit of the model parameters. The charged Higgs pair production can be influenced due to presence of the $Z^\prime$ boson at the High Luminosity LHC (HL-LHC) in addition to the neutral SM gauge bosons. The pair produced charged Higgs bosons decay into SM charged leptons and heavy neutrinos. Following the leading decay modes of the heavy neutrinos into charged leptons and $W$ boson we study the 5 and 6 lepton final states after the leptonic and hadronic decay of the $W$ bosons considering solely muons and electrons in the final state. Combining the electron and muon final states we estimate the significance of the 5 and 6 charged lepton processes in the $m_{H^\pm}-m_N$ plane for different benchmark points of $m_{Z^\prime}$. It is found that the 5 (6) charged lepton processes could be probed at the High Luminosity LHC (HL-LHC) with at least 5 (3) $σ$ significance and there are parameter regions where the significance could be larger.

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arXiv2023

$τ^\pm νγγ$ and $\ell^\pm \ell^\pm γγ{\rlap{\,/}{E}_T} X$ to probe the fermiophobic Higgs boson with high cutoff scales

The light fermiophobic Higgs boson $h_{\rm f}$ in the type-I two-Higgs-doublet model can evade the current search programs at the LHC since its production through the quark-antiquark annihilation and gluon fusion is not feasible. The particle can be more elusive if the model retains stability up to the Planck scale because the efficient discovery channels are missing from the existing search chart. Through the comprehensive scanning, we show that all the viable parameter points with the Planck cutoff scale require $ m_{h_{\rm f}} \in[80,\, 120]{\;{\rm GeV}}$ and $M_{A/H^\pm} \in [90,\,150]{\;{\rm GeV}}$. Since $h_{\rm f}h_{\rm f}\to γγW^+ W^-$ and $H^\pm \to τ^\pm ν/h_{\rm f}W^\pm$ are dominant in this case, two final states are more efficient to probe $h_{\rm f}$ than the conventional search mode of $4γ+W^\pm/Z$. One is $τ^\pmνγγ$ from $pp \to H^\pm(\toτ^\pmν) h_{\rm f}(\to γγ)$ and the other is $\ell^\pm \ell^\pm γγ{\rlap{\,/}{E}_T} X$ ($\ell^\pm=e^\pm,μ^\pm$) from $pp \to H^\pm(\to h_{\rm f}W^\pm) h_{\rm f} \to γγW^+ W^-W^\pm $, $pp \to H^\pm(\to h_{\rm f} W^\pm) A(\to h_{\rm f} Z) \to γγW^+ W^- W^\pm Z $, and $pp \to H^+(\to h_{\rm f} W^+)H^-(\to h_{\rm f} W^-)\to γγW^+ W^- W^+ W^-$. The inclusive $\ell^\pm \ell^\pm γγ{\rlap{\,/}{E}_T} X$ consists of a same-sign dilepton, two prompt photons, and missing transverse energy. We perform the signal-background analysis at the detector level. With the total integrated luminosity of $300\;{\rm fb}^{-1}$ and the 5\% background uncertainty, two proposed channels at the 14 TeV LHC yield signal significances above five in the entire viable parameter space of the fermiophobic type-I with a high cutoff scale.

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arXiv2022

CDF $W$ boson mass and muon $g-2$ in type-X two-Higgs-doublet model with a Higgs-phobic light pseudoscalar

The recent measurement of the $W$ boson mass by the CDF collaboration adds an anomaly to the long-standing discrepancy in the muon anomalous magnetic moment, $Δa_μ$. Although type-X in the two-Higgs-doublet model provides an attractive solution to $Δa_μ$ through a light pseudoscalar $A$, the model confronts the exotic Higgs decays of $h\to AA$ and the lepton flavor universality data in the $τ$ and $Z$ decays. To save the model, we propose that the light pseudoscalar be Higgs-phobic. Through the random scanning over the entire parameter space, we perform a comparative study of the Higgs-phobic type-X with and without the CDF $m_W$ measurement, called the CDF and PDG cases respectively. Both cases can explain the two anomalies as well as all the other constraints but have significant differences in the finally allowed parameter space. For example, a small region with almost degenerate masses of new Higgs bosons around 100 GeV is allowed only in the PDG case. The cutoff scale of the model is also studied via the analysis of renormalization group equations, which reaches up to $10^5~{\rm GeV}$ ($10^7~{\rm GeV}$) in the CDF (PDG) case. Since the dominant decay modes are $A\to ττ$, $H \to Z A$, and $H^\pm\to W^\pm A$ in most of the viable parameter space, we propose the $4τ+VV'$ states as the golden discovery channel at the LHC.

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arXiv2022

Fermiophobic light Higgs boson in the type-I two-Higgs-doublet model

The null results in the new physics searches at the LHC do not exclude an intermediate-mass new particle if it is fermiophobic. Type-I in the two-Higgs-doublet model accommodates a fermiophobic light Higgs boson $h_{\rm f}$ if $α=π/2$. The heavier $CP$-even Higgs boson explains the observed Higgs boson at a mass of 125 GeV. We first obtain the still-valid parameter space satisfying the theoretical requirements, flavor-changing neutral currents in $B$ physics, the cutoff scale above 1 TeV, Higgs precision data, and the direct collider search bounds at high energy colliders. We also study the high energy scale behavior via the analysis of the renormalization group equations. An important result is that the fermiophobic type-I can maintain the stability of the scalar potential all the way up to the Planck scale if $m_{h_{\rm f}}$ is larger than half the observed Higgs boson mass. Since the parameter space is severely curtailed, especially for the high cutoff scale, the signal rates in the multi-photon states of new Higgs bosons at the LHC are well predicted. We suggest the processes of $4γ+VV'$ ($V^{(\prime)}=Z, W^\pm$) as the golden discovery channels for the model since they enjoy an almost background-free environment and substantial selection efficiencies for four photons.

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arXiv2022

A radiatively induced inverse seesaw model with hidden $U(1)$ gauge symmetry

We propose an inverse seesaw scenario under hidden $U(1)$ gauge symmetry, having rather natural hierarchies among neutral fermion mass scales. The hierarchies are derived from theory and experimental constraints. The theory requires Majorana exotic masses have to be induced at one-loop level. The experimental side requests that the Dirac mass terms has to be highly suppressed to satisfy the constraints from the lepton flavor violations(LFVs) such as $μ\to eγ$. In order to induce such a small Majorana exotic masses we introduce exotic fermions and bosons that also provide us additional intriguing phenomenologies such as muon anomalous magnetic moment, dark matter candidate as well as LFVs and deviations in leptonic $Z$ decays. We analyze these phenomenologies including neutrino oscillation data numerically, and show allowed region. Finally, we discuss the DM candidate in both the cases of fermion and scalar boson, where we focus on rather lighter range that is equal or less than 10 GeV. The dominant contributions originate from interactions of hidden gauge sector, and we show allowed ranges for both cases.

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arXiv2022

Same sign trilepton as signature of charged Higgs in two Higgs doublet model

We explored the prospect of looking for a fermiophobic charged Higgs ($\hpm$) via the same sign trilepton signal at the LHC. A fermiophobic scenario appears in the type-I two Higgs doublet model where the coupling of the $\hpm$ with the Standard Model fermions is inversely proportional to $\tb$. Almost all the experimental searches rely on the fermionic production and decay of the charged Higgs. Consequently, the limit on $\hpm$ for fermiophobic scenarios is non-existent unless $\tb$ is small. We show that for a fermiophobic case, the electroweak production of $\hpm$ is dominant for most of the parameter space. Subsequent bosonic decay of the charged and neutral Higgses give rise to the same sign trilepton signal. With a thorough phenomenological analysis, we demonstrate that the same sign trilepton signal can be an excellent complementary search to explore the high $\tb$ regions.

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arXiv2021

Explaining Atomki anomaly and muon $g-2$ in $U(1)_X$ extended flavour violating two Higgs doublet model

We investigate a two Higgs doublet model with extra flavour depending $U(1)_X$ gauge symmetry where $Z'$ boson interactions can explain the Atomki anomaly by choosing appropriate charge assignment for the SM fermions. For parameter region explaining the Atomki anomaly we obtain light scalar boson with $\mathcal{O}(10)$ GeV mass, and we explore scalar sector to search for allowed parameter space. We then discuss anomalous magnetic dipole moment of muon and lepton flavour violating processes induced by Yukawa couplings of our model.

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