arXiv subjects

Sukanta Dutta

Publications and source records attributed to Sukanta Dutta.

At least 19 recordsLinked to original sources

arXiv2026

Dark Photon - ALP Freeze-in: 511 keV and H$\alpha$ Constraints

We investigate a freeze-in scenario of two component dark matter consisting of an axion-like particle (ALP) and a dark photon. The dark sector connects to the Standard Model through a dimension-five ALP-dark photon interaction, while a small kinetic mixing governs dark photon decays. Solving the coupled Boltzmann equations, we determine the parameter space consistent with the observed relic abundance. We find that, for a nearly degenerate dark sector, dark photon decay into an electron-positron pair through the kinetic mixing explains the Galactic 511 keV line while the dimension five operator can source the necessary production of dark photon and ALP particles to satisfy the relic density. We further confront the model with recent H$\alpha$ observations of dwarf galaxies, together with constraints from the cosmic microwave background, diffuse gamma rays, direct detection and collider searches. We identify viable regions of parameter space yielding $\Omega_{\rm DM}h^2\simeq0.12$, with an effective scale $\Lambda\sim10^{10}$-$10^{12}$ GeV, and dark photon lifetimes of order $10^{26}$-$10^{29}$ s, while remaining consistent with the observed 511 keV photon flux, $H\alpha$ constraints from Leo T and all other astrophysical constraints.

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arXiv2026

Probing Lepton-Flavor-Violating Four-Lepton Operators at a Muon Collider

We investigate charged lepton-flavour violation (LFV) induced by dimension-six four-lepton operators within the Standard Model Effective Field Theory at a proposed high-energy muon collider. We study the processes $\mu^{+}\mu^{-}\to e^{\pm}\tau^{\mp}$, $\mu^{+}\mu^{-}\to e^{\pm}\mu^{\mp}$, and $\mu^{+}\mu^{-}\to \mu^{\pm}\tau^{\mp}$ at $\sqrt{s}=3$, $10$, and $14$~TeV, incorporating beam polarisation and hadronic $\tau$ reconstruction. Using an optimal-observable analysis of the angular distributions, we perform a global fit to the relevant set of four-lepton operators. Projected sensitivities reach $C/\Lambda^{2}\sim(0.6$-$1.6)\times10^{-11}\,\mathrm{GeV}^{-2}$, depending on the flavour and chiral structure of the operator, exceeding current limits by up to an order of magnitude. A combined analysis of multiple centre-of-mass energies and beam polarisations significantly improves the resolution of correlations among the Wilson coefficients. These results highlight the strong sensitivity of a future multi-TeV muon collider to charged lepton flavour violating four-lepton interactions, establishing it as a powerful probe of the SMEFT parameter space.

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arXiv2026

Radiative Signature of New Scalar Boson Decays in the $m_{\ell \ell \gamma}$ Spectrum at the LHC

We investigate the radiative decay $S \to W^+W^-\gamma$ in the context of the multi-lepton anomalies and recent indications of a narrow scalar resonance near $m_S = 152 \pm 1~\text{GeV}$ in the $\gamma\gamma$, $Z\gamma$, and $W^+W^-$ channels at the Large Hadron Collider. These excesses arise in final states containing leptons, missing transverse momentum, and associated $b$-jets, and motivate a search for a corresponding localized excess in the invariant-mass spectrum of the dilepton--photon system, $m_{\ell\ell\gamma}$, in events with associated $b$-jets. We use recent CMS measurements of the ${t\bar{t}}\gamma$ differential cross sections~\cite{CMS:2025zbe} to study the $m_{\ell\ell\gamma}$ spectrum and perform a search for a scalar-resonance contribution. A localized excess is observed, compatible with the scalar-resonance hypothesis, with a global significance of $2.7\sigma$ at $m_S = 152~\text{GeV}$. This result provides additional support for the hypothesis of a narrow resonance. The ratio $\sigma(S \to W^+W^-\gamma)/\sigma(S \to W^+W^-) = (2.14 \pm 0.77)$\% is extracted. This value is compatible with an enhanced radiative contribution that could arise in scenarios beyond the Standard Model.

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arXiv2025

Effective LFV couplings at the electron-proton collider

We estimate the accuracy with which the coefficient of the lepton flavour-violating dimension-six operators can be measured at the proposed electron-proton collider. Cuts-based analysis is performed to compute the signal significance at the centre of mass energy of 1.3 TeV, with a total integrated luminosity upto $\sim$ab$^{-1}$. Using the optimal observables method for the kinematic distributions, we study the sensitivity of the effective couplings. We also study the impact of the initial electron beam polarisation.

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arXiv2025

Higgs Decay Signal Strengths in an Extended 2HDM

The combined CMS and ATLAS analysis of $h \to Zγ$ reveals a $2σ$ excess over the Standard Model (SM) prediction, hinting at potential new physics. In contrast, the observed agreement of $μ_{γγ}$ with the SM imposes stringent constraints on such extension. In this context, we investigate a Two Higgs Doublet Model (2HDM) extended by a complex scalar singlet and a vector-like lepton (VLL). This framework successfully accommodates the Higgs decay signal strengths $μ_{{}_{W \,W^\star}}$, $ μ_{Zγ}\,$, and $\, μ_{γγ}$ while also satisfying precision electroweak constraints, the observed experimental value of muon $g-2$, and bounds from LEP II data. We identify a viable region of parameter space that is consistent with all low energy data and current experimental limits on the Higgs decay signal strengths.

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arXiv2025

Effective Lepton Flavor Violating couplings at Muon Collider

We estimate the sensitivity of Wilson coefficients of the lepton flavor-violating dimension-six operators at the proposed $\mu^+\mu^-$ collider. We compute the signal significance at $\sqrt{s}$ = 3 and 10 TeV, respectively, with an integrated luminosity of 1 and 10 ab$^{-1}$ corresponding to unpolarized and polarized initial muon beams. Using the optimal observable method for the kinematic distributions, we study the measurement errors of the effective couplings at the 1-sigma level.

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arXiv2025

$W-$mass and Muon $g-2$ in Inert 2HDM Extended by Singlet Complex Scalar

The deviations of the recent measurements of the muon magnetic moment and the $W-$boson mass from their SM predictions hint to new physics beyond the SM. In this article, we address the observed discrepancies in the $W$-boson mass and muon anomalous magnetic moment in the Inert Two Higgs Doublet Model (I2HDM) extended by a complex scalar field singlet under the SM gauge group. The model is constrained from the existing LEP data and the measurements of partial decay widths to gauge bosons at LHC. It is shown that a large subset of this constrained parameter space of the model can simultaneously accommodate the $W$-boson mass and also explain the muon $g-2$ anomaly.

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arXiv2022

Limiting the Heavy-quark and Gluon-philic Real Dark Matter

We investigate the phenomenological viability of real spin half, zero and one dark matter candidates, which interact predominantly with third generation heavy quarks and gluons via the twenty-eight gauge invariant higher dimensional effective operators. The corresponding Wilson coefficients are constrained one at a time from the relic density $Ω^{\rm DM} h^2$ $\approx$ 0.1198. Their contributions to the thermal averaged annihilation cross-sections are shown to be consistent with the FermiLAT and H.E.S.S. experiments' projected upper bound on the annihilation cross-section in the $b\,\bar b$ mode. The tree-level gluon-philic and one-loop induced heavy-quark-philic DM-nucleon direct-detection cross-sections are analysed. The non-observation of any excess over expected background in the case of recoiled Xe-nucleus events for spin-independent DM-nucleus scattering in XENON-1T sets the upper limits on the eighteen Wilson coefficients. Our analysis validates the real DM candidates for the large range of accessible mass spectrum below 2 TeV for all but one interaction induced by the said operators.

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arXiv2022

Measuring $CP$ nature of $hτ{\barτ}$ coupling at $e^-p$ collider

The proposed future $e^- p$ collider provides sufficient energies to produce the Standard Model Higgs Boson ($h$) through $W^\pm$ and $Z$-Boson fusion in charged and neutral current modes, respectively and to measure its properties. We take this opportunity to investigate the prospect of measuring the $CP$ properties of $h$ through $h \to τ^+ τ^-$, where $τ^-\,\left(τ^+\right)$ decays to a charged pion $π^-\,\left(π^+\right)$ and a neutral pion $π^0$ in association with neutrino (anti-neutrino). An interesting $CP$ sensitive angular observable $α_{\rm CP}$ between the two $τ$-leptons decay plane in the $π^+π^-$ centre of mass frame is proposed and investigated in this work. For fixed electron energy of 150 GeV along with 7 (50) TeV of proton energy, the $CP$ phase can be measured approximately to $25^\circ$ ($14^\circ$) at integrated luminosity of 1~ab$^{-1}$ for $-$80\% polarised electron at 95\% confidence level.

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arXiv2021

Leptonic $g-2$ anomaly in an extended Higgs sector with vector-like leptons

We address the observed discrepancies in the anomalous magnetic dipole moments (MDM) of the muon and electron by extending the inert two Higgs Doublet Model (2HDM) with SM gauge singlet complex scalar field and singlet Vector-like Lepton (VLL) field. We obtain the allowed parameter space constrained from the Higgs decays to gauge Bosons at LHC, LEP II data and electro-weak precision measurements. The muon and electron MDM's are then explained within a common parameter space for different sets of allowed couplings and masses of the model particles.

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arXiv2019

Twist-2 operators induced Dark Matter Interactions

We study the effective interactions of the fermionic, scalar and vector dark matter (DM) with leptons and neutral electroweak gauge Bosons induced by the higher dimensional effective twist-2 tensor operators. We constrain these lepto-philic, $τ^\pm$-philic and $U(1)_Y$ gauge Boson B-philic effective interactions of DM with the visible world from the WMAP and Planck data. The thermally averaged indirect DM pair annihilation cross-section and the DM-electron direct-detection cross-section for such DM candidates are observed to be consistent with the respective experimental data. Constraining coefficients of the effective operators from the low energy LEP data for the DM $\le$ 80 GeV, we further study their sensitivities in the pair production of such DM $\ge$ 50 GeV in association with mono-photon at the proposed ILC and perform the $χ^2$ analysis to obtain the 99.73\% C.L. acceptance contours in the $m_{\rm DM}-Λ_{\rm eff}$ plane from the two dimensional differential distributions of the kinematic observables. We observe that ILC has rich potential to probe the contribution of such effective operators.

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arXiv2019

Lepto-philic 2-HDM + singlet scalar portal induced fermionic dark matter

We explore the possibility that the discrepancy in the observed anomalous magnetic moment of the muon $Δa _μ$ and the predicted relic abundance of Dark Matter by Planck data, can be explained in a lepto-philic 2-HDM augmented by a real SM singlet scalar of mass $\sim$ 10-80 GeV. We constrain the model from the observed Higgs Decay width at LHC, LEP searches for low mass exotic scalars and anomalous magnetic moment of an electron $Δa_e$. This constrained light singlet scalar serves as a portal for the fermionic Dark Matter, which contributes to the required relic density of the universe. A large region of model parameter space is found to be consistent with the present observations from the Direct and Indirect DM detection experiments.

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arXiv2018

Spin-$0^\pm$ portal induced Dark Matter

Standard model (SM) spin-zero singlets are constrained through their di-Bosonic decay channels via an effective coupling induced by a vector-like quark (VLQ) loop at the LHC for $\sqrt{s}$ = 13 TeV. These spin-zero resonances are then considered as portals for scalar, vector or fermionic dark matter particle interactions with SM gauge bosons. We find that the model is validated with respect to the observations from LHC data and from cosmology, indirect and direct detection experiments for an appreciable range of scalar, vector and fermionic DM masses greater than 300 GeV and VLQ masses $\ge$ 400 GeV, corresponding to the three choice of portal masses 270 GeV, 500 GeV and 750 GeV respectively.

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arXiv2017

Signals of Leptophilic Dark Matter at the ILC

Adopting a model independent approach, we constrain the various effective interactions of leptophilic DM particle with the visible world from the WMAP and Planck data. The thermally averaged indirect DM annihilation cross-section and the DM-electron direct-detection cross-section for such a DM candidate are observed to be consistent with the respective experimental data. We study the production of cosmologically allowed leptophilic DM in association with $Z\, (Z\to f\bar f)$, $f\equiv q,\,e^-,\, μ^-$ at the ILC. We perform the $χ^2$ analysis and compute the 99\% C.L. acceptance contours in the $m_χ$ and $Λ$ plane from the two dimensional differential distributions of various kinematic observables obtained after employing parton showering and hadronization to the simulated data. We observe that the dominant hadronic channel provides the best kinematic reach of 2.62 TeV ($m_χ$ = 25 GeV), which further improves to 3.13 TeV for polarized beams at $\sqrt{s} = 1$ TeV and an integrated luminosity of 1 ab$^{-1}$.

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arXiv2016

Investigating Unitarity in Presence of Anomalous Couplings

We perform a model independent analysis of the helicity amplitudes at high energy for all the $2\to2$ scattering processes involving gauge and Higgs bosons in the presence of anomalous $WWV$, $WWVV$, $VVH$, $VVHH$ ($V\equiv Z,γ$ and $W^\pm$), $HHHH$ and $HHH$ interactions. We obtain the perturbative unitarity constraints on anomalous couplings by demanding the vanishing of terms proportional to $s^2$ and $s^{3/2}$ in the helicity amplitudes. Using these constraints, we also compute the upper bound on all the anomalous couplings from terms linear in $s$. Further, assuming all anomalous couplings to have arisen only from dimension six operators, we show that the perturbative unitarity violation can be evaded up to $\sim$ 9 TeV corresponding to the best fit values of $f_{WW}/Λ^2$ and $f_{BB}/Λ^2$ from the combined analysis of Tevatron and LHC data.

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arXiv2015

Anomalous X-Ray Galactic signal from 7 keV spin-$3/2$ dark matter decay

In order to explain the recently reported peak at $3.55$ keV in the galactic x-ray spectrum, we propose a simple model. In this model, the Standard Model is extended by including a neutral spin-$3/2$ vector-like fermion that transforms like a singlet under SM gauge group. This $7.1$ keV spin-$3/2$ fermion is considered to comprise a portion of the observed dark matter. Its decay into a neutrino and a photon with decay life commensurate with the observed data, fits the relic dark matter density and obeys the astrophysical constraints from the supernova cooling.

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arXiv2015

Measuring anomalous $Wtb$ couplings at $e^-p$ collider

We study the accuracy with which the lowest order $CP$ conserving anomalous $Wtb$ couplings in the single top quark production at the proposed large hadron electron collider (LHeC) can be probed. The one dimensional distribution of various kinematic observables at the parton level MC and their asymmetries arising due to the presence of anomalous couplings both in the hadronic and leptonic $W$ decay is examined. \par We find that at 95 \% C.L. the anomalous coupling associated with the left handed vector current can be measured at an accuracy of the order of $\sim 10^{-2}-10^{-3}$, while those associated with the right handed vector and left as well as right handed tensor currents have sensitivity at the order of $\sim 10^{-1}-10^{-2}$ for the systematic uncertainty varying between 10\%-1\% at an integrated luminosity of 100 fb$^{-1}$. A comprehensive analysis of the combined covariance matrix derived from all one dimensional distributions of kinematical observables is used to compute the errors in anomalous couplings.

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arXiv2013

Top quark physics in the Vector Color-Octet Model

We study and constrain the parameter space of the vector color-octet model from observed data at Tevatron by studying top quark pair production and associated observables afbt and spin-correlation. In particular we study invariant mass and rapidity dependence of afbt at Tevatron. In addition to FC couplings we extend our study to include FV coupling involving first & third generation quarks for both these processes. In order to ensure that we remain within the constraints imposed by LHC data, we analyze the charge asymmetry, p_T spectrum & invariant mass in t\bar t production data at LHC. The constraints from dijet resonance searches performed by LHC are also considered. We also explore the contribution of this model to single top quark production mediated by charged & neutral color-octet vector bosons. FV couplings introduced then induce same-sign top-pair production process which is analyzed for both hadron colliders. We have incorporated effect of finite decay width of color octets on these processes. We find that it is possible to explain the observed afbt anomaly in color-octet vector model without transgressing production cross sections of all these processes both through FC and FV couplings at Tevatron. We predict best point sets in model parameter space for specific choices of color-octet masses corresponding to chi^2_min evaluated using mttb and dyy spectrum of afbt from observed data set at Tevatron (8.7 fb-1). We find that single top quark production is more sensitive to FC and FV couplings in comparison to top-pair production. We provide 95% exclusion contours on the plane of FV chiral couplings from recent data at Tevatron, CMS and ATLAS corresponding to nonobservability of large same-sign dilepton events. The four observed point sets are consistent with the cross section, charge asymmetry and spin-correlation measurements for t\bar t production & dijet searches at LHC.

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