arXiv subjects

Triparno Bandyopadhyay

Publications and source records attributed to Triparno Bandyopadhyay.

12 recordsLinked to original sources

arXiv2026

Potential for the discovery of the protophobic boson at the STCF

We study the morphology of the main drift chamber (MDC) to be built around the collision point of the proposed Super tau-charm facility (STCF), to check its suitability for discovering the 17 MeV protophobic boson (X17 boson), hypothesised as a solution to the persistent ATOMKI nuclear-transition anomalies. Using the TrackEff framework, we perform detector-level simulations of the STCF MDC, and evaluate displaced-vertex sensitivities towards the protophobic boson, across the relevant mass-coupling parameter space. We study benchmark scenarios with visible and dark decay channels to perform likelihood-based significance estimates in order to determine the 5~$σ$ discovery reach for the protophobic boson. We find that STCF can potentially discover the protophobic boson while tolerating $\sim 10^4$ background events for specific regions of the parameter space. Our analysis establishes the first feasibility study of displaced light-boson searches at the STCF, motivating a full Geant-4 simulation.

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arXiv2026

Constraining ALP-Meson overlaps from $Kπ$ form factors

We present the first constraints on the overlaps between an Axion-like particle (ALP) and the $π^0$ and $η$ mesons from the analysis of the distortions to the $\langle K|\overline{s}γ^μu | π\rangle$ form factors. We demonstrate that these distortions can be tightly constrained by combining data from $τ^-\to π^0 K^-ν$ and $K^+\to π^0\ell^+ν$ decays, and go on to map the constraints to the ALP-meson overlaps. We establish that, in general, the ALP-meson and meson-ALP overlaps are different due to the presence of ALP-quark derivative couplings in the UV Lagrangian, and need to be treated separately. Using lattice results and BaBar, Belle, and NA48/2 data, we obtain exclusion limits on the overlaps and give projections for Belle II. Our techniques are independent of the branching ratios of the ALP, hence, robust against ALP decay channel assumptions. For masses of the ALP below 1 GeV, the bounds on the effective scale of the ALP physics extend to $\mathcal{O}$(TeV) for restricted regions of the parameter space for the ALP-$π$ and $π$-ALP overlaps. On the other hand, these bounds persist for extended regions of the parameter space for ALP-$η$ and $η$-ALP overlaps.

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arXiv2025

The E6 route to multicomponent dark matter

We present a framework of dark- and visible-sector unification in the E6 embedding of the standard model. The demand for consistently getting the standard model leads to the existence of the dark-sector. We show that the hierarchy of vevs typifying unified models leads to multicomponent dark matter at the IR. The symmetry breaking itself categorises the matter content into dark- and visible-sector particles, the categorisation being uniform across different breaking chains. We discuss the stability of the dark matter particles and compare them to existing phenomenological models of dark matter. The central results follow from symmetry and hierarchy arguments. We present an indicative set of models of gauge coupling unification, to show that the framework can be embedded in realistic models of E6.

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arXiv2023

Dark Photons from displaced vertices

We investigate the unexplored regions of the dark photon parameter space to find a search strategy suitable to probe these. We show how displaced track searches at colliders with large 4pi trackers around the interaction point are excellent choices for exploring these uncharted regions. As an example, we study in detail the sensitivity of the Belle II trackers to dark photons which mediate interactions between the visible and dark sectors. We also show that the same strategy can be employed by other experiments to achieve the same goal.

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arXiv2023

A twisted tale of the transverse-mass tail

We propose a tantalizing possibility that misinterpretation of the reconstructed missing momentum may have yielded the observed discrepancies among measurements of the $W$-mass in different collider experiments. We introduce a proof-of-principle scenario characterized by a new physics particle, which can be produced associated with the $W$-boson in hadron collisions and contributes to the net missing momentum observed in a detector. We show that these exotic events pass the selection criteria imposed by various collaborations at reasonably high rates. Consequently, in the presence of even a handful of these events, a fit based on the ansatz that the missing momentum is primarily due to neutrinos (as it happens in the Standard Model), yields a $W$-boson mass that differs from its true value. Moreover, the best fit mass depends on the nature of the collider and the center-of-mass energy of collisions. We construct a barebones model that demonstrates this possibility quantitatively while satisfying current constraints. Interestingly, we find that the nature of the new physics particle and its interactions appear as a variation of the physics of Axion-like particles after a field redefinition.

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arXiv2022

Signatures of generalized ALP interactions in SM decays of mesons

In addition to giving rise to spectacular new physics signals in the final states of meson decays, Axion-like-particles also induce modifications in the standard model decays of mesons. These `indirect' signatures can be parametrized as the modifications of the hadronic form factors and can be probed using meson decay width and decay distribution measurements. Starting with a generalized ALP Lagrangian, we demonstrate these effects for semileptonic Kaon decays and derived bounds using NA48/2 data. We also briefly discuss other indirect signatures such as modification of meson mass spectrum and `sum rules' comprised of meson decay amplitudes which show deviation in presence of ALP.

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arXiv2022

ALP-Pions generalized

A light axion-like particle or an ALP not just gives rise to interesting and spectacular signals of new physics as final states in meson decays, it necessarily leaves tell-tale signatures in processes that involve standard model (SM) fields only (i.e., SM processes). These effects result in the violation of the Gell-Mann--Okubo mass relation, modified form factors, altered integrated and differential rates for various SM transitions etc. This suggests that in the presence of a low lying state, such as an ALP, extraction of masses, mixing angles, and form factors in an entirely data-driven way from meson-physics observables is a highly non-trivial exercise. However, once done correctly, these same observables may, in turn, provide important (indirect) bounds on ALP physics, which remain robust even in the limits where new physics effects conspire to weaken the bounds from direct searches. Starting with a generalized ALP-quark Lagrangian (where restrictions due to parity are removed) we demonstrate this approach by focussing on $K^+_{\ell_3}$ decays, where we derive (indirect) bounds on ALP physics using NA48/2 data and lattice results. We also find sum rules which not just show deviations in the presence of an ALP, but also give hints towards the specific nature of the ALP physics itself.

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arXiv2022

Displaced Searches for Light Vector Bosons at Belle II

With a design luminosity of 50 ab$^{-1}$ and detectors with tracking capabilities extending beyond 1 m, the Belle II experiment is the perfect laboratory for the search of particles that couple weakly to the Standard Model and have a characteristic decay length of a few centimetres and more. We show that for models of dark photons and other light vector bosons, Belle II will be successful in probing regions of parameter space which are as of now unexplored by any experiment. In addition, for models where the vector boson couples sub-dominantly to the electron and quarks as compared to muons, e.g. in the $L_μ-L_τ$ model, Belle II will probe regions of mass and couplings compatible with the anomalous magnetic moment of muon. We discuss these results and derive the projected sensitivity of Belle II for a handful of other models. Finally, even with the currently accumulated data, $\sim 200$ fb$^{-1}$, Belle II should be able to cover regions of parameter space pertaining to the X(17) boson postulated to solve the ATOMKI anomaly.

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arXiv2019

Complementary bound on $W^\prime$ mass from Higgs to diphoton decay

Using the left-right symmetric model as an illustrative example, we suggest a simple and straightforward way of constraining the $W'$ mass directly from the decay of the Higgs boson to two photons. The proposed method is generic and applicable to a diverse range of models with a $W'$-boson that couples to the SM-like Higgs boson. Our analysis exemplifies how the precision measurement of the Higgs to diphoton signal strength can have a pivotal role in probing the scale of new physics.

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arXiv2018

A reappraisal of constraints on $Z'$ models from unitarity and direct searches at the LHC

In a truly model-independent approach, we reexamine a minimal extension of the Standard Model (SM) through the introduction of an additional $U(1)$ symmetry leading to a new neutral gauge boson ($Z'$), allowing its kinetic mixing with the hypercharge gauge boson. An SM neutral scalar is used to spontaneously break this extra symmetry leading to the mass of the $Z'$. Except for three right-handed neutrinos no other fermions are added. We use the current LHC Drell-Yan data to put model-independent constraints in the parameter space of three quantities, namely, $M_{Z'}$, the $Z$-$Z'$ mixing angle ($α_z$) and the extra $U(1)$ effective gauge coupling ($g'_x$), which absorb all model dependence. We impose additional constraints from unitarity and low energy neutrino-electron scattering. However, limits extracted from direct searches turn out to be most stringent. We obtain $M_{Z'} > 4.4$ TeV and $|α_z| < 0.001$ at $95\%$ C.L., when the strength of the additional $U(1)$ gauge coupling is the same as that of the SM $SU(2)_L$.

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arXiv2017

Left-right model with TeV fermionic dark matter and unification

The ingredients for a model with a TeV right-handed scale, gauge coupling unification, and suitable dark matter candidates lie at the heart of left-right symmetry with broken D-parity. After detailing the contents of such a model, with SU(2)R self-conjugate fermions at the right-handed scale aiding in unification of couplings, we explore its dark matter implications and collider signatures.

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arXiv2016

Implications of the CMS search for W_R on Grand Unification

The CMS experiment at the Large Hadron Collider has reported a 2.8$σ$ excess in the $(2e)(2jets)$ channel around 2.1 TeV. Interpretation of this data is reconsidered in terms of the production of a right-handed weak gauge boson, $W_R$, of the left-right symmetric model and in an $SO(10)$ grand unified theory abiding by the Extended Survival Hypothesis. The left-right symmetric model can be consistent with this excess if (a) the heavy right-handed neutrino has a mass near $W_R$, or (b) if $g_L \neq g_R$, or (c) the right-handed CKM matrix is nontrivial. Combinations of the above possibilities are also viable. A $W_R$ with a mass in the TeV region if embedded in $SO(10)$ is not compatible with $g_L = g_R$. Rather, it implies $0.64 \leq g_R/g_L \leq 0.78$. Further, a unique symmetry-breaking route -- the order being left-right discrete symmetry breaking first, followed by $SU(4)_C$ and finally $SU(2)_R$ -- to the standard model is picked out. The $L \leftrightarrow R$ discrete symmetry has to be broken at around $10^{16}$ GeV. The grand unification scale is pushed to $10^{18}$ GeV making the detection of proton decay in ongoing searches rather unlikely. The $SU(4)_C$ breaking scale can be at its allowed lower limit of $10^6$ GeV so that $n - \bar{n}$ oscillation or flavour changing processes such as $K_L \rightarrow μe$ and $B_{d,s} \rightarrow μe$ may be detectable. The Higgs scalar multiplets responsible for $SO(10)$ symmetry breaking at various stages are uniquely identified so long as one adheres to a minimalist principle. We also remark, {\em en passant}, about a partially unified Pati-Salam model.

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