arXiv subjects

Priyotosh Bandyopadhyay

Publications and source records attributed to Priyotosh Bandyopadhyay.

At least 37 records · Page 2Linked to original sources

arXiv2021

Distinguishing Different BSM Signatures at Present and Future Colliders

We show how angular distributions can distinguish different scenarios beyond the standard model by characterising particles of different spins at the LHC. We illustrate the idea with scalar and vector leptoquarks along with the heavy fermions in Type-III seesaw as spin zero, spin one and spin half examples respectively. On the other hand, zeros of single photon tree level amplitude can separate different particles according their electromagnetic charges. This phenomenon can be used to distinguish leptoquarks of different gauge representations, even different excitations of same $SU(2)_L$ gauge group, within the same spin frame work. We explore electron-photon and electron-hadron colliders to discern such scenarios in the context of the leptoquark models by means of zeros in scattering amplitudes. We found that the discerning effect in these two colliders are complementary to each other and both of them are required for an exhaustive analysis of leptoquark models. The analyses are carried out for different leptoquark masses and centre of mass energies of the collisions which involve a PYTHIA based simulation.

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arXiv2021

Zeros of Amplitude in the Associated Production of Photon and Leptoquark at $e$-$p$ Collider

Though various extensions of the Standard Model with higher gauge group predict the existence of leptoquarks, none of them has been observed yet at any of the colliders. In this paper, we study the prospect of several past and future $e$-$p$ colliders like HERA, LHeC and FCC-he to detect them through radiation amplitude zero. We find that the leptoquarks showing zeros in the tree-level single-photon amplitudes at $e$-$p$ collider lie within the complementary set of those exhibiting zeros at $e$-$γ$ collider. We present a PYTHIA-based analysis for HERA, LHeC and FCC-he (run II) to detect the leptoquarks with masses 70 GeV, 900 GeV and 1.5 TeV (2.0 TeV) respectively through radiation amplitude zero.

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arXiv2021

Scrutinizing Vacuum Stability in IDM with Type-III Inverse seesaw

We consider the extension of the Standard Model (SM) with an inert Higgs doublet that also contains two or three sets of $SU(2)_L$ triplet fermions with hypercharge zero and analyze the stability of electroweak vacuum for the scenarios. The model represents a Type-III inverse seesaw mechanism for neutrino mass generation with a Dark matter candidate.An effective potential approach calculation with two-loop beta function have been carried out in deciding the fate of the electroweak vacuum. Weak gauge coupling $g_2$ shows a different behaviour as compared to the Standard Model. The modified running of $g_2$, along with the Higgs quartic coupling and Type-III Yukawa couplings become crucial in determining the stability of electroweak vacuum. The interplay between two and three generations of such triplet fermions reveals that extensions with two generations is favoured if we aspire for Planck scale stability. Bounds on the Higgs quartic couplings, Type-III Yukawa and number of triplet fermion generations are drawn for different mass scale of Type-III fermions. The phenomenologies of inert doublet and Type-III fermions at the LHC and other experiments are commented upon.

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arXiv2021

Obscure Higgs boson at Colliders

In this study we consider an extension of the Standard Model with a complex hypercharge zero triplet scalar. In this scenario one of the charged Higgs bosons remains purely triplet and does not couple to the fermions, making it elusive at colliders. Also the physical pseudoscalar is a pure triplet and this purity makes it a suitable dark matter candidate without the need of discrete symmetries, unlike other extensions. The bounds from relic density and direct dark matter search experiments select its mass to be $\sim 1.35-1.60$ TeV. The pure triplet charged Higgs gives rise to displaced signatures and their sensitivity at LHC and MATHUSLA have been studied. The prospects at present and future hadron/muon colliders of such exotic scalars are pointed out by calculating their productions cross-section and dominant decay modes. We present also the expected reach for the triplet states at a multi-TeV muon collider.

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arXiv2020

Vacuum Stability in Inert Higgs Doublet Model with Right-handed Neutrinos

We analyze the vacuum stability in the inert Higgs doublet extension of the Standard Model (SM), augmented by right-handed neutrinos (RHNs) to explain neutrino masses at tree level by the seesaw mechanism. We make a comparative study of the high- and low-scale seesaw scenarios and the effect of the Dirac neutrino Yukawa couplings on the stability of the Higgs potential. Bounds on the scalar quartic couplings and Dirac Yukawa couplings are obtained from vacuum stability and perturbativity considerations. The regions corresponding to stability, metastability and instability of the electroweak vacuum are identified. These theoretical constraints give a very predictive parameter space for the couplings and masses of the new scalars and RHNs which can be tested at the LHC and future colliders. The lightest non-SM neutral CP-even/odd scalar can be a good dark matter candidate and the corresponding collider signatures are also predicted for the model.

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arXiv2020

Distinguishing Inert Higgs Doublet and Inert Triplet Scenarios

In this article we consider a comparative study between Type-I 2HDM and $Y=0$, $SU(2)$ triplet extensions having one $Z_2$-odd doublet and triplet that render the desired dark matter(DM). For the inert doublet model (IDM) either a neutral scalar or pseudoscalar can be the DM, whereas for inert triplet model (ITM) it is a CP-even scalar. The bounds from perturbativity and vacuum stability are studied for both the scenarios by calculating the two-loop beta functions. While the quartic couplings are restricted to $0.1-0.2$ for a Planck scale perturbativity for IDM, these are much relaxed ($0.8$ ) for ITM. The RG-improved potentials by Coleman-Weinberg show the regions of stability, meta-stability and instability of the electroweak vacuum. The constraints coming from DM relic, the direct and indirect experiments like XENON1T, LUX and H.E.S.S., Fermi-LAT allow the DM mass $\gtrsim 700, \,1176$ GeV for IDM, ITM respectively. Though mass-splitting among $Z_2$-odd particles in IDM is a possibility for ITM we have to rely on loop-corrections. The phenomenological signatures at the LHC show that the mono-lepton plus missing energy with prompt and displaced decays in the case of IDM and ITM can distinguish such scenarios at the LHC along with other complementary modes.

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arXiv2020

Feeble neutrino portal dark matter at neutrino detectors

We explore the neutrino portal dark matter (DM) at its minimum of field content having two dark sector particles coupled to a right-handed neutrino. Assuming the feeble nature of their interactions with the standard model (SM) particles, we analyze the freeze-in production of the observed DM relic density characterized by three different categories depending on the major production mechanisms. The portal provides interesting signatures at the neutrino detectors like KamLAND, Super-Kamiokande and IceCube, from a very late decay of the scalar DM to the fermion DM and the SM neutrino. Such neutrino flux spectrum from the cosmic and galactic origins can produce anomalous signals at future experiments.

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arXiv2020

Investigating the Production of Leptoquarks by Means of Zeros of Amplitude at Photon Electron Collider

Leptoquarks are one of the possible candidates for explaining various anomalies in flavour physics. Nonetheless, their existence is yet to be confirmed from experimental side. In this paper we have shown how zeros of single photon tree-level amplitude can be used to extract information about leptoquarks in case of $e$-$γ$ colliders. Small number of standard model backgrounds keep the signal clean in this kind of colliders. Unlike other colliders, the zeros of single photon amplitude here depend on $\sqrt{s}$ as well as the mass of leptoquark along with its electric charge. We perform a PYTHIA based simulation for reconstructing the leptoquark from its decay products of first generation and estimating the background with luminosity of 100 fb$^{-1}$. Our analysis is done for all the leptoquarks that can be seen at $e$-$γ$ collider with three different masses (70 GeV, 650 GeV and 1 TeV) and three different centre of momentum energy (200 GeV, 2 TeV and 3 TeV). The effects of non-monochromatic photons on the zeros of amplitude under laser backscattering and equivalent photon approximation have also been addressed.

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arXiv2019

Phenomenology of Higgs bosons in inverse seesaw model with Type-X two Higgs doublet at the LHC

Type-X two Higgs doublet model is known to explain the muon $g-2$ anomaly with a relatively light charged Higgs boson at large $\tanβ$. The light charged Higgs boson has been searched in the main $τν$ mode at the colliders. Invoking a scenario of inverse seesaw as the origin of neutrino masses and mixing, the charged Higgs boson can decay additionally to right-handed neutrinos which leads to interesting phenomenology. Considering generic lepton flavour violating signatures at the final states, a $5σ$ discovery can be achieved with the early data of LHC, at 14 TeV, for relatively large inverse seesaw Yukawa coupling $Y_N$. The very light pseudoscalar and charged Higgs boson mass reconstruction are performed using the new modes and the results look promising. The inverse seesaw Yukawa coupling is shown to be probed down to $Y_N \sim 0.2$ at HL LHC with 3000 fb$^{-1}$.

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arXiv2018

Scrutinizing Right-Handed Neutrino Portal Dark Matter With Yukawa Effect

Analyzing the neutrino Yukawa effect in the freeze-out process of a generic dark matter candidate with right-handed neutrino portal, we identify the parameter regions satisfying the observed dark matter relic density as well as the current Fermi-LAT and H.E.S.S. limits and the future CTA reach on gamma-ray signals. In this scenario the dark matter couples to the Higgs boson at one-loop level and thus could be detected by spin-independent nucleonic scattering for a reasonable range of the relevant parameters.

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arXiv2018

Long-lived triplinos and displaced lepton signals at the LHC

We explore the possibility of having superpartners of triplet Higgs bosons, named as 'triplinos'. They form a part of light neutralinos and charginos in a $Y=0$ extended supersymmetric Standard Model. For this model such electroweakinos do not have direct couplings to the Standard Model fermions. On top of that, due to very compressed spectrum for lighter neutralinos and charginos, their decay products coming from three body decays are very soft and thus can evade the current collider bounds. These decays are particularly interesting since they give rise to displaced leptonic signatures. We categorise the parameter space, while exploring different displaced decay possibilities. A PYTHIA based simulation has been performed to find out the displaced charged lepton, jet and $b$-jet final states at the LHC with center of mass energy of 14 TeV.

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arXiv2018

Revisiting scalar leptoquark at the LHC

We investigate the Standard Model (SM) extended with a colored charged scalar, leptoquark, having fractional electromagnetic charge $-1/3$. We mostly focus on the decays of the leptoquark into second and third generations via $c\,μ, t\, τ$ decay modes. We perform a PYTHIA-based simulation considering all the dominant SM backgrounds at the LHC with 14\,TeV center of mass energy. Limits have been calculated for the leptoquark mass that can be probed at the LHC with an integrated luminosity of 3000 fb$^{-1}$. The leptoquark mass, reconstructed from its decay products into the third generation, has the maximum reach. However, the $μ+ c$ channel, comprising a very hard muon and $c$-jet produces a much cleaner mass peak. Single leptoquark production in association with a $μ$ or $ν$ provides some unique signatures that can also be probed at the LHC.

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arXiv2018

Scalar Dark Matter in Leptophilic Two-Higgs-Doublet Model

Two-Higgs-Doublet Model of Type-X in the large $\tanβ$ limit becomes leptophilic to allow a light pseudo-scalar $A$ and thus provides an explanation of the muon $g-2$ anomaly. Introducing a singlet scalar dark matter $S$ in this context, one finds that two important dark matter properties, nucleonic scattering and self-annihilation, are featured separately by individual couplings of dark matter to the two Higgs doublets. While one of the two couplings is strongly constrained by direct detection experiments, the other remains free to be adjusted for the relic density mainly through the process $SS\to AA$. This leads to the $4τ$ final states which can be probed by galactic gamma ray detections.

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arXiv2018

Implications of right-handed neutrinos in $B-L$ extended standard model with scalar dark matter

We investigate the Standard Model (SM) with a $U(1)_{B-L}$ gauge extension where a $B-L$ charged scalar is a viable dark matter (DM) candidate. The dominant annihilation process, for the DM particle is through the $B-L$ symmetry breaking scalar to right-handed neutrino pair. We exploit the effect of decay and inverse decay of the right-handed neutrino in thermal relic abundance of the DM. Depending on the values of the decay rate, the DM relic density can be significantly different from what is obtained in the standard calculation assuming the right-handed neutrino is in thermal equilibrium and there appear different regions of the parameter space satisfying the observed DM relic density. For a DM mass less than $\mathcal{O}$(TeV), the direct detection experiments impose a competitive bound on the mass of the $U(1)_{B-L}$ gauge boson $Z^\prime$ with the collider experiments. Utilizing the non-observation of the displaced vertices arising from the right-handed neutrino decays, bound on the mass of $Z^\prime$ has been obtained at present and higher luminosities at the LHC with 14 TeV centre of mass energy where an integrated luminosity of 100fb$^{-1}$ is sufficient to probe $m_{Z'} \sim 5.5$ TeV.

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arXiv2017

Distinguishing charged Higgs bosons from different representations at the LHC

Extending the Standard Model (SM) scalar sector via one or multiple Higgs field(s) in higher representation brings one or more charged Higgs bosons in the spectrum. Some of these gauge representations with appropriate hypercharge can bring up doubly charged Higgs boson and can be easily distinguished from the existing models with only singly charged Higgs boson. In this study we focus on distinguishing the singly charged Higgs bosons from different representations, viz. doublets and triplets of $SU(2)_L$ gauge group. We consider a supersymmetric extension of SM with a gauge singlet and $SU(2)_L$ triplet with $Y=0$ as a benchmark scenario with the possibility of rich phenomenology due to existence of light pseudoscalar for $Z_3$ symmetric superpotential. A detailed collider simulation considering all the SM backgrounds has been carried out in order to classify the final states which are favourable to charged Higgs boson from one particular representation than others. We show that such different representations can be probed an distinguished via looking at single charged Higgs boson phenomenology at the LHC with 14 TeV center of mass energy within $\sim 50$ fb$^{-1}$ of integrated luminosity.

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arXiv2017

Displaced lepton flavour violating signatures of right-handed sneutrinos in $U(1)'$ supersymmetric models

We consider a $U(1)'$ extended supersymmetric model with a right-handed neutrino superfield which can generate light neutrino mass by Type I seesaw mechanism. The lighter superpartner of the right-handed neutrino could be the scalar dark matter. These right-handed sneutrinos can come from the decay of $\tilde{Z'}$, superpartner of the extra gauge boson $Z'$. Left-right handed sneutrino mixings affect their decays further, giving rise to displaced "lepton flavour violating" signatures. A wino-like chargino NLSP (next to lightest supersymmetric particle) creates even more interesting decay topology. We investigate such displaced multi-leptonic final states with "lepton flavour violation" from the supersymmetric cascade decays of third generation squarks at the LHC.

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arXiv2017

Charged Higgs bosons in the extended supersymmetric scenario at the LHC

We investigate an extension of the Minimal Supersymmetric Standard Model (MSSM) containing a $SU(2)$ Higgs triplet of zero hypercharge and a gauge singlet. We focus on a scenario of this model which allows a light pseudoscalar and/or a scalar below $100$ GeV in the spectrum, consistent with the most recent data from the LHC and the earlier data from the LEP experiments. The triplet extension gives rise to two additional charged Higgs bosons which do not couple to fermions but can decay into $Z W^\pm$. The presence of a very light pseudoscalar opens $a_1 W^\pm$ decay mode for the light charged Higgs boson just like $Z_3$ symmetric singlet-extension (NMSSM). A triplet type charged Higgs can be produced via vector boson fusion at the tree-level which is absent in 2HDM and MSSM and NMSSM. If such charged Higgs boson is pair produced both $Z W^\pm$ and $a_1 W^\pm$ decay modes can be probed which can prove the existence of triplet and singlet both.

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arXiv2017

Vacuum stability in an extended standard model with a leptoquark

We investigate the standard model (SM) with the extension of a charged scalar having fractional electromagnetic charge of $-1/3$ unit and with lepton and baryon number violating couplings at tree level. Without directly taking part in the electro-weak (EW) symmetry breaking, this scalar can affect stability of the EW vacuum via loop effects. The impact of such a scalar, i.e., a leptoquark on the perturbativity of SM dimensionless couplings as well as on new physics couplings has been studied at two-loop order. The vacuum stability of the Higgs potential is checked using one-loop renormalization group (RG) improved effective potential approach with two-loop beta function for all the couplings. From the stability analysis various bounds are drawn on parameter space by identifying the region corresponding to metastability and stability of the EW vacuum. Later we also address the Higgs mass fine-tuning issue via Veltman condition and the presence of such scalar increases the scale up to which the theory can be considered as reasonably fine-tuned. All these constraints give a very predictive parameter space for leptoquark couplings which can be tested at present and future colliders. Especially, a leptoquark with mass $\mathcal{O}\,$(TeV) can give rise to lepton-quark flavor violating signatures via decaying into the $t\, τ$ channel at tree level, which can be tested at the LHC or future colliders.

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