arXiv subjects

AseshKrishna Datta

Publications and source records attributed to AseshKrishna Datta.

At least 19 recordsLinked to original sources

arXiv2026

The $Z'$-boson of the $B-L$ Supersymmetric Standard Model and its Large Hadron Collider Searches

We discuss how the $Z'$-boson of the $B-L$ Supersymmetric (SUSY) Standard Model (BLSSM) could evade the current lower bound of around 5 TeV on the mass of such a resonance (of sequential nature) from the Large Hadron Collider (LHC) by a significant margin. This happens when the experimental sensitivities are critically impaired as the $Z'$-boson becomes `fat' or develops some leptophobia or possesses an optimally large decay Branching Ratio (BR) to BLSSM-specific states (including the SUSY ones) or when some or all of these are at play simultaneously. We describe how such a $Z'$-boson could acquire there features while still respecting the non-negotiable precision constraints from the LEP and the SLC experiments running at the $Z$-pole as well as those from the multi-purpose experiments at the LHC that search for such a resonance. We explore the interplay of the aforementioned phenomena and identify the regions of the BLSSM parameter space that give rise to the described situation by carrying out a thorough scan of it. We find that $M_{Z'}$ masses as low as 2.24 TeV may still be allowed in the BLSSM under favorable circumstances.

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arXiv2026

Aspects of a Five-Dimensional $U(1)_{L_\mu - L_\tau}$ Model at Future Muon-Based Colliders

We study a five-dimensional (5D) framework based on the $U(1)_{L_\mu-L_\tau}$ gauge symmetry, where the associated gauge field $V$ propagates in the bulk, giving rise to an infinite tower of Kaluza--Klein (KK) excitations $V^{(n)}$ that couple selectively to the second- and third-generation leptons. Originally motivated by its potential to address the muon $g-2$ anomaly, this framework remains of interest as a minimal, anomaly-free, phenomenologically well-motivated extension of the Standard Model (SM) of particle physics. We focus on high-energy muon-based colliders, which could directly probe the gauge structure without relying on the kinetic mixing between the SM hypercharge gauge boson and the 5D gauge boson $V$. We explore a set of complementary processes: the elastic $\mu^+\mu^+ \to \mu^+\mu^+$ scattering via off-shell exchange of KK (gauge) excitations $V^{(n)}$; the bremsstrahlung production of $V^{(n)}$ followed by their decays into neutrinos and into $\mu^-\mu^+$ at a future $\mu$TRISTAN collider. Further, we study the $\mu^-\mu^+ \to \mu^-\mu^+$ scattering via resonant KK excitation(s) at a future muon collider. Our results show that these future muon-based colliders could offer sensitive and complementary probes into regions in the parameter space of the scenario that are beyond the reach of low-energy experiments. In particular, such experiments would be able to probe both heavier such KK gauge bosons with TeV-scale masses for relatively large gauge couplings, as well as the much lighter ones with masses in the MeV-scale for couplings as weak as $g_D \sim \mathcal{O}(10^{-5})$, thereby offering a promising $2\sigma$ exclusion reach for such KK excitations, over an extensive range of masses, at these facilities.

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arXiv2023

An EFT origin of Secluded Dark Matter

The present study aims to unveil a scenario with a non-minimal secluded dark sector (DS) in an effective field theory (EFT) framework. To explore this, we have examined a suitable extension of the type-X Two Higgs Doublet Model (2HDM) as a potential origin for the secluded DS. The DS comprises a dark matter (DM) candidate and a mediator particle `$a$' and possesses some non-minimal characteristics. It becomes non-thermally populated through diverse dim-6 four-Fermi operators, effectively generated by integrating out the heavier Higgs particles. The analysis further focuses on the consequences of the collision processes $\textit{DM}+ a \leftrightarrow a + a$ and $\textit{DM}+ \textit{DM} \leftrightarrow a + a$ occurring within the DS. We have investigated the significance of employing an EFT approach in tracking the temperature evolution of the DS. Within the present framework, the observed relic abundance of the DM can be realized through both dark freeze-out and freeze-in mechanisms. Further, we have delineated the permissible ranges of the relevant parameters, viz., the DM mass ($m_\chi \gtrsim 20 \, \text{GeV}$), the portal coupling ($C_\tau \lesssim 10^{-14}\, \text{GeV}^{-2}$), and the DS coupling ($\lambda \lesssim 10^{-6} \,\text{GeV}^{-2}$) by taking into account the perturbativity of the involved couplings while reproducing the observed DM relic and complying with the bounds from a successful Big Bang Nucleosynthesis (BBN) and $\gamma$-ray searches.

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arXiv2022

Hunting ewinos and a light scalar of $Z_3$-NMSSM with a bino-like dark matter in top squark decays at the LHC

We study the prospects of a simultaneous hunt at the Large Hadron Collider (LHC) of relatively light electroweakinos and a singlet-like scalar of the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model ($Z_3$-NMSSM) in the cascade decays of not so heavy ($\lesssim 1.5$ TeV) top squarks that are produced in pairs at the LHC which characteristically involve the singlet-like states. We work in a scenario where the lightest (next-to-lightest) SUSY particle is bino (singlino)-like with a mass below 100 GeV ($\gtrsim 100$ GeV), whereas a pair of immediately heavier neutralinos and the lighter chargino are higgsino-like with masses in the range $\sim 500$ GeV -- 1 TeV. Further, the singlet-like scalar present in the spectrum provides a funnel for a rapid enough mutual annihilation of the LSP thus making the latter meet the experimental upper bound on its relic abundance. The scenario is motivated by its ability to offer a bino-like dark matter with such a mass unlike what is now disfavored in the MSSM while avoiding the stringent lower bounds from the LHC experiments on the masses of these involved particles and still remaining reasonably `natural'. We find that while a usual cut-based analysis (CBA) on LHC data worth 300 $\text{fb}^{-1}$ would be unable to discover such excitations, a multivariate analysis (MVA) can be reasonably sensitive to higgsino-like electroweakinos having masses $\gtrsim 650$ GeV when the lighter top squark has a mass $\gtrsim 1$ TeV. On the other hand, with 3000 $\text{fb}^{-1}$ of data these masses become accessible in a CBA while even an MVA on such a data set is unlikely to find these electroweakinos with masses around 1 TeV when the mass of the lighter top squark hits $\sim 1.5$ TeV.

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arXiv2022

Associated production of heavy Higgs bosons with a $b\bar{b}$ pair in the Nonholomorphic MSSM and LHC searches

In the NonHolomorphic Supersymmetric Standard Model (NHSSM), the Yukawa couplings of the bottom quark ($y_b$) and the tau lepton ($y_τ$) might receive substantial supersymmetric (SUSY) radiative corrections which have prominent dependencies on the NHSSM-specific trilinear soft parameters, $A_b^\prime$ and $A_τ^\prime$, respectively, in addition to their well-known dependence on $\tanβ$ as is already present in the Minimal SUSY Standard Model (MSSM). We study to what extent these could affect the production cross sections of the heavy Higgs bosons ($H$ and $A$) in association with a pair of $b$-quarks and their decay branching ratios, in particular, to a $τ\barτ$ pair and compare them with those obtained in the MSSM. Requiring compliance with the recently observed upper bounds on the product of their total cross-section and the branching ratio to $τ\barτ$ at the 13 TeV run of the Large Hadron Collider (LHC), with data worth 139 fb$^{-1}$, results in an altered exclusion region in the customary $m_A-\tanβ$ plane in the framework of the NHSSM when compared to what is derived by the LHC experiments within an MSSM setup. Such alterations are estimated to be pronounced only for large $\tanβ$ ($\geq 40$) and for large, negative $A_b^\prime$ when one finds a reinforced exclusion of the $m_A-\tanβ$ plane with an excluded $m_A$ value larger by $\approx 200$ GeV, compared to the MSSM case, at $\tanβ=60$. On the other hand, the maximum relaxation in $m_A$, for a similarly large but positive $A_b^\prime$, barely exceeds $\approx 100$ GeV as a result of complementary variations in production cross-sections and decay branching fractions of the heavy, neutral Higgs bosons.

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arXiv2022

Electroweak Phase Transition in the $Z_3$-invariant NMSSM: Implications of LHC and Dark matter searches and prospects of detecting the gravitational waves

We study in detail the viability and the patterns of a strong first-order electroweak phase transition as a prerequisite to electroweak baryogenesis in the framework of $Z_3$-invariant Next-to-Minimal Supersymmetric Standard Model (NMSSM), in the light of recent experimental results from the Higgs sector, dark matter (DM) searches and those from the searches of the lighter chargino and neutralinos at the Large Hadron Collider (LHC). For the latter, we undertake thorough recasts of the relevant, recent LHC analyses. With the help of a few benchmark scenarios, we demonstrate that while the LHC has started to eliminate regions of the parameter space with relatively small $\mu_\mathrm{eff}$, that favors the coveted strong first-order phase transition, rather steadily, there remains phenomenologically much involved and compatible regions of the same which are yet not sensitive to the current LHC analyses. It is further noted that such a region could also be compatible with all pertinent theoretical and experimental constraints. We then proceed to analyze the prospects of detecting the stochastic gravitational waves, which are expected to arise from such a phase transition, at various future/proposed experiments, within the mentioned theoretical framework and find them to be somewhat ambitious under the currently projected sensitivities of those experiments.

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arXiv2020

A relatively light, highly bino-like dark matter in the $Z_3$-symmetric NMSSM and recent LHC searches

A highly bino-like Dark Matter (DM), which is the Lightest Supersymmetric Particle (LSP), could be motivated by the stringent upper bounds on the DM direct detection rates. This is especially so when its mass is around or below 100 GeV for which such a bound tends to get most severe. Requiring not so large a higgsino mass parameter, that would render the scenario reasonably natural, prompts such a bino-like state to be relatively light. In the Minimal Supersymmetric Standard Model (MSSM), in the absence of comparably light scalars, such an excitation, if it has to be a thermal relic, is unable to meet the stringent experimental upper bound on its abundance unless its self-annihilation hits a funnel involving either the $Z$-boson or the Standard Model (SM)-like Higgs boson. We demonstrate that, in such a realistic situation, a highly bino-like DM of the popular $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model (NMSSM) is viable over an extended range of its mass, from our targeted maximum in the vicinity of the mass of the top quark down to about 30 GeV. This is facilitated by the presence of comparably light singlet-like states that could serve as funnel (scalars) and/or coannihilating (singlino) states even as the bino-like LSP receives a minimal (but optimal) tempering triggered by suitably light higgsino states that, in the first place, evade stringent lower bounds on their masses that can be derived from the Large Hadron Collider (LHC) experiments only in the presence of a lighter singlino-like state. An involved set of blind spot conditions is derived for the DM direct detection rates by considering for the very first time the augmented system of neutralinos comprising of the bino, the higgsinos and the singlino which highlights the important roles played by the NMSSM parameters $λ$ and $\tanβ$ in delivering a richer phenomenology.

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arXiv2019

Revisiting singlino dark matter of the natural $Z_3$-symmetric NMSSM in the light of LHC

Inspired by the fact that relatively small values of the effective higgsino mass parameter of the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model (NMSSM) could render the scenario `natural', we explore the plausibility of having relatively light neutralinos and charginos (the electroweakinos or the ewinos) in such a scenario with a rather light singlino-like Lightest Supersymmetric Particle (LSP), which is a Dark Matter (DM) candidate, and singlet-dominated scalar excitations. By first confirming the indications in the existing literature that finding simultaneous compliance with results from the Large Hadron Collider (LHC) and those from various DM experiments with such light states is, in general, a difficult ask, we proceed to demonstrate, with the help of a few representative benchmark points, how exactly and to what extent could such a highly motivated `natural' setup with a singlino-like DM candidate still remains plausible.

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arXiv2018

Sbottoms as probes to MSSM with nonholomorphic soft interactions

Presence of nonholomorphic soft SUSY breaking terms is known to be a possibility in the popular setup of the Minimal Supersymmetric Standard Model (MSSM). It has been shown that such a scenario known as NonHolomorphic Supersymmetric Standard Model (NHSSM) could remain `natural' ( i.e., not fine-tuned) even in the presence of a rather heavy higgsino-like LSP. However, it turns out that distinguishing such a scenario from the MSSM is unlikely to be an easy task, in particular at the Large Hadron Collider (LHC). In a first study of such a scenario at colliders (LHC), we explore a possible way that focuses on the sbottom phenomenology. This exploits the usual $\tanβ$-dependence (enhancement) of the bottom Yukawa coupling but reinforced/altered in the presence of non-vanishing nonholomorphic soft trilinear parameter $A_b^{\prime}$. For a given set of masses of the sbottom(s) and the light electroweakinos (LSP, lighter chargino etc.) which are known from experiments, the difference between the two scenarios could manifest itself via event rate in the 2b-jets + ${\, \not \! \! E_T}$ final state, which could be characteristically different from its MSSM expectation. Impact on the phenomenology of the stops at the LHC is also touched upon.

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arXiv2017

Spontaneous breakdown of charge in the MSSM and in the NMSSM: Possibilities and Implications

We study the possibilities and the implications of a spontaneous breakdown of charge in the MSSM and in the $Z_3$-symmetric NMSSM. The breakdown is triggered by the charged states of the Higgs doublets acquiring vacuum expectation values. In the MSSM, it is known that the presence of a charge conserving minimum for the tree-level Higgs potential precludes a deeper (global) charge-breaking minimum. We find that the inclusion of radiative correction to the potential does not alter the situation while a deeper charge-conserving minimum could arise, albeit with no major practical consequences. In the NMSSM scenario, a charge-breaking global minimum, with or without an accompanying charge-conserving deeper minimum, could appear even with the tree-level Higgs potential thanks to the presence of a charge-neutral scalar state which transforms as a singlet under the Standard Model gauge group. Use of the NMSSM Higgs potential that includes both quantum and thermal corrections and the requirement of a viable (stable or long-lived) vacuum that breaks the electroweak symmetry, along with its compatibility with the latest Higgs data, lead to nontrivial constraints on the NMSSM parameter space.

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arXiv2017

Exploring viable vacua of the $Z_3$-symmetric NMSSM

We explore the vacua of the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model (NMSSM) and their stability by going beyond the simplistic paradigm that works with a tree-level neutral scalar potential and adheres to some specific flat directions in the field space. Key effects are demonstrated by first studying the profiles of this potential under various circumstances of physical interest via a semi-analytical approach. The results thereof are compared to the ones obtained from a dedicated package like \veva ~which further incorporates the thermal effects to the potential. Regions of the phenomenological NMSSM (pNMSSM) parameter space that render the desired symmetry breaking (DSB) vacuum absolutely stable, long- or short-lived (in relation to the age of the Universe) under quantum/thermal tunneling are delineated. Regions that result in color and charge breaking (CCB) minima are also presented. It is demonstrated that light singlet scalars along with a light LSP (lightest supersymmetric particle) having an appreciable singlino admixture are compatible with a viable DSB vacuum and are much relevant for the collider experiments.

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arXiv2017

Sbottoms of Natural NMSSM at the LHC

Search for the bottom squarks (sbottoms) at the Large Hadron Collider (LHC) has recently assumed a heightened focus in the hunt for Supersymmetry (SUSY). The popular framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) could conceive a naturally light sbottom which could easily be consistent with available constraints from the experiments at the LHC. Phenomenology of such sbottoms could in principle be as striking as that for a light top squark (stop) thanks to a rather nontrivial neutralino sector (with appreciable mixing among the neutral higgsinos and the singlino) that the scenario gives rise to. Nonetheless, finding such sbottoms might require a moderately large amount of data ($\sim 300$ $\text{fb}^{-1}$) at the 13 TeV run of the LHC. A multi-channel analysis establishing a generic depletion of events in the usual $2b$-$jets$ +$\text{\sout{E}}_T$ final state while registering, in conjunction, characteristically significant rates in various multi-lepton final states accompanied by $b$-$jets$ might point not only to the presence of light sbottom(s) but could also shed crucial light on their compositions and the (singlino) nature of the lightest SUSY particle (LSP).

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arXiv2017

Two Light Stops in the NMSSM and the LHC

We study the viability of having two relatively light top squarks (`stops') in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Such light stops render the NMSSM rather `natural'. These are shown to be allowed by the relevant direct searches at the Large Hadron Collider (LHC) and to be compatible with the latest LHC results on the Higgs sector, other low energy electroweak constraints and recent constraints from the dark matter (DM) sector. We propose dedicated searches for such light stops at the LHC within a `simplified' scenario that may have a bino-like or a singlino-like neutralino LSP as the DM candidate and point out various final states carrying the imprint of their collective presence. Under certain circumstances, in such a scenario, presence of two light stops may give rise to final states which are not so typical in their search. Thorough studies at the detector level reveal the status of such a scenario after the 8 TeV run of the LHC and shed light on the prospects of its 13 and 14 TeV runs. In favorable regions of the NMSSM parameter space, with low-lying spectra, signals with significance $\gtrsim 5σ$ is possible with a few tens to a few hundreds of $\text{fb}^{-1}$ of integrated luminosity in diverse final states.

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arXiv2017

LHC Collider Phenomenology of Minimal Universal Extra Dimensions

We discuss the collider phenomenology of the model of Minimal Universal Extra Dimensions (MUED) at the Large hadron Collider (LHC). We derive analytical results for all relevant strong pair-production processes of two level 1 Kaluza-Klein partners and use them to validate and correct the existing MUED implementation in the fortran version of the PYTHIA event generator. We also develop a new implementation of the model in the C++ version of PYTHIA. We use our implementations in conjunction with the CHECKMATE package to derive the LHC bounds on MUED from a large number of published experimental analyses from Run 1 at the LHC.

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arXiv2016

$h \rightarrow γγ$ in $U(1)_{R}-$ lepton number model with a right-handed neutrino

We perform a detailed study of the signal rate of the lightest Higgs boson in the diphoton channel ($μ_{γγ}$), recently analyzed by both the ATLAS and CMS collaborations at the Large Hadron Collider, in the framework of $U(1)_R-$ lepton number model with a right handed neutrino superfield. The corresponding neutrino Yukawa coupling, `$f$', plays a very important role in the phenomenology of this model. A large value of $f\sim\mathcal O(1)$ provides an additional tree level contribution to the lightest Higgs boson mass along with a very light (mass $\sim$ a few hundred MeV) bino like neutralino and a small tree level mass of one of the active neutrinos that is compatible with various experimental results. In the presence of this light neutralino, the invisible decay width of the Higgs boson can become important. We studied this scenario in conjunction with the recent LHC results. The signal rate $μ_{γγ}$ obtained in this scenario is compatible with the recent results from both the ATLAS and the CMS collaborations at 1$σ$ level. A small value of `$f$', on the other hand, is compatible with a sterile neutrino acting as a 7 keV dark matter that can explain the observation of a mono-energetic X-ray photon line by the XMM-Newton X-ray observatory. We also study the impact of $μ_{γγ}$ in this case.

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arXiv2016

Light top squarks in $U(1)_{R}$-lepton number model with a right handed neutrino and the LHC

We investigate the phenomenology of top squarks at the Large Hadron Collider (LHC) in a supersymmetric model where lepton number is identified with an approximate $U(1)_R$ symmetry in such a way that one of the left chiral sneutrinos can acquire a large vacuum expectation value ($vev$) and can play the role of the down-type Higgs. This $R$-symmetry allows a subset of trilinear $R$-parity violating interactions, which determine the collider phenomenology of this model in a significant way. The gauginos are Dirac particles and gluinos are relatively heavy in this class of models. The model contains a right handed neutrino superfield, which gives a tree level mass to one of the active neutrinos. An order one neutrino Yukawa coupling also helps enhance the Higgs boson mass at the tree level and results in a very light bino-like neutralino ($\widetilde χ_2^0$) with mass around a few hundred MeV, which is a carrier of missing (transverse) energy (\met). The model can accommodate two rather light top squarks, compatible with the observed mass of the Higgs boson. The lighter top squark (${\widetilde t}_1$) can decay into $t\widetildeχ_2^0$, and thus the signal would be similar to the signal of top quark pair production at the LHC. In addition, fully visible decays such as ${\widetilde t}_2 \rightarrow b e^+$ can give rise to interesting final states. Such signals at the LHC combined with other features like a heavy gluino could provide a strong evidence for this kind of a model. Our analysis shows that $m_{\widetilde t_1}\lsim 575~(750)$ GeV and $m_{\widetilde t_2}\lsim 1.2~(1.4)$ TeV can be probed with 5$σ$ statistical significance at the 13 TeV LHC with 300~(3000) fb$^{-1}$ of integrated luminosity. Finally, we observe that in the presence of super-light carriers of \met, the so-called `stealth' top squark scenario may naturally appear in our model.

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arXiv2015

$Z'$ search in non-minimal Universal Extra Dimensions: two bumps and interference

We discuss prospects of the $Z'$ search at the LHC in non-minimal Universal Extra Dimensions with tree-level brane-local terms in five dimensions. In this scenario, we find two major differences from the usual $Z'$ physics: (i) two $Z'$ candidates close-by in mass exist; (ii) the effective couplings to the SM fermions could be very large due to drastic overlapping of their profiles along the extra dimension. To evaluate the actual situation precisely, we reconsider the important issues of resonant processes, i.e., treatment of resonant propagators and including interference effects.

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arXiv2014

Non-minimal Universal Extra Dimensions with Brane Local Terms: The Top Quark Sector

We study the physics of Kaluza-Klein (KK) top quarks in the framework of a non-minimal Universal Extra Dimension (nmUED) with an orbifolded (S1/Z2) flat extra spatial dimension in the presence of brane-localized terms (BLTs). In general, BLTs affect the masses and the couplings of the KK excitations in a non-trivial way including those for the KK top quarks. On top of that, BLTs also influence the mixing of the top quark chiral states at each KK level and trigger mixings among excitations from different levels with identical KK parity (even or odd). The latter phenomenon of mixing of KK levels is not present in the popular UED scenario known as the minimal UED (mUED) at the tree level. Of particular interest are the mixings among the KK top quarks from level `0' and level `2' (driven by the mass of the Standard Model (SM) top quark). These open up new production modes in the form of single production of a KK top quark and the possibility of its direct decays to Standard Model (SM) particles leading to rather characteristic signals at the colliders. Experimental constraints and the restrictions they impose on the nmUED parameter space are discussed. The scenario is implemented in MadGraph 5 by including the quark, lepton, the gauge-boson and the Higgs sectors up to the second KK level. A few benchmark scenarios are chosen for preliminary studies of the decay patterns of the KK top quarks and their production rates at the LHC in various different modes. Recast of existing experimental analyzes in scenarios having similar states is found to be not so straightforward for the KK top quarks of the nmUED scenario under consideration.

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