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P. Poulose

Publications and source records attributed to P. Poulose.

At least 19 recordsLinked to original sources
arXiv2020

Exploring $0νββ$ and Leptogenesis in the Alternative Left-Right Model

We investigate the possibility of neutrinoless double beta decay ($0νββ$) and leptogenesis within the Alternative Left-Right Model (ALRM). Unlike the usual left-right symmetric model, ALRM features a Majorana right-handed neutrino which does not carry any charge. Further, in this picture the down-type quark and the charged leptons receive mass through the additional left-handed scalar field, rather than the usual doublet. Together, these features conspire to generate significant contributions to the $0νββ$ through vector-scalar ($WH$) mediation. For moderate masses of the relevant charged Higgs boson ($M_{H_1^\pm}\sim 200$ GeV), the half-life of $T_{\frac{1}{2}}^{WH}$ is $\sim 3\times 10^{26}~{\rm yrs}$ for both the case of $^{76}$Ge and $^{136}$Xe, well within the sensitivity expected by future experiments. Invoking the resonant leptogenesis, CP violation arising from the right-handed neutrino decay could be the required order to generate the correct baryogenesis, $ε\sim 10^{-6}$, for small Dirac phases and without any fine tuning.

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arXiv2018

Investigating the scalar sector of left-right symmetric models with leptonic probes

We investigate the potential collider signatures of singly-charged and doubly-charged Higgs bosons such as those arising in minimal left-right symmetric models. Focusing on multileptonic probes in the context of the high-luminosity run of the Large Hadron Collider, we separately assess the advantages of the four-leptonic and trileptonic final states for a representative benchmark setup designed by considering a large set of experimental constraints. Our study establishes possibilities of identifying singly-charged and doubly-charged scalars at the Large Hadron Collider with a large significance, for luminosity goals expected to be reached during the high-luminosity phase of the Large Hadron Collider. We generalise our results and demonstrate that existing limits can in principle be pushed much further in the heavy mass regime.

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arXiv2018

Seeking Heavy Higgs Bosons through Cascade Decays

We investigate the LHC discovery prospects for a heavy Higgs boson decaying into the Standard Model Higgs boson and additional weak bosons. We consider a generic model-independent new physics configuration where this decay proceeds via a cascade involving other intermediate scalar bosons and focus on an LHC final-state signature comprised either of four b-jets and two charged leptons or of four charged leptons and two b-jets. We design two analyses of the corresponding signals, and demonstrate that a 5σ discovery at the 14 TeV LHC is possible for various combinations of the parent and daughter Higgs-boson masses. We moreover find that the Standard Model backgrounds can be sufficiently rejected to guarantee the reconstrution of the parent Higgs boson mass. We apply our analyses to the Type-II Two-Higgs-Doublet Model and identify the regions of the parameter space to which the LHC is sensitive.

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arXiv2017

Direct searches of Type III seesaw triplet fermions at high energy $e^+e^-$ collider

The signatures of heavy fermionic triplets ($Σ$) arising in scenarios like Type III seesaw model are probed through their direct production and subsequent decay at high energy electron-positron collider. Unlike the case of LHC, the production process has strong dependence on the mixing parameter ($V_{e,μ}$), making the leptonic collider unique to probe such mixing. We have established that with suitably chosen kinematic cuts, a 1 TeV $e^+e^-$ collider could probe the presence of $Σ$ of mass in the range of 500 GeV having $V_e=0.05$ with a few inverse femto barn luminosity through single production. The cross section is found to be not sufficient to probe the case of triplet-muon mixing through single triplet production. On the other hand, the pair production considered at 2 TeV centre of mass energy is capable of probing both the mixing scenarios efficiently. Studying the mass reach, presence of charged fermionic triplets upto a mass of about 980 GeV could be established at $3σ$ level through single production at a 1 TeV $e^+e^-$ collider with moderate luminosity of 100 fb$^{-1}$, assuming $V_e = 0.05$ . The pair production case requires larger luminosity, as the cross section is smaller in this case. With an integrated luminosity of 300 fb$^{-1}$, the mass reach in this case is close to 1 TeV with triplet-muon mixing, while it is slightly lower at about 950 GeV in the case of $V_μ= 0.05$.

hep-ph↗
arXiv2016

Exploring the Inert Doublet Model through the dijet plus missing transverse energy channel at the LHC

In this study of the Inert Doublet Model (IDM), we propose that the dijet + missing transverse energy channel at the Large Hadron Collider (LHC) will be an effective way of searching for the scalar particles of the IDM. This channel receives contributions from gauge boson fusion, and $t-$channel production, along with contributions from $H^+$ associated production. We perform the analysis including study of the Standard Model (SM) background with assumed systematic uncertainty, and optimise the selection criteria employing suitable cuts on the kinematic variables to maximise the signal significance. We find that with high luminosity option of the LHC, this channel has the potential to probe the IDM in the mass range of up to about 400 GeV, which is not accessible through other leptonic channels. In a scenario with light dark matter of mass about 65 GeV, charged Higgs in the mass range of around 200 GeV provides the best possibility with a signal significance of about $2σ$ at an integrated luminosity of about 3000 fb$^{-1}$.

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arXiv2015

Type-III Seesaw fermionic triplets at the International Linear Collider

The signature of heavy fermionic triplets belonging to Type III seesaw at the International Linear Collider (ILC) is probed. Presence of charged fermionic triplets upto a mass of about $ 750$ GeV could be established through single production at a 1 TeV ILC with moderate luminosity of 300 fb$^{-1}$, assuming a fermion triplet-electron mixing of about 0.05. Unlike the case of LHC, the production process is highly sensitive to the mixing, making the process interesting. The single production of neutral triplet is found to be somewhat harder, considering the large SM background present. Pair production of triplets of mass 500 GeV considered at 2 TeV centre of mass energy presents convenient ways to study different mixing scenarios. The production process is sensitive to $V_e$. The pair production along with information regarding single production would be able to identify the mixing scenarios.

hep-ph↗
arXiv2015

Study of Higgs-gauge boson anomalous couplings through $e^-e^+ \rightarrow W^-W^+H$ at ILC

In this work, Higgs couplings with gauge bosons is probed through $e^-e^+ \rightarrow W^-W^+H$ in an effective Lagrangian framework. An ILC of 500 $GeV$ center of mass energy with possible beam polarization is considered for this purpose. The reach of ILC with integrated luminosity of 300 $fb^{-1}$ in the determination of both the CP-conserving and CP-violating parameters are obtained. Sensitivity of the probe of each of these couplings on the presence of other couplings is investigated. The most influential couplings parameters are $\bar c_W=-\bar c_B$. Other parameters of significant effect are $\bar c_{HW}$ and $\bar c_{HB}$ among the CP-conserving ones, and $\tilde c_{HW}$ and $\tilde c_{HB}$ among the CP-violating ones. CP-violating parameter, $\tilde c_γ$ seems to have very little influence on the process considered. Detailed study of the angular distributions have presented a way to disentangle the effect of some of these couplings.

hep-ph↗
arXiv2014

Influence of anomalous VVH and VVHH on determination of Higgs self couplings at ILC

The recent discovery of a Higgs boson at LHC, while establishing the Higgs mechanism as the way of electroweak symmetry breaking, started an era of precision measurements involving the Higgs boson. In an effective Lagrangian framework, we consider the e+e- --> ZHH process, at an ILC running at a centre of mass energy of 800 GeV to investigate the effect of the ZZH and ZZHH couplings on the sensitivity of HHH coupling on this process. Our results show that the sensitivity of the trilinear Higgs self couplings on this process has somewhat strong dependence on the Higgs-gauge boson couplings. Single and two parameter reach of ILC with integrated luminosity of 1000 /fb are obtained on the effective couplings, c6 and cH, which are related to the HHH couplings, indicating how these limits are affected by the presence of anomalous ZZH and ZZHH couplings. The kinematic distributions studied to understand the effect of the anomalous couplings, again, show strong influence of Z-H couplings on the dependence of these distributions on HHH coupling. Similar results are indicated in the case of the process, e+e- --> nu nu HH, considered at a centre of mass energy of 2 TeV, where the cross section is large enough. The effect of WWH and WWHH couplings on the sensitivity of HHH coupling is clearely established through our analyses of this process.

hep-ph↗
arXiv2014

The 125 GeV Higgs signal at the LHC in the CP Violating MSSM

The ATLAS and CMS collaborations have observed independently at the Large Hadron Collider (LHC) a new Higgs-like particle with a mass $M_h \sim$ 125 GeV and properties similar to that predicted by the Standard Model (SM). Although the measurements indicate that this Higgs-like boson is compatible with the SM hypothesis, however due to large uncertainties in some of the Higgs detection channels, one still has the possibility of testing this object as being a candidate for some Beyond the SM (BSM) physics scenarios, for example, the Minimal Supersymmetric Standard Model (MSSM), in the CP-conserving version (CPC-MSSM). In this paper, we evaluate the modifications of these CPC-MSSM results when CP-violating (CPV) phases are turned on explicitly, leading to the CP-violating MSSM (CPV-MSSM). We investigate the role of the CPV phases in (some of) the soft Supersymmetry (SUSY) terms on both the mass of the lightest Higgs boson $h_1$, and the rates for the processes $gg \rightarrow h_1 \rightarrow γγ$, $gg \rightarrow h_1 \rightarrow ZZ^*\rightarrow 4l$, $gg \rightarrow h_1 \rightarrow WW^*\rightarrow l νl ν$, $pp \rightarrow V h_1 \rightarrow V b\bar b$ and $pp \rightarrow V h_1 \rightarrow V τ^+τ^-$, ($V \equiv W^\pm, Z$) at the LHC, considering the impact of the flavor constraints as well as the constraints coming from the Electric Dipole Moment (EDM) measurements. We find that the imaginary part of the top and bottom Yukawa couplings can take very small but non-zero values even after satisfying the recent updates from LHC. Our study shows that the CPV-MSSM provides an equally potential solution (like its CP-conserving (CPC) counterpart) to the recent LHC Higgs data. Improvement in different Higgs coupling measurements is necessary in order to test the possibility of probing the small dependence on these CPV phases in the Higgs sector of the MSSM.

hep-ph↗
arXiv2014

Top Yukawa coupling measurement with indefinite CP Higgs in $e^+e^-\to t\bar{t}Φ$

We consider the issue of the top quark Yukawa coupling measurement in a model in dependent and general case with the inclusion of CP-violation in the coupling. Arguably the best process to study this coupling is the associa ted production of Higgs boson along with a $t\bar t$ pair in a machine like the International Linear Collider (ILC). While detailed analyses of the sensitivity of the measurement assuming a Standard Model (SM) - like coupling are available in the context of ILC, conclude that th e coupling could be pinned down at about 10\% level with modest luminosity, our investigations show that the scenario could be different in case of a more general coupling. The modified Lorentz structure resulting in a changed functional dependence of the cross section on the couplin g, along with the difference in the cross section itself leads to considerable deviation in the sensitivity. Our studies with an ILC of center of mass energies of 500 GeV, 800 GeV and 1000 GeV show that moderate CP-mixing in the Higgs sector could change the sensitivity to about 20\ %, while it could be worsened to 75\% in cases which could accommodate more dramatic changes in the coupling. While detailed considerations of the decay distributions point to a need for a relook at the analysis strategy followed for the case of SM such as for a model independent analysis of the top quark Yukawa coupling measurement. This study strongly suggests that, a joint analysis of the CP properties and the Yukawa coupling measurement would be the way forward at the ILC and that caution must be excercised in the measurem ent of the Yukawa couplings and the conclusions drawn from it.

hep-ph↗
arXiv2014

125 GeV Higgs Boson signal within the complex NMSSM

While the properties of the 125 GeV Higgs boson-like particle observed by the ATLAS and CMS collaborations are largely compatible with those predicted for the Standard Model state, significant deviations are present in some cases. We, therefore, test the viability of a Beyond the Standard Model scenario based on Supersymmetry, the CP-violating Next-to-Minimal Supersymmetric Standard Model, against the corresponding experimental observations. Namely, we identify possible model configurations in which one of its Higgs bosons is consistent with the LHC observation and evaluate the role of the explicit complex phases in both the mass and diphoton decay of such a Higgs boson. Through a detailed analysis of some benchmark points corresponding to each of these configurations, we highlight the impact of the CP-violating phases on the model predictions compared to the CP-conserving case.

hep-ph↗
arXiv2013

Probing the indefinite CP nature of the Higgs Boson through decay distributions in the process $e^+e^-\to t\bar{t}Φ$

The recently discovered scalar resonance at the LHC is now almost confirmed to be a Higgs Boson, whose CP properties are yet to be established. At the ILC with and without polarized beams, it may be possible to probe these properties at high precision. In this work, we study the possibility of probing departures from the pure CP-even case, by using the decay distributions in the process $e^+ e^- \to t \bar{t} Φ$, with $Φ$ mainly decaying into a $b\bar b$ pair. We have compared the case of a minimal extension of the SM case (Model I) with an additional pseudoscalar degree of freedom, with a more realistic case namely the CP-violating Two-Higgs Doublet Model (Model II) that permits a more general description of the couplings. We have considered the ILC with $\sqrt{s}=800$\,GeV and integrated luminosity of $300\, {\rm fb}^{-1}$. Our main findings are that even in the case of small departures from the CP-even case, the decay distributions are sensitive to the presence of a CP-odd component in Model II, while it is difficult to probe these departures in Model I unless the pseudoscalar component is very large. Noting that the proposed degrees of beam polarization increases the statistics, the process demonstrates the effective role of beam polarization in studies beyond the Standard Model. Further, our study shows that an indefinite CP Higgs would be a sensitive laboratory to physics beyond the SM.

hep-ph↗
arXiv2012

Probing strongly interacting W's at the ILC with polarized beams

We study the possibility of fingerprinting a strongly interacting $W$ boson sector which is consistent with present day LHC searches at the ILC with longitudinal as well as transversely polarized electron and positron beams. We account for the final state interaction using a suitable Omnès formalism in terms of a plausible resonance description, and carry out thorough analyses of cross sections, asymmetries and angular distributions of the $W's$. We carry out a comparison with other extensions of the Standard Model, where heavy additional $Z'$ bosons arise naturally. We also consider the effect of the strong final state interaction on a correlation that depends on $(ϕ_--ϕ_+)$, where the $ϕ_\mp$ are the azimuthal angles of decay leptons, and find that it is a useful discriminant.

hep-ph↗
arXiv2011

Study of Single W production in e-gamma collisions through the decay lepton spectrum to probe gamma-WW couplings

We investigate the effect of anomalous gamma-W-W couplings in e-gamma --> nu W through the angular and energy spectrum of the secondary leptons. Within the narrow-width approximation, a semi-analytical study of the secondary lepton energy-angle double distribution is considered. Utility of observables derived from this is demonstrated by considering the anomalous coupling, delta-kappa-gamma. Results of our investigation for typical ILC machine considered at Ecm = 300-1000 GeV re-affirms potential of this collider as a precision machine.

hep-ph↗
arXiv2011

Signals of additional Z boson in e+e-\to W+W^- at the ILC with polarized beams

We consider the possibility of fingerprinting the presence of heavy additional Z' bosons that arise naturally in extensions of the standard model such as E_6 models and left-right symmetric models, through their mixing with the standard model Z boson. By considering a class of observables including total cross sections, energy distributions and angular distributions of decay leptons we find significant deviation from the standard model predictions for these quantities with right-handed electrons and left-handed positrons at \sqrt{s}=800 GeV. The deviations being less pronounced at smaller centre of mass energies as the models are already tightly constrained. Our work suggests that the ILC should have a strong beam polarization physics program particularly with these configurations. On the other hand, a forward backward asymmetry and lepton fraction in the backward direction are more sensitive to new physics with realistic polarization due to interesting interplay with the neutrino t- channel diagram. This process complements the study of fermion pair production processes that have been considered for discrimination between these models.

hep-ph↗
arXiv2009

W physics at the ILC with polarized beams as a probe of the Littlest Higgs Model

We study the possibility of using W pair production and leptonic decay of one of the W's at the ILC with polarized beams as a probe of the Littlest Higgs Model. We consider cross-sections, polarization fractions of the W's, leptonic decay energy and angular distributions, and left-right polarization asymmetry as probes of the model. With parameter values allowed by present experimental constraints detectable effects on these observables at typical ILC energies of 500 GeV and 800 GeV will be present. Beam polarization is further found to enhance the sensitivity.

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