arXiv subjects

Paramita Dey

Publications and source records attributed to Paramita Dey.

13 recordsLinked to original sources

arXiv2012

Constraints on axino warm dark matter from X-ray observation at the Chandra telescope and SPI

A sufficiently long lived warm dark matter could be a source of X-rays observed by satellite based X-ray telescopes. We consider axinos and gravitinos with masses between 1 keV and 100 keV in supersymmetric models with small R-parity violation. We show that axino dark matter receives significant constraints from X-ray observations of Chandra and SPI, especially for the lower end of the allowed range of the axino decay constant $f_{a}$, while the gravitino dark matter remains unconstrained.

hep-ph↗

arXiv2010

Radiative contribution to neutrino masses and mixing in $μν$SSM

In an extension of the minimal supersymmetric standard model (popularly known as the $μν$SSM), three right handed neutrino superfields are introduced to solve the $μ$-problem and to accommodate the non-vanishing neutrino masses and mixing. Neutrino masses at the tree level are generated through $R-$parity violation and seesaw mechanism. We have analyzed the full effect of one-loop contributions to the neutrino mass matrix. We show that the current three flavour global neutrino data can be accommodated in the $μν$SSM, for both the tree level and one-loop corrected analyses. We find that it is relatively easier to accommodate the normal hierarchical mass pattern compared to the inverted hierarchical or quasi-degenerate case, when one-loop corrections are included.

hep-ph↗

arXiv2010

Bulk Higgs field in a Randall-Sundrum model with nonvanishing brane cosmological constant

We consider the possibility of Higgs mechanism in the bulk in a generalised Randall-Sundrum model, where a nonvanishing cosmological constant is induced on the visible brane. This scenario has the advantage of accommodating positive tension of the visible brane and thus ensures stability of the model. It is shown that several problems usually associated with this mechanism are avoided if some dimensionful parameters in the bulk are allowed to lie a little below the Planck mass. The most important of these is keeping the lowest massive mode in the scale of the standard electroweak model, and at the same time reducing the gauge coupling of the next excited state, thus ameliorating otherwise stringent phenomenological constraints.

hep-ph↗

arXiv2009

Neutrino masses, the cosmological constant and a stable universe in a Randall-Sundrum scenario

The Randall-Sundrum model of warped geometry in a five-dimensional scenario, aimed at explaining the hierarchy between the Planck and electroweak scales, is intrinsically unstable in its minimal form due to negative tension of the visible brane. A proposed solution to the problem yields a negative cosmological constant in four dimensions. We show that this wrong-sign cosmological constant is restricted to small values, therefore requiring less cancellation from hitherto unknown physics, if bulk neutrinos are postulated to explain the observed neutrino mass pattern. Thus neutrino masses, a stable Tev-brane configuration and new physics in the context of the cosmological constant get rather suggestively connected by the same thread.

hep-ph↗

arXiv2009

Unitarity violation in sequential neutrino mixing in a model of extra dimensions

We investigate the possibility of unitarity violation in the sequential neutrino mixing matrix in a scenario with extra compact spacelike dimensions. Gauge singlet neutrinos are assumed to propagate in one extra dimension, giving rise to an infinite tower of states in the effective four-dimensional theory. It is shown that this leads to small lepton-number violating entries in the neutrino mass matrix, which can violate unitarity on the order of one per cent.

hep-ph↗

arXiv2009

The impossibility of heavy neutrino dark matter in the Littlest Higgs Model with T-parity: constraints from direct search

We consider the Littlest Higgs Model with T-parity (LHT), in the parameter region where a heavy neutrino is the lightest T-odd particle (LTP). Having emphasized that this corresponds to a sizable region in the parameter space of the theory, we show that both the Cryogenic Dark Matter Search (CDMS) and Xenon10 experiments disallow the entire region where the masses of the new particles in LHT can lie within several TeV. Therefore, any observation of the signals of a heavy neutrino LTP is likely to seriously reopen the issue of cold dark matter in the universe.

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arXiv2008

Some consequences of a Higgs triplet

We consider an extension of the scalar sector of the Standard Model with a single complex Higgs triplet $X$. Such extensions are the most economic, model-independent way of generating neutrino masses through triplet interactions. We show that a term like $\azeroΦΦX^†$ must be included in the most general potential of such a scenario, in order to avoid a massless neutral physical scalar. We also demonstrate that $\azero$ must be real, thus ruling out any additional source of CP-violation. We then examine the implications of this term in the mass matrices of the singly-and doubly-charged scalar, neutral scalar and pseudoscalar fields. We find that, for small values of $\azero/\vtwo$, where $\vtwo$ is the triplet vev, the spectrum allows the decay of heavier scalars into lighter ones via gauge interactions. For large $\azero/\vtwo$, the doubly-charged, singly-charged and neutral pseudoscalar bosons become practically degenerate, while the even-parity neutral scalars remain considerably lighter, thus emphasizing the possibility of decay of the singly-charged or neutral pseudoscalar states into the neutral scalars. Constraints from the $ρ$-parameter are used to find nontrivial limits on the charged Higgs mass depending on $\azero$. We also study the couplings of the various physical states in this scenario. For small values of $|\azero|/\vtwo$, we find the lightest neutral scalar field to be triplet-dominated, and thus having extremely suppressed interactions with fermion as well as gauge boson pairs.

hep-ph↗

arXiv2008

Two-loop neutrino masses with large R-parity violating interactions in supersymmetry

We attempt to reconcile large trilinear R-parity violating interactions in a supersymmetric (SUSY) theory with the observed pattern of neutrino masses and mixing. We show that, with a restricted number of such interaction terms with the $λ'$-type couplings in the range (0.1-1.0), it is possible to forbid one-loop contributions to the neutrino mass matrix. This is illustrated with the help of a `working example' where an econnomic choice of SUSY parameters is made, with three non-vanishing and `large' R-parity violating terms in the superpotential. The two-loop contributions in such a case can not only generate the masses in the requisite order but can also lead us to specific allowed regions of the parameter space.

hep-ph↗

arXiv2007

Distinguishing the Littlest Higgs model with T-parity from supersymmetry at the LHC using trileptons

We analyse hadronically quiet trilepton signatures in the T-parity conserving Littlest Higgs model and in R-parity conserving supersymmetry at the Large Hadron Collider. We identify the regions of the parameter space where such signals can reveal the presence of these new physics models above the Standard Model background and distinguish them from each other, even in a situation when the mass spectrum of the Littlest Higgs model resembles the supersymmetric pattern.

hep-ph↗

arXiv2007

Neutrinos in flat extra dimension: towards a realistic scenario

We consider the simple extension of the Standard Model in which an additional right handed neutrino propagates along a flat extra dimension, while the Standard Model fields are confined on a 3-brane. The fifth dimension is $S^1/Z_2$ orbifold compactified. In this scenario, the neutrino mass can be naturally suppressed. By studying systematically the fundamental parameter space, we show that the strong phenomenological constraints on mixing angles between active and sterile neutrinos (especially those derived from the SNO experiment data) do not conflict with the possibility of generating a realistic neutrino mass spectrum. As a second step, we explore the possibility of a successful leptogenesis through the decays of the Kaluza-Klein excitations of the right handed neutrino.

hep-ph↗

arXiv2005

Probing Universal Extra Dimension at the International Linear Collider

In the context of an universal extra-dimensional scenario, we consider production of the first Kaluza-Klein electron positron pair in an $e^+e^-$ collider as a case-study for the future International Linear Collider. The Kaluza-Klein electron decays into a nearly degenerate Kaluza-Klein photon and a standard electron, the former carrying away missing energy. The Kaluza-Klein electron and photon states are heavy with their masses around the inverse radius of compactification, and their splitting is controlled by radiative corrections originating from bulk and brane-localised interactions. We look for the signal event $e^+e^- +$ large missing energy for $\sqrt s = 1$ TeV and observe that with a few hundred fb$^{-1}$ luminosity the signal will be readily detectable over the standard model background. We comment on how this signal may be distinguished from similar events from other new physics.

hep-ph↗

arXiv2004

A comparison of ultraviolet sensitivities in universal, nonuniversal, and split extra dimensional models

We discuss the origin of ultraviolet sensitivity in extra dimensional theories, and compare and contrast the cutoff dependences in universal, nonuniversal and split five dimensional models. While the gauge bosons and scalars are in the five dimensional bulk in all scenarios, the locations of the fermions are different in different cases. In the universal model all fermions can travel in the bulk, in the nonuniversal case they are all confined at the brane, while in the split scenario some are in the bulk and some are in the brane. A possible cure from such divergences is also discussed.

hep-ph↗

arXiv2003

Ultraviolet sensitivity of rare decays in nonuniversal extra dimensional models

We consider a nonuniversal five dimensional model in which fermions are localised on a four dimensional brane, while gauge bosons and a scalar doublet can travel in the bulk. As a result of KK number non-conservation at the brane-bulk intersection, the ultraviolet divergence does not cancel out in some physical observables. For example, the $B_d \to l^+l^-$ decay amplitude is linearly divergent, while $B$--$\bar{B}$ mixing amplitude is log divergent. We attempt to identify the exact source of this nonrenormalizability. We compare and contrast our results with those obtained in the universal five dimensional model where all particles travel in the extra dimension.

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