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Probir Roy

Publications and source records attributed to Probir Roy.

66 records · Page 4Linked to original sources
arXiv1996

Higgs-mediated Slepton Pair-production at the Large Hadron Collider

At the LHC, directly pair-produced sleptons may be easier to identify than those arising in cascade decays of squarks or gluinos. Higgs exchange processes leading to such slepton pair-production are calculated to one-loop in the MSSM. It turns out, surprisingly, that their total contribution can dominate the usual Drell-Yan production in certain regions of the parameter space. In particular, an interesting region with low $\tan β$ is covered by the dominant exchange of the heavier neutral scalar $H^0$.

hep-ph↗
arXiv1995

Model of Four Light Neutrinos in the Light of All Present Data

Motivated by existing and recent data on possible neutrino oscillations, we propose a model of four light neutrinos ($ν_e, ν_μ, ν_τ$, and a singlet $ν_S$) with a pattern of masses and mixing derivable from a $Z_5$ discrete symmetry and the seesaw mechanism. Atmospheric neutrino oscillations occur between $ν_μ$ and $ν_τ$ as pseudo-Dirac partners; whereas solar neutrino oscillations occur between $ν_e$ and $ν_S$, a linear combination of which is massless. Additional oscillations may occur between $ν_e$ and $ν_μ$ to account for the recent observation of the LSND (Liquid Scintillator Neutrino Detector) experiment.

hep-ph↗
arXiv1995

New Bounds on R-parity Violating Couplings

We use information from rare nonleptonic decays of heavy-quark mesons to put new bounds on the magnitudes of certain product combinations of baryon nonconserving R-parity violating couplings in supersymmetric models. Product combinations of lepton and baryon nonconserving R-parity violating couplings are also considered in the light of existing bounds on nucleon decay. Contrary to popular impression, a few such combinations are shown to remain essentially unconstrained.

hep-ph↗
arXiv1995

Beyond Standard Model: Report of Working Group II

Working group II at WHEPP3 concentrated on issues related to the supersymmetric standard model as well as SUSY GUTS and neutrino properties. The projects identified by various working groups as well as progress made in them since WHEPP3 are briefly reviewed.

hep-ph↗
arXiv1994

Constraints on Baryon-Nonconserving Yukawa Couplings in a Supersymmetric Theory

The 1-loop evolution of couplings in the minimal supersymmetric standard model, extended to include baryon nonconserving $(B\!\!\!/)$ operators through explicit $R$-parity violation, is considered keeping only $B\!\!\!/$ superpotential terms involving the maximum possible number of third generation superfields. If all retained Yukawa couplings $Y_i$ are required to remain in the perturbative domain $(Y_i < 1)$ upto the scale of gauge group unification, upper bounds ensue on the magnitudes of the $B\!\!\!/$ coupling strengths at the supersymmetry breaking scale, independent of the model of unification. They turn out to be similar to the corresponding fixed point values reached from a wide range of $Y_i$ (including all $Y_i$ greater than unity) at the unification scale. The coupled evolution of the top and $B\!\!\!/$ Yukawa couplings results in a reduction of the fixed point value of the former.

hep-ph↗
arXiv1993

Electroweak Processes and Precision Tests

Review of the electroweak sector of the minimal standard model, Basic LEP processes at the tree level, 1-loop radiative corrections in the on-shell renormalization scheme, Star scheme and oblique corrections, Introduction to oblique parameters.

hep-ph↗
arXiv1993

Neutrinos at high energy accelerators

PREAMBLE, BRIEF HISTORY AND PRELIMINARIES, QUICK REVIEW OF BASIC NEUTRINO PROPERTIES, CHARGED CURRENT NEUTRINO PROCESSES, NEUTRAL CURRENT NEUTRINO PROCESSES, VERY HEAVY NEUTRINOS, CONCLUDING SUMMARY

hep-ph↗
arXiv1993

Oblique electroweak corrections and triple vector boson couplings

We relate all $C$-- and $P$--invariant anomalous triple vector--boson couplings to the oblique electroweak parameters. LEP constraints on the latter then yield the strongest and most general simultaneous bounds to date on the former. Even if the oblique parameters assume their Standard Model values precisely, these bounds would not shrink to zero---thus underscoring the need for direct experimental probes at future colliders.

hep-ph↗
arXiv1993

Radiative Electroweak Parameters

The status of the present precision measurements of electroweak observables is reviewed with specific reference to the radiative parameters $S,T,U$ or equivalently $ε_1,ε_2,ε_3$. The significance of the obliqueness hypothesis is underlined and the importance of the ``local fit'' method of extracting these parameters from the data is emphasized. Possible new physics implications are briefly touched upon.

hep-ph↗
arXiv1992

Debajyoti Choudhury

Gluon fusion into a very heavy neutrino pair by Higgs exchange is shown to lead to substantial production cross sections at $pp$ supercolliders even without any extra generation of quarks. Rates are calculated for scalar as well as pseudoscalar Higgs. The angular correlation between dileptons emerging from the decays of the neutrinos shows distinctive features for Dirac and Majorana neutrinos as well as for scalar and pseudoscalar Higgs.

hep-ph↗
arXiv1992

Tau Signals of R-parity breaking at LEP 200

The detectability at LEP 200 of explicit $R$-parity breaking by tau-number $(L_τ)$ violating operators is considered. The assumption of $L_τ$-violation is motivated by the relative lack of constraints on such couplings but similar considerations apply to explicit $L_e$- or $L_μ$-violation. The $LSP$, now unstable, and not necessarily neutral, decays via $L_τ$-violating modes. Only signals from the production and decays of $LSP$ pairs are considered, thereby avoiding any dependence on the sparticle mass spectrum. Rather spectacular signals are predicted: spherical events with $m$ leptons (usually containing at least one $τ$) and $n$ jets $(m,n \leq 4)$, the most characteristic of which are like-sign $ττ$ events. These signals are enumerated for each $LSP$ candidate and quantitative estimates are provided for the favoured case when the $LSP$ is a neutralino. Other new physics signals, which can mimic these signatures, are also briefly discussed.

hep-ph↗