 Extra Dimensions: From 1998, there has been a resurgence of
interest in Kaluza Klein theories due to braneworld models. From the very
beginning, I have been engaged in the study of these models and their
consequences for highenergy experiments like the Tevatron and the LHC.
Some of the first papers to study the model of Large Extra Dimensions
proposing signatures to test this model were written by me and my
collaborators, Sreerup Raychaudhuri and Prakash Mathews. Over the years,
I have studied other models of extra dimensions like the RandallSundrum
Model. In recent years, the focus of my research has been on
realistic models of extradimensions and I am studying the signatures,
at leading
and nexttoleading order in QCD, from the point of view of the theory's
testability.
 Supersymmetry: In supersymmetry, I have largely focussed on
the study of Rparity violating models. In early papers with Gautam
Bhattacharyya, Debajyoti Choudhury and John Ellis, I studied the constraints
on these models arising from electroweak precision tests. With Magda Lola
and John Ellis, I later made a critical study of Rparity violating
explanations of the anomalous events seen at HERA. Later, with Ben Allanach
I studied an excess of muon+photon+missing transverse energy events reported
by the CDF experiment and attempted to explain this in terms of a Rparity
violating model of gauge mediated supersymmetry breaking.
 QCD: I have worked extensively in NonRelativistic QCD (NRQCD) and
its applications to the study of quarkonium production. My paper with D.P. Roy
was one of the earliest to uncover a fragmentation contribution in J/psi
production at the Tevatron. This model succesfully explained the huge
anomalous contribution in J/psi production reported by the CDF experiment.
I also studied other final states like psi(prime) and J/psi+photon. With
Alan Martin and James Stirling, I made a systematic study of J/psi production
of Tevatron and HERA and attempted to explain the combined data in NRQCD.
Using NRQCD, I made a prediction for the 1P1 charmonium state (h_c) at
the Tevatron and in a recent paper I have extended this analysis to the LHC.
Earlier, I had studied polarised structure functions and the proton spin
problem and also the effects of a nuclear environment on structure functions.
My QCD interests have resurfaced in recent years in the guise of nextto
leading order corrections to new physics processes that I have computed.
 GUTs: In my early years, I had worked on models of grand unification
and tried to obtain constraints on GUT models from the precise measurements of
couplings made at the Large ElectronPositron Collider. I also attempted to
study nonstandard models like nonperturbative unification scenarios in this
context.
 Higgs: With Fawzi Boudjema and Genevieve Belanger, I studied an
interesting model of supersymmetry with a very light stop. The stop
contributions to Higgs production at the LHC were shown to cancel the top
contributions so that the standard Higgs production via top loops does
not provide a viable signal at the LHC. Alternative production mechanisms
like the associated production of Higgs with a tt(bar) pair were studied
and the viability of the signals were critically analysed. I had earlier
studied invisible Higgs decays in the context of the singlet Majoron model
and had shown how, in spite of the invisible decay channels of the Higgs
in this model, the data from LEP could be used to constrain the Higgs mass
in this model.
