• Probir Roy

Articles written in Pramana – Journal of Physics

• Comments on the high energy behaviour of total cross-sections based on light-cone algebra

Based on considerations of the light-cone algebra of currents and pseudoscalar densities, it is suggested that either the high energy meson-nucleon cross-sections are constants (even though the pp-cross-section increases indefinitely) or that they deviate from constancy by logarithmic terms whose scale is set by a mass, of the order of at least tens of Gev, and which also characterises the consequent logarithmic violations of Bjorken scaling.

• Partial diagonality of stress trace

The trace of the stress energy tensor is shown to be diagonal between two states whose total four-momenta are equal. Additional comments are made on certain matrix-elements of the time-derivative of the dilation charge.

• Effect of gluons on neutral-current interactions in deep inelastic neutrino scattering

The contribution of neutral spin-1 gluons to the deep inelastic neutral-current processesv(v)+Nv(v)+ hadrons is worked out in the parton model. Such a contribution violates Bjorken scaling strongly.

• Colliding beam test of neutral isoscalar axial current

We discuss the condition for the presence of isoscalar parity violating neutral currents and notice that it is present in most gauge-theoretic models of weak interactions. We investigate the possibility of testing its presence in e+e colliding beams and find that parity violation in the reaction e+e→Λ°Λ° would provide an unambiguous test for such a current.

• Colour gluons and scaling in a unified gauge model

Deep inelastic weak and electromagnetic processes are considered within the parton framework taking the partons to be integrally charged quarks and coloured gluons. Despite the participation of the spin-one gluons in these processes, scaling is shown to be maintained by treating the problem in a unified gauge model based on the groupSU (3)colourSUL (2)⊗U(1). This is a consequence of the vector-dominance type of couplings between the gluons and the weak or electromagnetic vector bosons which are induced by the spontaneous breakdown of gauge symmetry. As a further consequence it is found that in the asymptotic region far above the gluon masses the colour octet parts of the weak and electromagnetic currents of the quarks are damped so that, in particular, the integrally charged quarks behave as fractionally charged quarks in this region.

• Explicit classical solutions to Euclidean Yang-Mills theory with spherical symmetry

All real classical solutions of the SU(2) Yang-Mills theory with spherical symmetry in 4-dimensional Euclidean space are constructed analytically and catalogued. The uniqueness of the solution of Belavinet al in possessing finite action is explicitly demonstrated.

• Neutron-antineutron oscillations and SO (10) grand unification

Within the framework of the survival hypothesis for Higgs scalars we comprehensively examine the following question: could there be neutron-antineutron oscillations in SO(10) grand unified theories which would be detectable in the forthcoming experiments? In the process of answering this, we critically discuss and supplement the existing knowledge of the relevant patterns of SO(10) symmetry breakdown in relation to the said oscillations. However, our conclusions are negative with the oscillation period being 1025 years or higher.

The status of the present precision measurements of electroweak observables is reviewed with specific reference to the radiative parametersS, T, U or equivalently ε12, ε3. 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.

• Group report: Beyond standard model

Working group II at WHEPP3 concentrated on issues related to the super-symmetric 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.

• Quantum chromodynamics: Working group report

• Beyond the standard model: Working group report

This report summarises the activities of the working group on ‘Physics beyond the Standard Model’. The results of investigations in incorporatingR-parity in grand unification, the possibility of a light charged Higgs boson in extension of MSSM and radiative generation of neutral vector boson self-couplings within the MSSM are described. Also given is an account of activities in neutrino physics, namely a proposal for a study of the atmospheric muon anomaly in deep underground mines, a field theoretic study of neutrino oscillations and a mechanism to generate appropriate masses of three active plus one sterile neutrino species.

• B and collider physics: Working group report

This report summarises the work done during WHEPP-6 (Institute of Mathematical Sciences, Chennai, India, Jan 3–15, 2000) in Working group on ‘B and collider physics’.

• Mechanisms of supersymmetry breaking in the minimal supersymmetric standard model

We provide a bird’s eyeview of current ideas on supersymmetry breaking mechanisms in the MSSM. The essentials of gauge, gravity, anomaly and gaugino/higgsino mediation mechanisms are covered briefly and the phenomenology of the associated models is touched upon. A few statement are also made on braneworld supersymmetry breaking.

• Working group report: Neutrino and astroparticle physics

This is the report of neutrino and astroparticle physics working group at WHEPP-7. Discussions and work on CP violation in long baseline neutrino experiments, ultra high energy neutrinos, supernova neutrinos and water Cerenkov detectors are discussed.

• Preface

• Developments in high energy theory

This non-technical review article is aimed at readers with some physics back-ground, including beginning research students. It provides a panoramic view of the main theoretical developments in high energy physics since its inception more than half a century ago, a period in which experiments have spanned an enormous range of energies, theories have been developed leading up to the Standard Model, and proposals – including the radical paradigm of String Theory – have been made to go beyond the Standard Model. The list of references provided here is not intended to properly credit all original work but rather to supply the reader with a few pointers to the literature, specifically highlighting work done by Indian authors.

• Complex scaling and residual flavour symmetry in the neutrino mass matrix

Using the residual symmetry approach, we propose a complex extension of the scaling ansatz on the neutrino Majorana mass matrix $M\nu$ which allows a nonzero mass for each of the three light neutrinos as well as a nonvanishing $\theta_{13}$. Leptonic Dirac CP violation must be maximal while atmospheric neutrino mixing need not be exactly maximal. Each of the two Majorana phases, to be probed by the search for $0\nu\beta\beta$ decay, has to be zero or $\pi$ and a normal neutrino mass hierarchy is allowed.

• # Pramana – Journal of Physics

Volume 94, 2020
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019