• Volume 55, Issue 1-2

July 2000,   pages  1-355

• Preface

• Results from atmospheric neutrinos

With the announcement of new evidence for muon neutrino disappearance observed by the super-Kamiokande experiment, the more than a decade old atmospheric neutrino anomaly moved from a possible indication for neutrino oscillations to an apparently inescapable fact. The evidence is reviewed, and new indications are presented that the oscillations are probably between muon and tau neutrinos. Implications and future directions are discussed.

• Phenomenology of neutrino oscillations

The phenomenology of solar, atmospheric, supernova and laboratory neutrino oscillations is described. Analytical formulae for matter effects are reviewed. The results from oscillations are confronted with neutrinoless double beta decay.

• Status of electroweak phase transition and baryogenesis

I review recent progress on the electroweak phase transition and baryogenesis, focusing on the minimal supersymmetric Standard Model as the source of new physics.

• The case for the cosmological constant

I present a short overview of current observational results and theoretical models for a cosmological constant. The main motivation for invoking a small cosmological constant (or A-term) at the present epoch has to do with observations of high redshift Type Ia supernovae which suggest an accelerating universe. A flat accelerating universe is strongly favoured by combining supernovae observations with observations of CMB anisotropies on degree scales which give the ‘best-fit’ values ΘA ⋍ 0.7 and Θm ⋍ 0.3. A time dependent cosmological A-term can be generated by scalar field models with exponential and power law potentials. Some of these models can alleviate the ‘fine tuning’ problem which faces the cosmological constant.

• Formation of disoriented chiral condensates in relativistic heavy-ion collisions

We present a brief review of the subject of disoriented chiral condensates (DCC). We describe the conventional scenarios for the formation of DCC which have been proposed in the literature. Observable signals, such as fluctuations in neutral to charged pion ratio, are discussed. We then discuss a novel scenario for DCC formation, recently proposed by us, where the entire region of hot partons can get converted into a single large DCC. Our arguments suggest that formation of such large DCC is unlikely in the collision of heavy nuclei, and ultra-high energy hadronic collisions may be better suited for this.

• Latest results from HERA

Highlights are presented of the latest measurements from the H1, ZEUS and HERMES experiments at HERA.

• What’s new at small x?

We discuss some recent developments in small x physics.

• Quantum chromodynamics studies at LEP2

Several studies have been made to the hadronic final states in e+e collisions at LEP. Studies of the annihilation process at LEP2 have given rise to results on jet rate, event shape, heavy flavour production, inclusive momentum spectra, Bose-Einstein correlation and colour reconnection effects. Event shape studies have given rise to accurate determination of the strong coupling constant αs using O (αs2) with resummed leading and next-to-leading log calculation and also with power law corrections. Studies of 2-photon processes have yielded results on γγ cross-section, heavy flavour production, photon structure function and γ*γ* scattering.

• Higher order corrections in perturbative quantum chromodynamics

We present some techniques which have been developed recently or in the recent past to compute Feynman graphs beyond one-loop order. These techniques are useful to compute the three-loop splitting functions in QCD and to obtain the complete second order QED corrections to Bhabha scattering.

• Two problems in thermal field theory

In this talk, I review recent progress made in two areas of thermal field theory. In particular, I discuss various approaches for the calculation of the quark gluon plasma thermodynamical properties, and the problem of its photon production rate.

• Quark-gluon plasma: Status of heavy ion physics

Lattice quantum chromodynamics (QCD), defined on a discrete space-time lattice, leads to a spectacular non-perturbative prediction of a new state of matter, called quark-gluon plasma (QGP), at sufficiently high temperatures or equivalently large energy densities. The experimental programs of CERN, Geneva and BNL, New York of relativistic heavy ion collisions are expected to produce such energy densities, thereby providing us a chance to test the above prediction. After a brief introduction of the necessary theoretical concepts, I will present a critical review of the experimental results already obtained by the various experiments in order to examine whether QGP has already been observed by them.

• Supersymmetric unification at the millennium

We argue that the discovery of neutrino mass effects at super-Kamiokande implies a clear logical chain leading from the Standard Model, through the MSSM and the recently developed minimal left right supersymmetric models with a renormalizable see-saw mechanism for neutrino mass, to left right symmetric SUSY GUTS: in particular, SO(10) and SU(2)L × SU(2)R × SU(4)C. The progress in constructing such GUTS explicitly is reviewed and their testability/falsifiability by lepton flavour violation and proton decay measurements emphasized. SUSY violations of the survival principle and the interplay between third generation Yukawa coupling unification and the structurally stable IR attractive features of the RG flow in SUSY GUTS are also discussed.

• Perspectives of SM Higgs measurements at the LHC

The latest unsuccessful Higgs searches at LEP have pushed its mass well into the domain where significant signals can be expected from the LHC experiments. The most sensitive LHC Higgs signatures are reviewed and the discovery year is estimated as a function of the Higgs mass. Finally, we give some ideas about: ‘What might be known about the production and decays of a SM Higgs boson’ after 10 years of LHC?

• Non-minimal and non-universal supersymmetry

I motivate and discuss non-minimal and non-universal models of supersymmetry and supergravity consistent with string unification at 1010 GeV.

• Large compact dimensions and high energy experiments

Models of spacetime with extra compact dimensions and having the Standard Model fields confined to a narrow slice of 4-dimensional spacetime can have strong gravitational effects at the TeV scale as well as electroweak-strength interactions at present-day colliders. Phenomenological consequences of such models are reviewed, with special emphasis on collider signatures.

• The status of supersymmetry phenomenology

In this brief review the following topics are discussed:

Direct searches for SUSY in mSUGRA: a brief review of the relevant mass limits, the clean trilepton signal, the hunt for the third generation of sfermions,

Direct searches beyond mSUGRA: search prospects in models with nonuniversal gaugino masses, search prospects in models with nonuniversal scalar masses,

Indirect searches for SUSY: precision electroweak observables and SUSY, ε′/ε and SUSY.

• Experimental status of B physics

In a short period of time, we will have a large amount of results from B-factories including ones on CP violation. In this talk, we briefly review the current experimental status of B-physics. After a quick description of b-facilities, we divide this vast field into two categories: (1) weak interaction and QCD, (2) unitarity triangle and CP violation. Only a few critical items are selected in each category for the sake of time and space.

• CP violation: the past, the present and the future

We have just entered a period during which we expect considerable progress toward understanding CP violation. Here we review what we have learnt so far, and what is to be expected in the near future. To do this we cover the foundation of CP violation at a level which can be understood by physicists who are not working in this field.

• New physics with beauty

We review the effects of new physics on CP asymmetries and decays of B mesons. Possible sources and corresponding signals for new physics are studied briefly. We discuss how the decay mode bs ℓℓ (and BK*ℓℓ) will enable us to understand the nature of new physics. We also examine the possibility of truly clean signature of new physics — a signature based on observables alone and without hadronic uncertainties.

• How neutrinos get mass and what other things may happen besides oscillations?

In this talk I address the theoretical issue of why new physics is required to obtain a nonzero neutrino mass. I then discuss what other things may happen besides neutrino oscillations. In particular I consider a possible new scenario of leptogenesis in R-parity nonconserving supersymmetry.

• Constraints on ms and ε′/ε from lattice quantum chromodynamics

Results for light quark masses obtained from lattice QCD simulations are compared and contrasted with other determinations. Relevance of these results to estimates of ε′/ε is discussed.

• Light front quantum chromodynamics: Towards phenomenology

We briefly review the application of light front QCD to inclusive deep inelastic scattering.

• Analysis of two recent tests of T-invariance

Inequality of the rates for K0 → π+e υ and K0 → πe+ν transitions, reported by CPLEAR, and an asymmetry in the distribution of the dihedral angle between the π+π and e+e planes in KL → π+πe+e decays, found by KTeV, have been announced as demonstrations of T-noninvariance. These results are critically interpreted and compared as proofs of the failure of reciprocity.

• Infra-red fixed points in supersymmetry

Model independent constraints on supersymmetric models emerge when certain couplings are drawn towards their infra-red (quasi) fixed points in the course of their renormalization group evolution. The general principles are first reviewed and the conclusions for some recent studies of theories with R-parity and baryon and lepton number violations are summarized.

• Measuring the chargino parameters

After the supersymmetric particles have been discovered, the priority will be to determine independently the fundamental parameters to reveal the structure of the underlying supersymmetric theory. In my talk I discuss how the chargino sector can be reconstructed completely by measuring the cross-sections with polarized beams at e+e collider experiments: e+e → $$\tilde \chi _i^ + \tilde \chi _j^\_$$ [i, j=1, 2]. The closure of the two-chargino system can be investigated by analysing sum rules for the production cross-sections.

• New physics effects from B meson decays

In this talk, we point out some of the present and future possible signatures of physics beyond the Standard Model from B-meson decays, taking R-parity conserving and violating supersymmetry as illustrative examples. An expanded version is available on hep-ph archive.

• Some aspects of R-parity violating supersymmetry

I briefly review a scenario where R-parity is explicitly broken through a term bilinear in the lepton and Higgs superfields in the superpotential. An immediate consequence of the presence of this term is the generation of a massive neutrino at the tree level. Constraints on the parameter space are discussed in the context of recent super-Kamiokande results on atmospheric neutrinos. The testability of such models is emphasized through the observation of comparable numbers of muons and taus, produced together with the H-boson, in decays of the lightest neutralino. Some other phenomenological implications of such a scenario are also discussed.

• Neutrino masses and mixing in supersymmetric theories

It has been known for sometime that supersymmetric theories with R-parity violation provide a natural framework where small neutrino masses can be generated. We discuss neutrino masses and mixing in these theories in the presence of trilinear lepton number violating couplings. It will be shown that simultaneous solutions to solar and atmospheric neutrino problems can be realized in these models.

• Bc meson properties and its leptonic radiative decays

The properties of the meson Bc are outlined. The leptonic radiative decays for Bc meson are presented. An outlook on the studies of the meson is given.

• High scale parity invariance as a solution to the SUSY CP problem and an explanation of small ε′/ε

It is shown that if the supersymmetric Standard Model (MSSM) emerges as the low energy limit of a high scale left-right symmetric gauge structure, the number of uncontrollable CP violating phases of MSSM are drastically reduced. In particular it guarantees the vanishing of the dangerous phases that were at the root of the so called SUSY CP problem. Such a symmetric gauge structure is independently motivated by the smallness of neutrino masses that arise via seesaw mechanism automatic in the theory. The minimal version of this theory also provides an explanation of the smallness of ε′/ε as a consequence of the high scale parity invariance.

• Ultra high energy cosmic rays above 1011 GeV: Hints to new physics beyond Standard Model

The observed cosmic ray events above 1012 GeV are difficult to explain within the context of known physics of propagation of known particles in the Universe and within the standard acceleration mechanisms that are likely to operate in powerful astrophysical objects. Several ideas of possible new physics beyond the Standard Model have been suggested in order to explain these events. The major suggestions are summarized here.

• Beyond the standard model: Working group report

This report summarises the work done in the ‘Beyond the Standard Model’ working group of the Sixth Workshop on High Energy Physics Phenomenology (WHEPP-6) held at the Institute of Mathematical Sciences, Chennai, Jan 3–15, 2000. The participants in this working group were: R Adhikari, B Ananthanarayan, K P S Balaji, Gour Bhattacharya, Gautam Bhattacharyya, Chao-Hsi Chang (Zhang). D Choudhury, Amitava Datta, Anindya Datta, Asesh K Datta, A Dighe, N Gaur, D Ghosh, A Goyal, K Kar, S F King, Anirban Kundu, U Mahanta, R N Mohapatra, B Mukhopadhyaya, S Pakvasa, P N Pandita, M K Parida, P Poulose, G Raffelt, G Rajasekaran, S Rakshit, Asim K Ray, A Raychaudhuri, S Raychaudhuri, D P Roy, P Roy, S Roy, K Sridhar and S Vempati.

• Neutrino and astroparticle physics: Working group report

The contributions made to the Working Group activities on neutrinos and astrophysics are summarized in this article. The topics discussed were inflationary models in Raman-Sundrum scenarios, ultra high energy cosmic rays and neutrino oscillations in 4 flavour and decaying neutrino models.

• Quantum chromodynamics: Working group report

This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering, and collider phenomenology are reported.

• 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’.

• Discussion on a possible neutrino detector located in India

We have identified some important and worthwhile physics opportunities with a possible neutrino detector located in India. Particular emphasis is placed on the geographical advantage with a stress on the complimentary aspects with respect to other neutrino detectors already in operation.

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