Volume 41, Issue S1
July 1993, pages 1-540
pp 1- July 1993 Editorial Note
pp 1-32 July 1993 Keynote Address
pp 33-44 July 1993 Standard Model
pp 45-53 July 1993 Standard Model
We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z0 pole. From measurements of the τ polarization in e+ e−→τ+τ−, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to begve/gae=0.066±0.015 andgVτ/gAτ=0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beGτ/Gμ=0.996±0.008.
pp 55-74 July 1993 Standard Model
The four experiments, ALEPH, DELPHI, L3 and OPAL at LEP, have performed a large number of precise measurements to test Quantum Chromodynamics. The strong coupling constant has been measured with high precision:αs(Mz) = 0.123±0.004. The coupling constant has been found to be independent of quark flavour. The running ofαs has been demonstrated by the data. Second order QCD matrix element calculations have been tested from several measured distributions in 3-jet and 4-jet events. These distributions give evidence of the vector nature of the gluon and provide measurements of the QCD colour factors. The hadronic distributions are well reproduced by QCD Monte Carlo programs as well as by analytical calculations with soft gluon coherence effects.
pp 75-82 July 1993 Standard Model
The status of the present precision measurements of electroweak observables is reviewed with specific reference to the radiative parametersS, T, U or equivalently ε1,ε2, 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.
pp 83-105 July 1993 Standard Model
In this talk I review theoretical bounds on mass of the Higgs scalar in the Standard Model (SM) and then summarise current experimental limits from the LEP experiments. Following this I discuss the search strategies for the SM Higgs at LEP 200 and the TeV energye+e− colliders which are under discussion. This will be followed by a summary of the Higgs search potential of the pp supercolliders such as SSC/LHC. I then close with a brief discussion of a ‘Dark Higgs’ whose dominant decay modes are into invisible channels.
pp 107-125 July 1993 Standard Model
pp 127-138 July 1993 Standard Model
During the last 18 months, experiments at bothe+e− andep colliders have begun to test earlier predictions for processes that probe the hadronic structure of the photon. All the main qualitative predictions have already been verified; more detailed analyses are now starting to improve our quantitative understanding of photon structure functions. Some comments on minijets and total cross sections are also included.
pp 139-165 July 1993 Standard Model
I review the current status of several lattice QCD results. I concentrate on new analytical developments and on numerical results relevant to phenomenology.
pp 167-181 July 1993 Heavy Flavour Physics
In the last year there have been new observations of beauty by two fixed target experiments (E672/706 and E653). A few new results on charm have recently been presented by the photoproduction experiment E687 and by E789 and E769. An intriguing result on the purely muonic decay of charm comes from the CERN experiment WA75. These results are summarized and we conclude with a hint of the promise of E791, the very high statistics charm experiment, which is beginning to produce physics results
pp 183-195 July 1993 Heavy Flavour Physics
pp 197-216 July 1993 Heavy Flavour Physics
The DØ Experiment started taking data in August 1992. We present preliminary results on inclusive jet production, direct photon production, W/Z production and decays, b Physics and first searches fort t production and new particles beyond the Standard Model.
pp 217-233 July 1993 Heavy Flavour Physics
Recent developments in the theory of heavy quarks have increased the prospects for the study of non-perturbative QCD in the weak decays of heavy mesons and baryons and for the reliable determination of some of the parameters of the Standard Model. It has been made possible due to the discovery of a spin-flavour symmetry for heavy quarks which arises in QCD when quark mass is taken to infinity. Certain properties in hadrons containing a heavy quark then become independent of its mass and spin. These ideas have tremendous impact on the phenemenology of heavy hadrons. In particular, these symmetries give rise to restrictive relations among weak decay amplitudes and reduce the number of independent form factors. By relating various matrix elements and fixing normalization of some matrix elements, the heavy quark symmetry has enhanced our predictive ability, allowing in some cases to bypass the difficulties of understanding hadronic structure.
pp 235-248 July 1993 Heavy Flavour Physics
pp 249-259 July 1993 Heavy Flavour Physics
The theory of loop induced rare B decays is reviewed. Both electromagnetic penguin processes and gluon mediated penguin processes are discussed. After consideringb→sy andb→se+e− decays, purely hadronic modes likeB→Kϕ are estimated. Constraints on the Higgs sector of SUSY theory fromb→sy is discussed. CP violation in charged B Decays is reviewed.
pp 261-269 July 1993
Recent developments on grand unified theories (GUTs) in the context of the LEP measurements of the coupling constants will be reviewed. The three coupling constants at the electroweak scale have been measured at LEP quite precisely. One can allow these couplings to evolve with energy following the renormalization group equations for the various groups and find out whether all the coupling constants meet at any energy. It was pointed out that the minimalSU (5) grand unified theory fails to satisfy this test. However, various extensions of the theory are still allowed. These extensions include (i) supersymmetricSU (5) GUT, with some arbitrariness in the susy breaking scale arising from the threshold corrections, (ii) non-susySU (5) GUTs with additional fermions as well as Higgs multiplets, which has masses of the order of TeV, and (iii) non-renormalizable effect of gravity with a fine tuned relation among the coupling constants at the unification energy. The LEP results also constrain GUTs with an intermediate symmetry breaking scale. By adjusting the intermediate symmetry breaking scale, one usually can have unification, but these theories get constrained. For example, the left-right symmetric theories coming from GUTs can be broken only at energies higher than about ∼ 1010GeV. This implies that if right handed gauge bosons are found at energies lower than this scale, then that will rule out the possibility of grand unification. Another recent interesting development on the subject, namely, low energy unification, will be discussed in this context. All the coupling constants are unified at energies of the order of ∼ 108GeV when they are embedded in anSU (15) GUT, with some particular symmetry breaking pattern. But even in this case the results of the intermediate symmetry breaking scale remain unchanged.
pp 271-282 July 1993 Beyond the Standard Model
We review general results on threshold effects and their implications on GUTs in the context of LEP data. Among the blooming grand-desert models, threshold effects are computed in the presence of a single real scalar ζ (3, 0, 8) with Mζ≃1010 GeV leading to experimentally testable predictions on the proton lifetimeτp in SU (5) and, in addition, small neutrino masses in SO (10) needed for the solar neutrino flux and the dark matter of the universe. The fine structure constant matching at MZ is ensured by including threshold effects on the unification coupling. In the minimal SUSY SU (5) such effects at the GUT scale modify the prediction of the supersymmetric mass threshold near the TeV scale and the precision measurments of the Standard Model couplings at MZ probe into the superheavy mass spectrum. Consequences of theorems proved very useful for threshold, compactification and multiloop effects are discussed. It is noted that in a class of GUTs the highest intermediate scale MI above which G224P becomes a good symmetry is not affected by the GUT threshold or compactification effects or multiloop contributions in the range MI-MU. But spontaneous compatification effects can decrease the intermediate scale drastically in models where parity and SU(2)R breakings are decoupled. Low mass WR-bsosns are permitted in models with decoupled parity and SU (2)R breakings.
pp 283-301 July 1993 Beyond the Standard Model
A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints.
pp 303-315 July 1993 Beyond the Standard Model
The effect of radiative corrections on the Higgs masses and couplings in supersymmetric models is summarized. Radiative corrections in both the minimal and nonminimal models are discussed. It is pointed out that large singlet Higgs vacuum expectation values are screened out from the radiative corrections to the lightest Higgs mass in nonminimal models. In supersymmetric models the crucial mass limit for the Higgs search may be around 150 GeV.
pp 317-331 July 1993 Beyond the Standard Model
After a brief introduction, we study the constraints on MSSM the Higgs sector parameters from the non-observation of any Higgs boson signals in experiments at LEP. We also review the range of Higgs boson masses that can be searched for at LEP 200. For the most part, we focus on the prospects for the detection of MSSM Higgs bosons in experiments at hadron supercolliders, assuming that these are too heavy to be discovered at LEP 200. We then show that supersymmetric decays of Higgs bosons can significantly reduce the rates for event topologies usually used for Higgs searches. Finally, we discuss some promising new channels for MSSM Higgs boson detection that become possible if these SUSY decays are allowed.
pp 333-346 July 1993 Beyond the Standard Model
This is a phenomenological review ofR parity violating SUSY models, with particular emphasis on explicitR parity violation.
pp 347-357 July 1993 Heavy Ion Collisions
pp 359-370 July 1993 Heavy Ion Collisions
pp 371-394 July 1993 Heavy Ion Collisions
I review the current status of the experimental searches for a Quark-Gluon Plasma in heavy ion collisions. The brief introduction covers important results of finite temperature lattice QCD and the intuitive Bjorken picture of Quark-Gluon Plasma (QGP) formation. Global features of the data, such as transverse energy distributions and the various signatures of QGP such asJ/ϕ-suppression, ψ-enhancement as well as thermal dileptons and photons are then discussed.
pp 395-411 July 1993 Non Accelerator Particle Physics
A review of the experimental efforts to search for a fifth force is presented. The talk begins with a brief history of the hypothesis of fifth force and goes on to describe the context in which the hypothesis gained considerable significance in the recent past. Then a review of many modern experiments is presented, highlighting some of the representative experiments and their results. The TIFR torsion pendulum experiments are described in some detail and the main results are summarized. The talk ends with a hint of future directions in the field.
pp 413-416 July 1993 Non Accelerator Particle Physics
pp 417-426 July 1993 Non Accelerator Particle Physics
Possible explanations of solar neutrino and atmospheric neutrino anomalies are summarized and future tests discussed.
pp 427-439 July 1993 Non Accelerator Particle Physics
It is well known that baryon (lepton) number is not conserved in the standard electroweak theory due to the anomaly. As a consequence, the electroweak phase transition provides plausible ground for producing the baryon number asymmetry of the universe, besides erasing any prexisting asymmetry. This occurs via processes which surmount the instanton potential barrier. The barrier is given by the static saddle point solution of the electroweak theory, called the sphaleron, which we shall briefly expose. This is followed by a pedagogical account of how the asymmetry can be created during the electroweak phase transition including the pitfalls that await the innocent practitioner.
pp 441-453 July 1993 Particle Astrophysics
I summarize the following current topics in cosmology: (1) The near-success of Cold Dark Matter (CDM) in predicting the COBE fluctuation amplitude, which favors the hypothesis that structure formed in the universe through gravitational collapse. (2) The indications that ω ≈ 1 and that the power spectrum has a little more power on supercluster and larger scales than CDM. These are suggested by the IRAS and CfA redshift surveys and POTENT galaxy peculiar velocity analysis, and also by the COBE data. (3) The consequent demise of CDM and the rise of hybrid schemes such as Cold+Hot Dark Matter (C+HDM). (4) The possible implications for neutrino masses and mixings, and for cosmology, of the recent results on solar neutrinos. (5) CERN experiments onvμ-vr oscillations, which may be sufficiently sensitive to detect thevr if its mass lies in the cosmologically interesting mass range 1–102 eV. (6) Dark matter searches, including the searches for WIMPs and axions, and the French, Polish, and Berkeley-Livermore-Mt. Stromlo MACHO searchs.
pp 455-472 July 1993 Particle Astrophysics
pp 473-484 July 1993 Particle Astrophysics
We review the basic features of the inflationary scenarios associated with phase transitions in the very early universe.
pp 485-492 July 1993 Formal Theory
Bell’s inequalities arising from the Einstein-Bell locality postulate or the Noncontextuality postulate provide valuable tests of the classical versus the quantum description independent of detailed dynamics. For 2n degrees of freedom, these inequalities are violated by the quantum theory by a factor 2(n−1)/2 raising important questions for measurement theory.
pp 493-502 July 1993
pp 503-508 July 1993 Formal Theory
In this lecture I review the construction of two dimensional Topologiccal Conformal Field Theories fromN=2 superconformal theories. We show that a BRST structure emerges upon a twisting of theN=2 superconformal algebra. Moreover, the energy-momentum tensor of the twisted theory is BRST-exact and all the physical correlation functions are independeent of the two dimensional metric. We briefly mention several generalizations such as the construction of topological superconformal theories as well as the topological conformal theories on higher genus Riemann surfaces.
pp 509-516 July 1993 Formal Theory
We review some of the recent developments in nonperturbative string theory and discuss their connections with black hole physics and low dimensional fermi systems.
pp 517-523 July 1993 Formal Theory
pp 525-540 July 1993 Concluding Talk
An enormous amount of material has been covered in the last five days and my summary talk is clearly biased by my limitations.
Volume 93 | Issue 6
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