摘要:

We consider the low energy phenomenology of superstrings. In particular we analyze supersymmetry breaking via gaugino condensate and we compare the phenomenology of the two different approaches to stabilize the dilaton field. We study the cosmological constant problem and we show that it is possible to have supersymmetry broken and zero cosmological constant. Finally, we discuss the possibility of having an inflationary potential. Requiring that the potential does not destabilize the dilaton field imposes an upper limit to the density fluctuations which can be consistent with the COBE data.

ISSN:0094-243X    

DOI:10.1063/1.48776

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The behavior of massive, mixed neutrinos in dense media is examined using the method of finite temperature field theory. Starting with the effective Dirac equation, a concise derivation of the evolution equation governing the neutrino flavor oscillations is presented. Particular attention is devoted to the nonlinear effects induced by the &ngr;‐&ngr; interactions when the neutrinos themselves are part of the background.

ISSN:0094-243X    

DOI:10.1063/1.48777

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

QCD sum rules are based on the Operator Product Expansion of current correlators, and on QCD‐hadron duality. An extension of this program to finite temperature is discussed. This allows for a study of deconfinement and chiral‐symmetry restoration. In addition, it is possible to relate certain hadronic matrix elements to expectation values of quark and gluon field operators by using thermal Finite Energy Sum Rules. In this way one can determine the temperature behavior of hadron masses and couplings, as well as form factors.

ISSN:0094-243X    

DOI:10.1063/1.48778

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Precision measurements of electroweak interactions at theZ0energy are performed at four experiments at the Large Electron Positron (LEP) Collider at CERN in Geneva, Switzerland. The large amount of data obtained from 1989 until today allows detailed comparisons with the predictions made by the Standard Model. Within the experimental errors the agreement with the Standard Model is good. Fits to the LEP data allow an indirect determination of the mass of thetopquark:Mt=173+12+18−13−20GeV, assuming aHiggsboson mass of 300 GeV. The first errors reflect the experimental errors (systematic and statistical) on the measurements. The second errors correspond to the variation of the central value when varying theHiggsmass between 60 and 1000 GeV. This paper reviews the results of the measurements of electroweak interactions, and compares the results with predictions made by the Standard Model.

ISSN:0094-243X    

DOI:10.1063/1.48779

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Since 1974, the study of the production, spectroscopy, and decays of the charm particles has been an extremely fruitful area of the elementary particle physics. The charmed quark is sufficiently massive that some aspects of pertubative QCD are applicable, both in production and decays. Because the weak couplings of the charmed quarks are known, charm decays offer a clean laboratory to study strong interaction effects at the boundary between the pertubative and non‐perturbative regimes. A selection of recent experimental results from fixed target charm experiments at Fermilab is presented and discussed.

ISSN:0094-243X    

DOI:10.1063/1.48780

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Precision measurements at the Z0resonance in e+e−collisions provide insight into the electroweak interactions of the Standard Model. The mass of the Z0is a fundamental parameter of the model. The decay widths, cross sections, and asymmetries for decays of the Z0into leptons and hadrons give information on the number of massless neutrinos, electroweak coupling constants, and possible new physics. Results from the most recent measurements at the LEP e+e−collider at CERN are presented.

ISSN:0094-243X    

DOI:10.1063/1.48781

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Progress in constructing the high temperature limit of quantum chromodynamics is presented. Such high temperatures are attained in heavy ion collisions and astrophysical settings. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.48782

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We use SU(3) flavor symmetry to analyze thePP′,VP, and baryon‐antibaryon decays ofJ/&psgr;. Both, the SU(3)‐invariant and ‐violating contributions are considered. Particular attention is paid to the interference of the electromagnetic and strong amplitudes.

ISSN:0094-243X    

DOI:10.1063/1.48783

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

New measurements have been made of the proton and deuteron spin structure functions,gp1andgd1, using deep‐inelastic scattering of longitudinally polarized electrons from polarized NH3and ND3targets. The data span the kinematic range 0.029<x<0.8 andQ2<10 (GeV/c)2. The integrals &Ggr;p=∫10gp1(x,Q2)dxand &Ggr;d=∫10gd1(x,Q2)dxhave been evaluated at fixedQ2=3 (GeV/c)2to yield &Ggr;p=0.127±0.004(stat.)±0.010(syst.) and &Ggr;d=0.041±0.003±0.004. Both measurements are well‐below the Ellis‐Jaffe predictions.

ISSN:0094-243X    

DOI:10.1063/1.48784

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We give a summary of the nonperturbative approach to quantum gravity based on Ashtekar’s new variables and loop quantization, intended for a general audience of physicists. We discuss the possible connections of this approach with other areas of physics and the basic ideas of quantizing the gravitational field.

ISSN:0094-243X    

DOI:10.1063/1.48785

出版商:AIP    

年代:1995

数据来源: AIP