摘要:

After recalling why most strong interaction phenomena cannot be studied with quark‐gluon perturbation theory, I suggest that a phenomenological form of the old dual string theory may be a good model for the nonperturbative aspects of QCD. I begin by describing some recent progress within this framework in understanding the status of the quark model within QCD. The resulting picture of the ordinary hadrons, hybrids, and glueballs provides a simple framework for studying these elements of hadron spectroscopy. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48207

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An introductory treatment of hadronization through functional integral calculus and bilocal Bose fields is given. Emphasis is placed on the utility of this approach for providing a connection between QCD and effective hadronic field theories. The hadronic interactions obtained by this method are nonlocal due to the QCD substructure, yet, in the presence of an electromagnetic field, maintain the electromagnetic gauge invariance manifest at the quark level. A local chiral model which is structurally consistent with chiral perturbation theory is obtained through a derivative expansion of the nonlocalities with determined, finite coefficients. Tree‐level calculations of the pion form factor and &pgr;–&pgr; scattering, which illustrate the dual constituent‐quark–chiral‐model nature of this approach, are presented. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48215

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We review two manifestations of chiral symmetry violation involving pions and nucleons, and leading to useful dynamical and structural information on strong interactions. The &pgr;&pgr; scattering amplitude at threshold is fully determined by the chiral symmetry breaking part of the interaction, and, thus, fundamentally constrains the form of the low energy effective lagrangians. We discuss the status and recent developments in the study of the low‐energy &pgr;&pgr; interaction, particularly the new results on reaction &pgr;N→&pgr;&pgr;Nnear threshold, and find that ambiguities persist in the determination of the s‐wave &pgr;&pgr; scattering lengths. The &pgr; Nsigma term is, analogously, determined by chiral symmetry breaking in the &pgr;Nlagrangian. The magnitude of &sgr;&pgr;Nprovides an independent constraint on the QCD structure of the nucleon, insofar as it sets a limit on the nucleon’sss¯content. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48194

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Recent results in the 3N and 4N systems are reviewed, including inelastic electron scattering. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48130

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A semiclassical S‐Matrix theory is described for electron–atom or electron–ion scattering. The development of semiclassical approximations is briefly reviewed and the justification for semiclassical perspectives in electronic problems is discussed and contrasted with the situation of nucleus–nucleus scattering. Special properties of classicalN–electron atoms are derived. On their basis quantitative results are presented for electron and positron impact ionization of hydrogen close to threshold. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48181

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Variational and Green’s Function Monte Carlo methods are reviewed as applied to the study of the few‐nucleon continuum at low‐ and intermediate‐energies. Results recently obtained for the radiative and weak capture reactions n+3He→4He+&ggr; and p+3He→4He+e++&ngr;e, the5He P‐wave resonances, and the inclusive and exclusive electron scattering reactions on3H and the helium isotopes are summarized. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48106

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Lattice calculations are used to show the dominant role of instantons in determining light hadron structure and quark propagation in the QCD vacuum. The instanton content of gluon fields sampling the Wilson action is extracted using cooling as a filter to selectively remove essentially all fluctuations of the gluon field except for instantons. Close agreement is demonstrated between quenched lattice QCD results including all gluonic contributions and including only instantons for vacuum correlation functions of hadronic currents and for density‐density correlation functions in hadronic bound states. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48087

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A review is presented of experimental results for electron scattering from the deuteron. The data encompass elastic, threshold inelastic and quasielastic scattering. The emphasis is on determining the active degrees of freedom (mesonic, nucleonic, ...) and testing the limits of validity of the meson‐nucleon picture. The role of new experimental capabilities, such as double polarization experiments and/or out‐of‐plane detection are described. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48213

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The status and future prospects of photo‐ and electroexcitation of nucleon resonances are discussed. Data are compared with calculations within the framework of the constituent quark model. It is shown that measurement of resonance transition amplitudes can be used as a sensitive tool to study the QCD structure of the nucleon. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48214

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The internal structure of proton and neutron is manifested in a variety of observables. The form factors for elastic electron scattering which describe the distribution of charge and magnetic moments provide information vital for our understanding of the confined quark system. In the case of the neutron they are still poorly known; the electric form factorGE,nin particular is very difficult to determine using the conventional method of Rosenbluth separation. A much better technique is to measure the asymmetry in the scattering of high energy polarized electrons from polarized targets or the spin transfer to the recoiling neutron from unpolarized targets. Experiments of this type are scheduled or have already been started at several laboratories. Our knowledge aboutGE,nand the status of experiments will be described along with first results. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48232

出版商:AIP    

年代:1995

数据来源: AIP