摘要:

The electron-proton collider HERA, like an electron-mycroscope, explores the structure of the proton down to10−16 cmand up to the situation of very high parton densities. The proton energy was upgraded from 820 to 920 GeV in the Fall of ’98 and the luminosity has also substantially improved, with another factor of 3 upgrade expected to follow this year. Inclusive proton structure functions have been studied with incidente+ande−of 27 GeV in the neutral (NC) and charged (CC) current interactions as functions of the squared four-momentum transfer,Q2,and of the fractional proton momentum carried by partons,x. The structure functionF2,as well as the&ggr;−Z0interference termxF3,have been measured in a range ofQ2and1/xthat extends by orders of magnitude that reached by fixed target experiments. The DGLAP evolution equations [1] allow for a perturbative NLO QCD fit of the measured non-perturbative structure functions in the available kinematic range:&agr;Sand the gluon density at lowxare fitted at the same time with good precision. The longitudinal structure function,FL,can be determined within the DGLAP formalism. With CC, the electroweak unification has been tested; at highx, a first flavor decomposition of the light quarks is achieved. The contribution toF2of the charm quark has been measured and results to be relevant. Bounds on the radius of quarks and on compositeness are derived from the data at the highestQ2,100<Q2⩽40,000 GeV2.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425492

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

In response to recent experimental studies we investigate Coulomb distortion effects on(e,e′)reactions from medium and heavy nuclei for the case of electrons and positrons. We extend our previously reported full DWBA treatment of Coulomb distortions to the case of positrons for the208Pb(e,e′)reaction in the quasielastic region for a particular nuclear model. In addition, we use previously reported successful approaches to treating Coulomb corrections in an approximate way to calculate the Coulomb distortion effects for(e,e′)reactions for both electrons and positrons for the case of a simple nuclear model for quasielastic knock-out of nucleons. With these results in hand we develop a simplead-hocapproximation for use in analyzing experiments, and discuss methods of extracting the “longitudinal structure function” which enters into evaluation of the Coulomb sum rule. These techniques are generally valid for lepton induced reactions on nuclei with momentum transfers greater than approximately 300MeV/c.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425493

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

AnSU(2)effective lagrangian is extended to anSUL(3)⊗SUR(3)by including the vector and axial vector meson. With this effective lagrangian, electromagnetic form factors of charged pion and kaon are calculated in both time- and space-like regions. Good agreement with experimental data is obtained for those form factors. Decay widths of&rgr;→&pgr;&pgr;and&fgr;→K+K−are also calculated and shown to agree with experimental data very well. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425494

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Magnetic moment of a relativistic three-body system of Dirac particles is studied. Special attention is paid to the Lorentz boost of the center of mass coordinate, which allows us to take the correct non-relativistic limit of the matrix element of the electromagnetic interaction. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425495

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

In this talk, we revisit the strange vector form factors of the nucleon within the framework of the SU(3) chiral quark-soliton model. We employ in this new work the prescription of the SU(3) quantization in order to remedy the charge problem arising from the nonlocality in time. We compute the neutral weak and strange vector form factors. We also incorporate two different asymptotics of the soliton field: pion and kaon tails. The results turn out to be compatible with the recent experimental data from the SAMPLE and HAPPEX collaborations. We also present the prediction for the A4 experiment. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425496

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Recent topics in hypernuclear physics are discussed with emphasis on the experimental progress. Correspondingly, the role of structure calculations with&Lgr;Nmeson theoretical potentials are also discussed by showing typical examples in close relation with spin-dependent interactions. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425497

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Our experimental project to study&Lgr;Ninteraction using high-resolution hypernuclear &ggr; spectroscopy is described. Employing a germanium detector array (Hyperball), we investigated level structure of&Lgr;7Liand&Lgr;9Bein high precision and obtained quantitative information on the strengths of the spin-spin force and the &Lgr;-spin-dependent spin-orbit force between &Lgr; andN. More experiments are in progress to investigate the tensor force and the nucleon-spin-dependent spin-orbit force. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425498

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Possible existence of deeply-bound nuclear states ofK¯is investigated theoretically for few-body systems. The nuclear ground states ofK¯in3Heand4Heare predicted to be discrete states with binding energies of 108 MeV and of 86 MeV and widths of 20 MeV and of 34 MeV, respectively. The formation of theT=0 K−⊗3He+K¯0⊗3Hstate in the4He(stoppedK−,n) reaction is proposed with a calculated branching ratio of about 2&percent;. It is discussed that a kaon injected into9Beforms a nuclear object of very high density and low temperature. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425499

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Roles of virtual mixings of the &Sgr; hyperon in hypernuclear structure and interactions are studied in the magnetic moments and transitions as well as nonmesonic weak decays of hypernuclei. It was found that effects of the mixing are significantly large so that their information is valuable in the study of the hyperon nucleon interaction. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425500

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

In spite of the recent progresses achieved at BNL and KEK, a consistent understanding of the non-mesonic weak decay is yet to be achieved. The rapid saturation of total decay rate in its mass dependence,&Ggr;n/&Ggr;pratio puzzle, opposite sign of decay asymmetry parameter between&Lgr;5Heand&Lgr;12C,and&Dgr;I=1/2rule of non-mesonic weak decay are the current concerns, but not understood yet. The difficulties are largely in the treatment of the final state interaction. In the paper, we discuss on the role of final state interaction in the interpretation of the newly measured decay particle spectra in the non-mesonic weak decay of &Lgr; hypernuclei. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425501

出版商:AIP    

年代:1901

数据来源: AIP