摘要:

An up‐to‐date review of the use of light mesons, in particular the &eegr;‐meson, as a probe of physics beyond the standard model is given. Emphasis is given to lepton number violation andCPviolation (CPV) processes.

ISSN:0094-243X    

DOI:10.1063/1.40348

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An experimental program aiming at a study of very rare processes is being prepared in Uppsala. The production and decays of the pseudoscalar mesons, &pgr; and &eegr;, will be studied using the cooler storage ring, CELSIUS and a wide angle 4&pgr; detector named WASA. Here we discuss some issues connected with the rare decays of the neutral pion and we give the status of the WASA project.

ISSN:0094-243X    

DOI:10.1063/1.40377

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A facility dedicated to the production of &eegr; mesons has been installed at the Saturne synchrotron with the purpose of investigating rare decays of this meson. The &eegr; are produced by the pd → 3He&eegr; reaction near threshold and tagged by the detection of3He in a magnetic spectrometer (SPES2). A rate of 105/s tagged &eegr; can be achieved. In the first experiment, &eegr; → &mgr;+&mgr;−, the &mgr; will be detected in range telescopes. Magnetic spectrometers for lepton detection are considered for future experiments.

ISSN:0094-243X    

DOI:10.1063/1.40384

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Physics topics from decays of the J/&psgr;, &psgr;’, and Y(1s) mesons are discussed. Comparisons between these particles and old and new puzzles are reviewed.

ISSN:0094-243X    

DOI:10.1063/1.40380

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The experiment on pp‐bremsstrahlung presented here aims at a detailed study of off‐shell effects in the strong interaction. A detector set‐up will be developed which allows measurements at maximum kinematically allowed photon energies, where the strongest deviations from the soft‐photon approximation (which incorporates only on‐shell information) are to be expected. The detector mainly consists of a large time‐of‐flight spectrometer covering the full solid angle.

ISSN:0094-243X    

DOI:10.1063/1.40381

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We are planning to use the Tagger facility at the Saskatchewan Accelerator Laboratory (SAL) to measure the total cross section for the reaction &ggr;p → n&pgr;+very close to threshold. The purpose is to extract the electric dipole amplitude Eo+(&pgr;+) to high accuray. The experimental techniques involve the use of a liquid hydrogen target and the detection of the reaction neutrons in coincidence with tagged photons.

ISSN:0094-243X    

DOI:10.1063/1.40352

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The eta photoproduction near threshold has a number of similarities and differences in comparison to the pi‐zero photoproduction near threshold. Both processes probe Born amplitudes involving the s‐ and u‐ channel nucleon exchanges. While eta production is also sensitive to the vector meson contribution in the t‐chennel and excitation of several baryond resonances the pi‐zero process is not. The former has a large s‐channelS11 (1535) excitation amplitude, but the latter has a relatively small contribution from the &Dgr;(1232) excitation. We discuss the implications of our analysis on the recent Bates data presented at this conference, and report the value of theA1/2amplitude for theS11 → N&ggr;transition that we can extract from the existing eta photoproduction experiments. The latter is of interest to the test of hadron models.

ISSN:0094-243X    

DOI:10.1063/1.40353

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Experiments at Saclay and Mainz to photoproduce neutral pions are reviewed. Differential cross sections and total cross sections in the photon energy range of 140 MeV to 160 MeV are shown. It is pointed out that the predictions of the low energy theorems are not verified. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.40354

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The predictions of low energy theorems on pion photoproduction are confronted with the exciting new experimental data near threshold. Isobars in the s‐ and u‐channels and heavier mesons exchanged in the t‐channel give only small corrections. The role of rescattering is discussed in some detail. A calculation of the threshold amplitude based on current algebra is able to describe the data but has serious shortcomings concerning gauge and Lorentz invariance. Following a derivation of the low energy theorems from field theory, we find that the discrepancy between experiment and theory could be due to a possible induced pseudoscalar of non‐pionic origin in the axial vector current.

ISSN:0094-243X    

DOI:10.1063/1.40355

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Results of computer simulation of pion production in photonuclear reactions are presented. Differential cross sections and photon absorption cross sections are shown. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.40373

出版商:AIP    

年代:1991

数据来源: AIP