Deutsche Physikalische Gesellschaft e. V. (DPG)

WWW-Server für Frühjahrstagungen und E-Verhandlungen

E-Verhandlungen 1998
Programm und Abstacts der Sitzung HK 57

•H. Backe
Institut für Kernphysik, Universität Mainz

High current and low emittance electron beams from modern accelerators present attractive sources for the production of brilliant electromagnetic radiation. The spectrum reaches from the far-infrared to the hard X-ray region. Production processes as the Smith-Purcell effect, channeling, transition, and parametric X-ray radiation are reviewed. A novel interferometer has been developed at the Mainz Microtron MAMI with which the complex index of refraction of thin self supporting foils can be measured in the soft X-ray region.

•N. Kalantar-Nayestanaki¹, J.C.S. Bacelar¹, M.J. van Goethem^1,2, M.N. Harakeh¹, M. Hoefman^1,2, H. Huisman¹, A. Kugler^3,2, H. Löhner^1,2, J.G. Messchendorp¹, R.W. Ostendorf^1,2, S. Schadmand^1,4,2, M. Seip¹, R. Simon^5,2, R. Turrisi^1,2, M. Volkerts¹, V. Wagner^3,2 und H.W. Wilschut^1,2
1KVI, Groningen
²for the TAPS collaboration
³NPI, e u Prahy
⁴Univ. Gieß en
⁵GSI, Darmstadt

A series of bremsstrahlung measurements have been performed at KVI with the new superconducting cyclotron, AGOR, aiming to investigate the ``off-shell'' behavior of the nucleon-nucleon interaction at energies below particle-production threshold. Nucleon-nucleon bremsstrahlung is the most fundamental process used for such studies as it involves the strong interaction between two nucleons and the well-known electromagnetic interaction. In addition, the cross section for nucleon-nucleon bremsstrahlung is the basis of all calculations which deal with photon production in heavy-ion collisions.

At KVI, we have used the high-quality polarized beam of 190 MeV protons to perform the most complete experiment to date on proton-proton and proton-deuteron systems. The second system was chosen such that one is able to study all possible bremsstrahlung channels and infer the contribution from the neutron-proton system. High precision cross-section and analyzing-power data have been obtained enabling one to extract information on the structure of the nucleon, the role of virtual nucleon-resonance excitation at these energies, the ``off-shell'' properties of the T-matrix and the role of two-body effects such as MEC. The measurements were performed with the Small-Angle Large-Acceptance Detector (SALAD) and the Two-Arm Photon Spectrometer (TAPS). Some of the results will be presented along with the most modern calculations which still disagree with the data in specific regions of phase space.

D. Drechsel, G. Knöchlein, A. Metz und •S. Scherer
Institut für Kernphysik, Johannes Gutenberg-Universität, J.J. Becher Weg 45, D-55099 Mainz

We discuss virtual Compton scattering off the proton as tested in the reaction ep® epg. At first order in the frequency of the final photon, the invariant amplitude beyond the low-energy theorem can be expressed in terms of ten generalized polarizabilities [1]. We show that four independent relations exist among the polarizabilities, once charge conjugation symmetry is implemented in combination with nucleon crossing [2]. We present predictions for the generalized polarizabilities which have been obtained in the framework of heavy baryon chiral perturbation theory at O(p³) [3] and the linear s model at one-loop level [4].

[1] P. A. M. Guichon, G. Q. Liu, and A. W. Thomas, Nucl. Phys. A591, 606 (1995)

[2] D. Drechsel, G. Knöchlein, A. Yu. Korchin, A. Metz, and S. Scherer, nucl-th/9704064

[3] T. R. Hemmert, B. R. Holstein, G. Knöchlein, and S. Scherer, Phys. Rev. Lett. 79, 22 (1997)

[4] A. Metz and D. Drechsel, MKPH-T-97-13 (1997)

[HOME]

[Archiv]

[E-Verhandlungen 1998]

[Bochum]

[Fachverband HK]

[Sitzung HK 57]

Zuletzt geändert am 14.08.1998

Fragen, Kommentare, Anregungen und Kritik