Göttingen 1997 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 41: Relativistische Schwerionenstöße VII
HK 41.6: Gruppenbericht
Mittwoch, 26. März 1997, 15:30–16:00, HS D
Polarization of projectile-like fragments at 500MeV/A ∗ — •M. Schäfer1, W.-D. Schmidt-Ott1, T. Dörfler1, T. Hild1, T. Pfeiffer1, R. Collatz2, H. Geissel2, M. Hellström2, Z. Hu2, H. Irnich2, N. Iwasa2, M. Pfützner2, E. Roeckl2, M. Shibata2, B. Pfeiffer3, K. Asahi4, H. Izumi4, H. Ogawa4, H. Sato4, H. Ueno5, and H. Okuno6 — 1II. Physikalisches Institut, Universität Göttingen, Bunsenstr. 7-9, D-37073 Göttingen — 2Gesellschaft für Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt — 3Institut für Kernchemie, Universität Mainz, D-55099 Mainz — 4Department of Applied Physics, Tokyo Insitute of Technology, Oh-okayama, Tokyo 152, Japan — 5Department of Physics, Osaka University, Toyonaka, Osaka 560, Japan — 6Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan
For the measurement of the polarization of projectile-like fragments a 500MeV/A 40Ca beam provided by the GSI-SIS facility was impinging on a 4g/cm2 Be-target at the entrance of the FRS. 37K fragments were separated. By tilting the primary beam on the target and adjusting the FRS entrance slits only one side of the fragments’ transverse momentum distribution was selected. In addition, asymmetric slits mounted in the dispersive focal plane of FRS were used to make cuts in the Goldhaber (GH) distribution. At the final focus the fragments were stopped in a single KBr crystal mounted in a 0.5T static magnetic field. NMR techniques were applied to achieve spin-reversal of 37K. Two scintillator stacks above and below the stopper were used to measure the up to down ratio of emitted β-particles. By making use of the known spatial asymmetry of the emitted positrons the polarization could be deduced.
For 37K a polarization of about 1% was seen and had the same sign for large and small values of momentum of the GH distribution. The sign of the polarization changed however, when the inclination of primaries on the target was reversed. We also investigated 35K and 39Ca fragments. For the latter no polarization was seen within the statistical limits.
The experimental results are compared to results of Monte Carlo calculations, using the polarization model [1] combined with the particle evaporation model [2].
[1] H. Okuno, K. Asahi, H. Ueno, H. Izumi, H. Sato, M. Adachi, T. Nakamura, T. Kubo, N. Inabe, A. Yoshida, N. Fukunishi, T. Shimoda, H. Miyatake, N. Takahashi, W.-D. Schmidt-Ott and M. Ishihara, Phys. Lett. B 354 (1995), 41
[2] J. J. Gaimard and K.-H. Schmidt, Nucl. Phys. A 531 (1991), 709 ∗ supported by BMBF under contract 06Gö667/TP3