Darmstadt 2008 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 38: Instrumentation und Anwendungen II

HK 38.7: Talk

Thursday, March 13, 2008, 18:15–18:30, 2D

Investigations of the properties of the GSI Pion Beam — •Christian Rehm for the HADES collaboration — II. Physikalisches Institut, JLU Giessen

HADES is a detector system at GSI for lepton pair spectroscopy in heavy ion collisions and elementary reactions. The physics program on elementary reactions includes experiments with π beams. Before using π beams in a production run, the focussing properties of this beam have to be understood. Beam transport simulations indicated that an additional quadrupole in front of the HADES target would improve the quality of the focus. This was verfied in a test experiment.

The pions were produced by collisions of ¹²C with a Be target. From the momentum distribution, pions with a momentum of 1.17 GeV/c ± 4% were selected by the beamline. Two hodoscopes (64 channel strip read out with linear multianode photomultipliers with a granularity of 2mm) were developed and installed at an intermediate focal plane to determine the momenta of the pions to an accuracy of about 0.1% from the position information.

At the HADES target position, segmented Nb/Be and Cu targets were used. A fiber detector in front and two scintillating strip detectors behind the target served to track the beam particles. Tracks of reaction products were reconstructed with the HADES Multiwire Drift Chambers. The reaction vertices provided information on the size of the beam focus which turned out to be almost independent of the π beam momentum. Results of the test beam time will be presented.