Darmstadt 2008 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 34: Postersitzung
HK 34.4: Poster
Thursday, March 13, 2008, 14:00–16:00, Poster C3
Precision Measurement of the η Mass at COSY — •Michael Papenbrock, Paul Goslawski, Alfons Khoukaz, Timo Mersmann, Malte Mielke, Tobias Rausmann, and Alexander Täschner — Institut für Kernphysik, Westfälische Wilhelms-Universität, Münster, Germany
Recent measurements on the η meson mass performed at different experimental facilities (i.e. COSY-GEM, MAMI, CLEO, KLOE, NA48) resulted in very precise data but differ by up to more than eight standard deviations, i.e. 500 keV/c2. Therefore, new precise experiments are required in order to clarify the situation.
In previous unpolarized experiments at the magnetic spectrometer ANKE/COSY it was possible to identify the production threshold of the two-body reaction dp → 3Heη with very high accuracy with respect to the excess energy Q. The COSY beam was slowly and linearly ramped over 300 s. In order to convert the precise value Q0 into the mass of the η meson, the beam energy has to be determined with high accuracy. Recently the SPIN@COSY collaboration has shown that this can be achieved for vector polarized deuterons by the spin resonance method. Accordingly, it is planned to perform a dedicated precision measurement to determine η mass at ANKE using the d→p → 3Heη reaction with a polarized beam. The experiment aims at a total uncertainty of < 50 keV/c2 on the η mass.
The methods involved in this measurement as well as preliminary estimations on the results will be shown in this presentation.
Supported by the COSY-FFE program