Tübingen 2003 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 28: Elektromagnetische und hadronische Proben IV

HK 28.3: Vortrag

Mittwoch, 19. März 2003, 11:30–11:45, F

Isospin Symmetry Breaking: Experimental Observation — •Bidyut Roy and Hartmut Machner — IKP, FZ Juelich

The isospin symmetry breaking (ISB) of strong interaction is one of the most interesting problems of nuclear and particle physics. In quark level this symmetry breaking is believed to be associated with the mass difference between the up and down quarks. In the pionic sector, the isospin symmetry violation could be responsible for the mixing of π^o and η mesons and also that of ρ^o and ω. However, there is little direct evidence for such violation in nuclear reactions. Experiments have been performed at COSY, Juelich to investigate this aspects by studying simultaneously the two reactions p+d→ ³H+π⁺ and p+d→ ³He+π^o at beam energies close to corresponding η production threshold. The beam momentum dependence of the ratio of cross section of these two reactions would be indicative of ISB, if any. The present measurement reports observation of strong ISB effect due to π^o − η mixing. The results will be presented.