Berlin 2005 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 22: Postersitzung
HK 22.7: Poster
Montag, 7. März 2005, 16:30–18:00, TU MA141
Analysing power measurements for the p→p→ ppη reaction at COSY-11 — •Rafał Czyżykiewicz — IKP, FZ-Jülich, Germany — Jagellonian University, Kraków, Poland
Supported by FZ-Jülich and DAAD.
It is generally expected that in NN collisions the
η meson is predominantly
created via the mesonic excitation of the S11(1535) resonance,
and its subsequent decay into a proton-η system.
At present it is still not established
what the relative production amplitudes for the S11(1535)
resonance are.
Among the available models Nakayama et al. [1]
postulated a dominance of π and η as exchange mesons, while
Fäldt and Wilkin [2] found a main contribution originating from the
vector meson exchange.
Both models are in good agreement with unpolarised observables, however
they differ significantly when
predicting polarisation observables – such as the analysing power Ay.
In this contribution we report on the COSY-11 measurements of
Ay for the p→p→ ppη reaction [3] determined at different
close-to-threshold energies. The techniques of the polarisation
determination at COSY-11 and their comparison with the results [4,5]
obtained
by means of the other polarimeters operating at COSY will be presented.
[1] K. Nakayama et al., Phys. Rev. C 65 (2002) 045210.
[2] G. Fäldt and C. Wilkin, Phys. Scripta 64 (2001) 427.
[3] COSY-11: P. Winter et al., Phys. Lett. B 544 (2002) 251;
erratum-ibid. B 553 (2003) 339.
[4] B. Lorentz, FZ-Jülich, private communication (2003).
[5] K. Ulbrich, Bonn University, private communication (2003).