The azimuthally symmetric WASA detector and the polarised proton beam of COSY, enable investigations of energy and angular dependence of the beam analysing power in the pp → ppη reaction. The aim of ...the studies is the determination of the partial wave contributions via interference terms which are inaccessible from spin averaged observables. The partial wave decomposition is mandatory for the understanding of the reaction dynamics and for the determination of the η-proton interaction, independently of the theoretical paradigm used.
Measurements of the analyzing power for the pp-->pp eta reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with zero, ...implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S11(1535) resonance is predominantly due to the exchange of the pi meson between the colliding nucleons.
The azimuthally symmetric WAS A detector and the polarised proton beam of COSY, enable investigations of energy and angular dependence of the beam analysing power in the pp arrow right ppeta ...reaction. The aim of the studies is the determination of the partial wave contributions via interference terms which are inaccessible from spin averaged observables. The partial wave decomposition is mandatory for the understanding of the reaction dynamics and for the determination of the eta-proton interaction, independently of the theoretical paradigm used.
Understanding of the production processes of the
η
meson will strongly rely on the precise determination of spin observables. So far these observables have been determined only for few excess ...energies and with low statistics (Winter et al. Eur. Phys. J.
A18
, 355
2003
; Czyzykiewicz et al. Phys. Rev. Lett.
98
, 122003
2007
; Balestra et al. Phys. Rev.
C69
, 064003
2004
). In the year 2010 WASA detector was used for the measurement of the
p
⃗
p
→
ppη
reaction with the polarized proton beam of COSY (Moskal and Hodana J. Phys. Conf. Ser
295
, 012080
2011
). The measurement was done for the excess energy of Q = 15 MeV and Q = 72 MeV. In total about 10
6
events corresponding to the
p
⃗
p
→
ppη
reaction have been collected.
We present new data for angular distributions and on the cross section ratio of the p+d →
3
He +
η
reaction at excess energies of
Q
= 48.8 MeV and
Q
= 59.8 MeV. The data have been obtained at the ...WASA-at-COSY experiment (Forschungszentrum Jülich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between
Q
= 20 MeV and
Q
= 60 MeV, which might indicate the variation of the production mechanism within this energy interval.
We present new data for angular distributions and on the cross section ratio of the p+d -> He-3+eta reaction at excess energies of Q - 48.8MeV and Q - 59.8 MeV. The data have been obtained at the ...WASA-at-COSY experiment (Forschungszentrum Julich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.
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![Study of the [eta] meson pr...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1742-6588/small "Study of the [eta] meson production with the polarised proton beam")
