Measurement of polarization observables of the associated strangeness production in proton proton interactions
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- The COSY-TOF Collaboration, Hauenstein, F., Borodina, E. et al. Eur. Phys. J. A (2016) 52: 337. doi:10.1140/epja/i2016-16337-1
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The \( \Lambda\) polarization, the analyzing power, and the \( \Lambda\) spin transfer coefficient of the reaction pp\( \rightarrow\)pK+\( \Lambda\) were measured at beam momenta of 2.70GeV/c and 2.95GeV/c corresponding to excess energies of 122MeV and 204MeV. While the analyzing power and the spin transfer coefficient do not change significantly with the excess energy, the \( \Lambda\) polarization varies strongly and changes its sign. As this is the first measurement of polarization observables below an excess energy of 200MeV, the change of the sign of the \( \Lambda\) polarization was not observed before. The high statistics of the data ( \( \approx\) 200 k events for each momentum) enables detailed studies of the dependence of the \( \Lambda\) polarization and the analyzing power on the center-of-mass momentum of the particles. The results of the spin transfer coefficient are in qualitative agreement with the DISTO experiment. The \( \Lambda\) polarization data of 2.95GeV/c are only conform with the DISTO experiment, while both the 2.70GeV/c and 2.95GeV/c data differ strongly from all previous measurements, whether exclusive or inclusive.