1207.1076 (T. Schlüter et al.)

Resonances of the systems π-ηand π-η' in the reactions π-p
--> π-ηp and π-p --> π-η' p at COMPASS    [PDF]

T. Schlüter, D. Ryabchikov, W. Dünnweber, M. Faessler, for the COMPASS Collaboration

We describe partial-wave analyses of the systems \pi-\eta and \pi-\eta' produced in interactions of a \pi- beam (190 GeV/c) with a liquid hydrogen target. The data were recorded during the 2008 COMPASS run, where a slow recoiling proton (|t|>0.1 GeV^2) was required by the trigger. We compare analyses of the \pi-\eta and \pi-\eta' data. Significant contributions can be attributed to the resonances a_2(1320), observed in the D_+-wave, and a_4(2040), observed in the G_+-wave. Between the two systems, we find similar compositions of the even partial waves D_+ and G_+ after taking phase-space factors into account, but a much enhanced P_+-wave in \pi-\eta'. Relative phase-differences indicate a large incoherent contribution of in the P_+-wave of the \eta'\pi- system, but other interpretations are not excluded. The known resonances a_2(1320), a_4(2040) and their parameters could be extracted from the data; their branchings are found to roughly agree with predictions from \eta\eta' mixing.

View original: http://arxiv.org/abs/1207.1076