Study of p(-) p1p- p and p(-)p 1 p(-) p at :s = 18.9 GeV with the COMPASS experiment

The COMPASS experiment at CERN studies diffractively produced states in the light quark sector with unprecedented statistics. The observation of f0(1500)/f'2(1525) decaying to in 2008 data with incoming negative pion beam at 190 GeV/c poses the question whether it is produced centrally or formed by the decay of a heavier diffractively produced p1 (1800)/p2 (1880). To decide, a dedicated amplitude analysis which includes different production mechanisms is formulated and compared with one which was used to fit centrally produced resonances including f0(1500) by the WA102 experiment. Unbinned mass-dependent log-likelihood fitting methods may serve to solve the ambiguities which are present in binned, mass-independent partial wave analyses.