Direct ϱ0 production at large pT

Abstract The production of ϱ 0 mesons in hadronic interactions is investigated at high transverse momentum (p T > 2 GeV/c). The data come from a sample of π-N interactions at 300 GeV/c obtained at the CERN Omega Spectrometer, requiring at ϱ 0 → π + π − with p T (pair) > 2 GeV/c to recoil against an opposite particle with p T (opposite) > 1 GeV/c. The signal/(signal + background) ratio of ϱ 0 production shows an increase of 38% as ξ E = p T (opposite)/p T (pair) decreases from 0.5 ξ E ξ E ⩽ 0.5. This increase is not compatible with a QCD model of parton scattering and subsequent fragmentation, and gives a strong indication that direct ϱ 0 production has been observed. Data has now been taken at 150 GeV/c and additional signatures to be used to identify direct ϱ 0 production are discussed.