Production of ω mesons in proton–proton collisions

Abstract

The cross section for the production of ω mesons in proton-proton collisions has been measured in a previously unexplored region of incident energies. Cross sections of σ = (7.5 ± 1.9) µb and σ = (30.8 ± 3.4) µb (with 20% systematic uncertainties) were extracted at ǫ = 92 MeV and 173 MeV excess energy above the ω threshold, respectively. The angular distribution of the ω at ǫ = 173 MeV is strongly anisotropic,

The legacy of the experimental hadron physics programme at COSY

“…The negative value of D N N found was taken as evidence for the dominance of kaon compared to pion exchange [198], but it is important to stress that the possibility of ρ exchange was not considered in this discussion. In contrast, the early COSY-TOF differential cross section results came down in favour of non-strange meson exchange by showing that the pp → K + pΛ data have evidence for the excitation of N * isobars in the final K + Λ channel [216,217]. This approach has far less model dependence than the D N N studies.…”

“…The COSY-TOF collaboration found that the S 11 (1650) plays a prominent role near threshold and there are certainly similarities with the pp → ppη reaction, which is dominated by the analogous S 11 (1535) near threshold. Away from the threshold region the group also found evidence from the Dalitz plots for the importance of the P 11 (1710) and/or the P 13 (1710) isobars in Λ production [216,217].…”

“…In some experiments only the two final protons were measured [165,166] but in more refined approaches the π + and π − from the three-pion decay of the ω were detected in coincidence [167,168,169,170,171]. However, in all cases one is still faced with the problem of separating the ω signal from the background.…”

“…In contrast, COSY-TOF has a much larger geometric acceptance and this enabled reliable measurements to be made up to higher energies and also yielded differential distributions that are so valuable for understanding the underlying physics [215,216,217,218,219,220]. Results on hyperon production were obtained at COSY-TOF at beam momenta of 2.5, 2.59, 2.68, 2.7, 2.75, 2.85, 2.95, 3.06, 3.2, and 3.3 GeV/c, though the data in later years were much more detailed as the equipment was refined through the addition of the straw tubes mentioned in sect.…”

“…61, obtained at ANKE at 2.16 GeV with wellidentified K + mesons [213]. [210,211,212], squares are from COSY-TOF [215,216,217,218], and circles from ANKE [213,214]. Note that not all systematic uncertainties have been included.…”