Abstract. The leading two meson doorway contributions to the reaction tip ~ r due to K*/( and pp intermediate states are calculated beyond unitarity approximation. The dependence of the results on the off-shell parametrization is explored and the effect of the finite width of the propagating mesons is estimated. The rates obtained from the rescattering mechanisms are in agreement with the data for ;0p ~ r annihilation at rest. The vertices entering the calculation do not require any unexplained OZI violation, in particular no substantial sg configuration in the nucleon appears to be needed.
The DIRAC spectrometer has been commissioned at CERN with the aim of detecting π + π − atoms produced by a 24 GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum, and the measurement of the latter with resolution around 0.6 MeV/c. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and setup performances are also given.
The spin-parity analysis of the np→ ϩ ϩ Ϫ exclusive reaction in flight is presented. The main aim is to study the ( ϩ Ϫ ) invariant mass spectrum in the region around 1500 MeV. The analysis was performed with a Breit-Wigner parametrization for all the resonant states and, for the scalar sector in the mass region below 1.2 GeV, by means of a K-matrix-like treatment. It clearly shows the need for two states, a scalar one (0 ϩϩ ) with mass and width (1522Ϯ25) MeV and (108Ϯ33) MeV, and a tensorial one (2 ϩϩ ) with mass (1575 Ϯ18) MeV and width (119Ϯ24) MeV, respectively. In addition, the analysis requires the presence of a scalar state at (1280Ϯ55) MeV, (323Ϯ13) MeV broad, and of a second vectorial one, in addition to the 0 (770) signal, with mass and width (1348Ϯ33) MeV and (275Ϯ10) MeV, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.