J.M. Martin

η-helium quasi-bound states

Abstract The cross section and tensor analysing power t20 of the d d → 4 He η reaction have been measured at six c.m. momenta, 10 ⩽ pη ⩽ 90 MeV/c. The threshold value of t20 is consistent with 1 2 , which follows from parity conservation and Bose symmetry. The much slower momentum variation observed for the reaction amplitude, as compared to that for the analogous pd → 3 He η case, strongly suggests the existence of a quasi-bound state in the η4He system and simple optical model fits tentatively indicate that this might also be the case for η3He.

Comparison of eta and eta ' production in the pp -g pp eta(eta ') reactions near threshold

Abstract The total cross section of the p p→p p η′ reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding η production, in good agreement with the predictions of a one-pion-exchange model.

Near threshold production of omega mesons in the p p ---> p p omega reaction

The first measurement of the pn --> dw total cross-section has been achieved at mean excess energies Q approximate to 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Julich and that of the slow spectator proton (p(sp)) from the pd --> p(sp)dw reaction in a silicon telescope placed close to the target. The cross-sections lie above those measured for pp --> ppw but seem to be below theoretical predictions.

Comparison of η and η′ production in the pp→ppη(η′) reactions near threshold

Abstract The total cross section of the p p→p p η′ reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding η production, in good agreement with the predictions of a one-pion-exchange model.

Comparison of eta and eta-prime production in the p p ---> p p eta (eta-prime) reactions near threshold

Abstract The total cross section of the p p→p p η′ reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding η production, in good agreement with the predictions of a one-pion-exchange model.

The tracking system of the ALICE dimuon spectrometer

The ALICE Muon Spectrometer is mainly dedicated to the measurement of the production of the J//spl psi/, and Y families through their decay into muon pairs, in Pb-Pb collisions. In this paper we give a description of the dimuon tracking system, mainly concentrating on the modular CSC chambers which occupy the last three stations. The R&D phase is now almost over and the production of the final modules started. A description of the main performances of the detectors based on test beam results on prototypes will be given.

Near-Threshold Production ofωMesons in thepp→ppωReaction

The first measurement of the pn --> dw total cross-section has been achieved at mean excess energies Q approximate to 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Julich and that of the slow spectator proton (p(sp)) from the pd --> p(sp)dw reaction in a silicon telescope placed close to the target. The cross-sections lie above those measured for pp --> ppw but seem to be below theoretical predictions.

Comparison of η and η′ production in the reactions near threshold

Abstract The total cross section of the p p→p p η′ reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding η production, in good agreement with the predictions of a one-pion-exchange model.