THE EUROPEAN HYBRID SPECTROMETER

The final version of the European hybrid spectrometer (EHS) is described. EHS was used in the NA27 experiment to study charm particles produced in View the MathML source interactions. A rapid cycling, high resolution bubble chamber (LEBC) produced bubbles of 17 \u3bcm diameter which were measured with a precision of 2.5 \u3bcm. Short-lived charm particles are observed with an efficiency up to 90% (D\ub1). The spectrometer accepts 70% of all particles produced, including approximately 100% of those in the forward hemisphere and the momenta of charged particles are measured to better than 1% over the whole momentum range. The charged particle identification detectors give information on 84% of the spectrometer tracks, half of which obtain unique identification. Two lead glass detectors measure the energy of electromagnetic showers such that the \u3c00 mass distribution has a fwhm of View the MathML source. Hadronic showers are measured with two iron/scintillator calorimeters. The mass resolutions are 3.0, 0.9 and 11 View the MathML source for K0, \u39b0 and D 12 charged particles respectively. The D0 mass is measured to be (1865.1 \ub1 1.8 \ub1 0.8

LAMBDA(c) PRODUCTION CHARACTERISTICS IN PROTON PROTON INTERACTIONS AT 400-GeV/c

We present the measurements of the Λc production cross section in proton-proton interactions at View the MathML source and give new limits on the exclusive branching ratio Λc→pK+π−

D MESON LIFETIMES

We present the final results on the D-meson liftime measurements obtained by the NA27 experiment. From a sample of 145 D0/D0bar and 149D\ub1 decays, we have measured \u3c4(D0)=(4.6+0.6 120.5) 710 1213 s, \u3c4(D\ub1)=(11.2+1.4 121.1) 710 1213 s, with a ratio R= \u3c4(D\ub1)/ \u3c4(D0)=2.4\ub10.4

D MESON PRODUCTION FROM 400-GeV/c p p INTERACTIONS

We have measured the inclusive production properties of D and bar D mesons produced from pp interactions at sqrt(s)=27.4 GeV. The differential production cross section is well represented by the empirical form, and the inclusive D/bar D cross section \u3c3(D/ barD) is (30.2\ub13.3) \u3c9b. The QCD fusion model predicts D/bar D production which is in good agreement with our data except for the magnitude of the cross section which depends sensitively on the assumed mass of the charm quark