P. Gras

Measurement of the mass and width of the charmed meson D∗+ (2010)

Abstract Using a high-resolution silicon vertex detector we have observed a very clean signal of 127 D∗+. After a careful study of the experimental resolution of our apparatus we have measured m( D ∗++ )−m( D 0 ) = 145.39±0.06±0.03 MeV . We have also obtained a 90% CL upper limit to γ(D∗+) of 131 keV.

Production of the charmed baryon Λ+c in π−Cu and K−Cu interactions at 230 GeV

Abstract We present results from the NA32 experiment at CERN on the production characteristics of the charmed baryon Λ + c in 230 GeV π − Cu and K − Cu interactions. A high resolution vertex detector consisting of change-coupled devices and silicon microstrip detectors allowed the selection of a very clean sample of 154 Λ + c → pK − π + (and charge conjugate) decays. Results on differential and integrated cross sections are given.

Measurement of the lifetime of the charmed baryon Λc

Abstract We present results on a sample of Λc decays obtained in the NA32 experiment in 1985 using charge-coupled devices for vertex reconstruction and a trigger on Λc→pK−π+ (and charge conjugate). We observe a distinct peak at the Λc mass on zero background. The lifetime of the Λc is determined to be (1.4±0.30.5±0.3)x10−13 s based on a sample of 14 events.

Measurement of various decay modes of charmed particlesD0,D+,D s + andΛ s c

In the CERN NA 32 experiment a high-resolution silicon vertex detector and a purely topological approach have been used to investigate various decays of charmed particles. We observe ∼620 fully reconstructed decays ofD0 in 12 channels and determine the branching ratios. For fourD0 decay modes involving a single (unseen) π0 the small and narrowD*+−D0 mass difference is used to measure their branching ratios. We also observe ∼280 fully reconstructedD+ decays in 10 channels, ∼90Ds+ decays in 11 channels as well as 160Λsc and 18 decay channels ofD+. For theDs+, we measure the branching fractions within a subset of 16 three- and five-prong decay channels. For theΛsc, we determine the branching fractions within a sample of 11 three- and five-prong decay channels, nearly all involving a proton.

Production ofD, D* andD s mesons in 200 GeV/c π−K− andp-Si interactions

The NA 32 experiment at the CERN SPS has collected 38 million hadronic interactions with incident 200 GeV/c π−,K− andp beam. Using a segmented silicon active target and a telescope of high resolution silicon microstrip counters we have selected fully reconstructedD0→K−π+,D0→K−π+π+π−,D+→K−π+π+,Ds+→K−K+π+π+ and charge conjugate decays. The integrated cross-sections forDo,D+D*+ andDs+ meson production and the dependence of the cross-section on longitudinal and transverse momentum of theD are presented.

Production properties of D0, D+, D*+ and D(s)+ in 230-GeV/c pi- and K- Cu interactions

AbstractWe have studied the hadronic production of charmed mesons in the NA 32 experiment at CERN. A special trigger together with a high resolution vertex detector consisting of charge coupled devices and silicon microstrip detectors allowed the selection of very clean samples of charmed mesons. We have collected 852 fully reconstructed decays: 60Ds+→K+K−π+, 543D°→K−π+ andK−π+π−π+ as well as 249D+→K−π+π+ (or charge conjugate). 147 mesons out of our

First measurement of the lifetime of the charmed strange baryon Ξc0

{{D^0 } \mathord{\left/ {\vphantom {{D^0 } {\bar D^0 }}} \right. \kern-\nulldelimiterspace} {\bar D^0 }}

A Study of the transverse polarization of Lambda0 and Anti-lambda0 hyperons produced in pi- Cu interactions at 230-GeV/c

sample were produced via chargedD* state. For all charmed mesons we determine the total production cross-section and study thexF andpt2 distributions.