S. Barlag

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.

Precise determination of the lifetime of the charmed baryon Λc

Abstract We present the final result on the measurement of the lifetime of the Λ c -baryon from a sample of Λ c -decays obtained in the NA32 experiment at the CERN SPS using silicon microstrip detectors and charge-coupled devices for vertex reconstruction. We observe a total of 160 Λ c in five different decay modes. A sample of 101 unambiguous decays of Λ c →pK − π + (and charge conjugate) above a background of 7 events is used for the Λ c mass and lifetime measurement. The mean Λ c lifetime is determined to be 1.96 −0.20 +0.23 ×10 −13 s and the Λ c mass to be 2285.8±0.6±1.2 MeV/ c 2 .

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 }}