We study the polarizations with respect to the normal to the production plane for a very clean sample of 27217 LAMBDA0/LAMBDA0BAR hyperons produced in 230 GeV/c pi--Cu interactions. In general we find P(LAMBDA0) almost-equal-to P(LAMBDA0BAR) almost-equal-to 0 except for x(F) > 0, p(T) > 1 GeV/c where P(LAMBDA(0)) = -0.28 +/- 0.09(stat.) +/- 0.02(syst.).

In the CERN NA32 experiment a high-resolution silicon vertex detector and a purely topological approach were used to collect 557 events consistent with associated charm production, both decay vertices being observed. The pseudorapidity gap distribution appears to be nearly independent of the nature of the charmed hadrons. This distribution is reasonably consistent with the next-to-leading order QCD calculations. However the azimuthal-angle distribution is significantly broader than the above predictions.

In the CERN NA32 experiment a high-resolution silicon vertex detector and a purely topological approach were used to collect a clean sample of A(c)+ decays into pK-pi+ with or without additional neutral particles. We study the subresonant structure of the LAMBDA(c)+ peak obtaining BR (LAMBDA(c)+ --> pKBAR*0(892)) = 0.35(-0.07)0.06 +/-0.03 with respect to the total LAMBDA(c)+ --> pK-pi+ decay. We also determine branching ratios for some channels with neutral decay products, namely BR(LAMBDA(c)+ --> pK-pi+pi0)=0.73+/-0.12+/-0.05 and BR(LAMBDA(c)+ --> pK-pi+pi0pi0)=0.16+/-0.07+/-0.03, again with respect to the total LAMBDA(c)+ --> pK-pi+decay.

Using data from the NA32 experiment at CERN we have studied the Λ+c decays containing a Σ+ among the decay products. The interactions of 230 GeV π− with a Cu target were analysed using a precise vertex telescope (charge-coupled devices and silicon microstrip detectors) and the ACCMOR spectrometer. We have found eleven Λ+c→Σ+π+π−, one Λ+c→Σ+K+K−, two Λ+c→Σ+K+π− and one Λ+c→Σ+π+π−π+π− decays practically without any backgroun d. We have measured the branching ratios with respect to the Λ+c→pK−π+ channel.

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(D0) = 145.39±0.06±0.03 MeV. We have also obtained a 90% CL upper limit to γ(D∗+) of 131 keV.

We combine highly complementary information on branching fractions of charmed mesons D0, D+ and D(s)+ coming from two experiments both yielding double-charm samples. The NA32 experiment provided exclusive branching fractions for channels with at least two charged decay products while a recent Mark III paper provides results on inclusive charm decay properties. The knowledge of channels with K0's in the former is used to recalculate the charged multiplicity distribution in the latter. We obtain [n(ch)] = 2.25 +/- 0.08 for D0, [n(ch)] = 1.96 +/- 0.08 for D+ and [n(ch)] = 2.41 +/- 0.38 for D(s)+. In tum the knowledge of the charged multiplicity improves the overall normalization of exclusive branching fractions. This reanalysis yields model-independent results for charmed mesons. In particular we obtain branching fractions for 16 D(s)+ decay channels including BF(D(s)+ --> phi-pi+) = (4.4(-1.8)+2.3)%.

We 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: 60D s + →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\({{D^0 } \mathord{\left/ {\vphantom {{D^0 } {\bar D^0 }}} \right. \kern-\nulldelimiterspace} {\bar D^0 }}\) sample were produced via chargedD* state. For all charmed mesons we determine the total production cross-section and study thex F andp t 2 distributions.

We 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: 60 D(s)+ --> K+ K- pi+, 543 D0 --> K- pi+ and K- pi+ pi- pi+ as well as 249 D+ --> K- pi+ pi+ (or charge conjugate). 147 mesons out of our D0/DBAR0 sample were produced via charged D* state. For all charmed mesons we determine the total production cross-section and study the x(F) and p(t)2 distributions.

Results are presented from a test in the CERN SPS North Area of a prototype of the DELPHI microvertex detector. Full-sized modules built up from prototype ac-coupled detectors and VLSI readout electronics were used. The spatial resolution of the detectors equipped with prototype VLSI chips was measured to be 6.5 μm. The system aspects, including the readout, were found to work well. Extrapolating to the final components we expect to achieve a measurement precision of 5 μm with the DELPHI microvertex detector.

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, ∼90D s + decays in 11 channels as well as 160Λ s c and 18 decay channels ofD+. For theD s + , we measure the branching fractions within a subset of 16 three- and five-prong decay channels. For theΛ s c , we determine the branching fractions within a sample of 11 three- and five-prong decay channels, nearly all involving a proton.

Data on the production of the neutralK*(892) resonances at lowpt by 200 GeVK− and π− is compared with the predictions of various models based on the quark parton model of hadrons.

We have observed four unambiguous decays of the charmed strange baryon Ξ c o in the NA32 experiment at CERN. Charge- coupled devices and silicon microstrip detectors were used to reconstruct the decay mode Ξ c o → pK − K ∗ (892) o seen in events produced by the interaction of 230 GeV/ c negative poins and kaons on a copper target. We present the first measurement of the lifetime of the Ξ c o , together with a determination of its mass and production cross section. The resonant components of the Ξ c o decay are studied. We use our earlier measurement of the mass of the Ξ c + in the determination of the isospin mass splitting of the Ξ c states.

Abstract We have observed four unambiguous decays of the charmed strange baryon Ξco in the NA32 experiment at CERN. Charge- coupled devices and silicon microstrip detectors were used to reconstruct the decay mode Ξ c o → pK − K ∗ (892) o seen in events produced by the interaction of 230 GeV/c negative poins and kaons on a copper target. We present the first measurement of the lifetime of the Ξco, together with a determination of its mass and production cross section. The resonant components of the Ξco decay are studied. We use our earlier measurement of the mass of the Ξc+ in the determination of the isospin mass splitting of the Ξc states.

The production of the neutralK− (892) resonances by 200 GeVK− andπ− has been studied over the kinematic range 0.0xfpt22. Longitudinal and transverse momentum distributions are presented. In addition the decay angular distributions inK− fragmentation to <img src="/fulltext-image.asp?format=htmlnonpaginated&src=KJ2RL2416Q57475P_html\10052_2005_Article_BF01560251_TeX2GIFIE2.gif" border="0" alt=" $$\bar K^{0*} $$ " /> have been investigated.

We present the final results on the measurement of the masses and lifetimes of the mesonsD0,D+ andD s + in the NA32 experiment at the CERN SPS, using silicon microstrip detectors and charge-coupled devices for vertex reconstruction. We measure the following lifetimes:\(\tau _{D^0 } = 3.88 \pm _{0.21}^{0.23} \cdot 10^{ - 13} s\) using a sample of 479D°→K−π+π−π+ and 162D°→K−π+ decays;\(\tau _{D^ + } = 10.5 \pm _{0.72}^{0.77} \cdot 10^{ - 13} s\) with a sample of 317D+→K−π+π+ decays;\(\tau _{D_s^ + } = 4.69 \pm _{0.86}^{1.02} \cdot 10^{ - 13} s\) with a sample of 54D s + →K+K−π+ decays. We measure the following masses:mD0=1864.6±0.3±1.0 MeV,mD+=1870.0±0.5±1.0 MeV and\(m_{D_s^ + } \)=1967.0±1.0±1.0 MeV.

We present the final result on the measurement of the lifetime of the Λc-baryon from a sample of Λc-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 Λc in five different decay modes. A sample of 101 unambiguous decays of Λc→pK−π+ (and charge conjugate) above a background of 7 events is used for the Λc mass and lifetime measurement. The mean Λc lifetime is determined to be 1.96−0.20+0.23×10−13s and the Λc mass to be 2285.8±0.6±1.2 MeV/c2.