Photograph Abstract Among the ground state charmed hadrons the 0 c is the least known particle. It has so far been observed in a few decay channels only and with low statistics. Using a data sample of 1993 from the CERN hyperon beam experiment WA89 the 0 c has been found in 7 decay modes which cover nal states with ? , ? and. We present a measurement of the 0 c mass and its lifetime.

The polarization of 0 , 0 , + and ? inclusively produced in ? induced interactions at 330 GeV has been measured in the experiment WA89 at CERN. This is the rst measurement of polarization of baryons produced by a hyperon beam. No polarization of 0 is observed, as was also the case in proton beam data. At transverse momenta of about 1 GeV/c 0 and + show little polarization, signiicantly lower than in the proton beam data, while ? have a polarization comparable to the polarization of 0 produced in proton beams.

We report on the observation of a KSp resonance signal at a mass of 1765±5 MeV/c , with intrinsic width Γ = 108 ± 22 MeV/c, produced inclusively in Σ-nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF > 0.7, in this region its production cross section rises approximately linearly with (1 − xF ), reaching BR(X → KSp) · dσ/dxF = (5.2 ± 2.3) μb per nucleon at xF = 0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ state. No corresponding peaks were observed in the Kp and Λπ mass spectra. PACS. 25.80.-e Mesonand hyperon-induced reactions – 13.60.Rj Baryon production – 14.20.Jn Hyperons a Deceased b Supported by Deutsche Forschungsgemeinschaft, contract number 436 RUS 113/465/0-2(R), and Russian Foundation for Basic Research under contract number RFFI 00-02-04018. c Now at TRIUMF, Vancouver, B.C., Canada V6T 2A3 d Now at Thomas Jefferson Lab, Newport News, VA 23606, USA. e Now at Instituto de Fisica, Universidad Autonoma de San Luis Potosi, S.L.P. 78240 Mexico. f Now at Fraunhofer Institut für Solar Energiesysteme, D79100 Freiburg, Germany. g Now at Physik Department E18, Technische Universitaät München, D-85747 Garching, Germany. h Now at Fakultät für Physik, Universität Freiburg, Germany. i Now at Department of Physics, University of Utah, Salt Lake City, Utah, USA.

We present a comprehensive study of the inclusive production of V0V0 pairs (V0=Λ, Λ̄ or KS ) by Σ- and π- of 340 GeV/c momentum and neutrons of 260 GeV/c mean momentum in copper and carbon targets. In particular, the dependence of the xF spectra on the combination of beam-particle and produced V0V0 pair is investigated and compared to predictions obtained from PYTHIA and QSGM calculations. The data and these predictions differ in many details, the agreement can at best be termed as qualitative. A signal from decays of the tensor meson f’2(1525) was observed in the KS KS mass distribution and inclusive production cross sections were measured. No signal was found from the double-strange H-dibaryon decaying to ΛΛ.

We present the measurement of the lifetime of the 0 c we have performed using three independent data samples from two diierent decay modes. Using a ? beam of 340 GeV/c we have obtained clean signals for the 0 c decaying into ? K ? + + and ? + ? + , avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the 0 c is demonstrated by a clear enhancement of the signals at short but nite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be 0 c =55 +13 ?11 (stat) +18 ?23 (syst) fs. This makes the 0 c the shortest living weakly decaying particle observed so far. The short value of the lifetime connrms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.

We report on the observation of a KSp resonance signal at a mass of 1765 ± 5 MeV/c 2, with intrinsic width Γ = 108 ± 22 MeV/c 2, produced inclusively in Σ--nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra.

CERN experiment WA89 has studied charmed particles produced by a ? beam at 340GeV=c on nuclear targets. Production of particles which have light quarks in common with the beam is compared to production of those which do not. Considerable production asymmetries between D ? and D + , D ? s and D + s and c and c are observed. The results are compared with pion beam data and with theoretical calculations.

We report on a high-statistics search for the Theta(1540)(+) resonance in Sigma(-)-nucleus collisions at 340 GeV/c. No evidence for this resonance was found in our data sample which contains 13 million K-s(0)->pi(+)pi(-) decays above background. For the decay channel Theta(+)-> K(s)(0)p and the kinematic range x(F)> 0.05, we find the production cross section to be BR(Theta(+)-> K(s)(0)p)sigma(0)< 1.8 mu b per nucleon at 99% C.L.

M.I. Adamovich, a Yu.A. Alexandrov, b S.P. Baranov, D. Barberis, M. Beck, C. Bérat, W. Beusch, M. Boss, S. Brons, c W. Brückner, M. Buénerd, C. Busch, C. Büscher, F. Charignon, J. Chauvin, E.A. Chudakov, d U. Dersch, F. Dropmann, J. Engelfried, e F. Faller, f A. Fournier, S.G. Gerassimov, 1, g M. Godbersen, P. Grafström, Th. Haller, M. Heidrich, E. Hubbard, R.B. Hurst, K. Königsmann, g I. Konorov, 1, h N. Keller, K. Martens, i Ph. Martin, S. Masciocchi, j R. Michaels, d U. Müller, H. Neeb, D. Newbold, C. Newsom, S. Paul, h J. Pochodzalla, k I. Potashnikova, B. Povh, R. Ransome, Z. Ren, M. Rey-Campagnolle, l G. Rosner, m L. Rossi, H. Rudolph, C. Scheel, L. Schmitt, h H.-W. Siebert, n A. Simon, g V.J. Smith, o O. Thilmann, A. Trombini, E. Vesin, B. Volkemer, K. Vorwalter, Th. Walcher, G. Wälder, R. Werding, E. Wittmann, and M.V. Zavertyaev b

We report on a high statistics search for the ${\ensuremath{\Xi}}^{\ensuremath{-}\ensuremath{-}}(1860)$ resonance in ${\ensuremath{\Sigma}}^{\ensuremath{-}}$-nucleus collisions at $340\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$. No evidence for this resonance is found in our data sample which contains 676000 ${\ensuremath{\Xi}}^{\ensuremath{-}}$ candidates above background. For the decay channel ${\ensuremath{\Xi}}^{\ensuremath{-}\ensuremath{-}}(1860)\ensuremath{\rightarrow}{\ensuremath{\Xi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ and the kinematic range $0.15<{x}_{F}<0.9$ we find a $3\ensuremath{\sigma}$ upper limit for the production cross section of 3.1 and $3.5\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{b}$ per nucleon for reactions with carbon and copper, respectively.

~The WA89 Collaboration ! Moscow Lebedev Physics Institute, RU-117924 Moscow, Russia Genoa University/INFN, Dipartimento di Fisica, I-16146 Genova, Italy Max-Planck-Institut fu ̈r Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany Grenoble ISN, F-38026 Grenoble, France CERN, CH-1211 Gene `v 23, Switzerland Universität Heidelberg, Physikalisches Institut, D-69120 Heidelberg, Germany Universität Mainz, Institut für Kernphysik, D-55099 Mainz, Germany University of Bristol, Bristol, United Kingdom University of Iowa, Iowa City, Iowa 52242 Rutgers University, Piscataway, New Jersey 08854 NIKHEFF, 1009 D8 Amsterdam, The Netherlands ~Received 21 September 2001; published 5 April 2002 !

We report on a measurement of the inclusive cross sections of Λ, Λ, KS , Ξ + and Ω− production by Σ−and π−of 345 GeV/c momentum and by neutrons of 260 GeV/c mean momentum in copper and carbon. The differential cross sections as function of pt show a distinct non-gaussian behavior above 1.2 (GeV/c). A comparison of the xF -dependence of Λ, Λ and K production with calculations using PYTHIA and the QGSM model is discussed. a Supported by Deutsche Forschungsgemeinschaft, contract number DFG 436 RUS 113/465/0-2(R), and Russian Foundation for Basic Research under contract number RFFI 00-0204018 b Now at TRIUMF, Vancouver, B.C., Canada V6T 2A3 c Now at Thomas Jefferson Lab, Newport News, VA 23606, USA d Now at Instituto de Fisica, Universidad Autonoma de San Luis Potosi, S.L.P. 78240 Mexico e Now at Fraunhofer Inst. für Solar Energiesysteme, 79100 Freiburg, Germany f Now at Technische Universität München, Garching, Germany g Now at Fakultät für Physik, Universität Freiburg, Germany h Now at Departament of Physics and Astronomy, SUNY at Stony Brook, NY 11794-3800, USA i Now at Max-Planck-Institut für Physik, München, Germany j University of Iowa, Iowa City, IA 52242, USA

We have measured the production of strange baryons and antibaryons in 340-GeV/c Sigma(-)+C and 260-GeV/c n+C interactions. The single x(F) distributions show the expected leading particle effect, and the single p(t)(2) distributions show a distinct nonthermal behavior. The x(F) distributions of Lambda-Lambda pairs indicate two different phase space distributions for the two coincident baryons. On the other hand two (Lambda) over bar 's show identical distributions. Momentum conservation during the formation process may represent a significant source for the observed behavior.

We report on a measurement of the inclusive production cross sections for Z(+/-), Z(1385)(+/-), Z(1660)(+/-) and (Σ) over bar ((1) over bar 385) in the CERN hyperon beam experiment WA89, using a Sigma(-)/pi(-) beam of 345 GeV/c momentum and neutrons of 260 GeV/c mean momentum. A strong leading particle effect was observed for all negative Sigma and Sigma*. The results are compared with predictions from phenomenological models.

Cross section ratios for deep-inelastic scattering from N-14 and He-3 with respect to H-2 have been measured by the HERMES experiment at DESY using a 27.5 GeV positron beam. The data cover a range in the Bjorken scaling variable x between 0.013 and 0.65, while the negative squared four-momentum transfer Q(2) Varies from 0.5 to 15 GeV2. The data are compared to measurements performed by NMC, E665, and SLAG on He-4 and C-12, and rue found to be different for x < 0.06 and Q(2) < 1.5 GeV2. The observed difference is attributed to an A-dependence of the ratio R = sigma(L)/sigma(Gamma) of longitudinal to transverse deep-inelastic scattering cross sections at low x and low Q(2). (C) 2000 Elsevier Science B.V. All rights reserved.

Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H, 3He, and 14N targets has been studied by the HERMES experiment at squared four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20 GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark- antiquark fluctuations with the nuclear medium.

Spin-polarized atomic hydrogen is used as a gaseous polarized-proton target in high-energy and nuclear-physics experiments operating with internal beams in storage rings. When such beams are intense and bunched, this type of target can be depolarized by a resonant interaction with the transient magnetic field generated by the beam bunches. This effect has been studied with the HERA positron beam in the HERMES experiment at DESY. Resonances have been observed and a simple analytic model has been used to explain their shape and position. Operating conditions for the experiment have been found where there is no significant target depolarization due to this effect. [S0031-9007(98)08340-9].

Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized hydrogen and He-3 targets, in the kinematic range 0.023 < x < 0.6 and 1 GeV2 < Q(2) < 10 GeV2. Polarized quark distributions are extracted as a function of x for up (u + (u) over bar) and down (d + (d) over bar) flavors. The up quark polarization is positive and the down quark polarization is negative in the measured range. The polarization of the sea is compatible with zero. The first moments of the polarized quark distributions are presented. The isospin non-singlet combination dq, is consistent with the prediction based on the Bjorken sum rule. The moments of the polarized quark distributions are compared to predictions based on SU(3)(f) flavor symmetry and to a prediction from lattice QCD. (C) 1999 Published by Elsevier Science B.V. All rights reserved.