Rapidity dependence of charged antihadron to hadron ratios in Au+Au collisions at sqrt[s(NN)]=200 GeV

We present ratios of the numbers of charged antihadrons to hadrons (pions, kaons, and protons) in Au+Au collisions at sqrt[s(NN)]=200 GeV as a function of rapidity in the range y=0-3. While the ratios at midrapidity are approaching unity, the K(-)/K(+) and p;/p ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from mu(B) approximately 130 MeV at y=3 to mu(B) approximately 25 MeV at y=0.     

Charge density: A probe for the nuclear interaction in microscopic transport models

The transport properties of the ³⁶Ar +⁵⁸Ni system at measured with the INDRA array, are studied within the BNV kinetic equation. A general protocol of comparison between the N-body experimental fragment information and the one-body distribution function is developed using global variables, with a special focus on charge density. This procedure avoids any definition of sources and any use of an afterburner in the simulation. We shall discuss the feasibility of such an approach and the distortions induced by the finite detection efficiency and the completeness requirements of the data selection. The sensitivity of the different global observables to the macroscopic parameters of the effective nuclear interaction will be studied in detail.Received: 21 January 2003, Published online: 5 August 2003PACS: 25.70.-z Low and intermediate energy heavy-ion reactions - 24.10.-i Nuclear reaction models and methodsN. Le Neindre: Permanent address: Institut de Physique Nuclaire, IN2P3-CNRS, F-91406 Orsay cedex, France.     

MINIBALL: The first gamma-ray spectrometer using segmented,encapsulated germanium detectors for studies with radioactive beams

MINIBALL is a new spectrometer of position-sensitive Ge detectors designed for nuclear-structure studies at the REX-ISOLDE (D. Habs et al. , Prog. Part. Nucl. Phys. 38, 111 (1997)) radioactive-beam facility at CERN. It combines high efficiency and high granularity, using pulse-shape analysis and 6-fold segmented Ge detectors.Received: 24 October 2002, Published online: 17 February 2004PACS: 29.30.-h Spectrometers and spectroscopic techniques     

Measurement of high-<Emphasis Type="Italic">Q</Emphasis><Superscript>2</Superscript> charged current cross sections in <Emphasis Type="Italic">e</Emphasis><Superscript> + </Superscript><Emphasis Type="Italic">p</Emphasis> deep inelastic scattering at HERA

Cross sections for e ⁺ p charged current deep inelastic scattering at a centre-of-mass energy of have been determined with an integrated luminosity of collected with the ZEUS detector at HERA. The differential cross sections , and for are presented. In addition, has been measured in the kinematic range and . The predictions of the Standard Model agree well with the measured cross sections. The mass of the W boson propagator is determined to be from a fit to . The chiral structure of the Standard Model is also investigated in terms of the (1-y)² dependence of the double-differential cross section. The structure-function has been extracted by combining the measurements presented here with previous ZEUS results from e ^- p scattering, extending the measurement obtained in a neutrino-nucleus scattering experiment to a significantly higher Q ² region.Received: 17 July 2003, Published online: 12 November 2003 ^a supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) ^b supported by the German Federal Ministry for Education and Research (BMBF), under contract numbers HZ1GUA 2, HZ1GUB 0, HZ1PDA 5, HZ1VFA 5 ^c supported by the MINERVA Gesellschaft für Forschung GmbH, the Israel Science Foundation, the U.S.-Israel Binational Science Foundation and the Benozyio Center for High Energy Physics ^d supported by the German-Israeli Foundation and the Israel Science Foundation ^e supported by the Italian National Institute for Nuclear Physics (INFN) ^f supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and its grants for Scientific Research ^g supported by the Korean Ministry of Education and Korea Science and Engineering Foundation ^h supported by the Netherlands Foundation for Research on Matter (FOM) ⁱ supported by the Polish State Committee for Scientific Research, grant no. 620/E-77/SPUB-M/DESY/P-03/DZ 247/2000-2002 ^j partially supported by the German Federal Ministry for Education and Research (BMBF) ^k supported by the Fund for Fundamental Research of Russian Ministry for Science and Education and by the German Federal Ministry for Education and Research (BMBF) ^l supported by the Spanish Ministry of Education and Science through funds provided by CICYT ^m supported by the Particle Physics and Astronomy Research Council, UK ⁿ supported by the US Department of Energy ^o supported by the US National Science Foundation ^p supported by the Polish State Committee for Scientific Research, grant no. 112/E-356/SPUB-M/DESY/P-03/DZ 301/2000-2002, 2 P03B 13922 ^q supported by the Polish State Committee for Scientific Research, grant no. 115/E-343/SPUB-M/DESY/P-03/DZ 121/2001-2002, 2 P03B 07022     

Di-jet production in photon-photon collisionsat $\sqrt{s_{\protect\bf\mathrm{ee}}}$ from 189 to 209 GeV

Di-jet production is studied in collisions of quasi-real photons at e ⁺ e^- centre-of-mass energies from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are reconstructed using an inclusive -clustering algorithm for all cross-section measurements presented. A cone jet algorithm is used in addition to study the different structure of the jets resulting from either of the algorithms. The inclusive di-jet cross-section is measured as a function of the mean transverse energy of the two leading jets, and as a function of the estimated fraction of the photon momentum carried by the parton entering the hard sub-process, , for different regions of . Angular distributions in di-jet events are measured and used to demonstrate the dominance of quark and gluon initiated processes in different regions of phase space. Furthermore the inclusive di-jet cross-section as a function of and is presented, where is the jet pseudo-rapidity. Different regions of the - -space are explored to study and control the influence of an underlying event. The results are compared to next-to-leading order perturbative QCD calculations and to the predictions of the leading order Monte Carlo generator PYTHIA.Received: 20 December 2002, Published online: 17 October 2003     

A measurement of semileptonic B decaysto narrow orbitally-excited charm mesons

The decay chain is identified in a sample of 3.9 million hadronic Z decays collected with the OPAL detector at LEP. The branching ratio BR is measured to be for the J ^P =1⁺ (D⁰ ₁) state. For decays into the J ^P =2⁺ (D₂ ^*0) state, an upper limit of 1.4 x 10^-3 is placed on the branching ratio at the 95% confidence level.Received: 20 December 2002, Revised: 15 April 2003, Published online: 12 September 2003     

The DISTO program on meson and hyperon production

A summary of the present status of the analysis of the DISTO data on pseudoscalar and vector meson production at 3.67 GeV/c is presented. The new data on spin observales for the exclusive reaction \(\vec pp \to pK^ + \vec \Lambda \) at the three beam momenta: 3.67, 3.31 and 2.94 GeV/c are also discussed.     

Measurement of the resonant d(mu)t molecular formation rate in solid HD

Measurements of muon-catalyzed dt fusion ( d(mu)t-->4He + n + mu(-)) in solid HD have been performed. The theory describing the energy dependent resonant molecular formation rate for the reaction (mu)t + HD-->[(d(mu)t)pee](*) is compared to experimental results in a pure solid HD target. Constraints on the rates are inferred through the use of a Monte Carlo model developed specifically for the experiment. From the time-of-flight analysis of fusion events in 16 and 37 microg x cm(-2) targets, an average formation rate consistent with 0.897+/-(0.046)(stat)+/-(0.166)(syst) times the theoretical prediction was obtained.     

Directed flow of lambda hyperons in (2-6 )A GeV Au+Au collisions

Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.