Search

The production of protons, anti-protons, neutrons, deuterons and tritons in minimum bias p+C interactions is studied using a sample of 385 734 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.9 GeV/c in transverse momentum and in Feynman x from −0.8 to 0.95 for protons, from −0.2 to 0.3 for anti-protons and from 0.1 to 0.95 for neutrons. Existing data in the far backward hemisphere are used to extend the coverage for protons and light nuclear fragments into the region of intra-nuclear cascading. The use of corresponding data sets obtained in hadron-proton collisions with the same detector allows for the detailed analysis and model-independent separation of the three principle components of hadronization in p+C interactions, namely projectile fragmentation, target fragmentation of participant nucleons and intra-nuclear cascading. [ABSTRACT FROM AUTHOR]

The NA49 results on hadron production obtained in PbPb collisions at SPS energies from 20 to 158 A GeV are shown and discussed as evidence for the onset of deconfinement. The primary measures are the pion yield, the kaon-to-pion ratio and the slope parameter of transverse mass distributions. The possible indication of the QCD critical point signatures was investigated in the event-by-event fluctuations of various observables such as the mean transverse momentum, particle multiplicity and azimuthal angle distributions as well as in the particle ratio fluctuations. The energy dependence of these observables was measured in central PbPb collisions in the full SPS energy range while for analysis of the system size dependence data from pp, CC, SiSi, and PbPb collisions at the top SPS energy were used. [ABSTRACT FROM AUTHOR]

New data on the production of charged kaons in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The kaons are identified by energy loss in a large TPC tracking system. Inclusive invariant cross sections are obtained in intervals from 0 to 1.7 GeV/c in transverse momentum and from 0 to 0.5 in Feynman x. Using these data as a reference, a new evaluation of the energy dependence of kaon production, including neutral kaons, is conducted over a range from 3 GeV to $\mathrm{p}+\overline{\mathrm{p}}$ collider energies. [ABSTRACT FROM AUTHOR]

New data on the production of protons, anti-protons and neutrons in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The charged baryons are identified by energy loss measurement in a large TPC tracking system. Neutrons are detected in a forward hadronic calorimeter. Inclusive invariant cross sections are obtained in intervals from 0 to 1.9 GeV/c (0 to 1.5 GeV/c) in transverse momentum and from −0.05 to 0.95 (−0.05 to 0.4) in Feynman x for protons (anti-protons), respectively. p T integrated neutron cross sections are given in the interval from 0.1 to 0.9 in Feynman x. The data are compared to a wide sample of existing results in the SPS and ISR energy ranges as well as to proton and neutron measurements from HERA and RHIC. [ABSTRACT FROM AUTHOR]

The production of charged pions in minimum bias p+C interactions is studied using a sample of 377000 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in Feynman xF. Inclusive invariant cross sections are given on a grid of 270 bins per charge, thus offering for the first time a dense coverage of the projectile hemisphere and of the cross-over region into the target fragmentation zone. [ABSTRACT FROM AUTHOR]

The NA49 fixed-target experiment studied high energy-density matter produced in nucleus-nucleus reactions at the CERN SPS. In central Pb+Pb collisions at 158A GeV the energy density at the early stage substantially exceeds the threshold for quark deconfinement predicted by lattice QCD. The produced matter shows strong transverse and longitudinal flow. Ratios of yields of produced particles are approximately consistent with statistical equilibration. An energy scan through the SPS range revealed structure in the energy dependence of π and K yields as well as of the inverse slopes of transverse mass distributions. These features suggest that a deconfined phase starts to be produced at around 30AGeV in central Pb+Pb collisions. The analysis of fluctuations and correlations has not yet provided evidence for the predicted critical point of QCD. [ABSTRACT FROM AUTHOR]

It is shown that the energy deposition pattern in deep calorimeters could be the spectacular and unconventional signature of different kinds of stable and unstable strangelets. As an example the detection method of strongly penetrating objects, such as strangelets possibly produced in the baryon-rich environment formed in central Pb-Pb collisions at LHC energies, is described. [ABSTRACT FROM AUTHOR]

The first results from the NA49 experiment, using a large acceptance tracking detector with particle identification, are presented which have been obtained from the recent Pb-ion run at the CERN SPS. Preliminary spectra of kaons and protons identified by the Grid-TOF detector as well as Bose-Einstein correlations are shown. [ABSTRACT FROM AUTHOR]

One particle distributions of π produced in the collisions of deuterons, alphas, and carbon nuclei with Ta target at 4.2 GeV/c per nucleon momentum, registered in the propane bubble chamber, are presented. Comparison of the data with multiple scattering model and additive quark model is attempted. [ABSTRACT FROM AUTHOR]

Correlations between secondary protons with small relative momenta have been studied in interactions of various light nuclei with the carbon target at 4.2 GeV/c per incident nucleon with the aim to determine the radius of the proton emission region. This radius is found to decrease with increasing momentum and transverse momentum of the proton pair, but it does not show any dependence on the mass of the projectile nucleus. [ABSTRACT FROM AUTHOR]

Correlations between secondary protons with small relative momenta have been studied in interactions of 3.5 GeV/c negative pions with xenon nuclei with the aim to find the radius of the proton emission region. Dependence of this radius on the momentum of the proton pair and on the proton multiplicity has been observed. A possible explanation of these dependences is given. [ABSTRACT FROM AUTHOR]

The composition of forward-going projectile spectator matter in fixed-target Pb+Pb collisions at 158 A · GeV at the CERN SPS has been studied as a function of centrality. The data were measured with the NA49 veto calorimeter. We observe that forward-going spectator matter in central collisions consists of 9 neutrons, 7 protons, and half a deuteron on average. At large impact parameters most spectator nucleons are bound in fragments. The relative resolution of the average impact parameter derived from the measurement of spectator neutrons is roughly 19% in the range from zero to half maximum impact parameters. [ABSTRACT FROM AUTHOR]

Results of a pion interferometry analysis are presented for the reactions S+C, S+S, S+Cu, S+Ag, S+Au and O+Au at 200 GeV per nucleon. Correlation functions were measured for pairs of negative pions in narrow windows of transverse momentum and rapidity, as a function of the three components of the momentum difference vector in cylindrical coordinates. The measured two-pion correlation functions suggest a space-time evolution of the system which proceeds in the following way for central nucleus-nucleus collisions. After interpenetration of the incident nuclei, the pion source expands in a boost invariant way along the collision axis. Estimates for the proper time interval between the onset of expansion and pion decoupling, as well as for the duration of pion emission are ∼ 4 fm/c and <2 fm/c, respectively. The k dependence observed for R is consistent with the effect of resonance decays, alone or combined with slow transverse expansion. A linear dependence of the decoupling volume on the multiplicity is observed and indicates pion decoupling at a constant particle density. Presently available model predictions are briefly discussed [ABSTRACT FROM AUTHOR]

Multiplicities and spectra of strange particles ( $$\Lambda ,\bar \Lambda ,K_S^0 ,K^ +$$ and K produced in centralS+S,S+Ag andS+Au collisions at 200 GeV per nucleon are presented and compared with data on strange particle production in protonnucleus and nucleon-nucleon interactions. It is shown that strangeness production inS+Ag collisions is enhanced by a factor of two, similar to that found previously in centralS+S collisions. [ABSTRACT FROM AUTHOR]

The intermittency phenomenon is investigated in proton-gold, oxygen-gold, sulphur-gold and sulphur-sulphur collisions at 200 GeV per nucleon. The data were taken with the NA 35 streamer chamber detector at the CERN SPS. The data samples are carefully corrected for double counting of tracks and for contamination from photon conversions, particle decays and secondary interactions. The analysis is carried out in terms of factorial moments, using a new definition, and of correlation integrals. Both methods show the presence of nonstatistical fluctuations ('intermittency'). The main conclusions are: The observation of the effect for pairs of hadrons with negative charges and its near absence for pairs of opposite charges is consistent with the assumption that Bose-Einstein correlations yield the dominant contribution. The 'intermittency' effect is not proportional to (d n/d y) which would be expected in superposition models. The measured relation between the second and third factorial moment for negative hadrons indicates that genuine 3-particle correlations are small. The predictions of a Monte Carlo simulation which is based on the Lund Fritiof model with the inclusion of Bose-Einstein correlations agree with the experimental results. [ABSTRACT FROM AUTHOR]

Production of charged kaons in proton-sulphur, proton-gold, sulphur-sulphur and oxygen-gold collisions at 200 GeV/nucleon has been studied in the NA35 Streamer Chamber experiment. Rapidity and transverse mass distributions as well as mean multiplicities were obtained. The results are compared with nucleon-nucleon data and with model predictions. [ABSTRACT FROM AUTHOR]

Multiplicity distributions of negatively charged particles have been studied in restricted phase space intervals for central S+S, O+Au and S+Au collisions at 200 GeV/nucleon. It is shown that multiplicity distributions are well described by a negative binomial form irrespectively of the size and dimensionality of phase space domain. A clan structure analysis reveals interesting similarities between complex nuclear collisions and a simple partonic shower. The lognormal distribution agrees reasonably well with the multiplicity data in large domains, but fails in the case of small intervals. No universal scaling function was found to describe the shape of multiplicity distributions in phase space intervals of varying size. [ABSTRACT FROM AUTHOR]

Multiplicity distributions and their second moments fornegatively charged particles produced inS-S central and minimum bias interactions at 200 A GeV are studied in various rapidity intervals. Fritiof and Venus models mostly describe the dependence of second moments on rapidity intervals in minimum bias interactions, but not in central collisions. For central collisions the behaviour of second moments might indicate enhanced multiplicity fluctuations. [ABSTRACT FROM AUTHOR]

We report on a systematic study of midrapidity transverse energy production and forward energy flow in interactions ofO andS projectiles with S, Cu, Ag and Au targets at 60 and 200 GeV/nucleon. The variation of the shape of the E distributions with target and projectile mass can be understood from collision geometry. Average E values determined for central collisions show an increasing stopping power for heavier target nuclei. A higher relative stopping is observed at 60 GeV/nucleon than at 200 GeV/nucleon. Bjorken estimates of the energy density reach approximately 3 GeV/fm in high E events at 200 GeV/nucleon withO andS projectiles. The systematics of the data and the shapes of E and pseudorapidity distributions are well described by the Lund model Fritiof. [ABSTRACT FROM AUTHOR]

Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed. [ABSTRACT FROM AUTHOR]

The production of Λ, $$\bar \Lambda$$ and K has been studied in 200 GeV/nucleon p+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared to p+p and p+S collisions. The latter collisions show no overall (relative) strangeness enhancement over p+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of Λ particles in the p+S and p+Au collisions. The Λ polarization in central S+S collisions was found to be compatible with zero up to p=2 GeV/c. [ABSTRACT FROM AUTHOR]

The production of neutral strange particles K , Λ and $$\bar \Lambda $$ has been studied in 60 and 200 GeV per nucleon OAu and pAu collisions with the streamer chamber vertex spectrometer of the NA35 experiment at the CERN-SPS accelerator. Ratios of neutral strange particle production to negatively charged particle production in selected regions of phase space were measured to be the same in OAu and pAu reactions. The rates of strange particle production in central OAu collisions are about a factor of 16 higher than in pAu collisions when compared in the same regions of phase space. If an enhancement of strange particle production in OAu collisions relative to pAu collisions is considered to be a signature for quark-gluon plasma formation, no evidence supporting it is observed. The experimental results are compared to the Lund FRITIOF model. [ABSTRACT FROM AUTHOR]

Results from a pion interferometric analysis of the system 200 GeV/nucleonO+Au, central collisions, are reported. Both a Gaussian source model and a model based on the inside-outside cascade are used to fit to the experimental correlation function, giving transverse and longitudinal shape parameters, a freezeout time parameter, and a chaoticity parameter for the pion emitting source. We find a transverse [ABSTRACT FROM AUTHOR]

We report a systematic study of mid-rapidity E production and forward energy flow in the interaction ofO projectiles on Al, Cu, Ag and Au at 60 and 200 GeV/nucleon. First results on E production withS projectiles are presented. [ABSTRACT FROM AUTHOR]

The results on spectra of negative particles produced inO+Au and p-Au collisions at 200 GeV/nucleon andO+Au at 60 GeV/nucleon are presented. The correlations of average rapidity and average transverse momentum with event multiplicity are studied. Spectral shapes are similar for centralO+Au and p-Au collisions. The transverse momentum and rapidity distributions for centralO+Au and p-Au collisions differ strongly from corresponding distributions for p+ p interactions. The FRITIOF model fails to describe the shapes of the transverse momentum distributions. The simple thermodynamical model of a single fireball does not fit the midrapidity transverse momentum distributions, and the rapidity distributions. [ABSTRACT FROM AUTHOR]

We present the first preliminary results on Λ, K and $$\bar \Lambda$$ production on a gold target with proton and oxygen beams in the NA35 streamer chamber. [ABSTRACT FROM AUTHOR]

Experimental data on the forward-backward asymmetry of π emission in (d,He,C)Ta interactions at p/A=4.2 GeV/c are presented. The absolute value of the asymmetry coefficient of the inclusive π production in the nucleon-nucleon CMS decreases as A with increasing atomic mass of projectile nucleus. A method of obtaining the target-to-projectile ratio of the numbers of participant nucleons N /N through measuring the velocity of the symmetric pion emission system is proposed. It has been found that N/N∼A. [ABSTRACT FROM AUTHOR]

Light ion collisions with carbon target at 4.2 GeV/c/N are studied. Pion multiplicity distributions, momentum and angular spectra are analysed. These data are described in terms of models assuming independent interactions of nucleons from the projectile nucleus with the target. [ABSTRACT FROM AUTHOR]

Two-particle small-angle correlations between negative pions and between protons in carbon-carbon collisions at P=4.2 GeV/c per nucleon have been studied, both for an unbiased sample and for 'central' events. A comparison of experimental π π and pp correlation functions with theoretical predictions has been made. A possible evidence for the existence of two fireballs in C+C interactions at P=4.2 GeV/c per nucleon is presented. [ABSTRACT FROM AUTHOR]

Experimental data on interactions of relativistic p, d, He and C nuclei with carbon and tantalum nuclei are presented. The data come from the 2− m propane bubble chamber with an internal tantalum target. It is found that interaction cross sections for carbon projectile fragments with charges Z=5,6 are 10% greater than expected. In central C+C collisions and in multinucleon interactions of d, He and C with tantalum a contribution is observed from cumulative interactions irreducible to the superposition of NN-collisions taking into account final state interactions, rescattering effects, etc. [ABSTRACT FROM AUTHOR]