Antiproton production in nucleon-nucleus and nucleus-nucleus collisions at the CERN-SPS

A model for antiproton production in nucleon-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon, based on the Wounded Nucleon Model is developed. The predictions are compared to published nucleon-nucleus and sulphur-nucleus data. The results suggest the presence of similar antiproton production processes in nucleon-nucleus and nucleus-nucleus collisions near midrapidity.     

Particle production in Pb+Pb collisions at the SPS

Experiment NA49 at the CERN SPS employs a large acceptance detector to study particle spectra, yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results on pion, kaon, A and ā production in central Pb+Pb collisions at 40, 80 and 158 A·GeV beam energy are shown and compared to measurements at lower and higher energies.     

Resolution of theK-factor ambiguity in QCD

The previously presented relations between inclusive cross sections for nucleus-nucleus, nucleon-nucleus and nucleon-nucleon scatterings with largep _T production were generalized to include effects of large momentum tail of nucleons inside the nucleus. Simple numerical estimations show that these effects are likely to dominate the inclusive cross section for nucleus-nucleus collisions at very largep _T.     

Search for deconfinement in NA49 at the CERN SPS

Experiment NA49 at the CERN SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A⋅GeV beam energy shown and compared to measurements at lower and higher energies.     

Regionwise absorption in nuclear optical model

A mathematical procedure to calculate the contribution to the reaction cross-section from a shell of radiusr and thickness Δ around the scattering centre within the frame work of a nuclear optical model is presented. The method is illustrated by describing graphically the regionwise absorption in nucleon-nucleus and nucleus-nucleus optical scattering. It is demonstrated that unlike in nucleon-nucleus scattering, in the nucleus-nucleus scattering volume absorptive optical potential, in general, does not imply that absorption is taking place in the entire nuclear volume; it is confined to mostly the surface region.     

Antiproton production in heavy-ion collisions at subthreshold energies

Within the framework of the Lanzhou quantum molecular dynamics model,the deep subthreshold antiproton production in heavy-ion collisions has been investigated thoroughly.The elastic scattering,annihilation and charge exchange reactions associated with antiproton channels are implemented in the model.The attractive antiproton potential extracted from the G-parity transformation of nucleon selfenergies reduces the threshold energies in meson-baryon and baryon-baryon collisions,and consequently enhances the antiproton yields to some extent.The calculated invariant spectra are consistent with the available experimental data.The primordial antiproton yields increase with the mass number of the colliding system.However,annihilation reactions reduce the antiproton production which becomes independent of the colliding partners.Anti-flow phenomena of antiprotons correlated with the mean field potential and annihilation mechanism is found by comparing them with the proton flows.Possible experiments at the high-intensity heavy-ion accelerator facility(HIAF) in China are discussed.     

A consistent parametrisation for the production rates of negatively charged hadrons and neutral strange particles in nucleon-nucleon,nucleon-nucleus and nucleus-nucleus collisions

A parametrisation of negative hadron and neutral strange particle production was developed which consistently describes presently available data from nucleon-nucleon, nucleon-nucleus and nucleus-nucleus collisions at a beam energy of 200 GeV per nucleon. Average multiplicities of negative hadrons are found to be proportional to the number of wounded nucleons, averageK _s ⁰ multiplicities proportional to the number of wounded quarks, and average and multiplicities proportional to the number of wounded quarks plus an additional contribution proportional to the number of interactions of secondary produced particles. Predictions are given for lead-lead collisions.On leave from Rudjer Boskovic Institute, Zagreb, Croatia     

Onset of deconfinement in nucleus-nucleus collisions

The energy dependence of hadron production in relativistic nucleus-nucleus collisions reveals anomalies-the kink, horn, and step. They were predicted as signals of the deconfinement phase transition and observed by the NA49 Collaboration in central PbPb collisions at the CERN SPS. This indicates the onset of the deconfinement in nucleus-nucleus collisions at about 30 A GeV.     

Signatures of the deconfinement transition in nucleus-nucleus collisions at the CERN SPS

The energy dependence of hadron production in relativistic nucleus-nucleus collisions reveals anomalies-kink, horn, and step. They have been predicted as the signals of the deconfinement phase transition and observed recently by the NA49 Collaboration in Pb + Pb collisions at the CERN SPS. This indicates the onset of deconfinement in nucleus-nucleus collisions at about 30 A GeV. The text was submitted by the author in English.     

Entrance-channel potentials in synthesis of the heaviest nuclei, muon catalysis of superheavy element formation

Entrance-channel potentials in nucleus-nucleus collisions, relevant for the synthesis of superheavy elements, are systematically studied within a semi-microscopic approach, where microscopic nuclear densities are used in semi-classical expressions of the energy-density functional. The existence of pockets in the entrance-channel potentials is crucial for heavy-ion fusion. It is shown that a muon bound with the light projectile induces the production of superheavy elements in nucleus-nucleus collisions.     

Higgs-boson production in nucleus-nucleus collisions

Cross-section calculations are presented for the production of intermediate-mass Higgs bosons produced in ultrarelativistic nucleus-nucleus collisions via two-photon fusion. The calculations are performed in position space using Baur's method for folding together the Weizsacker-Williams virtual-photon spectra of the two colliding nuclei. It is found that two-photon fusion in nucleus-nucleus collisions is a plausible way of finding intermediate-mass Higgs bosons at the Superconducting Super Collider or the CERN Large Hadron Collider.     

The importance of the reaction volume in hadronic collisions

The pair production in the thermodynamic model is shown to depend sensitively on the (hadronic) reaction volume. Strangeness production in nucleus-nucleus collisions is treated as an example.     

S+W中心碰撞的奇异粒子产生

用相对论核－核碰撞的事例产生器──LUCIAE产生和分析了200A GeV S＋W中心碰撞中的奇异介子K0s、奇异重子A和A,给出了它们的产额对横质量的分布及奇异介子对有异重子的产生比,并与实验数据进行了比较.     

From quantal multiple scattering theory to a classical transport equation—A soluble model for nucleon-nucleus and nucleus-nucleus collisions at high energy

Several ad hoc models describe inelastic nucleon-nucleus and nucleus-nucleus collisions at high energy. Why do they work and how are they related? We investigate this question by studying an exactly soluble model. It is based on Glauber's multiple scattering approach. The following results are derived and discussed: (1) The inclusive cross section for the observation of one nucleon is the space integral of a Wigner transform. (2) The Wigner transform obeys a classical transport equation. (3) The equation is equivalent to the Boltzmann equation at high energy. (4) The interpenetration of two nuclei is viewed as a diffusion phenomenon governed by a Fokker-Planck equation. (5) Hydrodynamic equations are shown to yield approximate solutions to the transport equation. (6) A kind of thermal equilibrium is quickly reached in a nuclear collision process. (7) The equilibrium equation of state corresponds to an ideal gas with two degrees of freedom.     

Density dependent interactions and the consistency of folding estimates of nucleon-nucleus and nucleus-nucleus potentials

It is shown that density dependence in the interaction does effect the consistency of the results obtained in folding calculations of nucleon-nucleus and nucleus-nucleus potentials. A modified density dependent version of the new G matrix interaction of Bertsch et al. gives reasonable results for both.     

Azimuthal correlations and alignment of particles in gamma families

Azimuthal angular correlations and the alignment of photons are studied in gamma families recorded by the Pamir Collaboration in a carbon x-ray emulsion chamber. The present interpretation of these experimental data is based on a model of semihard parton scattering in nucleon-nucleus collisions and on arguments favoring the production of exotic beam strings and heavy leading resonances undergoing quasicoplanar decays.     

Heavy quark production in order α S 3

We calculate one loop corrections to heavy quark production in proton antiproton collisions. We cancel ultraviolet and infrared singularities and give the cross sections on the partonic level.     

Charm and bottom production at RHIC

The current status of charm and bottom production measurements at RHIC is summarized. Heavy-flavor data from p+p collisions at provide a crucial testing ground for perturbative QCD calculations and serve as a baseline for measurements in nucleus-nucleus collisions. Due to their large mass heavy quarks are produced in hard parton scattering processes in the earliest phase of a nucleus-nucleus collisions such that they can be used to probe the hot and dense medium that is formed in the course of Au+Au collisions at RHIC.