System size dependence of particle production at the SPS

Recent results on the system size dependence of net-baryon and hyperon production as measured at the CERNSPS are discussed. The observed N _part dependences of yields, but also of dynamical properties, such as average transverse momenta, can be described in the context of the core corona approach. Other observables, such as antiproton yields and net-protons at forward rapidities, do not follow the predictions of this model. Possible implications for a search for a critical point in the QCD phase diagram are discussed. Event-by-event fluctuations of the relative core to corona source contributions might influence fluctuation observables (e.g., multiplicity fluctuations). The magnitude of this effect is investigated.     

Nuclear mass number dependence of inclusive pion production by pions and protons at 4.3GeV/c

The inclusive production of π⁺ for 0.4≤p_T<1.0 GeV/c in pion-nucleus and proton-nucleus collisions at 4.3 GeV/c was measured. A strong A-dependence of the cross sections at high p_T is observed to be persistent in the low energy region. The ratio of the cross sections for proton-nucleus and pion-nucleus collisions is also observed to be compatible with the quark-parton picture, for p_T>0.6 GeV/c.     

Energy andx dependence of inclusive particle production in annihilation and non-annihilation reactions in the quark recombination model

Existing data are used to show that the structure functions of meson production in \(\bar p\) p annihilation are characterized by (1?x)^α distributions with α consistently less than in \(\bar p\) p non-annihilation orpp interactions. The energy dependence of \(\bar p\) p annihilation is interpreted as being given by the probability of at least one valence quark of \(\bar p\) andp being in the wee region. The annihilation is attributed to the recombination of a sea antiquark with a quark of the dismembered spectator valence di-quark system. This model can describe the existing annihilation data. Other models are briefly reviewed with respect to features of annihilation data.     

Measurements of inclusive and exclusive particle production at ZEUS

Charged particle production, scaled momentum distributions of identified particles, K _s ⁰ and Λ, and charged particles for dijet events have been measured in ep scattering with the ZEUS detector. The evolution of these distributions with the photon virtuality, Q ², are studied in the kinematic region 10 < Q ² < 40000 GeV². The calculations reproduce the measured distributions reasonably well.     

Higher-order QCD corrections to inclusive particle production inp\bar p collisions

Inclusive single-particle production cross sections have been calculated including higher-order QCD corrections. Transverse-momentum and rapidity distributions are presented and the scale dependence is studied. The results are compared with experimental data from the CERN Collider and the Fermilab Tevatron.Supported by the Bundesministerium für Forschung und Technologie, 05 5HH 91P(8), Bonn, Germany     

Centrality dependence of particle production at RHIC and the combinational approach

The newly proposed combinational approach, called the grand combination of models (GCM), as will be described in detail in the text, is still under our careful scrutiny. By applying it, we have attempted to analyze here the characteristics of both the transverse momentum ( )-, and centrality dependence of the production of the main varieties of the secondaries measured in AuAu collisions at BNL-RHIC at both GeV and GeV by PHENIX Collaboration. Besides, with the help of it, we have also investigated the nature of the centrality dependence of the average transverse momenta of the various major categories of particles in AuAu collisions at RHIC. The model seems to survive quite smoothly the acid tests of the latest PHENIX data, as it accommodates data modestly well on these twin aspects. The study reveals a kind of universality of nature of the hadronic secondaries and also of the basic particle and nuclear interactions at high energies. However, in the end, we precisely point out both the strengths and limitations of the specific model under consideration here.Received: 2 April 2003, Revised: 29 July 2003, Published online: 23 December 2003PACS: 13.60.Hb Total and inclusive cross-sections (including deep-inelastic processes) - 25.75.-q Relativistic heavy-ion collisions     

Energy dependence of inclusive distributions in pion-induced reactions

We present data on the inclusive distributions π⁺p → π^± + anything and π⁻p → π⁻ + anything at momenta from 3.7 to 18.5 GeV/c. Distributions are presented in the laboratory, center-of-mass and projectile systems, and the approach to scaling is discussed.     

A dependence of inclusive pion double charge exchange

The A dependence of the forward cross section for inclusive pion double charge exchange on nine target nuclei from ⁶Li to ²⁰⁹Bi at T₀ = 0.59 GeV, as well as the cross section for ⁶Li, ⁷Li, and ¹²C nuclei at T₀ = 0.59, 0.75, and 1.1 GeV, was measured with the 3-m magnetic spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The resulting A dependence is well described within the model involving two sequential single charge exchanges and taking into account the renormalization of the amplitude for pion single charge exchange in a nucleus. A relatively weak energy dependence of the cross section for the ⁶Li, ⁷Li, and ¹²C nuclei agrees with the analogous dependence obtained previously for the ¹⁶O nucleus, but it contradicts the predicted sharp decrease in the cross section within the model involving two sequential single charge exchanges. This result provides an additional piece of evidence that the contribution from the mechanism of inelastic Glauber rescattering is significant at T₀ ? 0.6 GeV.     

Interference effects from inclusive resonance production

If pions produced at high-energy reactions are decay products of narrow resonances, Bose interference effects at small invariant pion-pion masses are model-independently calculable from (inclusive) resonance production cross sections. We find that the π^?π^? correlations due to the analogue of the Hanbury Brown-Twiss effect are narrower than those currently observed, the latter being due to more complicated interferences.     

Geometric scaling in inclusive charm production

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the DESY ep collider HERA kinematic domain the saturation momentum Q(2)(sat)(x) stays below the hard scale micro(2)(c)=4m(2)(c), implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the HERA data for the proton structure function at small values of the Bjorken variable x. A striking feature is the scaling on tau identical with Q(2)/Q(2)(sat)(x) above te saturation limit, corroborating recent theoretical studies.     

High-energy hadron production and inclusive reactions

Recent data on multiparticle production at high energies are reviewed. The major topics include exclusive analyses, multiplicity distributions, single-particle inclusive spectra, and correlations. An effort is made to explore the physical significance of these results.     

A study of inclusive vector meson production

Data are presented on the reactions π⁺n → ?⁰+X and $\text{K}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^1\text{0}\text{(890)+}\text{X}\text{at 6.0}\text{and}\text{7.3}\text{GeV}\text{/c}$, respectively. Comparisons are made with related reactions at higher energies.     

Nuclear size and rapidity dependence of the saturation scale from QCD evolution and experimental data

The solutions of the Balitsky-Kovchegov evolution equations are studied numerically and compared with known analytical estimations. The rapidity and nuclear size dependences of the saturation scale are obtained for the cases of fixed and running coupling constant. These same dependences are studied in experimental data, on lepton-nucleus, deuteron-nucleus and nucleus-nucleus collisions, through geometric scaling and compared with the theoretical calculations.Arrival of the final proofs: 18 March 2005PACS: 12.38.Bx - 13.60.Hb - 12.38.CyJoint contribution to the proceedings of the Hard Probes 2004 Conference based on the oral presentations by J.G. Milhano and C.A. Salgado     

Three particle inclusive correlations from relativistic heavy ion collisions

The life-time of the first excited member of the ground-state band in¹⁰¹Zr has been determined to 0.9(3) ns through the measurement of γ-γ-delayed coincidences with Ge detectors at the fission-product separator JOSEF. The result shows that this nucleus is strongly deformed with |ß|=0.32(6). This finding provides further important evidence for the fact that the odd-mass nuclei at A ~ 100 with more than 59 neutrons are good rotors.