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The A dependence of charged-particle spectra in π[sup +], K[sup +], and p interactions with Al and Au targets at 250 GeV/c are presented and compared to predictions of the Quark–Gluon String Model (QGSM). It is shown that the A dependence of invariant inclusive charged-particle spectra on the Feynman variable x is very weak between Al and Au targets. The QGSM shows a larger difference between fast-particle spectra for both Al and Au targets and different beam particles. The QGSM prediction for the leading-particle spectrum over an energy range from 250 GeV to 10 TeV in pAu(Pb) reactions is in a reasonable agreement with the results of NA22 data and a cosmic-ray experiment.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The characteristics of the charged-current neutrino—nuclear interactions are investigated for the first time at E ν = 1–3 GeV using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam at the Serpukhov accelerator. The E ν dependence of the mean multiplicities of different types of secondary particles and their multiplicity, momentum, and angular distributions are measured. [ABSTRACT FROM AUTHOR]

The nuclear effects in ρ0-meson neutrino production are investigated using the data obtained with the SKAT bubble chamber. The nuclear-medium influence on the ρ0 total yield and inclusive distributions on z = E ρ/ v and Feynman xF variable is found to be approximately the same as for pions. It is shown that these distributions with increasing A tend to shift toward smaller values of z and xF, thus indicating an increasing role of secondary intranuclear interactions. The predictions of a simple model incorporating the latter are found to be in qualitative agreement with experimental data. [ABSTRACT FROM AUTHOR]

Quasielastic muon-neutrino scattering on nuclei of propane-Freon mixture at energies in the range E v < 1 GeV is studied. The multiplicity, momentum, and emission-angle distributions of final protons are measured along with the dependence of the mean values for these distributions on the neutrino energy in the range 0.2 < E v < 1 GeV. [ABSTRACT FROM AUTHOR]

The A dependence of the production of K 0 and Λ is investigated for the first time in neutrino-nuclear reactions using the data obtained with the SKAT bubble chamber. An exponential parametrization (∼ A β) of the particle yields results in $$\beta _{V^0 } $$ = 0.20 ± 0.05 for V 0 particles ( K 0 and Λ), while for π − mesons the A dependence is much weaker ( $$\beta _{\pi ^ - } $$ = 0.068 ± 0.007). A nuclear enhancement of the ratio K 0/ π − is found; this ratio increases from 0.055 ± 0.013 for vN interactions up to 0.070 ± 0.011 at A ≈ 21 and 0.099 ± 0.011 at A ≈ 45. It is observed that the multiplicity rise of V 0 occurs predominantly in the backward hemisphere of the hadronic system. It is shown that the A dependence of the Λ0 and π − yields can be reproduced in the framework of a model incorporating the secondary intranuclear interactions of pions originating from the primary vN interactions. [ABSTRACT FROM AUTHOR]

Using the data obtained with the SKAT bubble chamber, the total yields of K*(892)+, Σ+(1385), and Σ0 are estimated for the first time in neutrino-induced reactions at moderate energy 〈 E v〉 = 10.4 GeV. It is shown that the recently observed enhancement of the K 0 and Λ yields in vA interactions as compared to vN interactions is contributed only slightly by the K*(892)+ and Σ+(1385) production. The contribution of resonances to the K 0 and Λ yields is found to be in qualitative agreement with higher energy (〈 E v〉 ≳ 40 GeV) data. It is shown that the energy dependence of the K*(892)+ mean multiplicity in vN interactions is approximately linear in the range of 〈 E v〉 ≈ 10−60 GeV, while that for Σ0 in vA interactions ( A = 20−21) is approximately logarithmic in the range of 〈 E v〉 ≈ = 10−150 GeV. [ABSTRACT FROM AUTHOR]

The influence of nuclear effects on the production of neutral strange particles ( V 0) is investigated using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E v =3−30 GeV) at the Serpukhov accelerator. The mean multiplicity of V 0 particles in nuclear interactions, $$\langle n_{V^0 } \rangle _A = 0.092 \pm 0.010$$ , is found to exceed significantly that in “quasideuteron” interactions, $$\langle n_{V^0 } \rangle _D = 0.063 \pm 0.013$$ . The ratio of $$\rho _{V^0 } = \langle n_{V^0 } \rangle A/\langle n_{V^0 } \rangle _D = 1.46 \pm 0.23$$ is larger than that for π− mesons, $$\rho _{\pi ^ - } = 1.10 \pm 0.03$$ . It is shown that the multiplicity gain of V 0 particles can be explained by intranuclear interactions of produced pions. [ABSTRACT FROM AUTHOR]

The influence of nuclear effects on the transverse momentum (pT) of neutrino-produced hadrons is investigated using the data obtained with the SKAT propane–freon bubble chamber irradiated in the neutrino beam (with Eν = 3–30 GeV) at the Serpukhov accelerator. It has been observed that the nuclear effects cause an enhancement of 〈pT2〉 of hadrons produced in the target fragmentation region at low invariant mass of the hadronic system (2 < W < 4 GeV) and at low energies transferred to the hadrons (2 < ν < 9 GeV). At higher W and ν, no influence of nuclear effects on 〈pT2〉 is observed. Measurement results are compared with predictions of a simple model, incorporating secondary intranuclear interactions of hadrons, which qualitatively reproduces the main features of the data.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The inclusive spectra of hadrons are measured with the aid of the SKAT propane-freon bubble chamber irradiated with a beam of 3- to 30-GEV neutrinos from the Serpukhov accelerator. The resulting data indicate that the intranuclear absorption of leading quark-fragmentation products is enhanced as the energy transfer to the quark involved decreases or as the quark-energy fraction z acquired by the product hadron increases. An analysis of the data on the basis of the color-string model reveals that the cross section for the intranuclear absorption of positively charged hadrons that are characterized by z values in the range between 0.7 and 0.9 is close to the inelastic cross section for pion-nucleon interaction. [ABSTRACT FROM AUTHOR]

The article presents abstracts of research concerning physics of atomic nuclei. They include "Role of Neutrons in the Fusions of Nuclei," "Measurement of Cross Sections for Double Charged-Pion Production in Proton-Proton Collisions at Energies Below 1 GeV" and "Eligibility of the Spherical-Well Approximation for Calculations of Nucleon-Transfer Matrix Elements."

The J/ ψ azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/ ψ mesons at SPS energies. Hence, the measurement of J/ ψ elliptic anisotropy, quantified by the Fourier coefficient v2 of the J/ ψ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/ ψ suppression observed in Pb-Pb collisions. We present the measured J/ ψ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v2 as a function of the collision centrality and of the J/ ψ transverse momentum. The reaction plane has been estimated from the azimuthal distribution of the neutral transverse energy detected in an electromagnetic calorimeter. The analysis has been performed on a data sample of about 100 000 events, distributed in five centrality or pT sub-samples. The extracted v2 values are significantly larger than zero for non-central collisions and are seen to increase with pT. [ABSTRACT FROM AUTHOR]

ψ′ production is studied in Pb–Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of the collision. The results are compared with those obtained for lighter colliding systems and also for the J/ψ meson produced under identical conditions. [ABSTRACT FROM AUTHOR]

We report a new measurement of J/ψ, ψ′ and Drell–Yan cross-sections, in the kinematical domain -0.425

Abstract: The NA50 Collaboration has measured heavy-quarkonium production in p–A collisions at 450 GeV incident energy (). We report here results on the production of the ϒ states and of high-mass Drell–Yan muon pairs (). The cross-section at midrapidity and the A-dependence of the measured yields are determined and compared with the results of other fixed-target experiments and with the available theoretical estimates. Finally, we also address some issues concerning the transverse momentum distributions of the measured dimuons. [Copyright &y& Elsevier]

Charmonium suppression in Pb-Pb collisions at 158 GeV/c per nucleon is investigated in detail with the study of the transverse momentum distributions of J/ψ as a function of the centrality of the collision. It is shown that the observed J/ψ suppression in Pb-Pb interactions is particularly significant mainly at low transverse momentum where it strongly depends on centrality. For peripheral Pb-Pb collisions, the transverse momentum dependence of the J/ψ cross section is, as a function of centrality, qualitatively similar to the dependence observed in p-A and S-U collisions. Comparing peripheral and central Pb-Pb collisions, the data show a relative suppression in the whole pT range although its amplitude significantly decreases with increasing pT and becomes almost pT independent for the highest pT values. [Copyright &y& Elsevier]

We present a new measurement ofproduction in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that thecross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that thecross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions. [ABSTRACT FROM AUTHOR]

The production of J/Ψand &Psi′ charmonium states in proton-nucleus interactions has been investigated by the NA50 experiment, at the CERN SPS. High statistics data sets were collected with collisions induced by 450 GeV protons incident on Be, Al, Cu, Ag and W targets. The J/ψand ψ production cross-sections have been determined for each p-A system and their dependences on the nucleus size have been studied, leading to the so-called normal nuclear absorption. Comparing the two patterns we see that the nuclear absorption is stronger for the &Psi′ than for the J/Ψ. Given the high statistics of the data samples, the xF (or rapidity) differential cross-sections of the J/Ψ and &Psi′ states have also been studied, for each of the target nuclei. [ABSTRACT FROM AUTHOR]

The mechanisms of cumulative proton production are studied on the basis of data from the S CAT propane-freon bubble chamber exposed to a wideband neutrino beam at the Serpukhov accelerator. Kinematic correlations between the cumulative proton and muon, as well as pair correlations of the final protons, are analyzed. The former correlations are predicted by the two-nucleon correlation mechanism (TCM), whereas the latter are caused by the mechanism of secondary pion absorption (SPA) in the nucleus. It is shown that the TCM contribution to the cumulative proton production is most significant in the peripheral interactions (about 50%). The SPA contribution accounts for about a quarter of the inclusive cross section of cumulative proton production. [ABSTRACT FROM AUTHOR]