A study of the double hadron neutrinoproduction on nuclei

The nuclear medium influence on the dihadron neutrinoproduction is investigated for the first time, using the data obtained with SKAT bubble chamber. An indication is obtained that the nuclear attenuation of the dihadron is more expressed for kinematically closest hadron pairs. The experimental data on the dihadron attenuation and on the ratio of the dihadron to single-hadron yields are compared with predictions of the two-scale string fragmentation model.Comment: 5 pages, 10 figure

A study of the nuclear medium influence on transverse momentum of hadrons produced in deep inelastic neutrino scattering

The influence of nuclear effects on the transverse momentum $(p_T)$ distributions of neutrinoproduced hadrons is investigated using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam (with $E_{\nu}$ = 3-30 GeV) at Serpukhov accelerator. Dependences of $$on the kinematical variables of inclusive deep-inelastic scattering and of the produced hadrons are measured. It has been observed, that the nuclear effects cause an enhancement of$$ of hadrons (more pronounced for the positively charged ones) produced in the target fragmentation region at low invariant mass of the hadronic system (2 $< W <$ 4 GeV) or at low energies transferred to the current quark (2 $< \nu < 9$ GeV). At higher $W$ or $\nu$, no influence of nuclear effects on $$ is observed. Measurement results are compared with predictions of a simple model, incorporating secondary intranuclear interactions of hadrons (with a formation length extracted from the Lund fragmentation model), which qualitatively reproduces the main features of the data.Comment: 23 pages, 7 figure

Charged rho meson production in neutrino-induced reactions at E_nu = 10 GeV

The neutrinoproduction of charged $\rho$ mesons on nuclei and nucleons is investigated for the first time at moderate energies ($\approx$ 10 GeV), using the date obtained with SKAT bubble chamber. No strong nuclear effects are observed in $\rho^+$ and $\rho^-$ production. The fractions of charged and neutral pions originating from $\rho$ decays are obtained and compared with higher energy data. From analysis of the obtained and available data on $\rho^+$ and $K^{*+}$(892) neutrinoproduction, the strangeness suppression factor in the quark string fragmentation is extracted: $\lambda_s = 0.18\pm0.03$. Estimations are obtained for cross sections of quasiexclusive single $\rho^+$ and coherent $\rho^+$ neutrinoproduction on nuclei. The estimated coherent cross section $\sigma_{\rho^+}^{coh}$ = (0.29$\pm0.16)\cdot 10^{-38}$ cm$^2$ is compatible with theoretical predictions.Comment: 7 pages, 6 figure

Highlights from the NA60 experiment

The NA60 experiment is a fixed-target experiment at the CERN SPS. It has measured the dimuon yield in Indium--Indium collisions with an In beam of 158 AGeV/c and in p-A collisions with a proton beam of 400 and 158 AGeV/c. The results allow to address three important physics topics, namely the study of the rho spectral function in nuclear collisions, the clarification of the origin of the dimuon excess measured by NA50 in the intermediate mass range, and the J/psi suppression pattern in a collision system different from Pb-Pb. An overview of these results will be given in this paper

J/psi azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon

The J/$\psi$ 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/$\psi$ mesons at SPS energies. Hence, the measurement of J/$\psi$ elliptic anisotropy, quantified by the Fourier coefficient v$_2$ of the J/$\psi$ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/$\psi$ suppression observed in Pb-Pb collisions. We present the measured J/$\psi$ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v$_{2}$ as a function of the collision centrality and of the J/$\psi$ 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 p$_{\rm T}$ sub-samples. The extracted v$_{2}$ values are significantly larger than zero for non-central collisions and are seen to increase with p$_{\rm T}$.Comment: proceedings of HP08 conference corrected a typo in one equatio