Transverse energy fluctuations and the pattern of J/Psi suppression in Pb-Pb collisions

The NA50 collaboration has recently observed that the J/psi production rate in Pb-Pb collisions decreases more rapidly as a function of the transverse energy for the most central collisions than for less central ones. We show that this phenomenon can be understood as an effect of transverse energy fluctuations in central collisions. A good fit of the data is obtained using a model which relates J/psi suppression to the local energy density. Our results suggest that the J/psi is completely suppressed at the highest densities achieved in Pb-Pb collisions.Comment: v2, 4 pages, LaTeX, 3 eps figures include

J/Psi suppression in central Pb-Pb collisions

We discuss the recent NA50 J/Psi production data in Pb--Pb collisions, in particular the second drop at high transverse energies which correspond to the most central collisions. Using a model which relates the J/Psi suppression to the local energy density, we show that the data can be explained by taking into account transverse energy fluctuations at a given impact parameter. Predictions of this model for RHIC are briefly discussed.Comment: to appear in the Proceedings of Quark Matter'200

Flow analysis from cumulants: a practical guide

We have recently proposed a new method of flow analysis, based on a cumulant expansion of multiparticle azimuthal correlations. Here, we describe the practical implementation of the method. The major improvement over traditional methods is that the cumulant expansion eliminates order by order correlations not due to flow, which are often large but usually neglected.Comment: 6 pages revtex. Proceedings of the International Workshop on the Physics of the Quark-Gluon Plasma, Palaiseau, France, 4-7 Sept. 0

Collective flow and multiparticle azimuthal correlations

The measurement of azimuthal distributions in nucleus-nucleus collisions relies upon the assumption that azimuthal correlations between particles result solely from their correlation with the reaction plane (i.e. flow). We show that at SPS energies, the ansatz is no longer valid, and two-particle correlations due to momentum conservation, final state interactions or resonance decays become of the same order as those arising from flow. This leads us to introduce new methods to analyse collective flow, based on a cumulant expansion, which enable to extract smaller values than those accessible to the standard analysis.Comment: 6 pages, no figure; Proceedings of the XXX International Symposium on Multiparticle Dynamics (ISMD 2000), Tihany (Hungary), October 9-15, 200

Thermalization and elliptic flow at RHIC

We discuss signatures of thermalisation in heavy ion collisions based on elliptic flow. We then propose a new method to analyse elliptic flow, based on multiparticle azimuthal correlations. This method allows one to test quantitatively the collective behaviour of the interacting system.Comment: 6 pages, talk given at XXXI International Symposium on Multiparticle Dynamics, Sept 1-7, 2001, Datong China. URL http://ismd31.ccnu.edu.cn

Microstructural characterization of a Canadian oil sand

The microstructure of oil sand samples extracted at a depth of 75 m from the estuarine Middle McMurray formation (Alberta, Canada) has been investigated by using high resolution 3D X-Ray microtomography ($\mu$CT) and Cryo Scanning Electron Microscopy (CryoSEM). $\mu$CT images evidenced some dense areas composed of highly angular grains surrounded by fluids that are separated by larger pores full of gas. 3D Image analysis provided in dense areas porosity values compatible with in-situ log data and macroscopic laboratory determinations, showing that they are representative of intact states. $\mu$CT hence provided some information on the morphology of the cracks and disturbance created by gas expansion. The CryoSEM technique, in which the sample is freeze fractured within the SEM chamber prior to observation, provided pictures in which the (frozen) bitumen clearly appears between the sand grains. No evidence of the existence of a thin connate water layer between grains and the bitumen, frequently mentioned in the literature, has been obtained. Bitumen appears to strongly adhere to the grains, with some grains completely being coated. The curved shape of some bitumen menisci suggests a bitumen wet behaviour

Non-thermal plasma abatement of trichloroethylene with DC corona discharges

The decomposition of trichloroethylene (TCE) in air by non-thermal plasma was investigated with a multi-pin-to-plate direct current (DC) discharge at atmospheric pressure and room temperature. The effects of various operating parameters on the removal efficiency (RE) were examined. The experiments indicated that for low energy densities higher removal could be obtained with positive corona. For negative corona and 10 % relative humidity (RH) a maximum RE of 99.5 % could be achieved at 1100 J L-1. Formation of by-products was qualitatively analyzed in detail with FT-IR spectroscopy and mass spectrometry. Detected by-products for negative corona operated at 300 J L-1 and 10 % RH include dichloroacetylchloride, trichloroacetaldehyde, phosgene, ozone, HCl, Cl2, CO and CO2. The highest RE for TCE was achieved with a relative humidity of 19 %