[en] We present results on the J/ ψ production in O-U and O-Cu collisions, and preliminary results on S-U interactions at 200 GeV/nucleon. It is found that in all processes the production of J/ ψ relative to the continuum is suppressed in events with large accompanying transverse energy; this effect is more pronounced at low J/ ψ Pt values

No abstract available

[en] In this paper, the authors measure the characteristics of muon pairs (continuum and resonates), correlated with the electromagnetic transverse energy E_T produced in the same event, in 200 GeV/nucleon oxygen-uranium and oxygen-copper collisions. The production of J/ψ is investigated and compared to the continuum in different intervals of E_T. The authors observe a relative decrease of the Jψ production with increasing E_T; this suppression is enhanced at low P_T

[en] We consider the Born-Infeld action for symmetry-preserving, orientable D-branes in compact group manifolds. We find classical solutions that obey the flux quantization condition. They correspond to conformally invariant boundary conditions on the world sheet. We compute the spectrum of quadratic fluctuations and find agreement with the predictions of conformal field theory, up to a missing level-dependent truncation. Our results extend to D-branes with the geometry of twined conjugacy classes; they illustrate the mechanism of flux stabilization of D-branes. (author)

[en] During the last decade there was a growing interest on the application of Positron Emission Tomography, PET, techniques to Breast Imaging. More recently, preliminary results suggested the use of dedicated devices to Breast Imaging using the same technique, the so-called Positron Emission Mammography cameras, PEM. In this article we review the arguments leading to a dedicated instrument. Based on these arguments we describe the concept of a PEM camera under development within the Crystal Clear Collaboration and the first results of its expected performance in terms of sensitivity and position resolution

[en] The main goal of the NA50 experiment is to study the J/ψ suppression pattern in Pb-Pb interactions, at 158 GeV/c per nucleon at the CERN SPS. We present here the results from the 1996 and 1998 data taking periods. We used new event selection procedures, different analysis techniques and different event centrality estimators and we can now confirm and extend our previous observation that the J/ψ is anomalously suppressed when going from peripheral to central Pb-Pb collisions. We observe that in peripheral collisions the J/ψ cross section per nucleon-nucleon collision agrees with the pattern inferred from a wide range of measurements with lighter systems, from p-p to S-U. When the collisions become more central a clear departure from this behavior is observed. The 1996 data show a sudden drop in the J/ψ production yield for transverse energy values above 40 GeV. The 1998 data provide a big improvement in the study of the most central region, where a second change in the pattern becomes visible. This suppression pattern is confirmed by an independent analysis which uses the zero degree energy (E_ZDC) as centrality estimator

[en] In this paper the like-sign muon pairs copiously recorded in the high luminosity NA38 experiment are interpreted as resulting from decays of π and K mesons. It is shown that the muon properties reflect the pion and kaon ones. The average transverse momentum is found to be similar for p - U, O¹⁶ - U and S³² - U reactions. The K/π ratio, which indicates strangeness production, is also the same for the three reactions. Both measurements increase slightly with E_T

[en] The J/ψ production in 158 A GeV Pb-Pb interactions is studied as a function of centrality. Its pattern, after a first sharp variation around E_T=40 GeV, continues to fall down and exhibits a curvature change around E_T=90 GeV. This trend excludes any conventional hadronic model and is in agreement with a deconfined quark-gluon phase scenario

No abstract available

[en] Heavy ion production of J/ψ mesons has been studied at CERN for a decade, in search for the Quark-Gluon Plasma predicted by lattice-QCD. The suppression observed very early in O-Cu, O-U and S-U reactions has been shown to be eventually explained by nuclear absorption, and follow the same exponential behavior as the proton-nucleus reactions. The new Pb-Pb data deviate from this behavior very strongly, indicating the onset of a new regime in J/ψ suppression