2,665 research outputs found
Latest results from NA50 on J/psi suppression in Pb-Pb collisions
No full textThe main goal of the NA50 experiment is to study the J/psi suppression pattern in PL-rb interactions, at 158 GeV/c per nucleon at the CERN SPS. We present here the results from the 1996 (final) and 1908 (preliminary) data taking periods. They confirm and extend our previous observation that the J/psi is anomalously supressed from peripheral to central collisions. With new event selection procedures and different analysis techniques, we observe that in peripheral collisions the J/psi cross section per nucleon-nucleon collision agrees with the pattern inferred from a wide range of measurements with lighter systems, from pp up to S-U. When the collisions become more central a clear departure from this behaviour is observed. The 1996 data show a sudden drop in the J/psi production yield for E-T values above 40 GeV, where E-T is the neutral transverse electromagnetic energy released in the colision and measured in the EM calorimeter. The 1998 data provide a big improvement in the study of the most central region, where a second change in the pattern becomes visible
The case of the pseudoscalar glueball
No full textGlueballs represent a key requirement of quantum chromodynamics as a non-Abelian field theory. Their search provides one of the strongest motivations for meson spectroscopy. The first glueball candidate was identified in 1980 in the J/Psi radiative decay. Its discovery actually dates back to 1963 and for four decades about 30 experiments, using six different production mechanisms, were dedicated to studying the pseudoscalar states lying in the 1.4-1.5 GeV/c(2) mass region. Today, the presence of two pseudoscalar states and an axial vector can be considered as established (see 2004 edition of the Review of Particle Properties). Assuming that.(1295) is established and the nonet filled, the lower mass pseudoscalar,.(1405), becomes a supernumerary and shows the properties of a non-(q) over barq state. Here, we review the experimental effort related to this long search, which can be considered a sort of paradigm for light-quark spectroscopy
Histological examination of the male gonad of hybrid specimens: Microtus savii x M. brachycercus (Rodentia Arvicolinae)Biogeographical and karyological data of the Microtus savii group (Rodentia, Arvicolidae ) in Italy
No full textA new PCI card for readout in high energy physics experiments
No full textRecently, some high energy physics experiments have started to adopt readout systems based on the PCI architecture. In this context, a new PCI card that can be adapted to several readout schemes has been designed. It contains a 64-MiB(1) local buffer, programmable FPGA logic, a hardware PCI bridge, and can be connected to mezzanine cards. The card is presently used in the NA60 experiment at the CERN SPS for the readout of several detectors. The interfacing to the different front-ends is provided by the mezzanine cards while the readout protocols are implemented in the FPGA. Moreover, it is used as a test readout system for the ALICE experiment muon chambers. This paper describes the card, with particular emphasis on its flexibility and relatively simple development, related to the use of an external PCI bridge. RI Tinoco Mendes, Andre David/D-4314-201
Desaturation maneuvers and precise orbit determination for the BepiColombo mission
No full textThe purpose of this work is the analysis of the consequences that desaturation maneuvers can have in the precise orbit determination expected from the radio science experiments (MORE) of the BepiColombo mission to Mercury. This is an ESA/JAXA joint project with very challenging objectives regarding geodesy, geophysics and fundamental physics. Due to the intense radiation environment, the attitude of the Mercury Planetary Orbiter (MPO) has to be controlled by means of inertial wheels that absorb the solar radiation pressure torques acting on the spacecraft. In this way the overall angular momentum is conserved as long as the wheels reach their maximum rotation state. Then they have to be slowed down by a series of thruster pulses, which induces a residual acceleration on the probe and this is what we call a desaturation maneuver. Here, we will show how such maneuvers affect the orbit of the s/c and the radio science measurements and how we can include them in the orbit determination and parameter estimation procedure. The non linear least square differential correction fit we consider is applied on a set of observational arcs separated by intervals of time where the MPO is not visible. With the current baseline of two ground stations, two maneuvers are performed per day, one during the observing session, the other in the dark. To reach the scientific goals of the mission, they have to be treated as "solve for quantities". We have developed a specific methodology based on the deterministic propagation of the orbit, which is able to deal with these variables, by connecting subsequent observational arcs in a smooth way. The numerical simulations we will show demonstrate that, under given hypotheses, this constrained multi-arc strategy is able to determine the maneuvers together with the other parameters of interest at the level of accuracy required. The future development consists in including accelerometer readings and calibrations in the correction
The zero degree calorimeters for the ALICE experiment
No full textThe Zero Degree Calorimeters (ZDC) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC, providing a direct measure of the centrality of the collisions. ZDC are spaghetti calorimeters, which detect the Cherenkov light produced by the shower particles in silica optical fibers embedded in a dense absorber. The main characteristics of the ZP and ZN detectors are described in this article. The calorimeters were tested at the CERN SPS using pion and electron beams with momenta ranging from 50 to 200 GeV/c. Test beam results such as the calorimeter response, the energy resolution, the signal uniformity and the localizing capability are presented. (C) 2007 Elsevier B.V. All rights reserved. RI Cortese, Pietro/G-6754-201
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