We report a new measurement of J/ψ, ψ′ and Drell–Yan cross-sections, in the kinematical domain -0.425<ycm<0.575 and -0.5<cosθCS<0.5, performed at the CERN-SPS using 400 GeV/c incident protons on Be, ...Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/ψ and ψ′ absorption cross-sections in the surrounding nuclear matter.
The Extreme Energy Events (EEE) Project is a Centro Fermi - CERN - INFN - MIUR Collaboration Project, for the study of extremely high-energy cosmic rays, which exploits the Multigap Resistive Plate ...Chamber (MRPC) technology. The excellent time resolution and good tracking capability of this detector allows us to study Extensive Air Showers (EAS) with an array of telescopes distributed all over the Italian territory. Each telescope is installed in a High School, with the additional goal to introduce students to particle and astroparticle Physics. The EEE array is composed, so far, of 47 telescopes, each made of three MRPC planes, spanning more than 10 degrees in latitude and 11 in longitude, organized in clusters and single telescope stations. The status of the experiment and the results, obtained during two recent coordinated data taking periods, will be reported. The observation of Forbush decreases, coincidence events among different telescopes and the muon decay, using more than 5 billion tracks collected in the last few months, are of particular interest.
Midrapidity production of π±, K±, and (¯p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √sNN=5.02 TeV, is presented. The invariant ...yields are measured over a wide transverse momentum (pT) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0–90%. The comparison of the pT-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √sNN=2.76 TeV show no significant energy dependence. Blast-wave fits of the pT spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π, K/π) as a function of pT show pronounced maxima at pT≈3GeV/c in central Pb-Pb collisions. At high pT, particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √sNN=2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high pT and compatible with measurements at √sNN=2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.
DarkSide is a multi-stage program devoted to direct searches of Dark Matter particles with detectors based on double phase liquid Argon Time Projection Chamber. The DarkSide-50 setup is running ...underground at the Laboratori Nazionali del Gran Sasso. First it was operated with Atmospheric Argon and during that run (1422 ± 67) kg×d of truly background-free exposure has been accumulated. Obtained data made it possible to set a 90% C.L. upper limit on the WIMP-nucleon cross section of 6.1 × 10−44 cm2 (for a WIMP mass of 100 GeV/c2). Presently the detector is filled with Underground Argon, which is depleted in 39Ar by a factor of (1.4 ± 0.2)×103 with respect to Atmospheric Argon. Acquired so far (2616 ± 43) kg×d (71 live days) in combination with the data from the Atmospheric Argon run give us the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section of 2.0×10−44 cm2 for a WIMP mass of 100 GeV/c2. Up to date this is the best limit obtained with an argon target.
The production of \({\rm J}/\psi\) and \(\psi^\prime\) 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 \({\rm J}/\psi\) and \(\psi^\prime\) 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 \(\psi^\prime\) than for the \({\rm J}/\psi\). Given the high statistics of the data samples, the \(x_{\rm F}\) (or rapidity) differential cross-sections of the \({\rm J}/\psi\) and \(\psi^\prime\) states have also been studied, for each of the target nuclei.
Abstract
We discuss the project “Per un pugno di libri … scientifici”, aimed at bringing the young generations closer to scientific culture through reading divulgation books about physics. The ...project, which is addressed to high-school students, is sponsored by INFN and other national and regional research institutions, along with physics departments of some Italian universities.
The pseudorapidity density of charged particles, dNch / d η , at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of √ s N N = 5.02 TeV . For the 5% ...most central collisions, we measure a value of 1943 ± 54 . The rise in dNch / d η as a function of √ s N N is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dNch / d η as a function of the average number of participant nucleons, ⟨ N part ⟩ , calculated in a Glauber model, is compared with the previous measurement at √ s N N = 2.76 TeV . A constant factor of about 1.2 describes the increase in dNch / d η from √ s N N = 2.76 to 5.02 TeV for all centrality classes, within the measured range of 0%–80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions.
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