P. Di Nezza

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The first measurement of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair ffiffiffiffiffiffiffiffi s NN p ¼ 2:76 TeV is presented. For an event sample corresponding to the most central 5% of the hadronic cross section, the pseudorapidity density of primary charged particles at(More)
The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from polarised targets of H, D, and 3 He. These data give information on the spin structure of the nucleon. This paper describes the forward angle spectrometer built for this purpose. The spectrometer includes numerous tracking chambers(More)
Results on J== production in ep interactions in the H1 experiment at HERA are presented. The J== mesons are produced by almost real photons (Q 2 0) and detected via their leptonic decays. The data have been taken in 1994 and correspond to an integrated luminosity of 2:7 pb ?1. The p cross section for elastic J== production is observed to increase strongly(More)
1 Abstract Polarized leptoproduction of charm is an experimentally completely unexplored and theoretically very interesting topic. Of particular interest in this area is the potential sensitivity of the polarization asymmetry to the contribution of the gluons to the nucleon spin. The present HERMES spectrometer is far from optimal for detecting the most(More)
We present a study of J== meson production in collisions of 26:7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J== mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of (ep ! J==X) = (8:8 2:0 2:2) nb is determined(More)
Photoproduction of 2-jet events is studied with the H1 detector at HERA. Parton cross sections are extracted from the data by an unfolding method using leading order parton-jet correlations of a QCD generator. The gluon distribution in the photon is derived in the fractional momentum range 0:04 x 1 at the average factorization scale 75 GeV 2. H1(More)
Measurements of cross sections of inelastic and diffractive processes in proton–proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudora-pidity distributions: for single diffraction (diffractive mass
A measurement is presented, using data taken with the H1 detector at HERA, of the contribution of diiractive interactions to deep{inelastic electron{proton (ep) scattering in the kinematic range 8:5 < Q 2 < 50 GeV 2 , 2:410 ?4 < Bjorken{x < 0:0133, and 3:7 10 ?4 < x IP < 0:043. The diiractive contribution to the proton structure function F 2 (x; Q 2) is(More)
A leading order determination of the gluon density in the proton has been performed in the fractional momentum range 1:9 10 ?3 < x g=p < 0:18 by measuring multi-jet events from boson-gluon fusion in deep-inelastic scattering with the H1 detector at the electron-proton collider HERA. This direct determination of the gluon density was performed in a kinematic(More)