Engineering topics
Bellini, F.
Publications and source records attributed to Bellini, F..
H Λ 3 and H ‾ Λ ¯ 3 production in Pb–Pb collisions at s NN = 2.76 TeV
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Production of light nuclei and anti-nuclei in p p and Pb-Pb collisions at energies available at the CERN Large Hadron Collider
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Multiplicity and transverse momentum evolution of charge-dependent correlations in pp, p–Pb, and Pb–Pb collisions at the LHC
Here, we report on two-particle charge-dependent correlations in pp, p–Pb, and Pb–Pb collisions as a function of the pseudorapidity and azimuthal angle difference, Δη and Δφ respectively. These correlations are studied using the balance function that probes the charge creation time and the development of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transverse momentum (p T ) in pp, p–Pb, and Pb–Pb collisions at √ s NN = 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for 0.2 < p T < 2.0 GeV/c, the balance function becomes narrower in both Δη and Δφ directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mechanisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low p T is a feature of bulk particle production.
Centrality dependence of pion freeze-out radii in Pb-Pb collisions at s N N = 2.76 TeV
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Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb–Pb collisions at s NN = 2.76 TeV
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Forward-central two-particle correlations in p–Pb collisions at s NN = 5.02 TeV
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Pseudorapidity and transverse-momentum distributions of charged particles in proton–proton collisions at s = 13 TeV
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Azimuthal anisotropy of charged jet production in s NN = 2.76 TeV Pb–Pb collisions
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Direct photon production in Pb–Pb collisions at s NN = 2.76 TeV
We studied the direct photon production at mid-rapidity in Pb-Pb collisions at √s NN = 2.76 TeV in the transverse momentum range 0.9 < p T < 14 GeV/c. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the ALICE detector material with the e + e - pair reconstructed in the central tracking system. Our results of the two methods were combined and direct photon spectra were measured for the 0-20%, 20-40%, and 40-80% centrality classes. For all three classes, agreement was found with perturbative QCD calculations for p T greater than or similar to 5 GeV/c. Direct photon spectra down to p T approximate to 1 GeV/c could be extracted for the 20-40% and 0-20% centrality classes. Furthermore, the significance of the direct photon signal for 0.9 < p T < 2.1 GeV/c is 2.6 sigma for the 0-20% class. The spectrum in this p T range and centrality class can be described by an exponential with an inverse slope parameter of (297 ± 12 stat ± 41 syst ) MeV. State-of-the-art models for photon production in heavy-ion collisions agree with the data within uncertainties.
Search for weakly decaying Λ n ‾ and ΛΛ exotic bound states in central Pb–Pb collisions at s NN = 2.76 TeV
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Double-beta decay investigation with highly pure enriched $^{82}$Se for the LUCIFER experiment
The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of 82 Se. The matrix which embeds the source is an array of ZnSe crystals, where enriched 82 Se is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3 % enriched 82 Se metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of 232 Th, 238 U and 235 U are respectively: <61, <110 and <74 μBq/kg at 90 % C.L. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the 82 Se allowed us to establish the most stringent lower limits on the half-lives of the double-beta decay of 82 Se to 0+1, 2+2 and 2+1 excited states of 82 Kr of 3.4•10 22 , 1.3•10 22 and 1.0•10 22 y, respectively, with a 90 % C.L.
Coherent ψ (2S) photo-production in ultra-peripheral Pb–Pb collisions at s NN = 2.76 TeV
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Centrality dependence of high-pT D meson suppression in Pb-Pb collisions at $ \sqrt{s_{\mathrm{N}\;\mathrm{N}}}=2.76 $ TeV
We measured the nuclear modification factor, R-AA, of the prompt charmed mesons D°, D + and D *+ , and their antiparticles, using the ALICE detector in Pb-Pb collisions at a centre-of-mass energy √s NN = 2.76 TeV in two transverse momentum intervals, 5 < p T < 8 GeV/c and 8 < p T < 16 GeV/c, and in six collision centrality classes. Furthermore, the R AA shows a maximum suppression of a factor of 5-6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. Finally, a comparison with the R AA of non-prompt J/Ψ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.
Centrality dependence of inclusive J/ψ production in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV
Here, we present a measurement of inclusive J/Ψ production in p-Pb collisions at √S NN = 5.02 TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. We also performed this measurement with the ALICE detector down to zero transverse momentum, p T , in the backward (-4.46 < y cms < -2.96) and forward (2.03 < y cms < 3.53) rapidity intervals in the dimuon decay channel and in the mid-rapidity region (-1.37 < y cms < 0.43) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The p T -differential J/Ψ production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average p T and p T2 values. The nuclear modification factor is presented as a function of centrality for the three rapidity intervals, and as a function of p T for several centrality classes at backward and forward rapidity. At mid-and forward rapidity, the J/Ψ yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. Furthermore, the degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing p T of the J/Ψ. At backward rapidity, the nuclear modification factor is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions.
One-dimensional pion, kaon, and proton femtoscopy in Pb-Pb collisions at s NN = 2.76 TeV
The size of the particle emission region in high-energy collisions can be deduced using the femtoscopic correlations of particle pairs at low relative momentum. Such correlations arise due to quantum statistics and Coulomb and strong final state interactions. In this paper, results are presented from femtoscopic analyses of π ± π ± , K ± K ± , K$0\atop{S}$K$0\atop{S}$, pp , and $\overline{p}$ $\overline{p}$ correlations from Pb-Pb collisions at s NN = 2.76 TeV by the ALICE experiment at the LHC. One-dimensional radii of the system are extracted from correlation functions in terms of the invariant momentum difference of the pair. The comparison of the measured radii with the predictions from a hydrokinetic model is discussed. The pion and kaon source radii display a monotonic decrease with increasing average pair transverse mass m T which is consistent with hydrodynamic model predictions for central collisions. Lastly, the kaon and proton source sizes can be reasonably described by approximate m T scaling.