Coherent ψ (2S) photo-production in ultra-peripheral Pb–Pb collisions at s NN = 2.76 TeV
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Engineering topics
Adam, J.
Publications and source records attributed to Adam, J..
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.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Study of secondary neutron interactions with 232 Th, 129 I, and 127 I nuclei with the uranium assembly “QUINTA” at 2, 4, and 8GeV deuteron beams of the JINR Nuclotron accelerator
The natural uranium assembly, “QUINTA”, was irradiated with 2, 4, and 8 GeV deuterons. The 232 Th, 127 I, and 129 I samples have been exposed to secondary neutrons produced in the assembly at a 20-cm radial distance from the deuteron beam axis. The spectra of gamma rays emitted by the activated 232 Th, 127 I, and 129 I samples have been analyzed and several tens of product nuclei have been identified. For each of those products, neutron-induced reaction rates have been determined. The transmutation power for the 129 I samples is estimated. Furthermore, experimental results were compared to those calculated with well-known stochastic and deterministic codes.
43 PARTICLE ACCELERATORS↗
SMWDs as SGRs/AXPs and the lepton number violation
Possible nature of strongly magnetized white dwarfs (SMWDs) is studied. It is shown that for relatively low values of the equatorial surface magnetic field B ∼ 10{sup 9} − 10{sup 11} G they can be good candidates for soft gamma-ray repeaters and anomalous X-ray pulsars (SGRs/AXPs). For the case of iron SMWDs the influence of a neutrinoless electron to positron conversion on the SGRs/AXPs luminosity is estimated.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at $\sqrt{s_{NN}}$ =2.76 TeV
We report the measurement of a new observable of jet quenching in central Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV, based on the semi-inclusive rate of charged jets recoiling from a high transverse momentum (high-p T) charged hadron trigger. Jets are measured using collinear-safe jet reconstruction with infrared cutoff for jet constituents of 0.15 GeV, for jet resolution parameters R = 0.2, 0.4 and 0.5. Underlying event background is corrected at the event-ensemble level, without imposing bias on the jet population. Recoil jet spectra are reported in the range 20 < p T,jet ch < 100 GeV. Reference distributions for pp collisions at $ \sqrt{s}=2.76 $ TeV are calculated using Monte Carlo and NLO pQCD methods, which are validated by comparing with measurements in pp collisions at $ \sqrt{s}=7 $ TeV. The recoil jet yield in central Pb-Pb collisions is found to be suppressed relative to that in pp collisions. No significant medium-induced broadening of the intra-jet energy profile is observed within 0.5 radians relative to the recoil jet axis. Additionally, the angular distribution of the recoil jet yield relative to the trigger axis is found to be similar in central Pb-Pb and pp collisions, with no significant medium-induced acoplanarity observed. Large-angle jet deflection, which may provide a direct probe of the nature of the quasi-particles in hot QCD matter, is explored.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of charm and beauty production at central rapidity versus charged-particle multiplicity in proton-proton collisions at $ \sqrt{s}=7 $ TeV
Prompt D meson and non-prompt J/ψ yields are studied as a function of the multiplicity of charged particles produced in inelastic proton-proton collisions at a centre-of-mass energy of √s = 7 TeV. The results are reported as a ratio between yields in a given multiplicity interval normalised to the multiplicity-integrated ones (relative yields). They are shown as a function of the multiplicity of charged particles normalised to the average value for inelastic collisions (relative charged-particle multiplicity). D 0 , D + and D *+ mesons are measured in five p T intervals from 1 GeV/c to 20 GeV/c and for |y| < 0.5 via their hadronic decays. The D-meson relative yield is found to increase with increasing charged-particle multiplicity. For events with multiplicity six times higher than the average multiplicity of inelastic collisions, a yield enhancement of a factor about 15 relative to the multiplicity-integrated yield in inelastic collisions is observed. The yield enhancement is independent of transverse momentum within the uncertainties of the measurement. The D0-meson relative yield is also measured as a function of the relative multiplicity at forward pseudo-rapidity. The non-prompt J/ψ, i.e. the B hadron, contribution to the inclusive J/ψ production is measured in the di-electron decay channel at central rapidity. It is evaluated for p T > 1.3 GeV/c and |y| < 0.9, and extrapolated to p T > 0. The fraction of non-prompt J/ψ in the inclusive J/ψ yields shows no dependence on the charged-particle multiplicity at central rapidity. Charm and beauty hadron relative yields exhibit a similar increase with increasing charged-particle multiplicity. The measurements are compared to PYTHIA 8, EPOS 3 and percolation calculations.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Coherent ρ 0 photoproduction in ultra-peripheral Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV
We report the first measurement at the LHC of coherent photoproduction of ρ o mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for ρ o production are studied in the π + π - decay channel at mid-rapidity. The production cross section in the rapidity range |y| < 0.5 is found to be dσ/dy = 425 ± 10(stat.) -50 + 42 (sys.) mb. Coherent ρ o production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. Lastly, the results are compared with those from lower energies and with model predictions.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Precision measurement of the mass difference between light nuclei and anti-nuclei
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Physics - Nuclear physics and radiation physics, P↗