Prompt D meson and non-prompt J/$\psi$ 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 ...$\sqrt{s}=7$ 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 $p_{\rm T}$ intervals from 1 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 D$^0$-meson relative yield is also measured as a function of the relative multiplicity at forward pseudorapidity. The non-prompt J/$\psi$, i.e. the B hadron, contribution to the inclusive J/$\psi$ production is measured in the di-electron decay channel at central rapidity. It is evaluated for $p_{\rm T}>1.3$ GeV/$c$ and $|y|<0.9$, and extrapolated to $p_{\rm T}>0$. The fraction of non-prompt J/$\psi$ in the inclusive J/$\psi$ 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.
The NA60 silicon pixel telescope Keil, M.; Arnaldi, R.; Banicz, K. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
09/2005, Letnik:
549, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
The NA60 experiment studies the production of open charm and prompt dimuons in proton–nucleus and nucleus–nucleus collisions at the CERN SPS. The main goal of NA60 is the study of various possible ...signatures of the transition from hadronic to deconfined partonic matter, e.g. anomalous charmonium suppression, dimuons from thermal radiation and modifications of vector meson properties. Reaching these goals is facilitated by the use of new state-of-the-art silicon detectors in the vertex region.
Downstream of the target and inside a 2.5
T dipole magnetic field a pixel telescope measures the charged tracks originating from the collisions. The full pixel telescope consists of 16 planes with 96 ALICE1LHCb pixel detector assemblies in total. This paper describes the setup of the pixel telescope, results from tests as well as the expected implications of the operation of the silicon detectors in the harsh radiation environment of the NA60 experiment, with heavy-ion collisions.
During the June 2002 run NA60 collected around 600 000 dimuon triggers in proton-nucleus collisions at 400 GeV. We show that the collected dimuon mass spectra can be understood in terms of known ...sources. The specific target setup, consisting of Beryllium, Indium and Lead targets, simultaneously exposed to the beam, allowed us to study the nuclear dependence of the production cross-section of the \(\omega\) and \(\phi\) resonances. The elementary nucleon-nucleon production cross-sections at 400 GeV for the \(\rho\), \(\omega\) and \(\phi\) mesons are also presented. By using the \(\eta\)-Dalitz decay, dominating the mass range below 450 MeV, we, furthermore, extracted the \(\eta\) production cross-section and its nuclear dependence. The results are discussed in the framework of previous measurements, mostly obtained in different decay channels, performed by NA27, HELIOS-1 and CERES-TAPS.
Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of ...5.02 TeV. The transverse-momentum range 0.7 $ < p_{\rm{T}, assoc} < p_{\rm{T}, trig} <$ 5.0 GeV/$c$ is examined, to include correlations induced by jets originating from low momen\-tum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range $|\eta|<0.9$. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton--parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p-Pb collisions. Further, the number scales in the intermediate multiplicity region with the number of binary nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.
We report on the measurement of the inclusive Υ (1S) production in Pb–Pb collisions at √ s NN = 2.76 TeV carried out at forward rapidity (2.5 < y < 4) and down to zero transverse momentum using its μ ...+ μ − decay channel with the ALICE detector at the Large Hadron Collider. A strong suppression of the inclusive Υ (1S) yield is observed with respect to pp collisions scaled by the number of independent nucleon– nucleon collisions. The nuclear modification factor, for events in the 0–90% centrality range, amounts to 0.30 ± 0.05(stat) ± 0.04(syst). The observed Υ (1S) suppression tends to increase with the centrality of the collision and seems more pronounced than in corresponding mid-rapidity measurements. Our results are compared with model calculations, which are found to underestimate the measured suppression and fail to reproduce its rapidity dependence. (creativecommons.org/licenses/by/3.0/). Funded by SCOAP 3 .
The ALICE experiment at the LHC has measured the production of {\Xi}- and {\Omega}- baryons and their anti-particles in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV. The transverse momentum spectra at ...mid-rapidity (|y| < 0.5) for charged {\Xi} and {\Omega} hyperons have been studied in the range 0.6 < pT < 8.0 GeV/c and 1.2 < pT < 7.0 GeV/c, respectively, and in several centrality intervals (from the most central 0-10% to the most peripheral 60-80% collisions). These spectra have been compared with the predictions of recent hydrodynamic models. In particular, the Krak{ó}w and EPOS models give a satisfactory description of the data, with the latter covering a wider pT range. Mid-rapidity yields, integrated over pT, have been determined. The hyperon-to-pion ratios are similar to those at RHIC: they rise smoothly with centrality up to ~ 150 and saturate thereafter. The enhancements (yields per participant nucleon relative to p-p collisions) increase both with the strangeness content of the baryon and with centrality, but are less pronounced than at lower energies.
The inclusive J/Psi nuclear modification factor Raa in Pb-Pb collisions at sqrt(sNN)=2.76TeV has been measured by ALICE as a function of centrality in the e+e- decay channel at mid-rapidity |y| < 0.8 ...and as a function of centrality, transverse momentum and rapidity in the u+u- decay channel at forward-rapidity 2.5 < y < 4.The J/Psi yields measured in Pb-Pb are suppressed compared to those in pp collisions scaled by the number of binary collisions.The Raa integrated over a centrality range corresponding to 90% of the inelastic Pb-Pb cross section is 0.72 +- 0.06 (stat.) +- 0.10 (syst.) at mid-rapidity and 0.57 +- 0.01 (stat.) +- 0.09 (syst.) at forward-rapidity.At low transverse momentum, significantly larger values of Raa are measured at forward-rapidity compared to measurements at lower energy.These features suggest that a contribution to the J/Psi yield originates from charm quarks (re)combination in the deconfined partonic medium.
We present the first measurement at the LHC of exclusive J/$\psi$ photoproduction off protons, in ultra-peripheral proton-lead collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Events are selected with a ...dimuon pair produced either in the rapidity interval, in the laboratory frame, $2.5
Charged particle multiplicity measurements in NA60 Floris, Michele; Collaboration, the NA60; Borer, K ...
Journal of Physics: Conference Series,
01/2005, Letnik:
5, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The NA60 experiment at the CERN SPS studies dimuon production in nucleusnucleus and proton-nucleus collisions. One of the main detectors in the apparatus is the silicon pixel vertex telescope, which ...tracks charged particles in the target region. This detector complements the information from the muon spectrometer, improving the dimuon mass resolution and signal-to-noise ratio of the experiment, overcoming the main limitations of its predecessors. The silicon vertex telescope also provides the experiment with the capability of measuring charged particle multiplicities. In this paper we briefly describe the experiment and some preliminary results on charged particle multiplicities for two different colliding systems at different incident beam energies (Pb-Pb at 30 AGeV and In-In at 158 AGeV).
A measurement of the transverse momentum spectra of jets in Pb-Pb collisions at sqrt(sNN)=2.76TeV is reported. Jets are reconstructed from charged particles using the anti-k_T jet algorithm with jet ...resolution parameters R of 0.2 and 0.3 in pseudo-rapidity |eta|<0.5. The transverse momentum p_T of charged particles is measured down to 0.15 GeV/c which gives access to the low p_T fragments of the jet. Jets found in heavy-ion collisions are corrected event-by-event for average background density and on an inclusive basis (via unfolding) for residual background fluctuations and detector effects. A strong suppression of jet production in central events with respect to peripheral events is observed. The suppression is found to be similar to the suppression of charged hadrons, which suggests that substantial energy is radiated at angles larger than the jet resolution parameter R=0.3 considered in the analysis. The fragmentation bias introduced by selecting jets with a high p_T leading particle, which rejects jets with a soft fragmentation pattern, has a similar effect on the jet yield for central and peripheral events. The ratio of jet spectra with R=0.2 and R=0.3 is found to be similar in Pb-Pb and simulated PYTHIA pp events, indicating no strong broadening of the radial jet structure in the reconstructed jets with R<0.3.
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