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    65 research outputs found

    Measurement of prompt J/ψ and beauty hadron production cross sections at mid-rapidity in pp collisions at √s =7 TeV

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    The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at s √ =7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5.6 nb−1. The fraction of J/ψ from the decay of long-lived beauty hadrons was determined for J/ψ candidates with transverse momentum p t > 1.3 GeV/c and rapidity |y| 1.3 GeV/c, |y| 1.3 GeV/c and |y| 1.3 GeV/c, |y| <0.9) = 1.46 ± 0.38 (stat.) +0.26 −0.32 (syst.) μb. The results are compared to QCD model predictions. The shape of the p t and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section t
    Portail HAL Nantes Université
    Archivio istituzionale della ricerca - Università di Bari
    Archivio istituzionale della ricerca - Università di Brescia
    RCAAP - Repositório Científico de Acesso Aberto de Portugal
    Archivio istituzionale della ricerca - Università di Cagliari
    Archivio Istituzionale della Ricerca- Università degli Studi di Foggia
    NORA - Norwegian Open Research Archives
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale
    Yıldız Technical University Research Information System
    Archivio istituzionale della ricerca - Università di Padova
    Archivio istituzionale della ricerca - Università di Trieste
    Bergen Open Research Archive (Univ. of Bergen)
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Repositório da Produção USP (Univ. de São Paulo)
    Repository of the Vinča Nuclear Institute (VinaR)
    HVL Open (Høgskulen på Vestlandet)
    Utrecht University Repository
    GSI Repository
    HAL
    Hal - Université Grenoble Alpes
    HAL Clermont Université
    HAL Mines Nantes
    HAL-CEA
    Repositorio da Producao Cientifica e Intelectual da Unicamp
    Lund University Publications
    HAL-IN2P3
    Crossref
    Politecnio die Bari - Catalogo di prodotti della Ricerca
    Springer - Publisher Connector
    Archivio della Ricerca - Università di Salerno
    Archivio della ricerca- Università di Roma La Sapienza
    Institutional Research Information System University of Turin

    Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at sNN\sqrt{s_NN} = 5.02 TeV with ALICE at LHC

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    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 < pT,assoc<pT,trigp_{T,assoc} < p_{T,trig} < 5.0 GeV/c is examined, to include correlations induced by jets originating from low momentum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |η| < 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.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<pT,assoc<pT,trig<5.0 GeV/c is examined, to include correlations induced by jets originating from low momentum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |η|<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 only in the intermediate multiplicity region with the number of binary nucleon–nucleon collisions estimated with a Glauber Monte-Carlo simulation.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 <pT,assoc<pT,trig< < p_{\rm{T}, assoc} < p_{\rm{T}, trig} < 5.0 GeV/cc 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 ∣η∣<0.9|\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
    CERN Document Server
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale
    Hochschulschriftenserver - Universität Frankfurt am Main

    Underlying Event measurements in pp collisions at s\sqrt{s} = 0.9 and 7 TeV with the ALICE experiment at the LHC

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    We present measurements of Underlying Event observables in pp collisions at s\sqrt{s} = 0.9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum pT,LT in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different pT thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track pT threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed pT in the Transverse region by about 10-30%.We present measurements of Underlying Event observables in pp collisions at s\sqrt{s} = 0.9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum pT,LTp_{\rm T, LT} in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different pTp_{\rm T} thresholds: 0.15, 0.5 and 1.0 GeV/cc. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p)Tp){\rm T} threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed pTp_{\rm T} in the Transverse region by about 10-30%
    Archivio istituzionale della ricerca - Università dell'Insubria
    Archivio istituzionale della ricerca - Università di Brescia
    RCAAP - Repositório Científico de Acesso Aberto de Portugal
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale
    Yıldız Technical University Research Information System
    Archivio istituzionale della ricerca - Università di Trieste
    Lund University Publications
    Crossref
    Springer - Publisher Connector
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Archivio della Ricerca - Università di Salerno
    Repositório da Produção USP (Univ. de São Paulo)
    CERN Document Server
    GSI Repository

    Multi-strange baryon production in pp collisions at with ALICE

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    A measurement of the multi-strange Xi- and Omega- baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for proton-proton collisions at centre of mass energy of 7 TeV. The transverse momentum (pt) distributions were studied at mid-rapidity (|y| 6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Omega-+Omega+)/(Xi-+Xi+) as a function of transverse mass.A measurement of the multi-strange Ξ− and Ω− baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton–proton collisions at a centre-of-mass energy of 7 TeV. The transverse momentum ( pT ) distributions were studied at mid-rapidity ( |y|6.0 GeV/c . We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Ω−+Ω¯+)/(Ξ−+Ξ¯+) as a function of transverse mass.A measurement of the multi-strange Ξ−\Xi^- and Ω−\Omega^- baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton-proton collisions at centre of mass energy of 7 TeV. The transverse momentum (pTp_{\rm T}) distributions were studied at mid-rapidity (|y| 6.0 GeV/cc. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Ω−+Ω+)/(Ξ−+Ξ+)\Omega^{-}+\Omega^+)/(\Xi^-+\Xi^+) as a function of transverse mass
    Archivio istituzionale della ricerca - Università dell'Insubria
    Portail HAL Nantes Université
    Archivio istituzionale della ricerca - Università di Bari
    Archivio istituzionale della ricerca - Università di Brescia
    RCAAP - Repositório Científico de Acesso Aberto de Portugal
    Archivio istituzionale della ricerca - Università di Cagliari
    Archivio Istituzionale della Ricerca- Università degli Studi di Foggia
    Dspace at IIT Bombay
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale
    Yıldız Technical University Research Information System
    Archivio istituzionale della ricerca - Università di Padova
    Archivio istituzionale della ricerca - Università di Trieste
    Copenhagen University Research Information System
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Repositório da Produção USP (Univ. de São Paulo)
    Repository of the Vinča Nuclear Institute (VinaR)
    GSI Repository
    HAL
    Hal - Université Grenoble Alpes
    HAL Clermont Université
    HAL Mines Nantes
    ePubs: the open archive for STFC research publications
    HAL-CEA
    Repositorio da Producao Cientifica e Intelectual da Unicamp
    Lund University Publications
    HAL-IN2P3
    Elsevier - Publisher Connector
    Crossref
    Politecnio die Bari - Catalogo di prodotti della Ricerca
    Archives ouvertes Hal IMT Atlantique
    Archivio della Ricerca - Università di Salerno
    CERN Document Server
    Archivio della ricerca- Università di Roma La Sapienza

    Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at √sNN = 2.76 TeV

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    Archivio istituzionale della ricerca - Università dell'Insubria

    D meson elliptic flow in non-central PbPb collisions at sqrt(s_NN)=2.76 TeV

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    Azimuthally anisotropic distributions of D0, D+, and D*+ mesons were studied in the central rapidity region (|y|<0.8) in Pb-Pb collisions at a center-of-mass energy sNN ̅ ̅ ̅ ̅√=2.76 TeV per nucleon-nucleon collision, with the ALICE detector at the LHC. The second Fourier coefficient v2 (commonly denoted elliptic flow) was measured in the centrality class 30%–50% as a function of the D meson transverse momentum pT, in the range 2–16 GeV/c. The measured v2 of D mesons is comparable in magnitude to that of light-flavor hadrons. It is positive in the range 2<pT<6 GeV/c with 5.7σ significance, based on the combination of statistical and systematic uncertainties
    Politecnio die Bari - Catalogo di prodotti della Ricerca

    Long-range angular correlations on the near and away side in p–Pb collisions at sNN=5.02TeV\sqrt{s_{NN}} = 5.02 TeV

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    Angular correlations between 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 for transverse momentum ranges within 0.5 &lt; P-T,P-assoc &lt; P-T,P-trig &lt; 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge
    Archivio istituzionale della ricerca - Università dell'Insubria
    Archivio istituzionale della ricerca - Università di Brescia
    Yıldız Technical University Research Information System
    Archivio istituzionale della ricerca - Università di Trieste
    Lund University Publications
    Elsevier - Publisher Connector
    Crossref
    Politecnio die Bari - Catalogo di prodotti della Ricerca
    Indian Academy of Sciences
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Archivio della Ricerca - Università di Salerno
    GSI Repository
    Hochschulschriftenserver - Universität Frankfurt am Main

    Pion, Kaon, and Proton Production in Central Pb-Pb Collisions at √sNN=2.76 TeV

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    In this Letter we report the first results on π±, K±, p, and p̅ production at midrapidity (|y|<0.5) in central Pb-Pb collisions at √sNN=2.76 TeV, measured by the ALICE experiment at the LHC. The pT distributions and yields are compared to previous results at √sNN=200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with √sNN, which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood
    Politecnio die Bari - Catalogo di prodotti della Ricerca

    Transverse sphericity of primary charged particles in minimum bias proton–proton collisions at √s = 0.9, 2.76 and 7 TeV

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    Measurements of the sphericity of primary charged particles in minimum bias proton–proton collisions at s√=0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is measured in the plane perpendicular to the beam direction using primary charged tracks with p T>0.5 GeV/c in |η|<0.8. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity (N ch) is reported for events with different p T scales (“soft” and “hard”) defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low N ch, whereas the event generators show an opposite tendency. The combined study of the sphericity and the mean p T with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators
    Politecnio die Bari - Catalogo di prodotti della Ricerca

    Charge correlations using the balance function in Pb?Pb collisions at ?sNN = 2.76 TeV

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    Archivio istituzionale della ricerca - Università dell'Insubria
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