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  1. Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at sqrt(s)=0.9, 2.76 and 7 TeV

    See paper for full list of authors - 21 pages, 11 figures ; Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at sqrt(s)=0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The... mehr

     

    See paper for full list of authors - 21 pages, 11 figures ; Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at sqrt(s)=0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with $p_{\rm T}\geq0.5$ GeV/c in $|\eta|\leq0.8$. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity ($N_{\rm ch}$) is reported for events with different $p_{\rm T}$ 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 $N_{\rm ch}$, whereas the event generators show the opposite tendency. The combined study of the sphericity and the mean $p_{\rm T}$ 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.

     

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    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1434-6044 ; EISSN: 1434-6052 ; European Physical Journal C: Particles and Fields ; http://hal.in2p3.fr/in2p3-00699404 ; European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2012, 72, pp.2124. ⟨10.1140/epjc/s10052-012-2124-9⟩
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]
  2. Measurement of prompt and non-prompt J/psi production cross sections at mid-rapidity in pp collisions at sqrt(s) = 7 TeV

    see paper for full list of authors ; The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at {\surd}s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L_int =... mehr

     

    see paper for full list of authors ; The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at {\surd}s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L_int = 5.6nb-1. The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum pt > 1.3 GeV/c and rapidity |y| < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the Psi(2S) and Csi_c resonances, is sigma_prompt-J/psi(pt > 1.3 GeV/c, |y| < 0.9) = 7.2 +- 0.7(stat.) +- 1.0(syst.)+1.3-1.2 (syst.pol.) mb. The pt-differential cross section for prompt J/psi has also been measured. The cross section for the production of b-hadrons decaying to J/psi with transverse momentum greater than 1.3 GeV/c in the rapidity range |y| < 0.9 is sigma_{J/psi<-h_B} = 1.26 +- 0.33 (stat.) +0.23-0.28 (syst.) mb. The results are compared to QCD model predictions. The shape of the pt and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the bb pair total cross section and dsigma/dy at midrapidity.

     

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    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1126-6708 ; EISSN: 1029-8479 ; Journal of High Energy Physics ; http://hal.in2p3.fr/in2p3-00702009 ; Journal of High Energy Physics, Springer, 2012, 2012, pp.065. &#x27E8;10.1007/JHEP11(2012)065&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]
  3. Measurement of charm production at central rapidity in proton-proton collisions at sqrt(s) = 2.76 TeV

    See paper for full list of authors ; The pt-differential production cross sections of the prompt (B feed-down subtracted) charmed mesons D0, D+, and D*+ in the rapidity range |y|<0.5, and for transverse momentum 1< pt <12 GeV/c, were measured in... mehr

     

    See paper for full list of authors ; The pt-differential production cross sections of the prompt (B feed-down subtracted) charmed mesons D0, D+, and D*+ in the rapidity range |y|<0.5, and for transverse momentum 1< pt 12 GeV/c, were measured in proton-proton collisions at sqrt(s) = 2.76 TeV with the ALICE detector at the Large Hadron Collider. The analysis exploited the hadronic decays D0 -> K pi, D+ -> K pi pi, D*+ -> D0 pi, and their charge conjugates, and was performed on a L_{int} = 1.35 nb^{-1} event sample collected in 2011 with a minimum-bias trigger. The total charm production cross section at sqrt(s) = 2.76 TeV and at 7 TeV was evaluated by extrapolating to the full phase space the pt-differential production cross sections at sqrt(s) = 2.76 TeV and our previous measurements at sqrt(s) = 7 TeV. The results were compared to existing measurements and to perturbative-QCD calculations. The fraction of cubar D mesons produced in a vector state was also determined.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1126-6708 ; EISSN: 1029-8479 ; Journal of High Energy Physics ; http://hal.in2p3.fr/in2p3-00705656 ; Journal of High Energy Physics, Springer, 2012, 7, pp.191. &#x27E8;10.1007/JHEP07(2012)191&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]