Filtern nach
Letzte Suchanfragen

Ergebnisse für *

Zeige Ergebnisse 1 bis 9 von 9.

  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.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    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.

     

    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/in2p3-00702009 ; 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. Direct-Photon Production in p+p Collisions at sqrt(s)=200 GeV at Midrapidity

    See paper for full list of authors ; PHENIX Collaboration, 383 authors, 16 pages, 14 figures, 7 tables. Submitted to Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be)... mehr

     

    See paper for full list of authors ; PHENIX Collaboration, 383 authors, 16 pages, 14 figures, 7 tables. Submitted to Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at www.phenix.bnl.gov/papers.html ; The differential cross section for the production of direct photons in p+p collisions at sqrt(s)=200 GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider. Inclusive-direct photons were measured in the transverse-momentum range from 5.5--25 GeV/c, extending the range beyond previous measurements. Event structure was studied with an isolation criterion. Next-to-leading-order perturbative-quantum-chromodynamics calculations give a good description of the spectrum. When the cross section is expressed versus x_T, the PHENIX data are seen to be in agreement with measurements from other experiments at different center-of-mass energies.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1550-7998 ; EISSN: 1550-2368 ; Physical Review D ; https://hal.in2p3.fr/in2p3-00703928 ; Physical Review D, American Physical Society, 2012, 86, pp.072008. &#x27E8;10.1103/PhysRevD.86.072008&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
  4. K0s-K0s correlations in pp collisions at sqrt{s}=7 TeV from the LHC ALICE experiment

    See paper for full list of authors - 10 pages + author list, 7 figures, to be submitted to Physics Letters B ; Identical neutral kaon pair correlations are measured in sqrt{s}=7 TeV pp collisions in the ALICE experiment. One-dimensional K0s-K0s... mehr

     

    See paper for full list of authors - 10 pages + author list, 7 figures, to be submitted to Physics Letters B ; Identical neutral kaon pair correlations are measured in sqrt{s}=7 TeV pp collisions in the ALICE experiment. One-dimensional K0s-K0s correlation functions in terms of the invariant momentum difference of kaon pairs are formed in two multiplicity and two transverse momentum ranges. The femtoscopic parameters for the radius and correlation strength of the kaon source are extracted. The fit includes quantum statistics and final-state interactions of the a0/f0 resonance. K0s-K0s correlations show an increase in radius for increasing multiplicity and a slight decrease in radius for increasing transverse mass, mT, as seen in pion-pion correlations in the pp system and in heavy-ion collisions. Transverse mass scaling is observed between the K0s-K0s and pion-pion radii. Also, the first observation is made of the decay of the f2'(1525) meson into the K0s-K0s channel in pp collisions.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 0370-2693 ; Physics Letters B ; https://hal.in2p3.fr/in2p3-00707149 ; Physics Letters B, Elsevier, 2012, 717, pp.151-161. &#x27E8;10.1016/j.physletb.2012.09.013&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
  5. Direct photon production in d+Au collisions at sqrt(s_NN)=200 GeV at midrapidity

    see paper for full list of authors - 547 authors, 7 pages, 4 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at... mehr

     

    see paper for full list of authors - 547 authors, 7 pages, 4 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at www.phenix.bnl.gov/papers.html ; The differential cross section for the production of direct photons in p+p collisions at √s=200 GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider. Inclusive direct photons were measured in the transverse momentum range from 5.5-25 GeV/c, extending the range beyond previous measurements. Event structure was studied with an isolation criterion. Next-to-leading-order perturbative-quantum-chromodynamics calculations give a good description of the spectrum. When the cross section is expressed versus xT, the PHENIX data are seen to be in agreement with measurements from other experiments at different center-of-mass energies.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1550-7998 ; EISSN: 1550-2368 ; Physical Review D ; http://hal.in2p3.fr/in2p3-00723336 ; Physical Review D, American Physical Society, 2012, 86, pp.072008. &#x27E8;10.1103/PhysRevD.86.072008&#x27E9;
    Schlagworte: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
  6. Deviation from quark number scaling of the anisotropy parameter v2 of pions, kaons, and protons in Au+Au collisions at √sNN=200 GeV

    See paper for full list of authors ; Measurements of the anisotropy parameter v2 of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum pT, and transverse kinetic energy KET at midrapidity (|η|<0.35) in Au... mehr

     

    See paper for full list of authors ; Measurements of the anisotropy parameter v2 of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum pT, and transverse kinetic energy KET at midrapidity (|η|<0.35) in Au + Au collisions at √sNN=200 GeV are presented. Pions and protons are identified up to pT= 6 GeV/c, and kaons up to pT= 4 GeV/c, by combining information from time-of-flight and aerogel Čerenkov detectors in the PHENIX Experiment. The scaling of v2 with the number of valence quarks (nq) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observed quark-number scaling is observed at large values of KET/nq in noncentral Au + Au collisions (20-60%), but this scaling remains valid in central collisions (0-10%).

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 2469-9985 ; EISSN: 2469-9993 ; Physical Review C ; http://hal.in2p3.fr/in2p3-00724075 ; Physical Review C, American Physical Society, 2012, 85, pp.064914. &#x27E8;10.1103/PhysRevC.85.064914&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
  7. Inclusive cross section and single-transverse-spin asymmetry for very forward neutron production in polarized p+p collisions at sqrt(s)=200 GeV

    see paper for full list of authors - 383 authors, 16 pages, 18 figures, 6 tables. Submitted to Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at... mehr

     

    see paper for full list of authors - 383 authors, 16 pages, 18 figures, 6 tables. Submitted to Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at www.phenix.bnl.gov/papers.html ; The energy dependence of the single-transverse-spin asymmetry, A_N, and the cross section for neutron production at very forward angles were measured in the PHENIX experiment at RHIC for polarized p+p collisions at sqrt(s)=200 GeV. The neutrons were observed in forward detectors covering an angular range of up to 2.2 mrad. We report results for neutrons with momentum fraction of x_F=0.45 to 1.0. The energy dependence of the measured cross sections were consistent with x_F scaling, compared to measurements by an ISR experiment which measured neutron production in unpolarized p+p collisions at sqrt(s)=30.6--62.7 GeV. The cross sections for large x_F neutron production for p+p collisions, as well as those in e+p collisions measured at HERA, are described by a pion exchange mechanism. The observed forward neutron asymmetries were large, reaching A_N=-0.08+/-0.02 for x_F=0.8; the measured backward asymmetries, for negative x_F, were consistent with zero. The observed asymmetry for forward neutron production is discussed within the pion exchange framework, with interference between the spin-flip amplitude due to the pion exchange and nonflip amplitudes from all Reggeon exchanges. Within the pion exchange description, the measured neutron asymmetry is sensitive to the contribution of other Reggeon exchanges even for small amplitudes.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1550-7998 ; EISSN: 1550-2368 ; Physical Review D ; http://hal.in2p3.fr/in2p3-00734009 ; Physical Review D, American Physical Society, 2012, 88, pp.032006. &#x27E8;10.1103/PhysRevD.88.032006&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
  8. Erratum: Measurement of transverse single-spin asymmetries for J/psi production in polarized p+p collisions at sqrt(s)=200 GeV [Phys. Rev. D 82, 112008 (2010)]

    431 authors from 62 institutions, 3 pages, 2 figures, and 3 tables. Erratum submitted to Physical Review D, see paper for full list of authors ; International audience ; We previously reported [Phys. Rev. D 82, 112008 (2010)] measurements of... mehr

     

    431 authors from 62 institutions, 3 pages, 2 figures, and 3 tables. Erratum submitted to Physical Review D, see paper for full list of authors ; International audience ; We previously reported [Phys. Rev. D 82, 112008 (2010)] measurements of transverse single-spin asymmetries, A_N, in J/psi production from transversely polarized p+p collisions at sqrt(s)=200 GeV with data taken by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2006 and 2008. Subsequently, we have found errors in the analysis procedures for the 2008 data, which resulted in an erroneous value for the extracted A_N. The errors affected the sorting of events into the correct left/right and forward/backward bins. This produced an incorrect value for the 2008 result, but the 2006 result is unaffected. We have conducted two independent reanalyses with these errors corrected, and we present here the corrected values for the 2008 data and the combined results for 2006 and 2008. The new combined spin asymmetry in the forward region is A_N = -0.026+/-0.026(stat)+/-0.003(sys). Since this asymmetry is consistent with zero, we no longer claim that our results suggest a possible non-zero trigluon correlation function in transversely polarized protons.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 1550-7998 ; EISSN: 1550-2368 ; Physical Review D ; https://hal.in2p3.fr/in2p3-00745786 ; Physical Review D, American Physical Society, 2012, 86, pp.099904. &#x27E8;10.1103/PhysRevD.86.099904&#x27E9;
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]
  9. Upsilon (1S+2S+3S) production in d+Au and p+p collisions at sqrt(s_NN)=200 GeV and cold-nuclear matter effects

    see paper for full list of authors, 495 authors, 11 pages, 9 figures, 5 tables. Submitted to Phys. Rev. C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at... mehr

     

    see paper for full list of authors, 495 authors, 11 pages, 9 figures, 5 tables. Submitted to Phys. Rev. C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at www.phenix.bnl.gov/papers.html ; The three Upsilon states, Upsilon(1S+2S+3S), are measured in d+Au and p+p collisions at sqrt(s_NN)=200 GeV and rapidities 1.2<|y|<2.2 by the PHENIX experiment at the Relativistic Heavy-Ion Collider. Cross sections for the inclusive Upsilon(1S+2S+3S) production are obtained. The inclusive yields per binary collision for d+Au collisions relative to those in p+p collisions (R_dAu) are found to be 0.62 +/- 0.26 (stat) +/- 0.13 (syst) in the gold-going direction and 0.91 +/- 0.33 (stat) +/- 0.16 (syst) in the deuteron-going direction. The measured results are compared to a nuclear-shadowing model, EPS09 [JHEP 04, 065 (2009)], combined with a final-state breakup cross section, sigma_br, and compared to lower energy p+A results. We also compare the results to the PHENIX J/psi results [Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity dependence of the observed Upsilon suppression is consistent with lower energy p+A measurements.

     

    Export in Literaturverwaltung   RIS-Format
      BibTeX-Format
    Quelle: BASE Fachausschnitt AVL
    Sprache: Englisch
    Medientyp: Aufsatz aus einer Zeitschrift
    Format: Online
    Übergeordneter Titel: ISSN: 0031-9007 ; EISSN: 1079-7114 ; Physical Review Letters ; http://hal.in2p3.fr/in2p3-00756698 ; Physical Review Letters, American Physical Society, 2012, 109, pp.242301. &#x27E8;10.1103/PhysRevLett.109.242301&#x27E9;
    Schlagworte: [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]