70 research outputs found
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV
We report on the first measurement of the triangular , quadrangular
, and pentagonal charged particle flow in Pb-Pb collisions at 2.76
TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show
that the triangular flow can be described in terms of the initial spatial
anisotropy and its fluctuations, which provides strong constraints on its
origin. In the most central events, where the elliptic flow and
have similar magnitude, a double peaked structure in the two-particle azimuthal
correlations is observed, which is often interpreted as a Mach cone response to
fast partons. We show that this structure can be naturally explained from the
measured anisotropic flow Fourier coefficients.Comment: 10 pages, 4 figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/387
Measurement of D+- and D0 production in deep inelastic scattering using a lifetime tag at HERA
The production of D-+/-- and D-0-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb(-1). The measurements cover the kinematic range 5 < Q(2) < 1000 GeV2, 0.02 < y < 0.7, 1.5 < p(T)(D) < 15 GeV and |eta(D)| < 1.6. Combinatorial background to the D-meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD, which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, F-2(c (c) over bar), to the proton structure function, F-2
Dynamic contributions of P- and E-selectins to beta(2)-integrin-induced neutrophil transmigration
Leukocyte transendothelial migrationis a key step in their recruitment to sites of inflammation. However, synergic regulation of endothelium-expressed selectins on leukocyte transmigration remains unclear. In this study, an in vitro model was developed to investigate the dynamic contributions of P- and E-selectin to polymorphonuclear neutrophil (PMN) transmigration under static conditions. Human umbilical vein endothelial cells (HUVECs) were treated with LPS for 4 or 12 h to induce different expression of selectins and intercellular adhesion molecule (ICAM)-1. PMN transmigration was increased significantly by LPS stimulation, which was higher on 4-h than on 12-h LPS treated HUVECs. Blocking and competitive tests indicated that P-selectin engages PSGL-1 to activate beta(2)-integrin and initiate PMN transmigration within the first 15 min, whereas E-selectin engages CD44 to influence PMN transmigration after 15 min. P-and E-selectin-induced beta(2)-integrin activation is likely conducted through the spleen tyrosine kinase signaling pathway. Complicated complementary and competitive mechanisms are involved in the interaction of P-/E-selectins and their ligands to promote PMN transmigration. These results provide direct evidence of the distinct and dynamic contribution of P- and E-selectins inmediating PMN transmigration and give new insight into PMN interaction with the vessel wall.-Gong, Y., Zhang, Y., Feng, S., Liu, X., Lu, S., Long, M. Dynamic contributions of P-and E-selectins to beta(2)-integrin-induced neutrophil transmigration.</p
Production of Excited Charm and Charm-Strange Mesons at HERA
The production of excited charm, D 1(2420)0 and D 2 * (2460)0, and charm-strange, D s1(2536)±, mesons in ep collisions was measured with the ZEUS detector at HERA using an integrated luminosity of 126 pb -1. Masses, widths and helicity parameters were determined. The measured yields were converted to the rates of c quarks hadronising as a given excited charm meson and to the ratios of the dominant D 2 * (2460)0 and D s1(2536) ± branching fractions. A search for the radially excited charm meson, D *(2640)±, was also performed. The results are compared with those measured previously and with theoretical expectations
Improved Potentiometric and Optic Sensitivity of Polyaniline Film to Dissolved Oxygen by Incorporating Iron-Porphyrin
Polyaniline (PAn) films can be used in an electrochemical and optical combination system to amplify the optical signal for dissolved oxygen (DO) detection. To further improve the sensitivity of PAn film to DO, an oxygen-sensitive molecule, Fe(III) meso-tetera (4-sulfonatophenyl) porphyrin (FeTSPP) is incorporated into PAn during the film generation. Results show that, after incorporating FeTSPP into the PAn matrix, both optical and potentiometric responses to DO are improved. The optimal optical signal is obtained under the application of -2.5 mu A to the modified electrode. Under this applied current, both optical and potentiometric signals show linear relations with the DO concentration within the range of 0.00-4.63 mgL(-1), and the sensitivities for optical and potentiometric signals are 4.18 grayscale units mg(-1)L and 13.39 mVmg(-1) L, respectively
Gamma-ray astronomy with ARGO-YBJ
ARGO-YBJ is a full coverage air shower array located at the YangBaJing Cosmic
Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm2) recording data with a duty
cycle ≥85% and an energy threshold of a few hundred GeV. In this paper the latest results
in Gamma-Ray Astronomy are summarized
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