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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
Ultrarelativistic nucleus-nucleus collisions and the quark-gluon plasma
We present an overview of selected aspects of ultrarelativistic
nucleus-nucleus collisions, a research program devoted to the study of strongly
interacting matter at high energy densities and in particular to the
characterization of the quark-gluon plasma (QGP). The basic features of the
phase diagram of nuclear matter, as currently understood theoretically, are
discussed. The experimental program, carried out over a broad energy domain at
various accelerators, is briefly reviewed, with an emphasis on the global
characterization of nucleus-nucleus collisions. Two particular aspects are
treated in more detail: i) the application of statistical models to a
phenomenological description of particle production and the information it
provides on the phase diagram; ii) the production of hadrons carrying charm
quarks as messengers from the QGP phase.Comment: Based on lectures given by P.Braun-Munzinger at the VIII Hispalensis
International Summer School, Oromana (Seville, Spain), June 9-21, 2003 32
pages, 20 figures. A clickable list of references available at
http://www-linux.gsi.de/~andronic/qgp/qgp.htm
Transport of a quantum degenerate heteronuclear Bose-Fermi mixture in a harmonic trap
We report on the transport of mixed quantum degenerate gases of bosonic 87Rb
and fermionic 40K in a harmonic potential provided by a modified QUIC trap. The
samples are transported over a distance of 6 mm to the geometric center of the
anti-Helmholtz coils of the QUIC trap. This transport mechanism was implemented
by a small modification of the QUIC trap and is free of losses and heating. It
allows all experiments using QUIC traps to use the highly homogeneous magnetic
fields that can be created in the center of a QUIC trap and improves the
optical access to the atoms, e.g., for experiments with optical lattices. This
mechanism may be cascaded to cover even larger distances for applications with
quantum degenerate samples.Comment: 7 pages, 8 figure
High-contrast dark resonance on the D2 - line of 87Rb in a vapor cell with different directions of the pump - probe waves
We propose a novel method enabling to create a high-contrast dark resonance
in the 87Rb vapor D2-line. The method is based on an optical pumping of atoms
into the working states by a two-frequency, linearly-polarized laser radiation
propagating perpendicularly to the probe field. This new scheme is compared to
the traditional scheme involving the circularly-polarized probe beam only, and
significant improvement of the dark resonance parameters is found. Qualitative
considerations are confirmed by numerical calculations.Comment: 7 pages, 4 figure
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
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