81 research outputs found
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
The Electronics and Data Acquisition System of the DarkSide Dark Matter Search
It is generally inferred from astronomical measurements that Dark Matter (DM)
comprises approximately 27\% of the energy-density of the universe. If DM is a
subatomic particle, a possible candidate is a Weakly Interacting Massive
Particle (WIMP), and the DarkSide-50 (DS) experiment is a direct search for
evidence of WIMP-nuclear collisions. DS is located underground at the
Laboratori Nazionali del Gran Sasso (LNGS) in Italy, and consists of three
active, embedded components; an outer water veto (CTF), a liquid scintillator
veto (LSV), and a liquid argon (LAr) time projection chamber (TPC). This paper
describes the data acquisition and electronic systems of the DS detectors,
designed to detect the residual ionization from such collisions
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
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
Gamma-ray astronomy and cosmic-ray physics with ARGO-YBJ
The ARGO-YBJ detector, located 4300 m a.s.l. on the Tibet plateau, is a ground-based, full-
coverage array of Resistive Plate Chambers (RPCs) covering a surface of 78×74 m2, surrounded
by a guard ring of RPCs enclosing a total surface of about 11000 m2. ARGO-YBJ was designed
to detect extensive air showers generated by cosmic rays and gamma rays with primary energy
greater than few hundred GeV, in order to study the region of the cosmic-ray spectrum out of the
reach of both satellite-based experiments and traditional ground-based arrays. The experiment has
been running with its complete layout since November 2007, collecting over 2:5×1011 events.
The main results obtained by ARGO-YBJ will be presented here, and specifically: the monitoring
of astronomical gamma-ray sources, such as the Crab nebula and the MRK 421 AGN, the moon
shadow, the medium-scale anisotropy map, the proton-proton inelastic cross section at center-of-
mass energy between 70 and 500 GeV where no accelerator data are available
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