27 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
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
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 â„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 78Ă74 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 2:5Ă1011 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
DarkSide-50, a background free experiment for dark matter searches
The existence of dark matter is inferred from gravitational effects, but its nature remains a deep mystery. One possibility, motivated by considerations in elementary particle physics, is that dark matter consists of elementary particles, such as the hypothesized Weakly Interacting Massive Particles (WIMPs), with mass ~ 100 GeV and cross-section ~ 10â47 cm2, that can be gravitationally trapped inside our galaxy and revealed by their scattering on nuclei. It should be possible to detect WIMPs directly, as the orbital motion of the WIMPs composing the dark matter halo pervading the galaxy should result in WIMP-nucleus collisions of sufficient energy to be observable in the laboratory. The DarkSide-50 experiment is a direct WIMP search using a Liquid Argon Time Projection Chamber (LAr-TPC) with an active mass of 50 kg with a high sensitivity and an ultra-low background detector
First Results from the DarkSide-50 Dark Matter Experiment at Laboratori Nazionali del Gran Sasso
We report the first results of DarkSide-50, a direct search for dark matter operating in the un-
derground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils
possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a
Liquid Argon Time Projection Chamber with a
(
46.4
0.7
)
kg active mass, operated inside a 30 t or-
ganic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov
veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for
a
(
1422
67
)
kg d exposure with an atmospheric argon fill. This is the most sensitive dark matter
search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon
spin-independent cross section of 6.1
1
The Electronics and Data Acquisition System of the DarkSide Dark Matter Search
It is generally inferred from astronomical measurements th
at Dark
Matter (DM) comprises approximately 27% of the energy-dens
ity of the universe.
If DM is a subatomic particle, a possible candidate is a Weakl
y Interacting Mas-
sive Particle (WIMP), and the DarkSide-50 (DS) experiment i
s a direct search for
evidence of WIMP-nuclear collisions. DS is located undergr
ound at the Laboratori
Nazionali del Gran Sasso (LNGS) in Italy, and consists of thr
ee active, embedded
components; an outer water veto (CTF), a liquid scintillato
r veto (LSV), and
a liquid argon (LAr) time projection chamber (TPC). This pap
er describes the
data acquisition and electronic systems of the DS detectors
, designed to detect
the residual ionization from