982 research outputs found
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 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 GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
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 , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean 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.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
AINUR: Atlas of Images of NUclear Rings
We present the most complete atlas of nuclear rings to date. We include 113
rings found in 107 galaxies, six of which are elliptical galaxies, five are
highly inclined disc galaxies, 18 are unbarred disc galaxies, and 78 are barred
disc galaxies. Star-forming nuclear rings occur in 20% of disc galaxies with
types between T=-3 and T=7. We aim to explore possible relationships between
the size and morphology of the rings and various galactic parameters. We
produce colour index and structure maps, as well as Halpha and Paalpha
continuum-subtracted images from HST archival data. We derive ellipticity
profiles from H-band 2MASS images in order to detect bars and find their metric
parameters. We measure the non-axisymmetric torque parameter, Qg, and search
for correlations between bar, ring metric parameters, and Qg.
Our atlas of nuclear rings includes star-forming and dust rings. Nuclear
rings span a range from a few tens of parsecs to a few kiloparsecs in radius.
Star-forming nuclear rings can be found in a wide range of morphological types,
from S0 to Sd, with a peak in the distribution between Sab and Sb, and without
strong preference for barred galaxies. Dust nuclear rings are found in
elliptical and S0 galaxies. For barred galaxies, the maximum radius that a
nuclear ring can reach is a quarter of the bar radius. We found a nearly random
distribution of PA offsets between nuclear rings and bars. There is some
evidence that nuclear ring ellipticity is limited by bar ellipticity. We
confirm that the maximum relative size of a star-forming nuclear ring is
inversely proportional to the non-axisymmetric torque parameter, Qg, and that
the origin of nuclear rings, even the ones in non-barred hosts, are closely
linked to the existence of dynamical resonances.Comment: Accepted for publication in MNRAS. A full resolution version of the
manuscript with high resolution figures can be found at
http://www.iac.es/folleto/research/preprints
Pasados releídos: el Dolmen del Portillo de las Cortes. Guadalajara / MAN
La oportunidad de retomar el estudio del dolmen del Portillo de las Cortes, Guadalajara, a partir de los materiales conservados en el MAN y de recientes trabajos de campo, ofrece un resultado positivo. Podemos aportar el conocimiento de fuentes de aprovisionamiento, una fecha C14 obtenida de un cráneo recientemente documentado en la reestructuración del MAN, y una nueva lectura de posibles refacturas del monumento
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
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