423 research outputs found
Suppression of high transverse momentum D mesons in central Pb-Pb collisions at √sNN= 2.76 TeV
The production of the prompt charm mesons D0, D+, D∗+, and their antiparticles,
was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a
centre-of-mass energy √sNN = 2.76 TeV per nucleon-nucleon collision. The pt-differential
production yields in the range 2 < pt < 16 GeV/c at central rapidity, |y| < 0.5, were used
to calculate the nuclear modification factor RAA with respect to a proton-proton reference
obtained from the cross section measured at √s = 7 TeV and scaled to √s = 2.76 TeV. For
the three meson species, RAA shows a suppression by a factor 3–4, for transverse momenta
larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for
peripheral collisions
An overview of the mid-infrared spectro-interferometer MATISSE: science, concept, and current status
MATISSE is the second-generation mid-infrared spectrograph and imager for the
Very Large Telescope Interferometer (VLTI) at Paranal. This new interferometric
instrument will allow significant advances by opening new avenues in various
fundamental research fields: studying the planet-forming region of disks around
young stellar objects, understanding the surface structures and mass loss
phenomena affecting evolved stars, and probing the environments of black holes
in active galactic nuclei. As a first breakthrough, MATISSE will enlarge the
spectral domain of current optical interferometers by offering the L and M
bands in addition to the N band. This will open a wide wavelength domain,
ranging from 2.8 to 13 um, exploring angular scales as small as 3 mas (L band)
/ 10 mas (N band). As a second breakthrough, MATISSE will allow mid-infrared
imaging - closure-phase aperture-synthesis imaging - with up to four Unit
Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. Moreover, MATISSE
will offer a spectral resolution range from R ~ 30 to R ~ 5000. Here, we
present one of the main science objectives, the study of protoplanetary disks,
that has driven the instrument design and motivated several VLTI upgrades
(GRA4MAT and NAOMI). We introduce the physical concept of MATISSE including a
description of the signal on the detectors and an evaluation of the expected
performances. We also discuss the current status of the MATISSE instrument,
which is entering its testing phase, and the foreseen schedule for the next two
years that will lead to the first light at Paranal.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June
2016, 11 pages, 6 Figure
Multiplicity dependence of the average transverse momentum in pp, p–Pb, and Pb–Pb collisions at the LHC
72
Inclusive J/ψ production in pp collisions at √s = 2.76 TeV
The ALICE Collaboration has measured inclusive J/ψ production in pp collisions at a center-of-mass energy √s = 2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y| < 0.9 and 2.5 < y < 4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are Le int = 1.1 nb−1 and L μ int = 19.9 nb−1, and the corresponding signal statistics are Ne+e− J/ψ = 59 ± 14 and Nμ+μ− J/ψ = 1364 ± 53. We present dσJ/ψ /dy for the two rapidity regions under study and, for the forward-y range, d2σJ/ψ /dy dpt in the transverse momentum domain 0 < pt < 8 GeV/c. The results are compared with previously published results at √s = 7 TeV and with theoretical calculations
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
Математична модель поверхні тіла у неявній формі на основі інтерфлетації функцій
В роботi запропоновано, з використанням iнтерфлетацiї функцiй, новий, загальний метод побудови рiвнянь поверхонь тiл складної форми в наявнiй формi ∂G : OG(x, y, z) = 0, де ∂G — поверхня 3D-тiла G. Функцiя OG(x, y, z) що належить C^r(R^3), r ≥ 1, є найкращим середньоквадратичним наближенням до функцiї f(x, y, z) що належить C(R^3), побудованої за допомогою R-функцiй, яка входить в рiвняння f(x, y, z) = 0, (x, y, z) що належить ∂G.A new general method, which uses the interflatation of functions, of construction of the equations of surfaces of bodies with complex shape in the implicit form OG(x, y, z) = 0, (x, y, z) belongs ∂G, where ∂G is the surface of the 3D body G, is offered. The function OG(x, y, z) belongs C^r(R^3), r ≥ 1 is the best mean-square approximation of the function f(x, y, z) belongs C(R^3) which is built with the use of R-functions and satisfies the equation f(x, y, z) = 0, (x, y, z) belongs ∂G
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
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
- …