41 research outputs found
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
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Mortality prediction in chronic obstructive pulmonary disease comparing the GOLD 2015 and GOLD 2019 staging: a pooled analysis of individual patient data
In 2019, The Global Initiative for Chronic Obstructive Lung Disease (GOLD) modified the grading system for patients with COPD, creating 16 subgroups (1A–4D). As part of the COPD Cohorts Collaborative International Assessment (3CIA) initiative, we aim to compare the mortality prediction of the 2015 and 2019 COPD GOLD staging systems.
We studied 17 139 COPD patients from the 3CIA study, selecting those with complete data. Patients were classified by the 2015 and 2019 GOLD ABCD systems, and we compared the predictive ability for 5-year mortality of both classifications.
In total, 17 139 patients with COPD were enrolled in 22 cohorts from 11 countries between 2003 and 2017; 8823 of them had complete data and were analysed. Mean±sd age was 63.9±9.8 years and 62.9% were male. GOLD 2019 classified the patients in milder degrees of COPD. For both classifications, group D had higher mortality. 5-year mortality did not differ between groups B and C in GOLD 2015; in GOLD 2019, mortality was greater for group B than C. Patients classified as group A and B had better sensitivity and positive predictive value with the GOLD 2019 classification than GOLD 2015. GOLD 2015 had better sensitivity for group C and D than GOLD 2019. The area under the curve values for 5-year mortality were only 0.67 (95% CI 0.66–0.68) for GOLD 2015 and 0.65 (95% CI 0.63–0.66) for GOLD 2019
Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC
Event-shape observables measured using charged particles in inclusive
-boson events are presented, using the electron and muon decay modes of the
bosons. The measurements are based on an integrated luminosity of of proton--proton collisions recorded by the ATLAS detector at the
LHC at a centre-of-mass energy TeV. Charged-particle
distributions, excluding the lepton--antilepton pair from the -boson decay,
are measured in different ranges of transverse momentum of the boson.
Distributions include multiplicity, scalar sum of transverse momenta, beam
thrust, transverse thrust, spherocity, and -parameter, which are
in particular sensitive to properties of the underlying event at small values
of the -boson transverse momentum. The Sherpa event generator shows larger
deviations from the measured observables than Pythia8 and Herwig7. Typically,
all three Monte Carlo generators provide predictions that are in better
agreement with the data at high -boson transverse momenta than at low
-boson transverse momenta and for the observables that are less sensitive to
the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures,
4 tables, submitted to EPJC, All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0
Inclusive J/psi production in pp collisions at sqrt(s) = 2.76 TeV
The ALICE Collaboration has measured inclusive J/psi production in pp
collisions at a center of mass energy sqrt(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 L^e_int=1.1
nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are
N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present
dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y
range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c.
The results are compared with previously published results at sqrt(s)=7 TeV and
with theoretical calculations.Comment: 7 figures, 3 tables, accepted for publication in Phys. Lett.
KK correlations in pp collisions at TeV from the LHC ALICE experiment
Identical neutral kaon pair correlations are measured in TeV pp
collisions in the ALICE experiment. One-dimensional KK correlation
functions in terms of the invariant momentum difference of kaon pairs are
formed in two multiplicity and two transverse momentum ranges. The femtoscopic
parameters for the radius and correlation strength of the kaon source are
extracted. The ft includes quantum statistics and final-state
interactions of the a/f resonance. KK correlations show an
increase in radius for increasing multiplicity and a slight decrease in radius
for increasing transverse mass, , as seen in correlations
in the pp system and in heavy-ion collisions. Transverse mass scaling is
observed between the KK and radii. Also, the frst
observation is made of the decay of the f(1525) meson into the
KK channel in pp collisions.Comment: 17 pages, 7 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/310
J/psi Production as a Function of Charged Particle Multiplicity in pp Collisions at sqrt{s} = 7 TeV
The ALICE collaboration reports the measurement of the inclusive J/psi yield
as a function of charged particle pseudorapidity density dN_{ch}/deta in pp
collisions at sqrt{s} = 7 TeV at the LHC. J/psi particles are detected for p_t
> 0, in the rapidity interval |y| < 0.9 via decay into e+e-, and in the
interval 2.5 < y < 4.0 via decay into mu+mu- pairs. An approximately linear
increase of the J/psi yields normalized to their event average
(dN_{J/psi}/dy)/ with (dN_{ch}/deta)/ is observed
in both rapidity ranges, where dN_{ch}/deta is measured within |eta| < 1 and
p_t > 0. In the highest multiplicity interval with = 24.1,
corresponding to four times the minimum bias multiplicity density, an
enhancement relative to the minimum bias J/psi yield by a factor of about 5 at
2.5 < y < 4 (8 at |y| < 0.9) is observed.Comment: Submitted to Phys. Lett.