522 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
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Impact of detecting potentially serious incidental findings during multi-modal imaging [version 3; referees: 2 approved, 1 approved with reservations]
Background: There are limited data on the impact of feedback of incidental
findings (IFs) from research imaging. We evaluated the impact of UK
Biobank’s protocol for handling potentially serious IFs in a multi-modal
imaging study of 100,000 participants (radiographer ‘flagging’ with
radiologist confirmation of potentially serious IFs) compared with systematic
radiologist review of all images.
Methods: Brain, cardiac and body magnetic resonance, and dual-energy
x-ray absorptiometry scans from the first 1000 imaged UK Biobank
participants were independently assessed for potentially serious IFs using
both protocols. We surveyed participants with potentially serious IFs and
their GPs up to six months after imaging to determine subsequent clinical
assessments, final diagnoses, emotional, financial and work or activity
impacts.
Results: Compared to systematic radiologist review, radiographer flagging
resulted in substantially fewer participants with potentially serious IFs
(179/1000 [17.9%] versus 18/1000 [1.8%]) and a higher proportion with
serious final diagnoses (21/179 [11.7%] versus 5/18 [27.8%]).
Radiographer flagging missed 16/21 serious final diagnoses (i.e., false
negatives), while systematic radiologist review generated large numbers o
Classification of Supernovae
The current classification scheme for supernovae is presented. The main
observational features of the supernova types are described and the physical
implications briefly addressed. Differences between the homogeneous
thermonuclear type Ia and similarities among the heterogeneous core collapse
type Ib, Ic and II are highlighted. Transforming type IIb, narrow line type
IIn, supernovae associated with GRBs and few peculiar objects are also
discussed.Comment: 16 Pages, 4 figures, to be published in "Supernovae and Gamma-Ray
Bursters," ed. Kurt W. Weile
Astronomical Distance Determination in the Space Age: Secondary Distance Indicators
The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)
Optical Light Curves of Supernovae
Photometry is the most easily acquired information about supernovae. The
light curves constructed from regular imaging provide signatures not only for
the energy input, the radiation escape, the local environment and the
progenitor stars, but also for the intervening dust. They are the main tool for
the use of supernovae as distance indicators through the determination of the
luminosity. The light curve of SN 1987A still is the richest and longest
observed example for a core-collapse supernova. Despite the peculiar nature of
this object, as explosion of a blue supergiant, it displayed all the
characteristics of Type II supernovae. The light curves of Type Ib/c supernovae
are more homogeneous, but still display the signatures of explosions in massive
stars, among them early interaction with their circumstellar material. Wrinkles
in the near-uniform appearance of thermonuclear (Type Ia) supernovae have
emerged during the past decade. Subtle differences have been observed
especially at near-infrared wavelengths. Interestingly, the light curve shapes
appear to correlate with a variety of other characteristics of these
supernovae. The construction of bolometric light curves provides the most
direct link to theoretical predictions and can yield sorely needed constraints
for the models. First steps in this direction have been already made.Comment: To be published in:"Supernovae and Gamma Ray Bursters", Lecture Notes
in Physics (http://link.springer.de/series/lnpp
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