408 research outputs found
Galaxy Clusters as Reservoirs of Heavy Dark Matter and High-Energy Cosmic Rays: Constraints from Neutrino Observations
Galaxy Clusters (GCs) are the largest reservoirs of both dark matter and
cosmic rays (CRs). Dark matter self-annihilation can lead to a high luminosity
in gamma rays and neutrinos, enhanced by a strong degree of clustering in dark
matter substructures. Hadronic CR interactions can also lead to a high
luminosity in gamma rays and neutrinos, enhanced by the confinement of CRs from
cluster accretion/merger shocks and active galactic nuclei. We show that
IceCube/KM3Net observations of high-energy neutrinos can probe the nature of
GCs and the separate dark matter and CR emission processes, taking into account
how the results depend on the still-substantial uncertainties. Neutrino
observations are relevant at high energies, especially at >10 TeV. Our results
should be useful for improving experimental searches for high-energy neutrino
emission. Neutrino telescopes are sensitive to extended sources formed by dark
matter substructures and CRs distributed over large scales. Recent observations
by Fermi and imaging atmospheric Cherenkov telescopes have placed interesting
constraints on the gamma-ray emission from GCs. We also provide calculations of
the gamma-ray fluxes, taking into account electromagnetic cascades inside GCs,
which can be important for injections at sufficiently high energies. This also
allows us to extend previous gamma-ray constraints to very high dark matter
masses and significant CR injections at very high energies. Using both
neutrinos and gamma rays, which can lead to comparable constraints, will allow
more complete understandings of GCs. Neutrinos are essential for some dark
matter annihilation channels, and for hadronic instead of electronic CRs. Our
results suggest that the multi-messenger observations of GCs will be able to
give useful constraints on specific models of dark matter and CRs. [Abstract
abridged.]Comment: 31 pages, 20 figures, 1 table, accepted for publication in JCAP,
references and discussions adde
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm
The PHENIX experiement has measured the electron-positron pair mass spectrum
from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions
from light meson decays to e^+e^- pairs have been determined based on
measurements of hadron production cross sections by PHENIX. They account for
nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair
yield remaining after subtracting these contributions is dominated by
semileptonic decays of charmed hadrons correlated through flavor conservation.
Using the spectral shape predicted by PYTHIA, we estimate the charm production
cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which
is consistent with QCD calculations and measurements of single leptons by
PHENIX.Comment: 375 authors from 57 institutions, 18 pages, 4 figures, 2 tables.
Submitted to Physics Letters B. v2 fixes technical errors in matching authors
to institutions. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Inclusive cross section and double helicity asymmetry for \pi^0 production in p+p collisions at sqrt(s)=200 GeV: Implications for the polarized gluon distribution in the proton
The PHENIX experiment presents results from the RHIC 2005 run with polarized
proton collisions at sqrt(s)=200 GeV, for inclusive \pi^0 production at
mid-rapidity. Unpolarized cross section results are given for transverse
momenta p_T=0.5 to 20 GeV/c, extending the range of published data to both
lower and higher p_T. The cross section is described well for p_T < 1 GeV/c by
an exponential in p_T, and, for p_T > 2 GeV/c, by perturbative QCD. Double
helicity asymmetries A_LL are presented based on a factor of five improvement
in uncertainties as compared to previously published results, due to both an
improved beam polarization of 50%, and to higher integrated luminosity. These
measurements are sensitive to the gluon polarization in the proton, and exclude
maximal values for the gluon polarization.Comment: 375 authors, 7 pages, 3 figures. Submitted to Phys. Rev. D, Rapid
Communications. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
System Size and Energy Dependence of Jet-Induced Hadron Pair Correlation Shapes in Cu+Cu and Au+Au Collisions at sqrt(s_NN) = 200 and 62.4 GeV
We present azimuthal angle correlations of intermediate transverse momentum
(1-4 GeV/c) hadrons from {dijets} in Cu+Cu and Au+Au collisions at sqrt(s_NN) =
62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is
broadened, non-Gaussian, and peaked away from \Delta\phi=\pi in central and
semi-central collisions in all the systems. The broadening and peak location
are found to depend upon the number of participants in the collision, but not
on the collision energy or beam nuclei. These results are consistent with sound
or shock wave models, but pose challenges to Cherenkov gluon radiation models.Comment: 464 authors from 60 institutions, 6 pages, 3 figures, 2 tables.
Submitted to Physical Review Letters. Plain text data tables for the points
plotted in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
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Measurement of Bottom versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations in p+p Collisions at sqrt(s)=200 GeV
The momentum distribution of electrons from semi-leptonic decays of charm and
bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is
measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC)
over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of
electrons from bottom to that from charm is presented. The ratio is determined
using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It
is found that the yield of electrons from bottom becomes significant above 4
GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative
quantum chromodynamics (pQCD) calculation agrees with the data within the
theoretical and experimental uncertainties. The extracted total bottom
production cross section at this energy is \sigma_{b\b^bar}= 3.2
^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.Comment: 432 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Global estimates of viral suppression in children and adolescents and adults on antiretroviral therapy adjusted for missing viral load measurements: a multiregional, retrospective cohort study in 31 countries
Background: As countries move towards the UNAIDS's 95-95-95 targets and with strong evidence that undetectable equals untransmittable, it is increasingly important to assess whether those with HIV who are receiving antiretroviral therapy (ART) achieve viral suppression. We estimated the proportions of children and adolescents and adults with viral suppression at 1, 2, and 3 years after initiating ART. Methods: In this retrospective cohort study, seven regional cohorts from the International epidemiology Databases to Evaluate AIDS (IeDEA) consortium contributed data from individuals initiating ART between Jan 1, 2010, and Dec 31, 2019, at 148 sites in 31 countries with annual viral load monitoring. Only people with HIV who started ART after the time a site started routine viral load monitoring were included. Data up to March 31, 2020, were analysed. We estimated the proportions of children and adolescents (aged <18 years at ART initiation) and adults (aged ≥18 years at ART initiation) with viral suppression (viral load <1000 copies per mL) at 1, 2, and 3 years after ART initiation using an intention-to-treat approach and an adjusted approach that accounted for missing viral load measurements. Findings: 21 594 children and adolescents (11 812 [55%] female, 9782 [45%] male) from 106 sites in 22 countries and 255 662 adults (163 831 [64%] female, 91 831 [36%] male) from 143 sites in 30 countries were included. Using the intention-to-treat approach, the proportion of children and adolescents with viral suppression was 7303 (36%) of 20 478 at 1 year, 5709 (30%) of 19 135 at 2 years, and 4287 (24%) of 17 589 at 3 years after ART initiation; the proportion of adults with viral suppression was 106 541 (44%) of 240 600 at 1 year, 79 141 (36%) of 220 925 at 2 years, and 57 970 (29%) of 201 124 at 3 years after ART initiation. After adjusting for missing viral load measurements among those who transferred, were lost to follow-up, or who were in follow-up without viral load testing, the proportion of children and adolescents with viral suppression was 12 048 (64% [plausible range 43–81]) of 18 835 at 1 year, 10 796 (62% [41–77]) of 17 553 at 2 years, and 9177 (59% [38–91]) of 15 667 at 3 years after ART initiation; the proportion of adults with viral suppression was 176 964 (79% [53–80]) of 225 418 at 1 year, 145 552 (72% [48–79]) of 201 238 at 2 years, and 115 260 (65% [43–69]) of 178 458 at 3 years after ART initiation. Interpretation: Although adults with HIV are approaching the global target of 95% viral suppression, progress among children and adolescents is much slower. Substantial efforts are still needed to reach the viral suppression target for children and adolescents. Funding: US National Institutes of Health
Diagnosis of biliary tract and ampullary carcinomas
Diagnostic methods for biliary tract carcinoma and the efficacy of these methods are discussed. Neither definite methods for early diagnosis nor specific markers are available in this disease. When this disease is suspected on the basis of clinical symptoms and risk factors, hemato-biochemical examination and abdominal ultrasonography are performed and, where appropriate, enhanced computed tomography (CT) and/or magnetic resonance cholangiopancreatography (MRCP) is carried out. Diagnoses of extrahepatic bile duct cancer and ampullary carcinoma are often made based on the presence of obstructive jaundice. Although rare, abdominal pain and pyrexia, as well as abnormal findings of the hepatobiliary system detected by hemato-biochemical examination, serve as a clue to making a diagnosis of these diseases. On the other hand, the early diagnosis of gallbladder cancer is scarcely possible on the basis of clinical symptoms, so when this cancer is found with the onset of abdominal pain and jaundice, it is already advanced at the time of detection, thus making a cure difficult. When gallbladder cancer is suspected, enhanced CT is carried out. Multidetector computed tomography (MDCT), in particular — one of the methods of enhanced CT — is useful for decision of surgical criteria, because MDCT shows findings such as localization and extension of the tumor, and the presence or absence of remote metastasis. Procedures such as magnetic resonance imaging, endoscopic ultrasonography, bile duct biopsy, and cholangioscopy should be carried out taking into account indications for these procedures in individual patients. However, direct biliary tract imaging is necessary for making a precise diagnosis of the horizontal extension of bile duct cancer
Scaling properties of azimuthal anisotropy in Au+Au and Cu+Cu collisions at sqrt(s_NN) = 200 GeV
Detailed differential measurements of the elliptic flow for particles
produced in Au+Au and Cu+Cu collisions at sqrt(s_NN) = 200 GeV are presented.
Predictions from perfect fluid hydrodynamics for the scaling of the elliptic
flow coefficient v_2 with eccentricity, system size and transverse energy are
tested and validated. For transverse kinetic energies KE_T ~ m_T-m up to ~1
GeV, scaling compatible with the hydrodynamic expansion of a thermalized fluid
is observed for all produced particles. For large values of KE_T, the mesons
and baryons scale separately. A universal scaling for the flow of both mesons
and baryons is observed for the full transverse kinetic energy range of the
data when quark number scaling is employed. In both cases the scaling is more
pronounced in terms of KE_T rather than transverse momentum.Comment: 422 authors from 58 institutions, 6 pages, 3 figures. Submitted to
Physical Review Letters. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
Correlated Production of p and p^bar in Au+Au Collisions at sqrt(s_NN) = 200 GeV
Correlations between p and pbar's at transverse momenta typical of enhanced
baryon production in Au+Au collisions are reported. The PHENIX experiment
measures same and opposite sign baryon pairs in Au+Au collisions at sqrt(s_NN)
= 200 GeV. Correlated production of p and p^bar with the trigger particle from
the range 2.5 < p_T < 4.0 GeV/c and the associated particle with 1.8 < p_T <
2.5 GeV/c is observed to be nearly independent of the centrality of the
collisions. Same sign pairs show no correlation at any centrality. The
conditional yield of mesons triggered by baryons (and anti-baryons) and mesons
in the same pT range rises with increasing centrality, except for the most
central collisions, where baryons show a significantly smaller number of
associated mesons. These data are consistent with a picture in which hard
scattered partons produce correlated p and p^bar in the p_T region of the
baryon excess.Comment: 420 authors from 58 institutions, 21 pages,5 figures. Submitted to
Physics Letters B. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
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