415 research outputs found
A proposal for Marchenko-based target-oriented full waveform inversion
The Hessian matrix plays an important role in correct interpretation of the
multiple scattered wave fields inside the FWI frame work. Due to the high
computational costs, the computation of the Hessian matrix is not feasible.
Consequently, FWI produces overburden related artifacts inside the target zone
model, due to the lack of the exact Hessian matrix. We have shown here that
Marchenko-based target-oriented Full Waveform Inversion can compensate the need
of Hessian matrix inversion by reducing the non-linearity due to overburden
effects. This is achieved by exploiting Marchenko-based target replacement to
remove the overburden response and its interactions with the target zone from
residuals and inserting the response of the updated target zone into the
response of the entire medium. We have also shown that this method is more
robust with respect to prior information than the standard gradient FWI.
Similarly to standard Marchenko imaging, the proposed method only requires
knowledge of the direct arrival time from a focusing point to the surface and
the reflection response of the medium.Comment: 5 pages, 4 figures, 82th EAGE Conference & Exhibitio
Measurements of double-helicity asymmetries in inclusive production in longitudinally polarized collisions at GeV
We report the double helicity asymmetry, , in inclusive
production at forward rapidity as a function of transverse momentum
and rapidity . The data analyzed were taken during
GeV longitudinally polarized collisions at the Relativistic Heavy Ion
Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision
energy, particles are predominantly produced through gluon-gluon
scatterings, thus is sensitive to the gluon polarization
inside the proton. We measured by detecting the decay
daughter muon pairs within the PHENIX muon spectrometers in the
rapidity range . In this kinematic range, we measured the
to be ~(stat)~~(syst). The
can be expressed to be proportional to the product of the
gluon polarization distributions at two distinct ranges of Bjorken : one at
moderate range where recent RHIC data of jet and
double helicity spin asymmetries have shown evidence for significant gluon
polarization, and the other one covering the poorly known small- region . Thus our new results could be used to further
constrain the gluon polarization for .Comment: 335 authors, 10 pages, 4 figures, 3 tables, 2013 data. Version
accepted for publication by Phys. Rev. D. 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
The role of early contrast-enhanced chest computed tomography in the aetiological diagnosis of patients presenting with cardiac tamponade or large pericardial effusion
AIMS:
The role of chest computed tomography (CT) is not well defined for either diagnosis or management of pericardial disease. The aim of this study was to evaluate the added value of early chest CT in the diagnostic workup for patients presenting with cardiac tamponade or large pericardial effusion of unknown aetiology as the first manifestation of disease.
METHODS AND RESULTS:
We performed CT scan on 55 patients with pericardial effusion as defined above, undergoing echo-guided pericardiocentesis. We compared the success rate in making diagnosis and/or staging the underlying disorder of three sequential workups, including, respectively, (i) clinical presentation, inflammatory markers, chest X-ray imaging, (ii) all of the above and pericardial fluid analysis, and (iii) all of the above and chest CT. We were able to make diagnosis in 53 patients (96%): the major cause of effusion was malignancy (38%). Clinical and biochemical data were not able to differentiate non-tumour from tumour patients. CT revealed pathological findings in all patients with malignancy: tumour mass in 15/21 (71%) and pathological lymphadenopathy in the remaining 6 cases. The workup including CT provided a significantly higher diagnostic yield than the other two workups (P < 0.0001), both in the overall population and in the two subgroups of neoplastic (Npl) and non-Npl patients.
CONCLUSION:
In all patients with cardiac tamponade or large pericardial effusion, CT was useful either in identifying the underlying disease or in excluding other potential causes of pericardial effusion. We conclude that chest CT is a very useful non-invasive diagnostic tool to identify and stage pericardial diseases
Single electron yields from semileptonic charm and bottom hadron decays in AuAu collisions at GeV
The PHENIX Collaboration at the Relativistic Heavy Ion Collider has measured
open heavy-flavor production in minimum bias AuAu collisions at
GeV via the yields of electrons from semileptonic decays
of charm and bottom hadrons. Previous heavy-flavor electron measurements
indicated substantial modification in the momentum distribution of the parent
heavy quarks due to the quark-gluon plasma created in these collisions. For the
first time, using the PHENIX silicon vertex detector to measure precision
displaced tracking, the relative contributions from charm and bottom hadrons to
these electrons as a function of transverse momentum are measured in AuAu
collisions. We compare the fraction of electrons from bottom hadrons to
previously published results extracted from electron-hadron correlations in
collisions at GeV and find the fractions to be
similar within the large uncertainties on both measurements for
GeV/. We use the bottom electron fractions in AuAu and along
with the previously measured heavy flavor electron to calculate the
for electrons from charm and bottom hadron decays separately. We find
that electrons from bottom hadron decays are less suppressed than those from
charm for the region GeV/.Comment: 432 authors, 33 pages, 23 figures, 2 tables, 2011 data. v2 is version
accepted for publication by Phys. Rev. C. 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 production at midrapidity in collisions at GeV
PHENIX measurements are presented for the cross section and double-helicity
asymmetry () in inclusive production at midrapidity from
collisions at ~GeV from data taken in 2012 and 2013 at
the Relativistic Heavy Ion Collider. The next-to-leading-order
perturbative-quantum-chromodynamics theory calculation is in excellent
agreement with the presented cross section results. The calculation utilized
parton-to-pion fragmentation functions from the recent DSS14 global analysis,
which prefer a smaller gluon-to-pion fragmentation function. The
results follow an increasingly positive asymmetry trend with
and with respect to the predictions and are in excellent
agreement with the latest global analysis results. This analysis incorporated
earlier results on and jet , and suggested a positive
contribution of gluon polarization to the spin of the proton for the
gluon momentum fraction range . The data presented here extend to a
currently unexplored region, down to , and thus provide additional
constraints on the value of . The results confirm the evidence for
nonzero using a different production channel in a complementary
kinematic region.Comment: 413 authors, 8 pages, 4 figures. v2 is version accepted as PRD Rapid
Communication. 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
Nuclear matter effects on production in asymmetric Cu+Au collisions at = 200 GeV
We report on production from asymmetric Cu+Au heavy-ion collisions
at =200 GeV at the Relativistic Heavy Ion Collider at both
forward (Cu-going direction) and backward (Au-going direction) rapidities. The
nuclear modification of yields in CuAu collisions in the Au-going
direction is found to be comparable to that in AuAu collisions when plotted
as a function of the number of participating nucleons. In the Cu-going
direction, production shows a stronger suppression. This difference is
comparable in magnitude and has the same sign as the difference expected from
shadowing effects due to stronger low- gluon suppression in the larger Au
nucleus. The relative suppression is opposite to that expected from hot nuclear
matter dissociation, since a higher energy density is expected in the Au-going
direction.Comment: 349 authors, 10 pages, 4 figures, and 4 tables. Submitted to Phys.
Rev. C. For v2, fixed LaTeX error in 3rd-to-last sentence. 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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