28,707 research outputs found
QCD sum rule Study of the
We systematically construct six-quark local interpolating
currents without derivative operators. We discuss the best choice of operator,
and select three - like operators to perform QCD sum rule
analyses to calculate the mass of the . The mass extracted from this
analysis is GeV, consistent with the mass
observed by the WASA detector at COSY. We also obtain a sum-rule lower mass
bound GeV. We also consider the effect of mixing of singlet
dibaryon fields with the same quantum numbers, and perform the QCD sum rule
analysis of the mixed interpolating current and extract the mass of the
and its lower mass bound. With optimized mixing parameters, we find
that the mixed current does not change the numerical result significantly.Comment: 9 pages, 4 figure
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Extreme ultraviolet mask surface cleaning effects on lithography process performance
Extreme UV (EUV) masks are expected to undergo cleaning processes in order to maintain the lifetimes necessary for high volume manufacturing. For this study, the impact of repetitive cleaning of EUV masks on imaging performance is evaluated. Two high quality industry standard EUV masks are used, with one of the masks undergoing repeated cleaning and the other one kept as a reference. Lithographic performance, in terms of process window analysis and line edge roughness, was monitored after every two cleans and was compared to the reference mask performance. Surface analysis by atomic force microscopy did not show changes in the midspatial frequency roughness measured after each clean. After a total of eight cleans, minimal degradation is observed in the lithographic performance of the mask. From these observations, the authors conclude that the cleaning cycles completed thus far did not damage the mask multilayer or the absorber structures. The cleaning cycles will be continued until significant loss in imaging fidelity is found. © 2010 American Vacuum Society
resonance as a tetraquark state and its isospin partner
We systematically construct tetraquark currents of and
classify them into types (antisymmetric), (symmetric)
and (mixed), based on flavor symmetries of diquarks and
antidiquarks composing the tetra quark currents. We use tetraquark currents of
type to perform QCD sum rule analyses, and find a tetraquark
current with quark contents ( or )
leading to a mass of GeV consistent with the state
recently observed by the COMPASS collaboration. Our results support tetraquark
explanations for both and , assuming that they are
isospin partners. We also study their possible decay patterns. As tetraquark
candidates, the possible decay modes of are -wave and -wave while
the possible decay patterns of are -wave and -wave . We speculate that
is partly responsible for the large isospin violation in the
decay mode which is reported by BESIII
collaboration in the process.Comment: 15 pages, 8 figures. Accepted by Phys. Rev.
Population synthesis of accreting white dwarfs: II. X-ray and UV emission
Accreting white dwarfs (WDs) with non-degenerate companions are expected to
emit in soft X-rays and the UV, if accreted H-rich material burns stably. They
are an important component of the unresolved emission of elliptical galaxies,
and their combined ionizing luminosity may significantly influence the optical
line emission from warm ISM. In an earlier paper we modeled populations of
accreting WDs, first generating WD with main-sequence, Hertzsprung gap and red
giant companions with the population synthesis code \textsc{BSE}, and then
following their evolution with a grid of evolutionary tracks computed with
\textsc{MESA}. Now we use these results to estimate the soft X-ray
(0.3-0.7keV), H- and He II-ionizing luminosities of nuclear burning WDs and the
number of super-soft X-ray sources for galaxies with different star formation
histories. For the starburst case, these quantities peak at Gyr and
decline by orders of magnitude by the age of 10 Gyr. For stellar
ages of ~10 Gyr, predictions of our model are consistent with soft X-ray
luminosities observed by Chandra in nearby elliptical galaxies and He II
4686 line ratio measured in stacked SDSS spectra of retired
galaxies, the latter characterising the strength and hardness of the UV
radiation field. However, the soft X-ray luminosity and
He~II~4686 ratio are significantly overpredicted for stellar
ages of Gyr. We discuss various possibilities to resolve this
discrepancy and tentatively conclude that it may be resolved by a modification
of the typically used criteria of dynamically unstable mass loss for giant
stars.Comment: 13 pages, 12 figures, MNRAS accepte
Latent Class Model with Application to Speaker Diarization
In this paper, we apply a latent class model (LCM) to the task of speaker
diarization. LCM is similar to Patrick Kenny's variational Bayes (VB) method in
that it uses soft information and avoids premature hard decisions in its
iterations. In contrast to the VB method, which is based on a generative model,
LCM provides a framework allowing both generative and discriminative models.
The discriminative property is realized through the use of i-vector (Ivec),
probabilistic linear discriminative analysis (PLDA), and a support vector
machine (SVM) in this work. Systems denoted as LCM-Ivec-PLDA, LCM-Ivec-SVM, and
LCM-Ivec-Hybrid are introduced. In addition, three further improvements are
applied to enhance its performance. 1) Adding neighbor windows to extract more
speaker information for each short segment. 2) Using a hidden Markov model to
avoid frequent speaker change points. 3) Using an agglomerative hierarchical
cluster to do initialization and present hard and soft priors, in order to
overcome the problem of initial sensitivity. Experiments on the National
Institute of Standards and Technology Rich Transcription 2009 speaker
diarization database, under the condition of a single distant microphone, show
that the diarization error rate (DER) of the proposed methods has substantial
relative improvements compared with mainstream systems. Compared to the VB
method, the relative improvements of LCM-Ivec-PLDA, LCM-Ivec-SVM, and
LCM-Ivec-Hybrid systems are 23.5%, 27.1%, and 43.0%, respectively. Experiments
on our collected database, CALLHOME97, CALLHOME00 and SRE08 short2-summed trial
conditions also show that the proposed LCM-Ivec-Hybrid system has the best
overall performance
Next generation population synthesis of accreting white dwarfs: I. Hybrid calculations using BSE + MESA
Accreting, nuclear-burning white dwarfs have been deemed to be candidate
progenitors of type Ia supernovae, and to account for supersoft X-ray sources,
novae, etc. depending on their accretion rates. We have carried out a binary
population synthesis study of their populations using two algorithms. In the
first, we use the binary population synthesis code \textsf{BSE} as a baseline
for the "rapid" approach commonly used in such studies. In the second, we
employ a "hybrid" approach, in which we use \textsf{BSE} to generate a
population of white dwarfs (WD) with non-degenerate companions on the verge of
filling their Roche lobes. We then follow their mass transfer phase using the
detailed stellar evolution code \textsf{MESA}. We investigate the evolution of
the number of rapidly accreting white dwarfs (RAWDs) and stably nuclear-burning
white dwarfs (SNBWDs), and estimate the type Ia supernovae (SNe Ia) rate
produced by "single-degenerate" systems (SD). We find significant differences
between the two algorithms in the predicted numbers of SNBWDs at early times,
and also in the delay time distribution (DTD) of SD SNe Ia. Such differences in
the treatment of mass transfer may partially account for differences in the SNe
Ia rate and DTD found by different groups. Adopting 100\% efficiency for helium
burning, the rate of SNe Ia produced by the SD-channel in a Milky-way-like
galaxy in our calculations is , more than an
order of magnitude below the observationally inferred value. In agreement with
previous studies, our calculated SD DTD is inconsistent with observations.Comment: 13 pages,11 figures, accepted by MNRA
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