9,203 research outputs found
Energy Dependence of Jet Quenching and Life-time of the Dense Matter in High-energy Heavy-ion Collisions
Suppression of high hadron spectra in high-energy heavy-ion collisions
at different energies is studied within a pQCD parton model incorporating
medium induced parton energy loss. The dependence of the nuclear
modification factor is found to depend on both the energy
dependence of the parton energy loss and the power-law behavior of the initial
jet spectra. The high hadron suppression at GeV and its
centrality dependence are studied in detail. The overall values of the
modification factor are found to provide strong constraints on the lifetime of
the dense matter.Comment: 6 pages in RevTex with 3 postscript figure
A NLO analysis on fragility of dihadron tomography in high energy collisions
The dihadron spectra in high energy collisions are studied within the
NLO pQCD parton model with jet quenching taken into account. The high
dihadron spectra are found to be contributed not only by jet pairs close and
tangential to the surface of the dense matter but also by punching-through jets
survived at the center while the single hadron high spectra are only
dominated by surface emission. Consequently, the suppression factor of such
high- hadron pairs is found to be more sensitive to the initial gluon
density than the single hadron suppression factor.Comment: 4 pages, 4 figures, proceedings for the 19th international Conference
on ultra-relativistic nucleus-nucleus collisions (QM2006), Shanghai, China,
November 14-20, 200
High Pt hadron-hadron correlations
We propose the formulation of a dihadron fragmentation function in terms of
parton matrix elements. Under the collinear factorization approximation and
facilitated by the cut-vertex technique, the two hadron inclusive cross section
at leading order (LO) in e+ e- annihilation is shown to factorize into a short
distance parton cross section and the long distance dihadron fragmentation
function. We also derive the DGLAP evolution equation of this function at
leading log. The evolution equation for the non-singlet and singlet quark
fragmentation function and the gluon fragmentation function are solved
numerically with the initial condition taken from event generators.
Modifications to the dihadron fragmentation function from higher twist
corrections in DIS off nuclei are computed. Results are presented for cases of
physical interest.Comment: 7 pages, 8 figures, Latex, Proceedings of Hot Quarks 2004, July
18-24, Taos, New Mexic
Hierarchical Neyman-Pearson Classification for Prioritizing Severe Disease Categories in COVID-19 Patient Data
COVID-19 has a spectrum of disease severity, ranging from asymptomatic to
requiring hospitalization. Understanding the mechanisms driving disease
severity is crucial for developing effective treatments and reducing mortality
rates. One way to gain such understanding is using a multi-class classification
framework, in which patients' biological features are used to predict patients'
severity classes. In this severity classification problem, it is beneficial to
prioritize the identification of more severe classes and control the
"under-classification" errors, in which patients are misclassified into less
severe categories. The Neyman-Pearson (NP) classification paradigm has been
developed to prioritize the designated type of error. However, current NP
procedures are either for binary classification or do not provide high
probability controls on the prioritized errors in multi-class classification.
Here, we propose a hierarchical NP (H-NP) framework and an umbrella algorithm
that generally adapts to popular classification methods and controls the
under-classification errors with high probability. On an integrated collection
of single-cell RNA-seq (scRNA-seq) datasets for 864 patients, we explore ways
of featurization and demonstrate the efficacy of the H-NP algorithm in
controlling the under-classification errors regardless of featurization. Beyond
COVID-19 severity classification, the H-NP algorithm generally applies to
multi-class classification problems, where classes have a priority order
Modification of conductive polymer for polymeric anodes of flexible organic light-emitting diodes
Author name used in this publication: Guang-Feng WangAuthor name used in this publication: Xiao-Ming TaoAuthor name used in this publication: John H. Xin2008-2009 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Adaptive conformal classification with noisy labels
This paper develops novel conformal prediction methods for classification
tasks that can automatically adapt to random label contamination in the
calibration sample, enabling more informative prediction sets with stronger
coverage guarantees compared to state-of-the-art approaches. This is made
possible by a precise theoretical characterization of the effective coverage
inflation (or deflation) suffered by standard conformal inferences in the
presence of label contamination, which is then made actionable through new
calibration algorithms. Our solution is flexible and can leverage different
modeling assumptions about the label contamination process, while requiring no
knowledge about the data distribution or the inner workings of the
machine-learning classifier. The advantages of the proposed methods are
demonstrated through extensive simulations and an application to object
classification with the CIFAR-10H image data set.Comment: 35 pages (98 pages including references and appendices
Where is the jet quenching in Pb+Pb collisions at 158 AGeV?
Because of the rapidly falling particle spectrum at large from jet
fragmentation at the CERN SPS energy, the high- hadron distribution should
be highly sensitive to parton energy loss inside a dense medium as predicted by
recent perturbative QCD (pQCD) studies. A careful analysis of recent data from
CERN SPS experiments via pQCD calculation shows little evidence of energy loss.
This implies that either the life-time of the dense partonic matter is very
short or one has to re-think about the problem of parton energy loss in dense
matter. The hadronic matter does not seem to cause jet quenching in
collisions at the CERN SPS. High- two particle correlation in the
azimuthal angle is proposed to further clarify this issue.Comment: 4 pages with 2 ps figures. Minors changes are made in the text with
updated references. Revised version to appear in Phys. Rev. Letter
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