639 research outputs found
Exploring Jet Properties in p-p Collisions at 200 GeV with STAR
The mechanisms underlying hadronization are not well understood, both in
vacuum and in hot QCD matter. Precise characterization of jet fragmentation to
hadrons in p-p collisions will help elucidate the fundamental process of
hadronization, and will serve as essential reference to measure the
modification of hadronization in heavy ion collisions. We present measurements
of fragmentation functions for unidentified particles in jets produced in p-p
collisions at 200 GeV using the STAR detector at RHIC. The results from
different jet reconstruction algorithms are compared, including variations of
the resolution parameter. It is found that the results are largely insensitive
to details of the jet-finding algorithm at RHIC energies. Particle production
inside and outside of these reconstructed jets will be compared to improve our
understanding of the hadronization mechanisms for soft and hard particles in
p-p events at RHIC energies.Comment: 4 pages, 7 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee Final version
after referee's comment
Finding the Needle in a Haystack: Unsupervised Rationale Extraction from Long Text Classifiers
Long-sequence transformers are designed to improve the representation of
longer texts by language models and their performance on downstream
document-level tasks. However, not much is understood about the quality of
token-level predictions in long-form models. We investigate the performance of
such architectures in the context of document classification with unsupervised
rationale extraction. We find standard soft attention methods to perform
significantly worse when combined with the Longformer language model. We
propose a compositional soft attention architecture that applies RoBERTa
sentence-wise to extract plausible rationales at the token-level. We find this
method to significantly outperform Longformer-driven baselines on sentiment
classification datasets, while also exhibiting significantly lower runtimes
Cluster analysis of multiplex ligation-dependent probe amplification data in choroidal melanoma.
PurposeTo determine underlying correlations in multiplex ligation-dependent probe amplification (MLPA) data and their significance regarding survival following treatment of choroidal melanoma (CM).MethodsMLPA data were available for 31 loci across four chromosomes (1p, 3, 6, and 8) in tumor material obtained from 602 patients with CM treated at the Liverpool Ocular Oncology Center (LOOC) between 1993 and 2012. Data representing chromosomes 3 and 8q were analyzed in depth since their association with CM patient survival is well-known. Unsupervised k-means cluster analysis was performed to detect latent structure in the data set. Principal component analysis (PCA) was also performed to determine the intrinsic dimensionality of the data. Survival analyses of the identified clusters were performed using Kaplan-Meier (KM) and log-rank statistical tests. Correlation with largest basal tumor diameter (LTD) was investigated.ResultsChromosome 3: A two-cluster (bimodal) solution was found in chromosome 3, characterized by centroids at unilaterally normal probe values and unilateral deletion. There was a large, significant difference in the survival characteristics of the two clusters (log-rank, p<0.001; 5-year survival: 80% versus 40%). Both clusters had a broad distribution in LTD, although larger tumors were characteristically in the poorer outcome group (Mann-Whitney, p<0.001). Threshold values of 0.85 for deletion and 1.15 for gain optimized the classification of the clusters. PCA showed that the first principal component (PC1) contained more than 80% of the data set variance and all of the bimodality, with uniform coefficients (0.28±0.03). Chromosome 8q: No clusters were found in chromosome 8q. Using a conventional threshold-based definition of 8q gain, and in conjunction with the chromosome 3 clusters, three prognostic groups were identified: chromosomes 3 and 8q both normal, either chromosome 3 or 8q abnormal, and both chromosomes 3 and 8q abnormal. KM analysis showed 5-year survival figures of approximately 97%, 80%, and 30% for these prognostic groups, respectively (log-rank, p<0.001). All MLPA probes within both chromosomes were significantly correlated with each other (Spearman, p<0.001).ConclusionsWithin chromosome 3, the strong correlation between the MLPA variables and the uniform coefficients from the PCA indicates a lack of evidence for a signature gene that might account for the bimodality we observed. We hypothesize that the two clusters we found correspond to binary underlying states of complete monosomy or disomy 3 and that these states are sampled by the complete ensemble of probes. Consequently, we would expect a similar pattern to emerge in higher-resolution MLPA data sets. LTD may be a significant confounding factor. Considering chromosome 8q, we found that chromosome 3 cluster membership and 8q gain as traditionally defined have an indistinguishable impact on patient outcome
What's Interesting About Strangeness Production? - An Overview of Recent Results
In this paper I highlight a few selected topics on strange particle
production in heavy-ion collisions. By studying the yield and spectra of
strange particles we hope to gain understanding of the conditions reached in,
and the ensuing dynamics of, the systems produced when ultra-relativistic
heavy-ions are collided.Comment: 17 Pages, 18 figures, Hot Quarks 2004 Proceeding
The Hot QCD White Paper: Exploring the Phases of QCD at RHIC and the LHC
The past decade has seen huge advances in experimental measurements made in
heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and more
recently at the Large Hadron Collider (LHC). These new data, in combination
with theoretical advances from calculations made in a variety of frameworks,
have led to a broad and deep knowledge of the properties of thermal QCD matter.
Increasingly quantitative descriptions of the quark-gluon plasma (QGP) created
in these collisions have established that the QGP is a strongly coupled liquid
with the lowest value of specific viscosity ever measured. However, much
remains to be learned about the precise nature of the initial state from which
this liquid forms, how its properties vary across its phase diagram and how, at
a microscopic level, the collective properties of this liquid emerge from the
interactions among the individual quarks and gluons that must be visible if the
liquid is probed with sufficiently high resolution. This white paper, prepared
by the Hot QCD Writing Group as part of the U.S. Long Range Plan for Nuclear
Physics, reviews the recent progress in the field of hot QCD and outlines the
scientific opportunities in the next decade for resolving the outstanding
issues in the field.Comment: 110 pages, 33 figures, 429 references. Prepared as part of the U.S.
Long-Range Plan for Nuclear Physic
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