853 research outputs found
Neutral pion production with respect to reaction plane in Au+Au collisions at RHIC-PHENIX
It has been observed that the yield of neutral pions at high transverse
momentum (pT 5 GeV/c) region is strongly suppressed in central Au+Au
collisions at Relativistic Heavy Ion Collider (RHIC), compared to the one
expected in p+p collisions. This suppression may be due to an energy loss of
hard scattered partons in the medium (jet quenching), that results in a
decrease of the yield at a given pT. The magnitude of the suppression would
depend on the path length of scattering partons in the medium, and therefore is
associated with azimuthal angle from reaction plane in non-central collisions.
Studying the path length dependence of energy loss would give additional
information on understanding the energy loss mechanism. We discuss the parton
energy loss mechanism using the nuclear modification factor () of
neutral pion with respect to reaction plane. A new reaction plane detector was
installed in the PHENIX detector in RHIC Year-7 run, and improved the reaction
plane resolution. More precise measurement of the hadron suppression with
respect to path length is expected using the detector. I will report about
analysis status of neutral pion production in Au+Au collisions at
GeV.Comment: 4 pages, 5 figures, Proceedings of the 20th International Conference
on Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008",
Jaipur, India, February 4-10, 200
Fabrication of low-cost, large-area prototype Si(Li) detectors for the GAPS experiment
A Si(Li) detector fabrication procedure has been developed with the aim of
satisfying the unique requirements of the GAPS (General Antiparticle
Spectrometer) experiment. Si(Li) detectors are particularly well-suited to the
GAPS detection scheme, in which several planes of detectors act as the target
to slow and capture an incoming antiparticle into an exotic atom, as well as
the spectrometer and tracker to measure the resulting decay X-rays and
annihilation products. These detectors must provide the absorption depth,
energy resolution, tracking efficiency, and active area necessary for this
technique, all within the significant temperature, power, and cost constraints
of an Antarctic long-duration balloon flight. We report here on the fabrication
and performance of prototype 2"-diameter, 1-1.25 mm-thick, single-strip Si(Li)
detectors that provide the necessary X-ray energy resolution of 4 keV for
a cost per unit area that is far below that of previously-acquired commercial
detectors. This fabrication procedure is currently being optimized for the
4"-diameter, 2.5 mm-thick, multi-strip geometry that will be used for the GAPS
flight detectors.Comment: Accepted for publication at Nuclear Instrumentation and Methods A, 12
pages, 11 figure
The Early Bird Catches The Term: Combining Twitter and News Data For Event Detection and Situational Awareness
Twitter updates now represent an enormous stream of information originating
from a wide variety of formal and informal sources, much of which is relevant
to real-world events. In this paper we adapt existing bio-surveillance
algorithms to detect localised spikes in Twitter activity corresponding to real
events with a high level of confidence. We then develop a methodology to
automatically summarise these events, both by providing the tweets which fully
describe the event and by linking to highly relevant news articles. We apply
our methods to outbreaks of illness and events strongly affecting sentiment. In
both case studies we are able to detect events verifiable by third party
sources and produce high quality summaries
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