352 research outputs found
Search for d^* Dibaryon by Double-radiative Capture on Pionic Deuterium
We report a search for d^* dibaryon production by double-radiative capture on
pionic deuterium. The experiment was conducted at the TRIUMF cyclotron using
the RMC cylindrical pair spectrometer, and detected gamma-ray coincidences
following pion stops in liquid deuterium. We found no evidence for narrow
dibaryons, and obtained a branching ratio upper limit, BR < 6.7 times 10^{-6}
(90% C.L.), for narrow d^* production in the mass range from 1920 to 1980 MeV.
Replaced with Physics Letter B accepted version and corrected normalization.Comment: 9 pages, 4 figure
Ortho-para transition rate in -molecular hydrogen and the proton's induced pseudoscalar coupling
We report a measurement of the ortho-para transition rate in the pp
molecule. The experiment was conducted at TRIUMF via the measurement of the
time dependence of the 5.2 MeV neutrons from muon capture in liquid hydrogen.
The measurement yielded an ortho-para rate s that is substantially larger than the
earlier result of Bardin {\it et al.} We discuss the striking implications for
the proton's induced pseudoscalar coupling .Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Test of isospin symmetry via low energy H(,) charge exchange
We report measurements of the differential cross
sections at six momenta (104-143 MeV/c) and four angles (0-40 deg) by detection
of -ray pairs from decays using the TRIUMF
RMC spectrometer. This region exhibits a vanishing zero-degree cross section
from destructive interference between s-- and p--waves, thus yielding special
sensitivity to pion-nucleon dynamics and isospin symmetry breaking. Our data
and previous data do not agree, with important implications for earlier claims
of large isospin violating effects in low energy pion-nucleon interactions.Comment: 5 pages, 3 figures, submitted to Physical Review Letter
Deep Eyes: Binocular Depth-from-Focus on Focal Stack Pairs
Human visual system relies on both binocular stereo cues and monocular
focusness cues to gain effective 3D perception. In computer vision, the two
problems are traditionally solved in separate tracks. In this paper, we present
a unified learning-based technique that simultaneously uses both types of cues
for depth inference. Specifically, we use a pair of focal stacks as input to
emulate human perception. We first construct a comprehensive focal stack
training dataset synthesized by depth-guided light field rendering. We then
construct three individual networks: a Focus-Net to extract depth from a single
focal stack, a EDoF-Net to obtain the extended depth of field (EDoF) image from
the focal stack, and a Stereo-Net to conduct stereo matching. We show how to
integrate them into a unified BDfF-Net to obtain high-quality depth maps.
Comprehensive experiments show that our approach outperforms the
state-of-the-art in both accuracy and speed and effectively emulates human
vision systems
Longitudinal muon spin relaxation in high purity aluminum and silver
The time dependence of muon spin relaxation has been measured in high purity
aluminum and silver samples in a longitudinal 2 T magnetic field at room
temperature, using time-differential \musr. For times greater than 10 ns, the
shape fits well to a single exponential with relaxation rates of
\lambda_{\textrm{Al}} = 1.3 \pm 0.2\,(\textrm{stat.}) \pm
0.3\,(\textrm{syst.})\,\pms and \lambda_{\textrm{Ag}} = 1.0 \pm
0.2\,(\textrm{stat.}) \pm 0.2\,(\textrm{syst.})\,\pms
Double radiative pion capture on hydrogen and deuterium and the nucleon's pion cloud
We report measurements of double radiative capture in pionic hydrogen and
pionic deuterium. The measurements were performed with the RMC spectrometer at
the TRIUMF cyclotron by recording photon pairs from pion stops in liquid
hydrogen and deuterium targets. We obtained absolute branching ratios of for hydrogen and for deuterium, and
relative branching ratios of double radiative capture to single radiative
capture of for hydrogen
and for
deuterium. For hydrogen, the measured branching ratio and photon energy-angle
distributions are in fair agreement with a reaction mechanism involving the
annihilation of the incident on the cloud of the target proton.
For deuterium, the measured branching ratio and energy-angle distributions are
qualitatively consistent with simple arguments for the expected role of the
spectator neutron. A comparison between our hydrogen and deuterium data and
earlier beryllium and carbon data reveals substantial changes in the relative
branching ratios and the energy-angle distributions and is in agreement with
the expected evolution of the reaction dynamics from an annihilation process in
S-state capture to a bremsstrahlung process in P-state capture. Lastly, we
comment on the relevance of the double radiative process to the investigation
of the charged pion polarizability and the in-medium pion field.Comment: 44 pages, 7 tables, 13 figures, submitted to Phys. Rev.
Observation of double radiative capture on pionic hydrogen
We report the first observation of double radiative capture on pionic
hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC
spectrometer, and detected --ray coincidences following stops
in liquid hydrogen. We found the branching ratio for double radiative capture
to be . The measured
branching ratio and angle-energy distributions support the theoretical
prediction of a dominant contribution from the
annihilation mechanism.Comment: 4 Pages, 4 Figures. accepted for publication in Phys. Rev. Let
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