8,386 research outputs found
Review of the ecohydrological processes and feedback mechanisms controlling sand-binding vegetation systems in sandy desert regions of China
Measurement of the chi_{c2} Polarization in psi(2S) to gamma chi_{c2}
The polarization of the chi_{c2} produced in psi(2S) decays into gamma
chi_{c2} is measured using a sample of 14*10^6 psi(2S) events collected by
BESII at the BEPC. A fit to the chi_{c2} production and decay angular
distributions in psi(2S) to gamma chi_{c2}, chi_{c2} to pi pi and KK yields
values x=A_1/A_0=2.08+/-0.44 and y=A_2/A_0=3.03 +/-0.66, with a correlation
rho=0.92 between them, where A_{0,1,2} are the chi_{c2} helicity amplitudes.
The measurement agrees with a pure E1 transition, and M2 and E3 contributions
do not differ significantly from zero.Comment: 6 pages, 4 figures, 1 tabl
Measurements of decays into Vector- Tensor final states
Decays of the into vector plus tensor meson final states have been
studied with 14 million events collected with the BESII detector.
Branching fractions of \psi(2S) \rt \omega f_{2}(1270), ,
and are
determined. They improve upon previous BESI results and confirm the violation
of the "12%" rule for decays to VT channels with higher precision.Comment: 7 pages, 7 figures and 2 table
\psi(2S) Decays into \J plus Two Photons
Using \gamma \gamma J/\psi, J/\psi \ra e^+ e^- and events
from a sample of \psip decays collected with the BESII
detector, the branching fractions for \psip\ra \pi^0\J, \eta\J, and
\psi(2S)\ar\gamma\chi_{c1},\gamma\chi_{c2}\ar\gamma\gamma\jpsi are measured
to be B(\psip\ra \pi^0\J) = (1.43\pm0.14\pm0.13)\times 10^{-3}, B(\psip\ra
\eta\J) = (2.98\pm0.09\pm0.23)%,
B(\psi(2S)\ar\gamma\chi_{c1}\ar\gamma\gamma\jpsi) = (2.81\pm0.05\pm 0.23)%,
and B(\psi(2S)\ar\gamma\chi_{c2}\ar\gamma\gamma\jpsi) = (1.62\pm0.04\pm
0.12)%.Comment: 7 pages, 6 figures. submitted to Phys. Rev.
Observation of decays into vector meson pairs , , and
Decays of to vector meson pairs , and
are observed for the first time using
\psip events accumulated at the BESIII detector at the BEPCII
collider. The branching fractions are measured to be , , and , for , , and ,
respectively. The observation of decays into a pair of vector
mesons , and indicates that the hadron
helicity selection rule is significantly violated in decays. In
addition, the measurement of gives the rate of doubly
OZI-suppressed decay. Branching fractions for and
decays into other vector meson pairs are also measured with improved precision.Comment: 4 pages, 2 figure
GPU-based ultra-fast direct aperture optimization for online adaptive radiation therapy
Online adaptive radiation therapy (ART) has great promise to significantly
reduce normal tissue toxicity and/or improve tumor control through real-time
treatment adaptations based on the current patient anatomy. However, the major
technical obstacle for clinical realization of online ART, namely the inability
to achieve real-time efficiency in treatment re-planning, has yet to be solved.
To overcome this challenge, this paper presents our work on the implementation
of an intensity modulated radiation therapy (IMRT) direct aperture optimization
(DAO) algorithm on graphics processing unit (GPU) based on our previous work on
CPU. We formulate the DAO problem as a large-scale convex programming problem,
and use an exact method called column generation approach to deal with its
extremely large dimensionality on GPU. Five 9-field prostate and five 5-field
head-and-neck IMRT clinical cases with 5\times5 mm2 beamlet size and
2.5\times2.5\times2.5 mm3 voxel size were used to evaluate our algorithm on
GPU. It takes only 0.7~2.5 seconds for our implementation to generate optimal
treatment plans using 50 MLC apertures on an NVIDIA Tesla C1060 GPU card. Our
work has therefore solved a major problem in developing ultra-fast
(re-)planning technologies for online ART
First Observation of the Decays chi_{cJ} -> pi^0 pi^0 pi^0 pi^0
We present a study of the P-wave spin -triplet charmonium chi_{cJ} decays
(J=0,1,2) into pi^0 pi^0 pi^0 pi^0. The analysis is based on 106 million
\psiprime decays recorded with the BESIII detector at the BEPCII electron
positron collider. The decay into the pi^0 pi^0 pi^0 pi^0 hadronic final state
is observed for the first time. We measure the branching fractions B(chi_{c0}
-> pi^0 pi^0 pi^0 pi^0)=(3.34 +- 0.06 +- 0.44)*10^{-3}, B(chi_{c1} -> pi^0 pi^0
pi^0 pi^0)=(0.57 +- 0.03 +- 0.08)*10^{-3}, and B(chi_{c2} -> pi^0 pi^0 pi^0
pi^0)=(1.21 +- 0.05 +- 0.16)*10^{-3}, where the uncertainties are statistical
and systematical, respectively.Comment: 7 pages, 3 figure
Study of radiative decays into a vector meson
The decays () are studied with
a sample of radiative \psip\to\gamma\chi_{cJ} events in a sample of
(1.06\pm0.04)\times 10^{8} \psip events collected with the BESIII detector.
The branching fractions are determined to be: , , and . The decay is observed for the first time. Upper limits at the 90% confidence
level on the branching fractions for and \chict decays into these
final states are determined. In addition, the fractions of the transverse
polarization component of the vector meson in decays
are measured to be for , for , and for , respectively. The first errors are statistical and the second
ones are systematic.Comment: 8 pages, 3 figure
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