194 research outputs found
Observation of a charged charmoniumlike structure in at GeV
We study the process at a
center-of-mass energy of 4.26GeV using a 827pb data sample obtained with
the BESIII detector at the Beijing Electron Positron Collider. Based on a
partial reconstruction technique, the Born cross section is measured to be
pb. We observe a structure near the
threshold in the recoil mass spectrum, which we denote as the
. The measured mass and width of the structure are
MeV/c and MeV, respectively. Its
production ratio is determined to be . The first uncertainties
are statistical and the second are systematic.Comment: 7 pages, 4 figures, 1 table; version accepted to be published in PR
Search for Baryonic Decays of \psi(3770) and \psi(4040)
By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482
pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt
s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the
BEPCII storage ring, we search for \psi(3770) and \psi(4040) decay to baryonic
final states, including \Lambda\bar\Lambda\pi^+\pi^-, \Lambda \bar\Lambda\pi^0,
\Lambda\bar\Lambda\eta, \Sigma^+ \bar\Sigma^-, \Sigma^0 \bar\Sigma^0,
\Xi^-\bar\Xi^+ and \Xi^0\bar\Xi^0 decays. None are observed, and upper limits
are set at the 90% confidence level.Comment: 9 pages, 3 figure
Search for the Lepton Flavor Violation Process at BESIII
We search for the lepton-flavor-violating decay of the into an
electron and a muon using events
collected with the BESIII detector at the BEPCII collider. Four candidate
events are found in the signal region, consistent with background expectations.
An upper limit on the branching fraction of (90% C.L.) is obtained
Precision Measurement of the Mass of the Lepton
An energy scan near the pair production threshold has been performed
using the BESIII detector. About pb of data, distributed over four
scan points, was collected. This analysis is based on pair decays to
, , , , , , , and
final states, where denotes a charged or . The mass of the
lepton is measured from a maximum likelihood fit to the pair production
cross section data to be )
MeV/, which is currently the most precise value in a single measurement.Comment: 13 pages, 7 figure
Search for the radiative transitions and
By using a 2.92 fb data sample taken at GeV with
the BESIII detector operating at the BEPCII collider, we search for the
radiative transitions and
through the hadronic decays . No
significant excess of signal events above background is observed. We set upper
limits at a 90% confidence level for the product branching fractions to be
and
. Combining our result with world-average
values of , we find the
branching fractions
and at a 90%
confidence level.Comment: 10 pages, 4 figure
Search for C-parity violation in and
Using events recorded in
collisions at 3.686 GeV with the BESIII at the BEPCII collider, we
present searches for C-parity violation in and decays via . No significant
signals are observed in either channel. Upper limits on the branching fractions
are set to be and
at the 90\%
confidence level. The former is one order of magnitude more stringent than the
previous upper limit, and the latter represents the first limit on this decay
channel.Comment: 7 pages, 2 figure
Observation of at BESIII
Using events collected with the BESIII detector
at the BEPCII storage rings, we observe for the first time the process
,
with a significance of ( including systematic
uncertainties). The product branching fraction of is measured to be
, where the first error is statistical and the
second is systematic. This measurement provides information on the
production near threshold coupling to and improves the understanding
of the dynamics of decays to four body processes.Comment: 8 pages, 7 figure
Observation of and a neutral charmoniumlike structure
Using data collected with the BESIII detector operating at the Beijing
Electron Positron Collider at center-of-mass energies of , 4.26,
and 4.36~GeV, we observe \EE\to \pphc for the first time. The Born cross
sections are measured and found to be about half of those of \EE\to
\pi^+\pi^-h_c within less than 2. In the mass spectrum, a
structure at 4.02~GeV/ is found. It is most likely to be the neutral
isospin partner of the \zcp^{\pm} observed in the process of \EE\to
\pi^+\pi^-h_c is found. A fit to the invariant mass spectrum, with
the width of the \zcpn fixed to that of its charged isospin partner and
possible interferences with non-\zcpn amplitudes neglected, gives a mass of
()~MeV/ for the \zcpn, where the first error is
statistical and the second systematic.Comment: 7 pages, 2 figure
The associations between serum brain-derived neurotrophic factor, potential confounders, and cognitive decline: A longitudinal study
Brain-derived neurotrophic factor (BDNF) plays a role in the maintenance and function of neurons. Although persons with Alzheimer's disease have lower cortical levels of BDNF, evidence regarding the association between circulating BDNF and cognitive function is conflicting. We sought to determine the correlates of BDNF level and whether BDNF level was prospectively associated with cognitive decline in healthy older adults. We measured serum BDNF near baseline in 912 individuals. Cognitive status was assessed repeatedly with the modified Mini-Mental Status Examination and the Digit Symbol Substitution test over the next 10 years. We evaluated the association between BDNF and cognitive decline with longitudinal models. We also assessed the association between BDNF level and demographics, comorbidities and health behaviors. We found an association between serum BDNF and several characteristics that are also associated with dementia (race and depression), suggesting that future studies should control for these potential confounders. We did not find evidence of a longitudinal association between serum BDNF and subsequent cognitive test trajectories in older adults, although we did identify a potential trend toward a cross-sectional association. Our results suggest that serum BDNF may have limited utility as a biomarker of prospective cognitive decline
Hawk Eyes II: Diurnal Raptors Differ in Head Movement Strategies When Scanning from Perches
Background
Relatively little is known about the degree of inter-specific variability in visual scanning strategies in species with laterally placed eyes (e.g., birds). This is relevant because many species detect prey while perching; therefore, head movement behavior may be an indicator of prey detection rate, a central parameter in foraging models. We studied head movement strategies in three diurnal raptors belonging to the Accipitridae and Falconidae families. Methodology/Principal Findings
We used behavioral recording of individuals under field and captive conditions to calculate the rate of two types of head movements and the interval between consecutive head movements. Cooper\u27s Hawks had the highest rate of regular head movements, which can facilitate tracking prey items in the visually cluttered environment they inhabit (e.g., forested habitats). On the other hand, Red-tailed Hawks showed long intervals between consecutive head movements, which is consistent with prey searching in less visually obstructed environments (e.g., open habitats) and with detecting prey movement from a distance with their central foveae. Finally, American Kestrels have the highest rates of translational head movements (vertical or frontal displacements of the head keeping the bill in the same direction), which have been associated with depth perception through motion parallax. Higher translational head movement rates may be a strategy to compensate for the reduced degree of eye movement of this species. Conclusions
Cooper\u27s Hawks, Red-tailed Hawks, and American Kestrels use both regular and translational head movements, but to different extents. We conclude that these diurnal raptors have species-specific strategies to gather visual information while perching. These strategies may optimize prey search and detection with different visual systems in habitat types with different degrees of visual obstruction
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