329 research outputs found
A tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure
Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV=m ļ¬eld strength can be achieved by using appropriate grating parameter
Recognizing basal cell carcinoma on smartphoneācaptured digital histopathology images with a deep neural network
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154530/1/bjd18026.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154530/2/bjd18026_am.pd
Search for Invisible Decays of and in and
Using a data sample of decays collected with the BES
II detector at the BEPC, searches for invisible decays of and
in to and are performed.
The signals, which are reconstructed in final states, are used
to tag the and decays. No signals are found for the
invisible decays of either or , and upper limits at the 90%
confidence level are determined to be for the ratio
and for . These are the first
searches for and decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo
Production of the -Wave Excited -States through the Boson Decays
In Ref.[7],we have dealt with the production of the two color-singlet
-wave -quarkonium states and
through the boson decays. As an
important sequential work, we make a further discussion on the production of
the more complicated -wave excited -quarkonium states, i.e.
and (with
). More over, we also calculate the channel with the two color-octet
quarkonium states and , whose contributions to the decay width maybe at the same order of
magnitude as that of the color-singlet -wave states according to the naive
nonrelativistic quantum chromodynamics scaling rules. The -wave states shall
provide sizable contributions to the production, whose decay width is
about 20% of the total decay width . After summing up all
the mentioned -quarkonium states' contributions, we obtain
KeV, where the errors are caused
by the main uncertainty sources.Comment: 8 pages, 5 figures and 2 tables. basic formulae in the appendix are
cut off to match the published version, which can be found in v1. to be
published in Eur.Phys.J.
Observation of Two New N* Peaks in J/psi -> and Decays
The system in decays of is limited to be
isospin 1/2 by isospin conservation. This provides a big advantage in studying
compared with and experiments which mix
isospin 1/2 and 3/2 for the system. Using 58 million decays
collected with the Beijing Electron Positron Collider, more than 100 thousand
events are obtained. Besides two well known
peaks at 1500 MeV and 1670 MeV, there are two new, clear peaks in
the invariant mass spectrum around 1360 MeV and 2030 MeV. They are the
first direct observation of the peak and a long-sought "missing"
peak above 2 GeV in the invariant mass spectrum. A simple
Breit-Wigner fit gives the mass and width for the peak as MeV and MeV, and for the new peak above 2 GeV
as MeV and MeV, respectively
Space-time evolution induced by spinor fields with canonical and non-canonical kinetic terms
We study spinor field theories as an origin to induce space-time evolution.
Self-interacting spinor fields with canonical and non-canonical kinetic terms
are considered in a Friedman-Robertson-Walker universe. The deceleration
parameter is calculated by solving the equation of motion and the Friedman
equation, simultaneously. It is shown that the spinor fields can accelerate and
decelerate the universe expansion. To construct realistic models we discuss the
contributions from the dynamical symmetry breaking.Comment: 16 pages, 19 figure
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar
The branching ratios and Angular distributions for J/psi decays to Lambda
Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
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