68,237 research outputs found
Study of and and
We study the decays of and to the final states
and based on a single
baryon tag method using data samples of
and events collected with
the BESIII detector at the BEPCII collider. The decays to
are observed for the first time. The
measured branching fractions of and
are in good agreement with, and much
more precise, than the previously published results. The angular parameters for
these decays are also measured for the first time. The measured angular decay
parameter for , , is found to be negative, different to the other
decay processes in this measurement. In addition, the "12\% rule" and isospin
symmetry in the and and
systems are tested.Comment: 11 pages, 7 figures. This version is consistent with paper published
in Phys.Lett. B770 (2017) 217-22
Measurement of in oscillation using quantum correlations in at = 3.773\,GeV
We report a measurement of the parameter in
\ensuremath{D^0}\xspace-\ensuremath{\overline{D}^{0}}\xspace oscillations
performed by taking advantage of quantum coherence between pairs of
\ensuremath{D^0}\xspace \ensuremath{\overline{D}^{0}}\xspace mesons produced
in annihilations near threshold. In this work, doubly-tagged
\ensuremath{D^0}\xspace \ensuremath{\overline{D}^{0}}\xspace events, where
one decays to a eigenstate and the other decays in a semileptonic
mode, are reconstructed using a data sample of 2.92\,fb collected with
the BESIII detector at the center-of-mass energy of = 3.773\,GeV. We
obtain , where the first uncertainty is
statistical and the second is systematic. This result is compatible with the
current world average.Comment: 13 pages, 3 figure
An optical diode made from a `flying' photonic crystal
Optical diodes controlling the flow of light are of principal significance
for optical information processing 1. They transmit light from an input to an
output, but not in reverse direction. This breaking of time reversal symmetry
is typically achieved via non-linear 2,3 or magnetic effects 4, which imposes
limits to all-optical control 5-7, on-chip integration 7-11, or single-photon
operation 12. Here, we propose an optical diode which requires neither magnetic
fields nor strong input fields. It is based on a flying photonic crystal. Due
to the Doppler effect, the crystal has a band gap with frequency depending on
the light propagation direction relative to the crystal motion.
Counter-intuitively, our setup does not involve the movement of any material
parts. Rather, the flying photonic crystal is realized by optically inducing a
spatially periodic but moving modulation of the optical properties of a
near-resonant medium. The flying crystal not only opens perspectives for
optical diodes operating at low light levels or integrated in small solid state
devices, but also enables novel photonic devices such as optically tunable
mirrors and cavities.Comment: 13 pages, 4 figures, presented in PQE 201
Observation of near = 4.42 and 4.6 GeV
Based on data samples collected with the BESIII detector operating at the
BEPCII storage ring at center-of-mass energies 4.4 GeV, the
processes are observed for the first
time. With an integrated luminosity of near 4.42
GeV, a significant signal is found, and the cross section is
measured to be (20.9 \pm 3.2 \pm 2.5)\pb. With near 4.6 GeV, a clear signal is seen, and the cross section is
measured to be (9.5 \pm 2.1 \pm 1.3) \pb, while evidence is found for an
signal. The first errors are statistical and the second are
systematic. Due to low luminosity or low cross section at other energies, no
significant signals are observed. In the cross section, an
enhancement is seen around 4.42 GeV. Fitting the cross section
with a coherent sum of the Breit-Wigner function and a phase space
term, the branching fraction is
obtained to be of the order of .Comment: 7 pages, 3 figure
In-beam spectroscopy of medium- and high-spin states in Ce
Medium and high-spin states in Ce were investigated using the
Cd(Ne, ) reaction and the Gammasphere array. The level
scheme was extended up to an excitation energy of MeV and spin 93/2
. Eleven bands of quadrupole transitions and two new dipole bands are
identified. The connections to low-lying states of the previously known,
high-spin triaxial bands were firmly established, thus fixing the excitation
energy and, in many cases, the spin parity of the levels. Based on comparisons
with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant
density functional theory, it is shown that all observed bands are
characterized by pronounced triaxiality. Competing multiquasiparticle
configurations are found to contribute to a rich variety of collective
phenomena in this nucleus.Comment: 20 pages, 11 figure
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