704 research outputs found
Coexistence of superconductivity and magnetism in K0.8Fe2Se1.4S0.4
High-quality single crystals of K0.8Fe2Se1.4S0.4 are successfully synthesized
by self-flux method with the superconducting transition temperatures Tconset =
32.8 K and Tczero = 31.2 K. In contrast to external pressure effect on
superconductivity, the substitution of S for Se does not suppress Tc, which
suggests that chemical doping may mainly modulate the anion height from
Fe-layer rather than compressing interlayer distance. The investigation of the
micromagnetism by electron spin resonance shows clear evidence for strong spin
fluctuation at temperatures above Tc. Accompanied by the superconducting
feature spectra, a novel resonance signal develops gradually upon cooling below
Tc, indicating the coexistence of superconductivity and magnetism in
K0.8Fe2Se1.4S0.4 crystal
The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite
The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field
X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched
onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July
2022. In this paper, we introduce the design and on-ground test results of the
LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide
field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the
X-ray imager is realized. An optical assembly composed of 36 MPO chips is used
to focus incident X-ray photons, and four large-format complementary
metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the
focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin
(in FWHM) for the central focal spot of the point spread function, and an
effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within
the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and
the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000
second observation. The total weight of LEIA is 56 kg and the power is 85 W.
The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous
orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way
for future missions by verifying in flight the technologies of both novel
focusing imaging optics and CMOS sensors for X-ray observation, and by
optimizing the working setups of the instrumental parameters. In addition, LEIA
is able to carry out scientific observations to find new transients and to
monitor known sources in the soft X-ray band, albeit limited useful observing
time available.Comment: Accepted by RA
Search for psi(3770)\ra\rho\pi at the BESII detector at the Beijing Electron-Positron Collider
Non- decay \psppto \rhopi is searched for using a data sample of
taken at the center-of-mass energy of 3.773 GeV by the
BESII detector at the BEPC. No \rhopi signal is observed, and the upper limit
of the cross section is measured to be \sigma(\EETO \rhopi)<6.0 pb at 90% C.
L. Considering the interference between the continuum amplitude and the \pspp
resonance amplitude, the branching fraction of \pspp decays to is
determined to be \BR(\pspp\ra\rho\pi)\in(6.0\times10^{-6}, 2.4\times10^{-3})
at 90% C. L. This is in agreement with the prediction of the - and -wave
mixing scheme of the charmonium states for solving the ``\rhopi puzzle''
between \jpsi and \psp decays.Comment: 15 pages, 5 figure
Partial Wave Analysis of
A partial wave analysis of in
decay is presented using a sample of 14 million
events accumulated by the BES II detector. The data are fitted to
the sum of relativistic covariant tensor amplitudes for intermediate resonant
decay modes. From the fit, significant contributions to decays from
the channels , , ,
, , , and are found. Flavor-SU(3)-violating
asymmetry is observed. Values obtained for the masses and
widths of the resonances , , , and
are presented.Comment: 16 pages, 9 figures, and 4 table
Measurement of the cross section for e^+e^- -> ppbar at center-of-mass energies from 2.0 to 3.07 GeV
Cross sections for e^+e^- -> ppbar have been measured at 10 center-of-mass
energies from 2.0 to 3.07 GeV by the BESII experiment at the BEPC, and proton
electromagnetic form factors in the time-like region have been determined.Comment: 6 pages, 3 figure
Measurements of the continuum and values in annihilation in the energy region between 3.650 and 3.872 GeV
We report measurents of the continuum near the center-of-mass
energy of 3.70 GeV, the and the values in annihilation at 68 energy points in the energy
region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC
Collodier. We obtain the for the continuum light hadron
(containing u, d and s quarks) production near the threshold to be
.Comment: 5 pages, 3 figure
Experimental study of decays to \K^+ K^- \pi^+ \pi^- \pi^0 final states
final states are studied using a sample of
decays collected with the Beijing Spectrometer
(BESII) at the Beijing Electron-Position Collider. The branching fractions of
decays to , , , , , and are determined. The first two agree with previous
measurements, and the last five are first measurements.Comment: 19 pages, 9 figure
Observation of a resonance X(1835) in J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime}
The decay channel J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime} is analyzed
using a sample of 5.8\times 10^7 J\psi events collected with the BESII
detector. A resonance, the X(1835), is observed in the \pi^+ \pi^-
\eta^{\prime} invariant mass spectrum with a statistical significance of 7.7
\sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 \pm
6.1(stat) \pm 2.7(syst) MeV/c^2, a width \Gamma = 67.7 \pm 20.3(stat) \pm
7.7(syst) MeV/c^2 and a product branching fraction B(J/\psi --> \gamma X) B(X
--> \pi^+ \pi^- \eta^{\prime}) = (2.2 \pm 0.4(stat) \pm 0.4(syst)) \times
10^{-4}. The mass and width of the X(1835) are not compatible with any known
meson resonance. Its properties are consistent with expectations for the state
that produces the strong p\bar{p} mass threshold enhancement observed in the
J\psi -->\gamma p \bar{p} process at BESII.Comment: 5 pages, 3 figures, RevTex4, Submitted to Phys. Rev. Let
Measurements of the braching fractions for psi(3770)--> D0D0-bar,D+D-,DD-bar$ and the resonance parameters of psi(3770) and psi(2S)
We report measurements of the branching fractions for and resonance parameters of and .
By analyzing the line-shapes of the cross sections for inclusive hadron, and event production in the range from 3.660 GeV to 3.872
GeV covering both and resonances, we extract the
branching fractions for decay into
respectively to be and
, which give and non- branching fraction of
to be . We
meanwhile obtain the resonance parameters of and to be
MeV, MeV and eV; MeV, keV and keV; as well as the value for the light hadron production
directly through one photon annihilation to be in this energy region.Comment: 7 pages, 4 figure
First observation of
Using 14 million events collected with the Beijing Spectrometer
(BESII) at the Beijing Electron-Positron Collider, the branching fractions of
decays to and and the branching
fractions of the main background channels ,
, , and are determined. The contributions of the
resonances in are also
discussed.Comment: 19 pages, 8 figures, add vertex requirement systematic erro
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