Using 2917 pb−1 of data accumulated at 3.773 GeV, 44.5 pb−1 of data accumulated at 3.65 GeV and data accumulated during a ψ(3770) line-shape scan with the BESIII detector, the reaction e+e−→pp¯ is ...studied considering a possible interference between resonant and continuum amplitudes. The cross section of e+e−→ψ(3770)→pp¯, σ(e+e−→ψ(3770)→pp¯), is found to have two solutions, determined to be (0.059−0.020+0.070±0.012) pb with the phase angle ϕ=(255.8−26.6+39.0±4.8)° (<0.166 pb at the 90% confidence level), or σ(e+e−→ψ(3770)→pp¯)=(2.57−0.13+0.12±0.12) pb with ϕ=(266.9−6.3+6.1±0.9)° both of which agree with a destructive interference. Using the obtained cross section of ψ(3770)→pp¯, the cross section of pp¯→ψ(3770), which is useful information for the future PANDA experiment, is estimated to be either (9.8−3.9+11.8) nb (<27.5 nb at 90% C.L.) or (425.6−43.7+42.9) nb.
Abstract
We report a search for a heavier partner of the recently observed
state, denoted as
, in the process
, based on
collision data collected at the center-of-mass energies of
, 4.682 and 4.699 ...GeV with the BESIII detector. The
is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark. A partial-reconstruction technique is used to isolate
recoil-mass spectra, which are probed for a potential contribution from
(
). We find an excess of
(
) candidates with a significance of
, after considering systematic uncertainties, at a mass of
. As the data set is limited in size, the upper limits are evaluated at the 90% confidence level on the product of the Born cross sections (
) and the branching fraction (
) of
, under different assumptions of the
mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies. The upper limits of
are found to be at the level of
pb at each energy. Larger data samples are needed to confirm the
state and clarify its nature in the coming years.
Abstract
Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb
, collected by the BESIII detector in the energy region between
and
, we report the ...first observations of the Cabibbo-suppressed decays
,
, and the Cabibbo-favored decay
with statistical significances of
,
, and
, respectively. The branching fractions of these decays are measured to be
%,
%, and
%, where the first uncertainties are statistical and the second are systematic. We find that the branching fraction of the decay
is about one order of magnitude higher than that of
.
We investigate quasi-periodic pulsations (QPPs) of high-energy nonthermal emissions from an X9.3 flare (SOL2017-Sep-06T11:53), the most powerful flare since the beginning of solar cycle 24. The QPPs ...are identified as a series of regular and repeating peaks in the light curves in the gamma- and hard X-ray (HXR) channels recorded by the Konus-Wind, as well as the radio and microwave fluxes measured by the CALLISTO radio spectrograph during the impulsive phase. The periods are determined from the global wavelet and Fourier power spectra, as 24-30 s in the HXR and microwave channels which are associated with nonthermal electrons, and ~20 s in the gamma-ray band related to nonthermal ions. Both nonthermal electrons and ions may be accelerated by repetitive magnetic reconnection during the impulsive phase. However, we could not rule out other mechanisms such as the MHD oscillation in a sausage mode. The QPP detected in this study is useful for understanding the particle acceleration and dynamic process in solar flares and also bridging the gap between stellar and solar flares since the energy realm of the X9.3 solar flare is almost compared with a typical stellar flare.
Using an e(+)e(-) collision data sample of 2.93 fb(-1) collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D-0 -> a(0)(980)(-)e(+)nu(e) ...and evidence for D+ -> a(0)(980)(0)e(+)nu(e) with significances of 6.4 sigma and 2.9 sigma, respectively. The absolute branching fractions are determined to be B(D-0 -> a(0)(980)(-)e(+)nu(e)) x B(a(0)(980)(-) -> eta pi(-)) = 1.33(-0.29)(+0.33)(stat) +/- 0.09(syst) x 10(-4) and B(D+ -> a(0)(980)(0)e(+)nu(e)) x B(a(0)(980)(0) -> eta pi(0)) = 1.66(-0.66)(+0.81)(stat) +/- 0.11(syst) x 10(-4). This is the first time the a(0)(980) meson has been measured in a D-0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling a(0)(980) states.
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