We report a first study of the semileptonic decay $D^0\rightarrow
K^-\pi^0\mu^{+}\nu_{\mu}$ by analyzing an $e^+e^-$ annihilation data sample of
$7.9~\mathrm{fb}^{-1}$ collected at the center-of-mass ...energy of 3.773 GeV with
the BESIII detector. The absolute branching fraction of $D^0\to
K^-\pi^0\mu^{+}\nu_{\mu}$ is measured for the first time to be $(0.729 \pm
0.014_{\rm stat} \pm 0.011_{\rm syst})\%$. Based on an amplitude analysis, the
$S\text{-}{\rm wave}$ contribution is determined to be $(5.76 \pm 0.35_{\rm
stat} \pm 0.29_{\rm syst})\%$ of the total decay rate in addition to the
dominated $K^{*}(892)^-$ component. The branching fraction of $D^0\to
K^{*}(892)^-\mu^+\nu_\mu$ is given to be $(2.062 \pm 0.039_{\rm stat} \pm
0.032_{\rm syst})\%$, which improves the precision of the world average by a
factor of 5. Combining with the world average of ${\mathcal B}(D^0\to
K^{*}(892)^-e^+\nu_e)$, the ratio of the branching fractions obtained is
$\frac{{\mathcal B}(D^0\to K^{*}(892)^-\mu^+\nu_\mu)}{{\mathcal B}(D^0\to
K^{*}(892)^-e^+\nu_e)} = 0.96\pm0.08$, in agreement with lepton flavor
universality. Furthermore, assuming single-pole dominance parameterization, the
most precise hadronic form factor ratios for $D^0\to K^{*}(892)^{-}
\mu^+\nu_\mu$ are extracted to be $r_{V}=V(0)/A_1(0)=1.37 \pm 0.09_{\rm stat}
\pm 0.03_{\rm syst}$ and $r_{2}=A_2(0)/A_1(0)=0.76 \pm 0.06_{\rm stat} \pm
0.02_{\rm syst}$.
Using 9.0 $\rm fb^{-1}$ of $e^+e^-$ collision data collected at
center-of-mass energies from 4.178 to 4.278 GeV with the BESIII detector at the
BEPCII collider, we perform the first search for the ...radiative transition
$\chi_{c1}(3872)\to\gamma \psi_2(3823)$. No $\chi_{c1}(3872)\to\gamma
\psi_2(3823)$ signal is observed. The upper limit on the ratio of branching
fractions $\mathcal{B}(\chi_{c1}(3872)\to\gamma \psi_2(3823),
\psi_2(3823)\to\gamma\chi_{c1})/\mathcal{B}(\chi_{c1}(3872)\to\pi^+\pi^-
J/\psi)$ is set as 0.075 at the 90\% confidence level. Our result contradicts
theoretical predictions under the assumption that the $\chi_{c1}(3872)$ is the
pure charmonium state $\chi_{c1}(2P)$.
The number of $\psi(3686)$ events collected by the BESIII detector during the
2021 run period is determined to be $(2259.3\pm 11.1)\times 10^6$ by counting
inclusive $\psi(3686)$ hadronic events. The ...uncertainty is systematic and the
statistical uncertainty is negligible. Meanwhile, the numbers of $\psi(3686)$
events collected during the 2009 and 2012 run periods are updated to be
$(107.7\pm0.6)\times 10^6$ and $(345.4\pm 2.6)\times 10^6$, respectively. Both
numbers are consistent with the previous measurements within one standard
deviation. The total number of $\psi(3686)$ events in the three data samples is
$(2712.4\pm14.3)\times10^6$.
Based on $(2712.4\pm14.1)\times10^{6}$ $\psi(3686)$ events collected with the
BESIII detector, we study the decays $h_{c}\to3(\pi^{+}\pi^{-})\pi^{0}$,
$h_{c}\to2(\pi^{+}\pi^{-})\omega$, ...$h_{c}\to2(\pi^{+}\pi^{-})\pi^{0}\eta$,
$h_{c}\to2(\pi^{+}\pi^{-})\eta$, and $h_{c}\to p\bar{p}$ via
$\psi(3686)\to\pi^{0}h_{c}$. The decay channel
$h_{c}\to3(\pi^{+}\pi^{-})\pi^{0}$ is observed for the first time, and its
branching fraction is determined to be $\left( {9.28\pm 1.14 \pm 0.77} \right)
\times {10^{ - 3}}$, where the first uncertainty is statistical and the second
is systematic. In addition, first evidence is found for the modes $h_{c} \to
2(\pi^{+}\pi^{-})\pi^{0}\eta$ and $h_{c}\to2(\pi^{+}\pi^{-})\omega$ with
significances of 4.8$\sigma$ and 4.7$\sigma$, and their branching fractions are
determined to be $(7.55\pm1.51\pm0.77)\times10^{-3}$ and $\left( {4.00 \pm 0.86
\pm 0.35}\right) \times {10^{ - 3}}$, respectively. No significant signals of
$h_c\to 2(\pi^+\pi^-)\eta$ and $h_{c}\to p\bar{p}$ are observed, and the upper
limits of the branching fractions of these decays are determined to be
$<6.19\times10^{-4}$ and $<4.40\times10^{-5}$ at the 90% confidence level,
respectively.
Using the data samples of (1310.6±7.2)×106 J/ψ events and (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector, we search for the rare decays J/ψ→D0e+e−+c.c. and ψ(3686)→D0e+e−+c.c. No ...significant signals are observed and the corresponding upper limits on the branching fractions at the 90% confidence level are determined to be B(J/ψ→D0e+e−+c.c.)<8.5×10−8 and B(ψ(3686)→D0e+e−+c.c.)<1.4×10−7, respectively. Our limit on B(J/ψ→D0e+e−+c.c.) is more stringent by 2 orders of magnitude than the previous results, and B(ψ(3686)→D0e+e−+c.c.) is measured for the first time.
We measure the Born cross section for the reaction $e^{+}e^{-} \rightarrow
\eta h_c$ from $\sqrt{s} = 4.129$ to $4.600$~GeV using data sets collected by
the BESIII detector running at the BEPCII ...collider. A resonant structure in the
cross section line shape near 4.200~GeV is observed with a statistical
significance of 7$\sigma$. The parameters of this resonance are measured to be
\MeasMass\ and \MeasWidth, where the first uncertainties are statistical and
the second systematic.
Using $(2.712\pm0.014)\times 10^9$ $\psi(3686)$ events collected by the
BESIII detector operating at the BEPCII collider, we report the first
observation of $\psi(3686)\to 3\phi$ decay with a ...significance larger than
10$\sigma$. The branching fraction of this decay is determined to be
$(1.46\pm0.05\pm0.17)\times10^{-5}$, where the first uncertainty is statistical
and the second is systematic. No significant structure is observed in the
$\phi\phi$ invariant mass spectra.
Because of the small square dimension, a soldered-stacked-square (3S) high-temperature superconducting (HTS) wire with 1 mm width is considered as a candidate for cabling large current conductors ...through twist process. For studying the twist structure, in this work, we prepared several twisted 3S wire samples fabricated from the same piece of the 3S wire with 10 m length. For the 3S wire, the uniformity of critical current was evaluated. As well, we investigated basic electrical and mechanical characteristics for the twisted 3S wire. The main results show that the critical current distribution for the 3S wire is relatively uniform at the average value of 90 A; the allowable minimum twist pitch of the twisted 3S wire is about 60 mm; the critical current of the twisted 3S wire shows isotropy characteristics; through the test for frequency dependence of self-field loss, we can know the eddy-current loss in the twisted 3S wire can be ignored, and the measured losses are identical to the calculated one from the thin strip equation; the minimum bending diameter and allowable tensile force for the twisted 3S wire are approximately 80 mm and 400 N, respectively.
Using data samples collected with the BESIII detector operating at the BEPCII
storage ring, the cross section of the inclusive process $e^{+}e^{-} \to \eta +
X$, normalized by the total cross section ...of $e^{+}e^{-} \to \text{hadrons}$,
is measured at eight center-of-mass energy points from 2.0000 GeV to 3.6710
GeV. These are the first measurements with momentum dependence in this energy
region. Our measurement shows a significant discrepancy from calculations with
the existing fragmentation functions. To address this discrepancy, a new QCD
analysis is performed at the next-to-next-to-leading order with hadron mass
corrections and higher twist effects, which can explain both the established
high-energy data and our measurements reasonably well.
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