A search has been performed for the semileptonic decays $D^{0}\to K_{S}^{0}
K^{-} e^{+}\nu_{e}$, $D^{+}\to K_{S}^{0} K_{S}^{0} e^{+}\nu_{e}$ and $D^{+}\to
K^{+}K^{-} e^{+}\nu_{e}$, using ...$7.9~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation
data collected at the center-of-mass energy $\sqrt{s}=3.773$ GeV by the BESIII
detector operating at the BEPCII collider. No significant signals are observed,
and upper limits are set at the 90\% confidence level of $2.13\times10^{-5}$,
$1.54\times10^{-5}$ and $2.10\times10^{-5}$ for the branching fractions of
$D^{0}\to K_{S}^{0} K^{-} e^{+}\nu_{e}$, $D^{+}\to K_{S}^{0} K_{S}^{0}
e^{+}\nu_{e}$ and $D^{+}\to K^{+}K^{-} e^{+}\nu_{e}$, respectively.
The first observation of the decays $J\!/\!\psi \rightarrow \bar{p}
\Sigma^{+} K_{S}^{0}$ and $J\!/\!\psi \rightarrow p \bar{\Sigma}^{-} K_{S}^{0}$
is reported using $(10087\pm44)\times10^{6}$ ...$J\!/\!\psi$ events recorded by
the BESIII detector at the BEPCII storage ring. The branching fractions of each
channel are determined to be $\mathcal{B}(J\!/\!\psi \rightarrow \bar{p}
\Sigma^{+} K_{S}^{0})=(1.361 \pm 0.006 \pm 0.025) \times 10^{-4}$ and
$\mathcal{B}(J\!/\!\psi \rightarrow p \bar{\Sigma}^{-} K_{S}^{0})=(1.352 \pm
0.006 \pm 0.025) \times 10^{-4}$. The combined result is
$\mathcal{B}(J\!/\!\psi \rightarrow \bar{p} \Sigma^{+} K_{S}^{0} +c.c.)=(2.725
\pm 0.009 \pm 0.050) \times 10^{-4}$, where the first uncertainty is
statistical and the second systematic. The results presented are in good
agreement with the branching fractions of the isospin partner decay $J\!/\!\psi
\rightarrow p K^- \bar\Sigma^0 + c.c.$.
The Beijing Spectrometer (BESIII) collaboration uses \(e^+e^-\) collisions in the tau-charm energy region to study a broad spectrum of topics. These include studies of light mesons and light baryons, ...studies of charmonium, including exotic mesons and baryons containing charmonium, studies of charmed mesons and baryons, studies of QCD and tau physics, as well as searches for new physics. The following is a Snowmass white paper that outlines the BESIII accomplishments and potential in each of these areas.
Phys. Rev. D 108, 092011 (2023) Based on $(27.08\pm 0.14)\times10^{8}$ $\psi(3686)$ events collected with the
BESIII detector operating at the BEPCII collider, the
...$\psi(3686)\to\Sigma^{+}\bar{\Sigma}^{-}\omega$ and
$\Sigma^{+}\bar{\Sigma}^{-}\phi$ decays are observed for the first time with
statistical significances of 13.8$\sigma$ and 7.6$\sigma$, respectively. The
corresponding branching fractions are measured to be
$\mathcal{B}(\psi(3686)\to\Sigma^{+}\bar{\Sigma}^{-}\omega)=(1.90 \pm 0.18 \pm
0.21) \times 10^{-5}$ and
$\mathcal{B}(\psi(3686)\to\Sigma^{+}\bar{\Sigma}^{-}\phi)=(2.96 \pm 0.54 \pm
0.41) \times 10^{-6}$, where the first uncertainties are statistical and the
second systematic.
Using a sample of about 10 billion $J/\psi$ events with the BESIII detector,
we search for the weak decays of $J/\psi \to \bar{D}^0\pi^0 + c.c.$, $J/\psi
\to \bar{D}^0\eta + c.c.$, $J/\psi \to ...\bar{D}^0\rho^0 + c.c.$, $J/\psi \to
D^-\pi^+ + c.c.$, and $J/\psi \to D^-\rho^+ + c.c.$. Since no significant
signal is observed, we set the upper limits of the branching fractions of these
decays to be $\mathcal{B}(J/\psi \to \bar{D}^0\pi^0 + c.c.) < 4.7 \times
10^{-7}$, $\mathcal{B}(J/\psi \to \bar{D}^0\eta + c.c.) < 6.8 \times 10^{-7}$,
$\mathcal{B}(J/\psi \to \bar{D}^0\rho^0 + c.c.) < 5.2 \times 10^{-7}$,
$\mathcal{B}(J/\psi \to D^-\pi^+ + c.c.) < 7.0 \times 10^{-8}$, and
$\mathcal{B}(J/\psi \to D^-\rho^+ + c.c.) < 6.0 \times 10^{-7}$ at the 90\%
confidence level.
Using $(10087\pm44)\times 10^{6}$ $J/\psi$ events collected with the BESIII
detector, numerous $\Xi^-$ and $\Lambda$ decay asymmetry parameters are
simultaneously determined from the process $J/\psi ...\to \Xi^- \bar{\Xi}^+ \to
\Lambda(p\pi^-) \pi^- \bar{\Lambda}(\bar{n} \pi^0) \pi^+$ and its
charge-conjugate channel. The precisions of $\alpha_0$ for $\Lambda \to n\pi^0$
and $\bar{\alpha}_0$ for $\bar{\Lambda} \to \bar{n}\pi^0$ compared to world
averages are improved by factors of 4 and 1.7, respectively. The ratio of decay
asymmetry parameters of $\Lambda \to n\pi^0$ to that of $\Lambda \to p\pi^-$,
$\langle \alpha_0 \rangle/ \langle \alpha_{\Lambda -} \rangle $, is determined
to be $ 0.873 \pm 0.012^{+0.011}_{-0.010}$, where the first and the second
uncertainties are statistical and systematic, respectively. The ratio is
smaller than unity more than $5\sigma$, which signifies the existence of the
$\Delta I = 3/2$ transition in $\Lambda$ for the first time. Beside, we test
for CP violation in $\Xi^- \to \Lambda \pi^-$ and in $\Lambda \to n \pi^{0}$
with the best precision to date.
JHEP01(2024)180 Based on $e^{+}e^{-}$ collision data collected at center-of-mass energies
from 2.000 to 3.080 GeV by the BESIII detector at the BEPCII collider, a
partial wave analysis is performed ...for the process $e^{+}e^{-}\to K_{S}^{0}
K_{L}^{0} \pi^{0}$. The results allow the Born cross sections of the process
$e^{+}e^{-}\to K_{S}^{0} K_{L}^{0} \pi^{0}$, as well as its subprocesses
$e^{+}e^{-}\to K^{*}(892)^{0}\bar{K}^{0}$ and $K^{*}_{2}(1430)^{0}\bar{K}^{0}$
to be measured. The Born cross sections for $e^{+}e^{-}\to
K_{S}^{0}K_{L}^{0}\pi^{0}$ are consistent with previous measurements by BaBar,
but with substantially improved precision. The Born cross section lineshape of
the process $e^{+}e^{-}\to K^{*}(892)^{0}\bar{K}^{0}$ is consistent with a
vector meson state around 2.2 GeV with a significance of 3.2$\sigma$. A
Breit-Wigner fit determines its mass as
$M_Y=(2164.7\pm9.1\pm3.1)~{\rm{MeV}}/c^{2}$ and its width as
$\Gamma_{Y}=(32.4\pm21.0\pm1.8)~\rm{MeV}$.
By analyzing 7.33\,fb$^{-1}$ of $e^+e^-$ collision data collected at
center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector,
we search for the semileptonic decays $D^+_s \to ...K_1(1270)^0 e^+\nu_e$ and
$D^+_s \to b_1(1235)^0 e^+\nu_e$ for the first time. No significant signals are
observed for either decay mode. The upper limits on the (product) branching
fractions are determined to be ${\mathcal B}D^+_s \to K_1(1270)^0 e^+\nu_e <
4.1\times 10^{-4}$ and ${\mathcal B}D^+_s \to b_1(1235)^0 e^+\nu_e\cdot
{\mathcal B}b_1(1235)^0\to \omega\pi^0 < 6.4\times 10^{-4}$ at 90\%
confidence level.
We perform a study of the $X(3872)$ lineshape using the data samples of
$e^+e^-\to\gamma X(3872)$, $X(3872)\to D^0\bar{D}^0 \pi^0$ and $\pi^+\pi^-
J/\psi$ collected with the BESIII detector. The ...effects of the coupled-channels
and the off-shell $D^{*0}$ are included in the parameterization of the
lineshape. The lineshape mass parameter is obtained to be $M_{X}=(3871.63\pm
0.13^{+0.06}_{-0.05})$ MeV. Two poles are found on the first and second Riemann
sheets corresponding to the $D^{*0}\bar{D}^0$ branch cut. The pole location on
the first sheet is much closer to the $D^{*0}\bar{D}^0$ threshold than the
other, and is determined to be $7.04\pm0.15^{+0.07}_{-0.08}$ MeV above the
$D^0\bar{D}^0\pi^0$ threshold with an imaginary part
$-0.19\pm0.08^{+0.14}_{-0.19}$ MeV.
Phys. Rev. D 109, L011102 (2024) With a data sample corresponding to an integrated luminosity of
11.5~fb$^{-1}$
collected with the BESIII detector operating at the BEPCII storage ring, for
the first ...time the light hadron decay $\chi_{c1}(3872) \rightarrow
\pi^{+}\pi^{-}\eta$
is searched for. While no significant signal is observed, the upper limits at
the 90\% confidence level for
$\sigmae^{+}e^{-} \rightarrow \gamma \chi_{c1}(3872)
\mathcal{B}\chi_{c1}(3872) \rightarrow \pi^{+}\pi^{-}\eta$ at center-of-mass
energies from 4.13 to 4.34 GeV are determined.
By normalizing to the $\chi_{c1}(3872)\to\pi^+\pi^- J/\psi$ decay channel, a
90\% confidence level upper limit for the branching fraction ratio
$\mathcal{R}=\mathcal{B}\chi_{c1}(3872)
\rightarrow\pi^{+}\pi^{-}\eta/\mathcal{B}\chi_{c1}(3872) \rightarrow
\pi^{+}\pi^{-} J/\psi < 0.12$ is given.
These measurements provide important inputs for understanding the internal
structure of the $\chi_{c1}(3872)$ resonance.
