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Register a new userMeasurement of higher-order multipole amplitudes in $psi(3686)rightarrowgammachi_{c1,2}$ with $chi_{c1,2}togamma J/psi$ and search for the transition $eta_{c}(2S)togamma J/psi$
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Using 106~million $psi(3686)$ events collected with the BESIII detector, we measure multipole amplitudes for the decay $psi(3686)rightarrowgammachi_{c1,2}togammagamma J/psi$ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole amplitude for $psi(3686)rightarrowgammachi_{c1,2}rightarrowgammagamma J/psi$ and the normalized electric-octupole amplitudes for $psi(3686)rightarrowgammachi_{c2}$,~$chi_{c2}rightarrowgamma J/psi$ are determined. The M2 amplitudes for $psi(3686)rightarrowgammachi_{c1}$ and $chi_{c1,2}rightarrowgamma J/psi$ are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of $psi(3686)$ and $J/psi$ decays to $chi_{c1,2}$, $b_{2}^{1}/b_{2}^{2} = 1.35pm0.72$ and $a_{2}^{1}/a_{2}^{2} = 0.617pm0.083$, which agree well with theoretical expectations. By considering the multipole contributions of $chi_{c1,2}$, we measure the product branching fractions for the cascade decays $psi(3686)rightarrowgammachi_{c0,1,2}togammagamma J/psi$ and search for the process $eta_{c}(2S)togamma J/psi$ through $psi(3686)rightarrowgammaeta_{c}(2S)$. The product branching fraction for $psi(3686)rightarrowgammachi_{c0}togammagamma J/psi$ is 3$sigma$ larger than published measurements, while those of $psi(3686)rightarrowgammachi_{c1,2}togammagamma J/psi$ are consistent. No significant signal for the decay $psi(3686)togamma eta_c(2S)togamma gamma J/psi$ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.
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We report a measurement of the branching fraction of $psi(3770)togammachi_{c1}$ and search for the transition $psi(3770)rightarrow gamma chi_{c2}$ based on 2.92~fb$^{-1}$ of $e^+e^-$ data accumulated at $sqrt{s}=3.773$~GeV with the BESIII detector at the BEPCII collider. The measured branching fraction of $psi(3770) rightarrow gamma chi_{c1}$ is $mathcal B(psi(3770) rightarrow gamma chi_{c1})=(2.48 pm 0.15 pm 0.23) times 10^{-3}$, which is the most precise measurement to date. The upper limit on the branching fraction of $psi(3770)rightarrow gamma chi_{c2}$ at a $90%$ confidence level is $mathcal B(psi(3770) rightarrow gamma chi_{c2})<0.64 times 10^{-3}$. The corresponding partial widths are $Gamma(psi(3770) to gamma chi_{c1}) =(67.5pm 4.1pm 6.7)$~keV and $Gamma(psi(3770) to gamma chi_{c2}) < 17.4$~keV.
Using a data sample of $448.1times10^6$ $psi(3686)$ events collected with the BESIII detector operating at the BEPCII, we perform search for the hadronic transition $h_crightarrowpi^+pi^-J/psi$ via $psi(3686)rightarrowpi^0h_c$. No signals of the transition are observed, and the upper limit on the product branching fraction $mathcal{B}(psi(3686)rightarrowpi^0h_c)mathcal{B}(h_crightarrowpi^+pi^-J/psi)$ at the 90% confidence level is determined to be $2.0times10^{-6}$. This is the most stringent upper limit to date.
Motivated by a recent successful dynamical explanation for the newly observed fully-charm structure $X(6900)$ in the mass spectrum of di-$J/psi$ by LHCb [J.~Z.~Wang textit{et al.} arXiv:2008.07430], in this work, we extend the same dynamical rescattering mechanism to predict the line shape of more potential fully-heavy structures in the invariant mass spectrum of $J/psi psi(3686)$, $J/psi psi(3770)$, $psi(3686) psi(3686)$, and $J/psi Upsilon(1S)$ at high energy proton-proton collisions, whose verification in experiments should be helpful to further clarify the nature of $X(6900)$. The above final states of vector heavy quarkonia can be experimentally reconstructed more effectively by a $mu^+mu^-$ pair in the muon detector compared with $Qbar{Q}$ meson with other quantum numbers. Furthermore, the corresponding peak mass positions of each of predicted fully-heavy structures are also given. Our theoretical studies here could provide some valuable information for the future measurement proposals of LHCb and CMS, especially based on the accumulated data after completing Run III of LHC in the near future.
Using $106times10^6$ $psi(2S)$ events collected with the BESIII detector at the BEPCII storage ring, the higher-order multipole amplitudes in the radiative transition $psi(2S)togammachi_{c2}togammapipi/gamma KK$ are measured. A fit to the $chi_{c2}$ production and decay angular distributions yields $M2=0.046pm0.010pm0.013$ and $E3=0.015pm0.008pm0.018$, where the first errors are statistical and the second systematic. Here $M2$ denotes the normalized magnetic quadrupole amplitude and $E3$ the normalized electric octupole amplitude. This measurement shows evidence for the existence of the $M2$ signal with $4.4sigma$ statistical significance and is consistent with the charm quark having no anomalous magnetic moment.
Using $4.479 times 10^{8}$ $psi(3686)$ events collected with the BESIII detector, we search for the decays $psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}$ and $chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi$. The decays $psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}$ and $chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi$ are observed for the first time. The measured branching fractions are $mathcal{B}(psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}) = (11.7 pm 2.5 pm 1.0)times10^{-4}$, $(8.6 pm 0.3 pm 0.6)times10^{-4}$, $(6.9 pm 0.5 pm 0.6)times10^{-4}$, and $mathcal{B}(chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi) = (1.51 pm 0.30 pm 0.13)times10^{-4}$, $(3.73 pm 0.09 pm 0.25)times10^{-3}$, $(2.48 pm 0.08 pm 0.16)times10^{-3}$. The ratios of the branching fractions $frac{mathcal{B}(psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2})}{mathcal{B}(psi(3686) rightarrow gammachi_{c0,1,2})}$ and $frac{mathcal{B}(chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi)}{mathcal{B}(chi_{c0,1,2} rightarrow gamma J/psi)}$ are also reported.
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