Measurement of higher-order multipole amplitudes in $\psi (3686)\to \gamma {\chi }_{c1,2}$ with ${\chi }_{c1,2}\to \gamma J/\psi$ and search for the transition ${\eta }_c(2S)\to \gamma J/\psi$

Abstract

Using 106~million $\psi (3686)$ events collected with the BESIII detector, we measure multipole amplitudes for the decay $\psi (3686)\to \gamma {\chi }_{c1,2}\to \gamma \gamma J/\psi$ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole amplitude for $\psi (3686)\to \gamma {\chi }_{c1,2}\to \gamma \gamma J/\psi$ and the normalized electric-octupole amplitudes for $\psi (3686)rightarrow\gamma {\chi }_{c2}$,~${\chi }_{c2}\to \gamma J/\psi$ are determined. The M2 amplitudes for $\psi (3686)\to \gamma {\chi }_{c1}$ and ${\chi }_{c1,2}\to \gamma J/\psi$ 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 ${\chi }_{c1,2}$, $b_2^1/b_2^2=1.35\pm 0.72$ and $a_2^1/a_2^2=0.617\pm 0.083$, 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 $\psi (3686)\to \gamma {\chi }_{c0,1,2}\to \gamma \gamma J/\psi$ and search for the process ${\eta }_c(2S)\to \gamma J/\psi$ through $\psi (3686)\to \gamma {\eta }_c(2S)$. The product branching fraction for $\psi (3686)\to \gamma {\chi }_{c0}\to \gamma \gamma J/\psi$ is 3$\sigma$ larger than published measurements, while those of $\psi (3686)rightarrow\gamma {\chi }_{c1,2}\to \gamma \gamma J/\psi$ are consistent. No significant signal for the decay $\psi (3686)\to \gamma {\eta }_c(2S)\to \gamma \gamma J/\psi$ is observed, and the upper limit of the product branching fraction at the 90\% confidence level is determined.

arXiv comment12 pages, 5 figures

References in corpus (20)

• Design and Construction of the BESIII Detector
• The Precision Monte Carlo Event Generator KK For Two-Fermion Final States In e+e- Collisions
• Coherent Exclusive Exponentiation For Precision Monte Carlo Calculations
• Higher Charmonia
• Search for hadronic transition ${\chi }_{cJ}\to {\eta }_c{\pi }^{+}{\pi }^{-}$ and observation of ${\chi }_{cJ}\to K\bar{K}\pi \pi \pi$
• Matching perturbative and Parton Shower corrections to Bhabha process at flavour factories
• Exotic and excited-state radiative transitions in charmonium from lattice QCD
• Lattice QCD study of the radiative decays $J/\psi \to {\eta }_c\gamma$ and $h_c\to {\eta }_c\gamma$
• Determination of the number of ${\psi }^{\prime }$ event at BESIII
• Branching Fractions for Transitions of psi(2S) to J/psi
• Measurement of the $e^{+}{e}^{-}\to \eta J/\psi$ cross section and search for $e^{+}{e}^{-}\to {\pi }^{0}J/\psi$ at center-of-mass energies between 3.810 and 4.600~GeV
• Higher-order multipole amplitudes in charmonium radiative transitions
• Precision Measurements of $\mathcal{B}[\psi (3686)\to {\pi }^{+}{\pi }^{-}J/\psi ]$ and $\mathcal{B}[J/\psi \to l^{+}{l}^{-}]$
• Two-photon widths of the ${\chi }_{c0,2}$ states and helicity analysis for $χ_{c2}\arγγ$}
• Higher-order multipole amplitude measurement in $\psi (2S)\to \gamma {\chi }_{c2}$
• Search for the ${\eta }_c(2S)/h_c\to p\bar{p}$ decays and measurements of the ${\chi }_{cJ}\to p\bar{p}$ branching fractions
• Measurement of the chi_{c2} Polarization in psi(2S) to gamma chi_{c2}
• Evidence for the Direct Two-Photon Transition from $\psi (3686)$ to $J/\psi$
• Precision measurements of branching fractions for ${\psi }^{\prime }\to {\pi }^{0}J\psi$ and $\eta J\psi$
• M2 signatures in psi(2S) radiative decays

Cited by in corpus (8)

• The prospect of charm quark magnetic moment determination
• Observation of $\psi (3686)\to e^{+}{e}^{-}{\chi }_{cJ}$ and ${\chi }_{cJ}\to e^{+}{e}^{-}J/\psi$
• Screening of quark charge and mixing effects on transition moments and M1 decay widths of baryons
• Improved evaluation of the electroweak contribution to muon $g-2$
• Observation of OZI suppressed decays ${\chi }_{cJ}\to \omega \varphi$
• First observation of the decay ${\chi }_{cJ}\to {\Sigma }^{+}\bar{p}{K}_S^0+c.c.(J=0,1,2)$
• Observation of the decays ${\chi }_{cJ}\to {\Sigma }^0\bar{p}{K}^{+}+c.c.(J=0,1,2)$
• Branching fraction measurements of $\psi (3686)\to \gamma {\chi }_{cJ}$