Amplitude Analysis of the Isospin-Violating Decay $J/\psi \to \gamma \eta {\pi }^0$

Abstract

Using $(10087\pm 44)\times 10^6$ $J/\psi$ events collected with the BESIII detector, we perform the first amplitude analysis of the process $J/\psi \to \gamma \eta {\pi }^0$. The decay is dominated by the intermediate processes $J/\psi \to {\pi }^0{b}_1(1235{)}^0\to \gamma \eta {\pi }^0$, $J/\psi \to {\pi }^0\rho (1450{)}^0\to \gamma \eta {\pi }^0$ and $J/\psi \to \eta h_1(1170)\to \gamma \eta {\pi }^0$. Contributions from $J/\psi \to \gamma a_0(980{)}^0\to \gamma \eta {\pi }^0$, $J/\psi \to \gamma a_2(1320{)}^0\to \gamma \eta {\pi }^0$ and $J/\psi \to \gamma a_2(1700{)}^0\to \gamma \eta {\pi }^0$ are observed with a statistical significance exceeding $5\sigma$, constituting the first observation of radiative transitions of $J/\psi$ to isospin-triplet scalar mesons. The total branching fraction of $J/\psi \to \gamma \eta {\pi }^0$ is measured to be $(25.7\pm 0.3\pm 1.5)\times 10^{-6}$, where the first uncertainty is statistical and the second systematic. This result is consistent with the previous measurement, with the precision improved by more than a factor of two.

12 pages, 2 figures

References in corpus (17)

• STCF Conceptual Design Report: Volume 1 -- Physics & Detector
• 50 Years of Quantum Chromodynamics
• Number of $J/\psi$ events at BESIII
• Observation of an isoscalar resonance with exotic $J^{PC}=1^{-+}$ quantum numbers in $J/\psi \to \gamma \eta {\eta }^{\prime }$
• Interplay of quark and meson degrees of freedom in a near-threshold resonance
• On the radiative decays of light vector and axial-vector mesons
• Study a0(980)-f0(980) mixing from a0(980) -> f0(980) transition
• Determination of spin-parity quantum numbers of X(2370) as $0^{-+}$ from $J/\psi \to \gamma K_S^0{K}_S^0{\eta }^{\prime }$
• Multivariate side-band subtraction using probabilistic event weights
• Observation of $a_0(1710{)}^{+}\to K_S^0{K}^{+}$ in study of the $D_s^{+}\to K_S^0{K}^{+}{\pi }^0$ decay
• Quantum loops in radiative decays of the $a_1$ and $b_1$ axial-vector mesons
• Precision measurement of the branching fractions of ${\eta }^{\prime }$ decays
• Theoretical description of the $\mathbf{J}/\mathbf{\psi }\to \mathbf{\eta }({\mathbf{\eta }}^{\prime }){\mathbf{h}}_1(1380)$, $\mathbf{J}/\mathbf{\psi }\to \mathbf{\eta }({\mathbf{\eta }}^{\prime }){\mathbf{h}}_1(1170)$ and $\mathbf{J}/\mathbf{\psi }\to {\mathbf{\pi }}^0{\mathbf{b}}_1(1235{)}^0$ reactions
• Radiative decay into $\gamma P$ of the low lying axial-vector mesons
• Observation of $J/\psi \to \gamma \eta {\pi }^0$
• Study of the Decay $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}\eta$ and Observation of the W-annihilation Decay $D_s^{+}\to a_0(980{)}^{+}{\rho }^0$
• Improved measurement of the branching fraction of $h_c\to \gamma {\eta }^{\prime }/\eta$ and search for $h_c\to \gamma {\pi }^0$