Strong and electromagnetic amplitudes, direct and isospin asymmetries in the decays
M Ablikim, MN Achasov, P Adlarson, XC Ai… - arXiv preprint arXiv …, 2026 - arxiv.org
M Ablikim, MN Achasov, P Adlarson, XC Ai, CS Akondi, R Aliberti, A Amoroso, Q An, YH An…
arXiv preprint arXiv:2606.12493, 2026•arxiv.orgUsing $ e^+ e^-$ annihilation data collected at 26 center-of-mass energy points between
3000.00 and $3119.88~\text {MeV} $ with the BESIII detector, corresponding to a total
integrated luminosity of about $440.7~\text {pb}^{-1} $, we study the cross section lineshape
of $ e^+ e^-\to K_S^ 0 K^+\pi^-+ cc $. The relative phases and magnitudes between $ J/\psi
$ strong and electromagnetic decay amplitudes are measured to be $(123.7\pm5. 3)^\circ;
4.31\pm0. 22$ or $(-123.1\pm5. 2)^\circ; 4.38\pm0. 22$, with corresponding branching …
3000.00 and $3119.88~\text {MeV} $ with the BESIII detector, corresponding to a total
integrated luminosity of about $440.7~\text {pb}^{-1} $, we study the cross section lineshape
of $ e^+ e^-\to K_S^ 0 K^+\pi^-+ cc $. The relative phases and magnitudes between $ J/\psi
$ strong and electromagnetic decay amplitudes are measured to be $(123.7\pm5. 3)^\circ;
4.31\pm0. 22$ or $(-123.1\pm5. 2)^\circ; 4.38\pm0. 22$, with corresponding branching …
Using annihilation data collected at 26 center-of-mass energy points between 3000.00 and with the BESIII detector, corresponding to a total integrated luminosity of about , we study the cross section lineshape of . The relative phases and magnitudes between strong and electromagnetic decay amplitudes are measured to be or , with corresponding branching fractions $\mathcal{B}(J/\psi\to K_S^0 K^+\pi^-+c.c.)=(5.17\pm0.20)$ or . Based on a partial wave analysis, the cross sections of and are obtained. For these subprocesses, the relative phases and magnitudes are determined as or and , respectively. The large relative phases deviate from the orthogonality relation expected from experiment and from the assumption of purely real amplitudes by more than . The measured branching fractions $\mathcal{B}(J/\psi\to\bar K^0 K^*(892)^0)+c.c.=(4.18\pm0.18)$ or , $\mathcal{B}(J/\psi\to K^+ K^*(892)^-+c.c.)=(7.09\pm0.28)\times10^{-3}$ are all consistent with the world average values, but achieve better than a twofold improvement in precision. The ratios between the branching fractions of and are or . After subtracting the electromagnetic contribution, the corresponding strong amplitude ratios are or , which deviate or from the unity. No evidence for direct violation is observed.
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