论文标题
$ e^+e^ - \至λ\的横截面在vector charmonia的衰减中，作为违反同胞蛋白的试训，将σ^0+{\ rm c.c。} $作为$λ\ carmenia的衰减中的测试。
The cross section of $e^+e^- \to Λ\overline Σ^0+{\rm c.c.}$ as a litmus test of isospin violation in the decays of vector charmonia into $Λ\overline Σ^0+{\rm c.c.}$
论文作者
论文摘要
在iSospin保护的宙斯盾下，天生近似中的幅度，即考虑衰减$ψ\toλ\λ\上行σ^0+{\ rm c.c。 $ψ$质量处的σ^0+{\ rm c.c。} $由相同的电磁耦合参数化。因此，可以将这种耦合的模量在两个观察值上提取：衰减分支分数和歼灭横截面。通过考虑前两个矢量charmonia，$ j/ψ$和$ψ（2s）$，发现，尤其是在$ψ（2s）$的情况下，相同电磁耦合的模量值之间从分支比率和横截面中提取的相同电磁耦合的值之间存在很大差异。我们提出，作为对这种分歧的可能解释，是由基于物理（壳体）中间状态的机制驱动的同胞违反贡献的衰减幅度的存在，由于其本质，由于其自身的性质，应在$ψ（2s）$ decay中比$ j/ψ$的衰减更有效。
Under the aegis of isospin conservation, the amplitudes in Born approximation, i.e., considering the only one-photon-exchange mechanism, of the decay $ψ\to Λ\overline Σ^0+{\rm c.c.}$, where $ψ$ is a vector charmonium, and of the reaction $e^+e^- \to Λ\overline Σ^0+{\rm c.c.}$ at the $ψ$ mass, are parametrized by the same electromagnetic coupling. It follows that, the modulus of such a coupling can be extracted the data on the two observables: the decay branching fraction and the annihilation cross section. By considering the first two vector charmonia, $J/ψ$ and $ψ(2S)$, it is found that, especially in the case of $ψ(2S)$, there is a substantial discrepancy between the values of the modulus of the same electromagnetic coupling extracted from the branching ratio and the cross section. We propose, as a possible explanation for such a disagreement, the presence in the decay amplitude of an isospin-violating contribution driven by a mechanism based on physical (on-shell) intermediate states, that, due to their own nature, should be more effective in the $ψ(2S)$ decay than in that of the $J/ψ$.
