The decay process mentioned is $$ \psi^{\prime}(3.7) \rightarrow \psi(3.1) + \text{hadrons} $$. Here, $\psi^{\prime}(3.7)$ and $\psi(3.1)$ are both charmonium states, which are bound states of a charm quark ($c$) and its antiquark ($\bar{c}$). The
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