Where to find $X(17)$?

Jun Jiang, Cong-Feng Qiao, Yu-Han Zhao

The Atomki group puts forward the hypothesis of an $X(17)$ particle to explain its anomaly observation in ${}^8{\text{Be}}^{\ast }\to {}^8\text{Be}{e}^{+}{e}^{-}$ transition. Utilizing exp…