First Observation of an Exotic Reggeon

Abstract

We present new \compass high-statistics measurements of the peripheral production of $\hat{I}\cdot \ddot{I}{€}^{-}$ and $\hat{I}{\cdot }^{\prime }\ddot{I}{€}^{-}$ pairs in the reactions $\ddot{I}{€}^{-}p\to \hat{I}{\cdot }^{(\prime )}\ddot{I}{€}^{-}p$. For the first time, we perform an unbinned analysis of the high-mass region of the $\hat{I}\cdot \ddot{I}{€}^{-}$ and $\hat{I}{\cdot }^{\prime }\ddot{I}{€}^{-}$ systems, which allows us to disentangle the exchange mechanisms governing their production. We report the first observation in high-energy scattering of an exotic Reggeon with high significance exceeding $5\ddot{I}ƒ$ for both channels, which is, most likely, related to the exotic $\ddot{I}{€}_1(1600)$.8

8 pages, 7 figures + supplement material