Odd and Even Partial Waves of $\eta {\pi }^{-}$ and ${\eta }^{\prime }{\pi }^{-}$ in ${\pi }^{-}p\to {\eta }^{(\prime )}{\pi }^{-}p$ at $191\text{GeV}/c$

Abstract

Exclusive production of $\eta {\pi }^{-}$ and ${\eta }^{\prime }{\pi }^{-}$ has been studied with a $191\text{GeV}/c$ ${\pi }^{-}$ beam impinging on a hydrogen target at COMPASS (CERN). Partial-wave analyses reveal different odd/even angular momentum ($L$) characteristics in the inspected invariant mass range up to $3\text{GeV}/c^2$. A striking similarity between the two systems is observed for the $L=2,4,6$ intensities (scaled by kinematical factors) and the relative phases. The known resonances $a_2(1320)$ and $a_4(2040)$ are in line with this similarity. In contrast, a strong enhancement of ${\eta }^{\prime }{\pi }^{-}$ over $\eta {\pi }^{-}$ is found for the $L=1,3,5$ waves, which carry non-$q\bar{q}$ quantum numbers. The $L=1$ intensity peaks at $1.7\text{GeV}/c^2$ in ${\eta }^{\prime }{\pi }^{-}$ and at $1.4\text{GeV}/c^2$ in $\eta {\pi }^{-}$, the corresponding phase motions with respect to $L=2$ are different.

16 pages, 5 figures and 1 table

References in corpus (2)

• Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts
• The COMPASS Experiment at CERN

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