A NEW LOOK AT EXOTIC DECAYS: li(1- ÷, I = 1) ~ ~l'n VERSUS pn


We study the decays of the exotic meson 15 ( 1- +, I = 1) into rl'x and ~x. We assume hybrid quark-glue structure and exhibit a large contribution to this decay in the QCD sum rules approach, and suggest that 1] ' x rather than px might be the dominant decay channel. Exotic mesons, in particular hybrid (valence gluon+quarks) states have recently received re-newed attention, both from the experimental and theoretical sides. Central to that interest are the ap-parently conflicting data dealing with the jec I = 1- + 1 state often named b. Ref. [ 1] reports a signal at 1400 MeV in a partial wave analysis of n-p~°q°+ neutrals, which could be interpreted in terms of 15~ qn, with an unspecified production mechanism. Due to its focus on neutrals, this experiment is blind to the pn channel. Ref. [2], on the other hand, bases itself on the widely held theoretical prejudice that 15--, On is by far the dominant decay channel. Since ~Tx is directly related to 15--.px by vector domi-nance considerations, they can, by consideration of the Primakoffproduction in x-nucleus cattering put the strict bound F(15--.pn) < 20 MeV for too< 1.5 GeV. The two results conflict with the usually expected values of F(15--,px)>> r(15--,la'Tt)> F(15~Iqx). ( 1) This situation prompted us to reconsider the argu-ments leading to ( 1), more specifically in the context of QCD sum rules which seem to provide the strong-est statements in that domain. We conclude that p'n is most likely the dominant decay mode. We thus focus on 0°--,1]' ~ ° and take the following choices for the currents associated with q ' , I1, no, 15 ' Chercheur qualifi6 du FNRS

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