Nature of the a_0(980) Meson in the Light of Photon-Photon Collisions

Abstract

New high-statistics Belle data on the reaction γγ\toπ^0ηare analyzed to clarify the two-photon production mechanisms and the nature of the a_0(980) meson. The obtained solution for the amplitude γγ\toπ^0ηis consistent with the chiral theory expectation for the πηscattering length, with the strong coupling of the a_0(980) to the πη, K\bar K, and πη' channels, and with a key role of the rescattering mechanisms a_0(980)\to(K\bar K+ π^0η+π^0η')\toγγin the a_0(980)\toγγdecay. Such a picture argues in favor of the q^2\bar q^2 nature of the a_0(980) meson and is in agreement with the properties of its partners, the σ_0(600) and f_0(980) mesons, in particular, with those that manifest themselves in γγ\toππ. An important role of the vector meson exchanges in the formation of the nonresonant background in γγ\toπ^0ηis also revealed. The preliminary information on the reaction π^0η\toπ^0ηis obtained.

7 pages, 5 figures, minor corrections and some comments added

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