Study of the hp 0 spectrum and search for a JPC Ä 1 À ¿ exotic meson

A partial wave analysis~PWA! of thehp system~whereh→gg) produced in the charge exchange reaction p2p→hp0n at an incident momentum of 18 GeV/ c is presented as a function of thep invariant mass mhp0 and momentum transfer squared tp2→hp , from the incidentp 2 to the outgoinghp system.S, P, and D waves were included in the PWA. The a0(980) anda2(1320) states are clearly observed in the overall hp 0 effective mass distribution as well as in the amplitudes associated with S ave andD waves, respectively, after partial wave decomposition. The observed distributions in moments ~averages of spherical harmonics ! were compared to the results from the PWA and the two are consistent. The distribution in p2→hp for individual D waves associated with natural and unnatural parity exchange in the t c annel are consistent with Regge phenomenology. Of particular interest in this study is the P wave since this leads to an exotic J51 for the hp system. AP wave is present in the data; however, attempts to describe the mass dependence of the amplitude and phase motion with respect to the D wave as a Breit-Wigner resonance are problematic. This has implications regarding the existence of a reported exotic J51 meson decaying into hp with a mass near 1.4 GeV/c.