Tensor Polarization of the phi meson Photoproduced at High t

As part of a measurement of the cross section of $ϕ$ meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing $K^+$ in the channel $ϕ\to K^+K^-$ in the $ϕ$ center-of-mass frame (the helicity frame). We find that s-channel helicity conservation (SCHC) holds in the kinematical range where $t$-channel exchange dominates (up to $-t \sim 2.5$ GeV$^2$ for $E_γ$=3.6 GeV). Above this momentum, $u$-channel production of a $ϕ$ meson dominates and induces a violation of SCHC. The deduced value of the $ϕNN$ coupling constant lies in the upper range of previously reported values.

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