As part of a measurement [E. Anciant et al., Phys. Rev. Lett. 85, 4682 (2000)] of the cross section of $\varphi$ meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing $K^{+}$ in the channel $\varphi \to K^{+}{K}^{-}$ in the $\varphi$ 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 $-t\sim 2.5{\text{GeV}}^2$ for $E_{\gamma }=3.6\text{GeV}$). Above this momentum, $u$-channel production of a $\varphi$ meson dominates and induces a violation of SCHC. The deduced value of the $\varphi NN$ coupling constant lies in the upper range of previously reported values.

• Received 11 November 2003

DOI:https://doi.org/10.1103/PhysRevC.69.032203