Tensor Polarization of the phi meson Photoproduced at High t

TL;DR

This study investigates the polarization of phi mesons produced at high momentum transfer, revealing the dominance of different production mechanisms and their effects on helicity conservation.

Contribution

It provides the first measurement of the phi meson tensor polarization at high t, demonstrating the transition from t-channel to u-channel dominance and its impact on SCHC violation.

Findings

SCHC holds up to -t ~ 2.5 GeV^2

u-channel production causes SCHC violation at higher -t

phi NN coupling constant is in the upper range of previous estimates

Abstract

As part of a measurement of the cross section of $\phi$ meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing $K^+$ in the channel $\phi \to K^+K^-$ in the $\phi$ 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 $E_{\gamma}$=3.6 GeV). Above this momentum, $u$-channel production of a $\phi$ meson dominates and induces a violation of SCHC. The deduced value of the $\phi NN$ coupling constant lies in the upper range of previously reported values.