Observation of a 1750 MeV/c^2 Enhancement in the Diffractive Photoproduction of K^+K^-

TL;DR

This paper reports a high-statistics observation of a 1750 MeV/c^2 enhancement in diffractive photoproduction of K+K-, providing precise measurements and challenging previous interpretations of similar signals.

Contribution

The study confirms and refines the properties of a 1750 MeV/c^2 resonance in photoproduction with significantly improved data quality and statistical significance.

Findings

Observed a resonance at 1753.5 MeV/c^2 with a width of 122.2 MeV/c^2

No enhancement observed at 1750 MeV/c^2 in K*K channel

Results challenge the interpretation of this enhancement as the φ(1680)

Abstract

Using the FOCUS spectrometer with photon beam energies between 20 and 160 \gev, we confirm the existence of a diffractively photoproduced enhancement in $K^+K^-$ at 1750 \mevcc with nearly 100 times the statistics of previous experiments. Assuming this enhancement to be a single resonance with a Breit-Wigner mass shape, we determine its mass to be $1753.5\pm 1.5\pm 2.3$ \mevcc and its width to be $122.2\pm 6.2\pm 8.0$ \mevcc. We find no corresponding enhancement at 1750 \mevcc in $K^*K$, and again neglecting any possible interference effects we place limits on the ratio $\Gamma (X(1750) \to K^*K)/\Gamma (X(1750) \to K^+K^-)$. Our results are consistent with previous photoproduction experiments, but, because of the much greater statistics, challenge the common interpretation of this enhancement as the $\phi (1680)$ seen in $e^+e^-$ annihilation experiments.