Observation of a 1750 MeV/c2 enhancement in the diffractive photoproduction of K+ K-

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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 MeV/c2 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 ± 1.5 ± 2.3 MeV/c2 and its width to be 122.2 ± 6.2 ± 8.0 MeV/c2. We find no corresponding enhancement at 1750 MeV/c2 in K*K, and again neglecting any possible interference effects we place limits on the ratio Γ(X(1750) → K*K)/Γ(X(1750) → 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 φ(1680) seen in e+e- annihilation experiments. © 2002 Elsevier Science B.V. All rights reserved.

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