Evidence for a high mass enhancement in K+K− photoproduction

Partial wave analysis of ψ(3686)→K+K−η

“…Interestingly, the fitted mass and width of this structure are 1784 þ12þ0 −12−27 MeV=c 2 and 106 þ22þ8 −19−36 MeV, respectively, which are in agreement with those of the Xð1750Þ reported by the FOCUS Collaboration [15]. The Xð1750Þ was originally interpreted as the photoproduction mode of the ϕð1680Þ [12][13][14] with the limited statistics. The observation of both the ϕð1680Þ and the Xð1750Þ in the K þ K − mass spectrum implies that the Xð1750Þ is a gnew structure instead of the photoproduction mode of the ϕð1680Þ.…”

“…A comprehensive study of the strangeonium spectrum is useful to test the theoretical models and also in the search for light exotica (resonances that are not dominantly qq states, often with nonexotic quantum numbers). Strangeonia have been studied in different experiments, such as the study of the initial-state radiation [3][4][5][6][7] and ψð3686Þ decays [8][9][10][11], and photoproduction data [12][13][14][15]. However, the strangeonium spectrum is much less well understood, and only a few states have been established.…”

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

“…Previous photoproduction experiments have consistently observed an enhancement in K + K − at a mass near 1750 MeV/c 2 (referred to here as the X(1750)) [1][2][3]. However, with signals consisting of only around 100 events and with a statistical significance of the enhancement of, at best, only 3.5 σ over background, these experiments have suffered from a lack of statistics.…”

“…First, assuming the enhancement is a single resonance, we determine a mass of 1753.5 ± 1.5 ± 2.3 MeV/c 2 from our sample of more than 10,000 signal events, which is clearly inconsistent with 1680 MeV/c 2 . One previous photoproduction experiment [1], using less than 50 signal events and guided by e + e − annihilation results, presented a mass of 1690 ± 10 MeV/c 2 after an analysis based on a model including interference and Deck-like effects. With orders of magnitude more statistics, we are unable to reproduce this result.…”

Search for New and Unusual Strangeonia States Using yp -> pfe With GlueX at Thomas Jefferson National Accelerator Facility

“…Six months after the discovery of the φ(1680), the X(1750) meson was observed by the Omega Photon collaboration at CERN [12]. The experiment analysed a K + K − final state from photoproduction and found an enhancement in the invariant mass spectrum of the K + K − pair.…”