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تسجيل مستخدم جديدPhotoproduction of the $f_1(1285)$ Meson
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The $f_1(1285)$ meson with mass $1281.0 pm 0.8$ MeV/$c^2$ and width $18.4 pm 1.4$ MeV (FWHM) was measured for the first time in photoproduction from a proton target using CLAS at Jefferson Lab. Differential cross sections were obtained via the $etapi^{+}pi^{-}$, $K^+bar{K}^0pi^-$, and $K^-K^0pi^+$ decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the $etapi^{+}pi^{-}$ final-state Dalitz distribution are consistent with the axial-vector $J^P=1^+$ $f_1(1285)$ identity, rather than the pseudoscalar $0^-$ $eta(1295)$. The production mechanism is more consistent with $s$-channel decay of a high-mass $N^*$ state, and not with $t$-channel meson exchange. Decays to $etapipi$ go dominantly via the intermediate $a_0^pm(980)pi^mp$ states, with the branching ratio $Gamma(a_0pi text{ (no} bar{K} Ktext{)}) / Gamma(etapipi text{(all)}) = 0.74pm0.09$. The branching ratios $Gamma(K bar{K} pi)/Gamma(etapipi) = 0.216pm0.033$ and $Gamma(gammarho^0)/Gamma(etapipi) = 0.047pm0.018$ were also obtained. The first is in agreement with previous data for the $f_1(1285)$, while the latter is lower than the world average.
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