Photoproduction of the $f_1(1285)$ Meson

Abstract

The f1(1285) meson with mass 1281.0 ± 0.8 MeV/c 2 and width 18.4 ± 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 ηπ + π − , K + K0 π − , and K − K 0 π + decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the ηπ + π − final-state Dalitz distribution are consistent with the axial-vector J P = 1 + f1(1285) identity, rather than the pseudoscalar 0 − η(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 ηππ go dominantly via the intermediate a ± 0 (980)π ∓ states, with the branching ratio Γ(a0π (no KK))/Γ(ηππ (all)) = 0.74±0.09. The branching ratios Γ(K Kπ)/Γ(ηππ) = 0.216±0.033 and Γ(γρ 0 )/Γ(ηππ) = 0.047 ± 0.018 were also obtained. The first is in agreement with previous data for the f1(1285), while the latter is lower than the world average.

A second look at string-inspired models for proton-proton scattering via Pomeron exchange

“…In general, this method agrees reasonably well with experimental results in some respects but has significant discrepancies in others [9]. It is possible these discrepancies arise due to the limitations of using a toy dual model to generate the low energy coupling constants; recent work has suggested for example that the Sakai-Sugimoto model systematically underestimates coupling constant values [11]. However, it is also possible that the Reggeization procedure used is not ideal: perhaps the assumptions made about string amplitudes in a weakly curved background are not correct.…”

The production of the $f_1(1285) γ$ and $a_1(1260) γ$ in colliding $e^{+}e^{-}$-beams in threshold domain

“…Unfortunately, the description presented here is valid only in a very restricted range of energies and, thus, should be corrected at energies √ s ≥ 1.5 GeV, where the new excited states ρ(1570), ω(1650) must be included. We also did not take into account the mixing effects of the f 1 (1285), f 1 (1420) and f 1 (1510) mesons [26]. The latter could not exert a strong influence on the results.…”

On the transition form factors of the axial-vector resonance $f_1(1285)$ and its decay into $e^+e^-$

“…The PDG fit proceeds in terms of the five branching fractions for f 1 → 4π, a 0 (980)π (excluding a 0 (980) → K K), ηππ (excluding a 0 (980)π), K Kπ, and ργ, including data on [133,134,137], however, with the notable exception of the constraint from Ref. [81].…”

“…[81] in the fit, leading to a slightly smaller ργ branching fraction of 5.3%, with χ 2 /dof = 33.5/15 = 2.23. The origin of the tensions can be traced back to the input for Γ(f 1 → ηππ)/Γ(f 1 → ργ), which is measured as 21.3(4.4) [133], 10(1)(2) [134], and 7.5(1.0) [137], 12 with some additional sensitivity to the ργ channel from Γ(f 1 → ργ)/Γ(f 1 → 4π) [131].…”

“…[80]), close to the naive average of Refs. [131,133,134,137] when taking the respective normalization channel from the fit. Including in addition the measurement from Ref.…”