f₁(1285) → e⁺e^- decay and direct f₁ production in e⁺e^- collisions

Abstract

Abstract.

Consistent analysis of f1(1285) meson form factors

“…Recently, the first observation of f 1 meson production in e + e − annihilation has been reported [7]. An estimate of the cross section of this process was made in [17] for another parameterization of the form factors. However, the predictions for the cross section of the process e + e − → e + e − f 1 following from that parameterization differ substantially from the experimental data [5].…”

“…Therefore, the probability of these processes can be sensitive to the f 1 meson internal structure, i.e., to the dependence of the form factors on photon virtualities. At present, there are a few experimental [2][3][4][5][6][7] and theoretical [8][9][10][11][12][13][14][15][16][17] results on production and decays of f 1 meson. Unfortunately, QCD cannot predict now the shapes of the corresponding form factors at moderate photon virtualities.…”

“…II. GENERAL STRUCTURE OF f 1 → γ * γ * AMPLITUDE Since f 1 meson has positive parity, the amplitude M of the f 1 meson decay into two vector particles with negative parities, momenta k 1 and k 2 , and polarization vectors e µ 1 and e µ 2 has the form [8,17]…”

Hadronic decays of the $J/ψ$ meson

“…Such an assumption is supported by the strong affinity of the two-pion system with quantum numbers J P C = 1 −− and the ρ 0 , experimentally confirmed by the BR B(ρ 0 → π + π − ) = 1 [28]. It follows that the amplitudes read [106,107] A(ππ → ηγ) = g ππ ηγ…”

Axial-vector exchange contribution to the Hyperfine Splitting

“…The axial-vector meson decays to a lepton pair play a central role in computing their contribution to the HFS, to be discussed in the section below. Furthermore, they can provide important information regarding A → γ * γ * transitions [9,14](see also the comments at the end of this section). We outline next the evaluation of the relevant matrix element appearing in these decays, which comparison to existing results will provide an additional (intermediate) crosscheck of our evaluation.…”