Annihilation into channels with strangeness and the OZI rule violation

Abstract

Two-step mechanisms in the NN annihilation and their role in the OZI rule violating reactions are discussed. In particular the two meson rescattering mechanism for πφ channel including all off-shell effects is typically two orders of magnitude bigger than the OZI tree level expectation and explains the observed ratio φπ/ωπ in the annihilation at rest. The rates for the final states including photons, γω and γφ, can be explained in the vector dominance model. The observed rate for pp → γω is suppressed due to destructive interference between the intermediate ρ and ω states while the interference in pp → γφ is required to be constructive leading to a large ratio γφ/γω.

OZI rule violation in p¯p annihilation into φππ by two step processes

“…The rate of the φππ production at rest from the 3 S 1 state is in good agreement with the experimental data [1,6,30]. Thus no unexplained OZI rule violation is required in this case -the same conclusion was obtained earlier for the φπ 0 , φφ, φγ channels as well (see [24,26,27] and references therein). The φ production due to resonant FSI decreases with increasing total energy as the fraction of the total phase space favourable for the resonance formation gets smaller.…”

“…5. For earlier reviews concerning the two-step mechanisms we refer to [24,25,26,27,28]. 2 The OZI Rule Violation in pp → φπ + π − , φρ, φω Table 1 gives a summary of the experimental data on the OZI rule violation in the φπ + π − and φρ channels at different energies.…”

Radiative proton-antiproton annihilation and isospin mixing in protonium

“…In Refs. [42,11] the apparently large value for the branching ratio B(γφ) for pp annihilation in liquid hydrogen is explained within the framework of the VDM. Using the experimental rates of B(ρφ) = (3.4 ± 1.0) × 10 −4 and B(ωφ) = (5.3 ± 2.2) × 10 −4 [43] as inputs, the branching ratio B(γφ) is given in the VDM by:…”

Loop calculations and OZI rule

“…Lipkin cancellations [33,34] seem to be unlikely in pp annihilation because the standard arguments based on the symmetry of intermediate states (like in the case of the vector meson octet mixing) do not apply. As an example where interference effects are important, we recall that the OZI rule violation in the pp → φγ at rest finds its natural explanation in the framework of the vector meson dominance where a constructive interference between the intermediate states φω and φρ is required, contrary to the case of annihilation into ωγ channel where the interference between the ωω and ωρ is destructive (see discussion in [31] and references therein).…”

“…One approach [17][18][19][20][21][22][23][24][25] is based on higher order processes beyond the tree level (rescattering mechanisms), the second one assumes that the nucleon (a) two-meson doorway mechanism with intermediate state 1 2, (b) three-meson doorway mechanism with intermediate state 1 2 3. has a significant intrinsic ss component [26,27]. This paper, supplementing the earlier reviews [28][29][30][31][32], focuses on recent studies of the rescattering mechanisms in pp annihilation.…”