Radiative proton-antiproton annihilation and isospin mixing in protonium

Abstract

A detailed analysis of the radiative pp annihilation is made in the framework of a two-step formalism, the pp annihilates into meson channels containing a vector meson with a subsequent conversion into a photon via the vector dominance model (VDM). Both steps are derived from the underlying quark model. First, branching ratios for radiative protonium annihilation are calculated and compared with data. Then, details of the isospin interference are studied for different models of the initial protonium state and also for different kinematical form factors. The isospin interference is shown to be uniquely connected to the pp − nn mixing in the protonium state. Values of the interference terms directly deduced from data are consistent with theoretical expectations, indicating a dominant pp component for the 1 S 0 and a sizable nn component for the 3 S 1 protonium state. The analysis is extended to the pp → γΦ transition, where the large observed branching ratio remains unexplained in the VDM approach.

Antinucleon–nucleon interaction at low energy: scattering and protonium

“…This was done by Kaufmann and Pilkhun [147], Richard and Sainio [220], Gutsche et al [278], and others. Carbonell et al [265] have estimated the ratio of the integrated isovector to isoscalar annihilation widths 1 = 0 with various potentials.…”

Role of pentaquark components inϕmeson production proton-antiproton annihilation reactions

“…The fraction Γ tot (i) denotes the total annihilation width of the pp atomic state with fixed principal quantum number [24]. Nevertheless, the model dependence due to the harmonic oscillator approximation may be reduced by applying a simplified phenomenological approach for NN annihilation [23,25]. In stead of the obtained kinematical phasespace factor f (φ, X), we use the phenomenological form f (φ, X) = q · exp{−(1.2) GeV −1 (s − s φX ) 1/2 } with s φX = [26].…”

P c resonances in the compact pentaquark picture

“…The kinematical phase-space factor in Eq. ( 10) has been fitted to the cross section of various pp annihilation channels [25] and applied successfully to other works [26][27][28]. The numerical values of the kinematical phase-space factor are shown in Appendix B for the masses of P c (4312) P c (4440) and P c (4457) resonances and various decay channels.…”