Common explanation of the behavior of some e+e− annihilation processes around s=1.9  GeV

Abstract

We show that the behavior of the excitation curves of some e + e − annihilation processes close to the nucleon-antinucleon threshold can be explained either by the ρ(1900) resonance itself or by its interference with other resonances. Besides the six-pion annihilation and the e + e − → K + K − π + π − and e + e − → φ π 0 processes, we also analyze the final states η π + π − , K + K − π + π − π 0 , and K + K − π 0 π 0 , the behavior of which around 1.9 GeV has not yet attracted attention. Analysis of the data on the e + e − → pp and e + e − → nn reactions clearly shows that the ρ(1900) resides above the nn threshold.

Mass spectra and decay properties of the higher excited $ρ$ mesons

“…The deviations between the predictions of MGI and GI models are about 300 ∼ 500 MeV, which implies the screening potential plays an important role in studying the masses of the higher excited ρ mesons. The recent analyses of the BABAR measurements about the process e + e − → K + K − π + π − π 0 indicate the existence of one resonance with mass M = (2550 ± 13) MeV [20], which is in good agreement with our predicted mass of ρ(5 3 S 1 ). In addition, the cross section of the process e + e − → ωπ + π − π 0 measured by BABAR indicates that there are hints of the higher excited ρ mesons.…”

“…In 2007, the BABAR Collaboration presented the cross section of the process e + e − → K + K − π + π − π 0 , where there is a peak structure around 2.5 GeV [19]. The analysis of the BABAR measurements within the Vector Meson Dominance model shows the existences of the ρ(1900) and another resonance with mass of M = 2550 ± 13 MeV and width of Γ = 209 ± 26 MeV [20], where the latter one is expected to have the same quantum numbers as ρ(1900). In addition, the cross sections of e + e − → η ′ π + π − and e + e − → f 1 (1285)π + π − processes reported by BABAR indicate that there exist some structures around 2.5 GeV, and it is difficult to claim the existences of new resonances due to the insufficient data statistics [19].…”

Electromagnetic form factors of Λ hyperon in the vector meson dominance model

“…Experimentally, the cross sections for the e + e − → ΛΛ has been measured by BaBar and BESIII Collaborations [38,39,41], a notable feature of the extracted effective form factor G eff is the near threshold enhancement. Similar enhancement effect can also be observed in the timelike effective form factor of proton [14,17,18,20] and such phenomena can be interpreted by the Coulomb final-state interactions [42,43], since the proton is a charged particle. As for Λ hyperon, Λ hyperon is neutral, thus, such kind of final-state interactions vanish.…”

The electromagnetic form factors of $$\Lambda _c$$ hyperon in the vector meson dominance model

“…Thus, we only take into account the contributions from the relevant charmonium excitations: ψ(1S), ψ(2S), ψ(3770), ψ(4040), ψ(4160) and ψ(4415). Thirdly, the Coulomb final-state interactions should be considered, which is similar to the case of the proton [29,43]. Based on the above consideration, we can obtain the formula of the time-like form factors for c by analytic continuation of the space-like form factors.…”