Derives λ, ρ1, ρ2, σ1, and σ2 Regge trajectories for the hexaquark (ū(cc))(b(b̄b̄)) in the triquark-antitriquark picture, showing substructure is required for most series and giving rough mass estimates for excited states.
Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements
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abstract
The ABC effect - a puzzling low-mass enhancement in the $\pi\pi$ invariant mass spectrum - is well-known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on first exclusive and kinematically complete measurements of the most basic double pionic fusion reaction $pn \to d \pi^0\pi^0$ at 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a $(\pi\pi)_{I=L=0}$ channel phenomenon associated with both a resonance-like energy dependence in the integral cross section and the formation of a $\Delta\Delta$ system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.
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$\lambda$, $\rho$, and $\sigma$ Regge trajectories for the hexaquark ${(\bar{u}(cc))(b(\bar{b}\bar{b}))}$ in the triquark-antitriquark picture
Derives λ, ρ1, ρ2, σ1, and σ2 Regge trajectories for the hexaquark (ū(cc))(b(b̄b̄)) in the triquark-antitriquark picture, showing substructure is required for most series and giving rough mass estimates for excited states.