ABC Effect and Resonance Structure in the Double-Pionic Fusion to ${}^3$He

Abstract

Exclusive and kinematically complete measurements of the double pionic fusion to ${}^3$He have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the $\pi \pi$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observations in the basic $pn\to d{\pi }^0{\pi }^0$ reaction and in the $dd{\to }^4$He${\pi }^0{\pi }^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of $d^{\ast }$ resonance formation during the reaction process in addition to the conventional $t$-channel $\Delta \Delta$ mechanism. The deduced $d^{\ast }$ resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.

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Cited by in corpus (20)

• On the History of Dibaryons and their Final Observation
• Hidden dibaryons in one- and two-pion production in NN collisions
• The $d^{\ast }(2380)$ in neutron stars - a new degree of freedom?
• Hexaquark picture for $d^{\ast }(2380)$
• Dibaryons: Molecular versus Compact Hexaquarks
• Double-charm heptaquark states composed of two charmed mesons and one nucleon
• Six-quark structure of $d^{\ast }(2380)$ in chiral constituent quark model
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• Total and differential cross sections of $\eta$-production in proton-deuteron fusion for excess energies between $Q_{\eta }=13\text{MeV}$ and $Q_{\eta }=81\text{MeV}$
• Search for $C$ violation in the decay $\eta \to {\pi }^0+e^{+}+e^{-}$ with WASA-at-COSY
• Resonance-like coherent production of a pion pair in the reaction $pd\to pd\pi \pi$ in the GeV region
• The opportunity to find ${\bar{d}}^{\ast }(2380)$ in the ${\rm Y}(nS)$ decay
• Isospin symmetry breaking in double-pion production in the region of $d^{\ast }(2380)$ and the scalar $\sigma$ meson
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• On the Production of an Isotensor Dibaryon in the $pp\to pp{\pi }^{+}{\pi }^{-}$ Reaction
• A Study of Degenerate Two-Body and Three-Body Coupled-Channel Systems -Renormalized Effective AGS Equations and Near-Threshold Resonances-
• Production of dibaryon $d_{N\Omega }$ in kaon induced reactions
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• Study of the pd(dp) -> 3He pi pi reactions close to threshold
• Dibaryons at COSY