Exclusive Measurements of $pd{\to }^{3}He\pi \pi$ : the $ABC$ Effect Revisited

Abstract

Exclusive measurements of the reactions $pd\to$ ${}^{3}He{\pi }^{+}{\pi }^{-}$ and $pd\to$ ${}^{3}He{\pi }^0{\pi }^0$ have been carried out at $T_p=0.895$ GeV at the CELSIUS storage ring using the WASA detector. The ${\pi }^{+}{\pi }^{-}$ channel evidences a pronounced enhancement at low invariant $\pi \pi$ masses - as anticipated from previous inclusive measurements of the ABC effect. This enhancement is seen to be even much larger in the isoscalar ${\pi }^0{\pi }^0$ channel. The differential distributions prove this enhancement to be of scalar-isoscalar nature. $\Delta \Delta$ calculations give a good description of the data, if a boundstate condition is imposed for the intermediate $\Delta \Delta$ system.

extended version, 8 pages, 7 figures, theoretical model calculations added

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Cited by in corpus (23)

• ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?
• Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements
• On the History of Dibaryons and their Final Observation
• The WASA Detector Facility at CELSIUS
• Phenomenological analysis of the double pion production in nucleon-nucleon collisions up to 2.2 GeV
• Two-Pion Production in Proton-Proton Collisions -- Experimental Total Cross Sections and their Isospin Decomposition
• Exclusive Measurement of the eta --> pi+ pi- gamma Decay
• The $d^{\ast }(2380)$ in neutron stars - a new degree of freedom?
• ABC Effect and Resonance Structure in the Double-Pionic Fusion to ${}^3$He
• Delta Delta Excitation in Proton-Proton Induced pi0pi0 Production
• ABC Resonance Structure in the Double-Pionic Fusion to 4He
• Exclusive Measurements of pp -> dpi+pi0: Double-Pionic Fusion without ABC Effect
• Dibaryons: Molecular versus Compact Hexaquarks
• Experimental and theoretical evidences for an intermediate $\sigma$-dressed dibaryon in the NN interaction
• Exclusive measurement of two-pion production in the dd --> 4Hepipi reaction
• Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
• Single- and Double-Pion Production in Nucleon Collisions on the Nucleon and on Nuclei -- the ABC Effect and its Possible Origin in a Dibaryonic Resonance
• Isospin effects in the exclusive dp -> 3Heπ+π- reaction
• The pd --> ^3He eta pi0 reaction at T_p = 1450 MeV
• Two-pion production in deuteron-deuteron collisions at low energies
• Study of the pd(dp) -> 3He pi pi reactions close to threshold
• The ABC Effect in Double-Pionic Nuclear Fusion and a pn Resonance as its Possible Origin
• Dibaryons at COSY