Delta Delta Excitation in Proton-Proton Induced pi0pi0 Production

Abstract

Exclusive measurements of the $pp\to pp{\pi }^0{\pi }^0$ reaction have been performed at CELSIUS/WASA at energies from threshold up to $T_p$ = 1.3 GeV. Total and differential cross sections have been obtained. Here we concentrate on energies $T_p\ge$ 1 GeV, where the $\Delta \Delta$ excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional $t$-channel $\Delta \Delta$ excitation. This holds also for the double-pionic fusion to the quasibound ${}^2$He. The data are compared to model predictions, which are based on both pion and $\rho$ exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the $\rho$-exchange. A phenomenological modification allowing only a small $\rho$ exchange contribution leads to a quantitative description of the data.

References in corpus (17)

• Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004)
• Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements
• New results on the Roper resonance and the P_{11} partial wave
• Theoretical study of the N N --> N N pi pi reaction
• 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
• Study of the p p -> p p pi+ pi- Reaction in the Low-Energy Tail of the Roper Resonance
• Exclusive Measurements of $pd{\to }^{3}He\pi \pi$ : the $ABC$ Effect Revisited
• Two-Pion Production in Proton-Proton Collisions with Polarized Beam
• The role of the Roper resonance in n p --> d (pi pi)
• Exclusive Measurements of pp -> dpi+pi0: Double-Pionic Fusion without ABC Effect
• Observation of an ABC effect in proton-proton collisions
• Exclusive measurement of two-pion production in the dd --> 4Hepipi reaction
• Structure in two_pion production in the d d -> alpha X reaction
• An explanation of the ABC enhancement in the dd -> alpha X reaction at intermediate energies
• 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

Cited by in corpus (19)

• ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?
• On the History of Dibaryons and their Final Observation
• Isospin Decomposition of the Basic Double-Pionic Fusion in the Region of the ABC Effect
• Measurement of the $pn\to pp{\pi }^0{\pi }^{-}$ Reaction in Search for the Recently Observed Resonance Structure in $d{\pi }^0{\pi }^0$ and $d{\pi }^{+}{\pi }^{-}$ systems
• Neutron-Proton Scattering in the Context of the $d^{\ast }$(2380) Resonance
• Measurement of the $np\to np{\pi }^0{\pi }^0$ Reaction in Search for the Recently Observed $d^{\ast }(2380)$ Resonance
• ABC effect as a signal of chiral symmetry restoration in hadronic collisions
• Hidden dibaryons in one- and two-pion production in NN collisions
• ABC Effect and Resonance Structure in the Double-Pionic Fusion to ${}^3$He
• Study of the quasi-free $np\to np{\pi }^{+}{\pi }^{-}$ reaction with a deuterium beam at 1.25 GeV/nucleon
• On a Possible Explanation of the DLS-Puzzle
• π^0 π^0 Production in Proton-Proton Collisions at Tp=1.4 GeV
• Measurement of the $\vec{n}p\to d{\pi }^0{\pi }^0$ Reaction with Polarized Beam in the Region of the $d^{\ast }(2380)$ Resonance
• Nature of $\mathbf{S}$-wave $\mathbf{NN}$ interaction and dibaryon production at nucleonic resonance thresholds
• An Isotensor Dibaryon in the $pp\to pp{\pi }^{+}{\pi }^{-}$ Reaction?
• From CELSIUS to COSY: on the observation of a dibaryon resonance
• On the Production of an Isotensor Dibaryon in the $pp\to pp{\pi }^{+}{\pi }^{-}$ Reaction
• Resonance $d^{\ast }(2380)$ and higher isospin states
• Dibaryons at COSY