학술논문
Analysis of the exclusive final state npee in the quasi-free np reaction.
Document Type
Article
Author
Source
Subject
*NEUTRON-proton interactions
*QUASI-free reactions
*DEUTERON reactions
*KINETIC energy
*BREMSSTRAHLUNG
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*
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Language
ISSN
1434-6001
Abstract
We report on the investigation of dielectron production in tagged quasi-free neutron-proton collisions by using a deuteron beam of kinetic energy 1.25GeV/u impinging on a liquid hydrogen target. Our measurements with HADES confirm a significant excess of $e^{+}e^{-}$ pairs above the $\pi^{0}$ mass in the exclusive channel $dp \rightarrow npe^{+}e^{-}(p_{spect})$ as compared to the exclusive channel $ ppe^{+}e^{-}$ measured in proton-proton collisions at the same energy. That excess points to different bremsstrahlung production mechanisms. Two models were evaluated for the role of the charged pion exchange between nucleons and double- $\Delta$ excitation combined with intermediate $\rho$ -meson production. Differential cross sections as a function of the $e^{+}e^{-}$ invariant mass and of the angles of the virtual photon, proton and electrons provide valuable constraints and encourage further investigations on both experimental and theoretical sides. [ABSTRACT FROM AUTHOR]