2003/05/28 by E. J. Stephenson, A. D. Bacher, A.D. Bacher +19 · 2 citations
Physics and Astronomy · #Nuclear physics research studies #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #nucl-ex
paper · pdf · doi:10.1103/physrevlett.91.142302
published as Phys.Rev.Lett. 91 (2003) 142302 · 7 pages, 2 figures, plain TeX
arxiv created 2003/05/28 · openalex publication_date 2003/10/02 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We report the first observation of the charge symmetry breaking d+d\ensuremath→4He+\ensuremathπ0 reaction near threshold. Measurements using a magnetic channel (gated by two photons) of the 4He scattering angle and momentum (from time of flight) permitted reconstruction of the \ensuremathπ0 ``missing mass,'' the quantity used to separate 4He+\ensuremathπ0 events from the continuum of double radiative capture 4He+\ensuremathγ+\ensuremathγ events. We measured total cross sections for neutral pion production of 12.7\ifmmode±\else\textpm\fi2.2 pb at 228.5 MeV and 15.1\ifmmode±\else\textpm\fi3.1 pb at 231.8 MeV. The uncertainty is dominated by statistical errors. These cross sections arise fundamentally from the down-up quark mass difference and quark electromagnetic effects that contribute in part through meson mixing (e.g., \ensuremathπ0\ensuremath-\ensuremathη) mechanisms.