title: Observation of the charge symmetry breaking d+d-->4He+pi(0) reaction near threshold.
abstract: We report the first observation of the charge symmetry breaking d+d-->4He+pi(0) 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 pi(0) "missing mass," the quantity used to separate 4He+pi(0) events from the continuum of double radiative capture 4He+gamma+gamma events. We measured total cross sections for neutral pion production of 12.7+/-2.2 pb at 228.5 MeV and 15.1+/-3.1 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., pi(0)-eta) mechanisms.
authors: Indiana University Cyclotron Facility, Bloomington, Indiana 47408, USA.
authors: E J
authors: EJ
authors: Stephenson
authors: A D
authors: AD
authors: Bacher
authors: C E
authors: CE
authors: Allgower
authors: A
authors: A
authors: Gårdestig
authors: C M
authors: CM
authors: Lavelle
authors: G A
authors: GA
authors: Miller
authors: H
authors: H
authors: Nann
authors: J
authors: J
authors: Olmsted
authors: P V
authors: PV
authors: Pancella
authors: M A
authors: MA
authors: Pickar
authors: J
authors: J
authors: Rapaport
authors: T
authors: T
authors: Rinckel
authors: A
authors: A
authors: Smith
authors: H M
authors: HM
authors: Spinka
authors: U
authors: U
authors: van Kolck