Observation of the charge symmetry breaking d+d-->4He+pi(0) reaction near threshold.
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.
Stephenson
E J
EJ
Indiana University Cyclotron Facility, Bloomington, Indiana 47408, USA.
Bacher
A D
AD
Allgower
C E
CE
Gårdestig
A
A
Lavelle
C M
CM
Miller
G A
GA
Nann
H
H
Olmsted
J
J
Pancella
P V
PV
Pickar
M A
MA
Rapaport
J
J
Rinckel
T
T
Smith
A
A
Spinka
H M
HM
van Kolck
U
U