A recent paper indicates that part of stellar proton-proton chain reaction can be reproduced in the lab without neutron or gamma emission --
"Observation of Electron Emission in the Nuclear Reaction between Protons and Deuterons"
Abstract
Proton-deuteron fusion reaction has been studied using a proton beam with an energy of 260 keV and a deuterium-implanted graphite target. The reaction product, 3He, usually de-excites by γ-ray emission. However, instead of a γ ray, 3He can emit an electron with a discrete energy of 5.6 MeV, due to electron screening in graphite. Such electrons were identified with the ΔE-E technique. The emission of fast electrons shows that electron screening causes the electrons to approach the nuclei during the reaction very closely. Different behavior of nuclear reactions at low and high energies was also demonstrated.