Tunneling positron

In the case of the p-p reaction, if the tunnelling operation is successful, an unstable nuclide consisting of 2 protons is created. What can happen next is that either the inverse reaction occurs (one proton escapes from the nucleus) or else one proton quickly releases a positron to remove excess electric charge, and a neutrino to conserve momentum and lepton number, and becomes a neutron thus forming a deuterium nucleus. 

Figure 7. The (electrostatic) harmonic oscillator potential in the Dirac equation cannot bind particles. Any wave packet that is initially inside the potential (in the region I) can tunnel through the classically forbidden region II into the positronic region III.

Baugher, A. H., Kossler, W. J., and Petzinger, K. G., Does quantum mechanical tunneling affect the validity of hole volume distributions obtained from positron annihilation lifetime measurements Macromolecules, 29, 7280-7283 (1996). 

CERN (Conseil Europeen pour la Recherche Nucleaire) The European Laboratory for Particle Physics, formerly known as the European Organization for Nuclear Research, which is situated close to Geneva in Switzerland and is supported by a number of European nations. It runs the Super Proton Synchrotron (SPS), which has a7-kilometre underground tunnel enabling protons to be accelerated to 400 GeV, and the Lai e Electron-Positron Collider (LEP), in which 50 GeV electron and positron beams are collided. The Large Hadron Collider began operation in September 2008. 

Electrons and positrons are accelerated along the tunnels at the Stanford Linear Accelerator Center. 

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