Final answer:
It's inaccurate to divide the proton's energy evenly among its quarks because energy within a proton is influenced by complex interactions bound by the strong force. In high-energy collisions at particle accelerators, the total collision energy includes kinetic energy and the mass-energy of particles. Proton decay is theoretical, with research ongoing to determine if they release energy when decaying.
Step-by-step explanation:
If a proton has a kinetic energy of 50 GeV, it is not accurate to say that each of the three quarks inside the proton has roughly a mean energy of around 17 GeV. The distribution of energy within a proton among its constituent quarks (and the gluons that bind them) is highly complex and governed by the dynamics of the strong force. The energy of a single quark is not simply one-third of the proton's energy because quarks interact strongly within the proton, and a significant portion of the proton's mass and energy comes from the gluonic field and quarks' interactions.
In high-energy processes like those in particle accelerators, such as the Large Hadron Collider (LHC), protons may be given energies of several TeV—much higher than their rest mass energies. However, when considering collision energies and potential annihilation, like the collision between a proton and antiproton, the total collision energy takes into account the kinetic energy of both particles plus the energy equivalent of their rest masses (as per Einstein's equation E=mc^2).
Regarding the collision at the SLAC facility, where an electron and positron each have 50 GeV of kinetic energy, the totality of the collision energy is just about the sum of their kinetic energies, since the annihilation energy (related to their rest masses) is negligible due to the particles being highly relativistic.
As for the proton potentially decaying into other particles, this is an area of theoretical speculation and ongoing research. While protons are considered stable in the Standard Model of particle physics, some Grand Unified Theories suggest they might decay with an extremely long lifetime, releasing energy in the process.