They found extremely high pressure from the center of the proton to the outside.
Nuclear physicists working at the National accelerator laboratory Jefferson (USA), first measured the pressure distribution inside the proton. It turned out that the quarks that make up subatomic particles, under pressure, equal to 100 decillion (10 to 35 degree) Pascal (PA), which is only 10 times greater than the values in the center of the neutron star. It is reported online edition of the Chronicle.info with reference to lenta.ru.
The measurement became possible by combining the parton model with the model of gravitational form factors. The first assumes that hadrons (in this case protons) are composed of several point entities, of the partons that contribute to the inelastic scattering of electrons. It was proposed by Richard Feynman in 1969 and later became clear that the partons are the quarks and the gluons (carriers of the strong interaction).
Gravitational form factors allow us to describe the structure of the hadron in the impact on other particles via the gravitational interaction. However, this type of interaction is too weak to register. Association of the parton model and form factors allows to determine the structure using the electromagnetic probe consisting of an electron beam. Last fired in the nuclei of atoms, where they interact with quarks, triggering deeply virtual Compton scattering (DVCS).
DVCS at an electron placed in a proton, the exchanged virtual photon with a quark, handing the proton energy. Subsequently, the proton emits it in the form of another photon. In the result, the electron undergoes inelastic scattering (as is generated by a new particle — photon), in the course of which the elastic (Compton) scattering of photons (the total energy of the system photon-proton is not changed). This process can be described by the same equations as the interaction of the proton beam of the hypothetical gravitons. So, two photons, each with spin 1 that is equivalent to the graviton, which must have spin 2.
According to the researchers, they found extremely high pressure from the center of the proton to the outside, and a much lower pressure near the periphery and directed inward. This distribution is due to the strong nuclear interaction, which holds the three quarks together.