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From Special theory of relativity we know that $E=m_0 c^2$, which says about mass energy equivalency. But my question : **Is there any real experiment where some mass is created purely from energy? **

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  • $\begingroup$ Rajesh, the duplicate I've suggested is actually asking about matter turning into energy, rather than energy turning into matter, but it's the same physics and it does mention how energy is coverted to particles in the LHC. $\endgroup$ – John Rennie Nov 14 '14 at 16:28
  • $\begingroup$ But John I'v asked for a specific example where energy really is converted into mass. $\endgroup$ – Rajesh Sardar Nov 14 '14 at 16:40
  • $\begingroup$ @RajeshSardar He gave you an example of energy being converted into mass. That is what pair production is. $\endgroup$ – dmckee Nov 14 '14 at 16:44
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    $\begingroup$ The point is that whenever any two particles collide some of their kinetic energy may be used to produce excitations in quantum fields i.e. matter. For example when you collide two protons, weighing about a GeV each, in the LHC the collision can create a Higgs boson weighing 125GeV. The extra 123GeV of mass came from the kinetic energy of the colliding protons (well, quarks). $\endgroup$ – John Rennie Nov 14 '14 at 16:44
  • $\begingroup$ Likewise in beta decay neutrons turn into lighter particles and the missing mass turns into kinetic energy. The key thing to understand about all this is that matter is an excitation in a quantum field, as I discuss in the linked question. However I concede that the linked question doesn't directly answer what you've asked here. $\endgroup$ – John Rennie Nov 14 '14 at 16:47
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Every particle collider does that. You shoot two very fast particles at each other, and the (sum of the) mass of the many resulting particles after collision is greater than the rest mass of the initial two particles.

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  • $\begingroup$ That means, you are saying that whenever two particle collides they will gain some mass from its kinetic energy. $\endgroup$ – Rajesh Sardar Nov 14 '14 at 16:28
  • $\begingroup$ @RajeshSardar you should not generalize so . When the energies are large enought for particles to be created they may. The scattering could also be elastic, there is a probability. $\endgroup$ – anna v Nov 14 '14 at 16:47
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Sufficiently high energy photon can spontaneously convert into a pair of leptons as long as there is a heavy charged spectator (i.e. an atomic nucleus) nearby to absorb some momentum. This is the largest energy-loss mechanism for very energetic photons in high $A$ materials.

You can also get two-photon interaction to ends with massive particles in the final state, but that is suppressed by a coupling constant relative the single-photon plus spectator case.

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Photons, which have zero rest mass, can be "collided" to form particles with nonzero rest mass if the original photons had sufficiently high energy (in the gamma range), see two-photon physics. See this article for discussion of some experimental confirmation.

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