Understanding Stable Particles: Neutrons, Electrons, Photons, and Neutrinos

[Garrulo]

How can be sure than the unique stable particles are the neutrons, the electrons, the photons and the neutrinos? Couln´t it be possible than at low energies were there more particles??

 

[Vanadium 50]

Protons are stable. Free neutrons are not.

There could be more particles, but they cannot interact strongly with ordinary matter, or we would have seen them by now.

 

[jtbell]

Physicists have been looking strenuously for proton decay since the 1980s, so far without success. Of course, a more sensitive experiment may actually find something in the future.

http://en.wikipedia.org/wiki/Proton_decay#Experimental_evidence

 

[jerromyjon]

A 2014 result with 260kT·yr of data, searching for decay to K-mesons set a lower limit of 5.9 × 1033 yr,[5] close to a supersymmetry (SUSY) prediction of near 1034yr.[6]
And the universe is 13.8 x 10⁹ yrs old so that's pretty stable.

 

[mathman]

A 2014 result with 260kT·yr of data, searching for decay to K-mesons set a lower limit of 5.9 × 1033 yr,[5] close to a supersymmetry (SUSY) prediction of near 1034yr.[6]
And the universe is 13.8 x 10⁹ yrs old so that's pretty stable.

1033 and 1034 should be 10³³ and 10³⁴.

 

[jerromyjon]

1033 and 1034 should be 10³³ and 10³⁴.

Sorry, I copy and pasted from jtbell's link...