## Tuesday, July 05, 2011

### Antineutrinos Might Be Different Than Neutrinos

The latest result out of MINOS seem to indicate that muon antineutrino seem to have a different oscillation than muon neutrinos.

A test of CPT symmetry was recently performed by the MINOS experiment at Fermilab, which, due to its magnetic field, is the first experiment to distinguish μ- and μ+ tracks and separately measure the disappearance of muon neutrinos and muon antineutrinos [1]. (Previous experiments have measured a mixture of neutrino and antineutrino oscillations.) Remarkably, as reported in Physical Review Letters, MINOS appears to observe a difference between muon neutrino and muon antineutrino disappearance

This seems to be consistent with an earlier report out of MiniBooNE.

If this effect is real, then as the article pointed out, the consequences will be highly profound.

If the apparent difference between muon neutrino and muon antineutrino disappearance is not due to a statistical fluctuation or to nuclear effects, then we would have to consider new physics beyond the standard model. Indeed, global fits to the world neutrino and antineutrino oscillation data [5] encounter tension between the neutrino and antineutrino data sets and favor different neutrino and antineutrino oscillation parameters. One possible beyond the standard model solution involves nonstandard interactions [6], which would affect neutrinos and antineutrinos passing through matter (as is the case for MINOS) differently. A more extreme possibility is that Lorentz symmetry is violated [7] or CPT symmetry is violated [8], and that neutrino oscillation parameters are different from antineutrino parameters. If this were the case, then the impact on nuclear and particle physics would be profound.

Stay tune. With all the new experiments about to come on line, there's plenty of surprises in store!

Zz.