The CERN - OPERA (Oscillation Project with Emulsion-tRacking Apparatus) experiment was designed to measure in a straightforward way neutrino oscillations. The experiment was aimed to detect tau-neutrnos from the oscillation of mu-neutrinos during their travel from Geneva to Gran Sasso (L'aquila) in about 2.4ms. In OPERA, tau-leptons resulting from the interaction of tau-neutrinos will be observed in "bricks" of photographic emulsion films interleaved with lead plates.
Little has been discussed about neutrino transmutation so far, instead all of the attention has been focused on the apparently faster-than-light speed of the neutrinos (still to be confirmed by the scientific community by different experiments).
Relativistic Background
It is interesting to see how the laws of physics came under scrutiny after experiments involving the measurement of the space-time coordinates of a couple of related events, as happened with the Fizeau or Michaelson-Morley experiments.
The laws of electromagnetism predict the existence of a field which propagates at about 299,792,458 meters per second. H Lorentz discovered that the laws of electromagnetism where not invariant under Galilean transformations and investigated the type of transformations that would leave Maxwell's equations invariant. The final result was the Lorentz transformations.
The principle of relativity of Galileo states that:
All laws are identical in all inertial systems of reference
From Maxwell equations it is deduced that the speed of light is finite and is the maximum speed at which electromagnetic interactions can propagate.
The combination of the principle of relativity with the finiteness of propagation of the electromagnetic field is called the principle of relativity of Einstein in contrast with the principle of relativity of Galileo, which was based on an infinite speed of propagation of interactions.
From the principle of relativity it follows in particular that the speed of light is the same in all inertial systems of reference.
Fundamental Forces
In nature, as far as we know there are four fundamental forces:
- Electromagnetic (responsible for electromagnetic phenomena)
- Nuclear Strong (responsible for binding nucleons together)
- Nuclear Weak (responsible for the radioactive decay of subatomic particles)
- Gravity (responsible for the gravitational interaction)
These four forces are independent in a deep sense. They can be studied independently because they are related to different types of processes.
Propagation Speed
When studying the electromagnetic field one can deduce that the field propagates at a velocity related to the electric and magnetic properties of the media. Special Relativity was developed while studying electromagnetic problems and it was accepted that the speed of light was the unreachable upper limit to the speed of all material particles as well as the speed of propagation of light signals.
The CERN - OPERA experiment has found (if the instrument where registering correctly) that the neutrino beam sent from Geneva to Gran Sasso travelled some 60ns faster than light signal.
It would really be surprising if:
- The beam is proven to have travel faster than light (in the same medium)
- The weak force can somehow be reduced to electromagnetic
This would mean a contradiction in the logic framework because in this case, we could produce interactions with a velocity superior than
the maximum possible velocity for the propagation of interactions, which is absurd.
In any other case the discovery would only mean that the weak interaction travels faster than the electromagnetic interaction and the result of the experiment would be the first straightforward measurement for the speed of propagation of the weak interaction but logically does not create any conflict with the principle of relativity of Einstein. One just has to swap the electromagnetic field by the field under consideration (weak force in this case) and the framework is left unchanged.
Frames of Reference
A rather striking discovery would be if an interaction could somehow violate the principle of relativity which is the cornerstone of Special Relativity. This would open a door to a compete different type of physics where the inertial frame does play a role in the result of physical processes, but this has never been observed so far.
Conclusion
Whether the result of the experiment can be confirmed independently or not, the principle of relativity would not be challenged as far as the weak force cannot be reduced to the electromagnetic force.
The only reading from the result (if confirmed) would be that the weak interaction can travel faster than the electromagnetic interaction which by itself is not contradictory because they are different fields.
When studying problems of interactions, the speed of propagation for the considered field (electromagnetic, weak, strong or gravitational) should be the one used in the principle of relativity.
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