There are two primary experiments that give constraints on the muon sector. First, spin transitions in
muonium () have been used to place a bound on
for the muon (see Equation (52
) for the
definition of
) [149]. Even though muonium is a muon-electron system, the muon sector of the mSME
can be isolated by placing the muonium in a strong magnetic field and looking for a particular frequency
resonance that corresponds to muon spin flips. The sidereal variation of this transition frequency is then
tracked yielding a limit on
of
The second muon experiment that yields strong limits is the g-2 experiment [58
, 39, 72
]. In
this experiment relativistic
(or
) are injected into a storage ring and allowed to decay. The
deposit rate of the decay products along the detector is sensitive to the evolution of the spin of the muon,
which in turn is a function of
for the muon. Lorentz violation changes this evolution equation, and
therefore this type of
experiments can bound the mSME. As in the case of the
experiments
in Section 5.1, two types of bounds can be placed from the muon
experiment. The first is a direct
comparison between the
factors for
and
, which limits the CPT violating
coefficient
. Furthermore, an analysis of sidereal variations involving only one of
the
at the current sensitivity in [72] could bound the
coefficient at the level of
[58].
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