Transverse Muon Polarization and Time Reversal Invariance Violation
The transverse muon polarization (PT) in the
K+ → π0μ+ν decay
(K+μ3) is the pollarization compornet
The transverse muon polarization normal to decay plane (PT)
in the K+ → π0μ+ν decay
is a T-odd correlation of
PT = σμ•
A non-vanishing PT would be a clear sign for T violation
because the spurious effect from final state interactions is known to be
negligibly small (order of magnitude of 10-6.
The imaginary part of the ratio of two decay form factors
ξ = f-(q2) / f+(q2)
is responsible for T violation and PT can be written as
with Imξ and a kinematical factor.
E246 is aiming for a sensitivity of about σ(Imξ) = 0.01.
Under the assumption of CPT invariance, T violation provides a test of
CP violation models.
The most distinct feature here is the fact that the standard model has
no experimentally detectable contribution up to a vertex correction
contribution of ≈10-7.
Thus, PT is a sensitiveˇˇprobe of new physics beyond
the standard model.
The very small final state interaction is in sharp contrast to
in which there is a spurious PT as large as 10-3.
This gives a unique advantage to K+μ3
in the PT study.
The history of PT experiments is long but there has
been only one K+μ3 experiment performed
before using an in-flight decay technique.