Geant4 Simulations for the Radon Electric Dipole Moment Search at

1.1.1 CP Violation
Following the observation of ˆP violations in the β decay, it was believed that ˆ CP
was a true symmetry of nature. CP violation was, however, observed in the decay
of K mesons [11] and also more recently in the decay of B mesons [12, 13]. CP
violation implies the existence of T violation via the CPT Theorem. Direct evidence
for time-reversal violation has been suggested in the transition rates of the antikaon
to kaon process, and its reverse, kaon to antikaon. However, these results remain
controversial [14, 15].
In1967,AndreiSakharovdemostrated[16]thatCP violationisessentialforbaryogenesis,
the physical processes required to produce the asymmetry between baryons
and antibaryons in the early universe. In the Standard Model, CP violation enters
via weak interaction flavor mixing represented by the complex phase δ CKM of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix and via θ QCD , the vacuum expectation
value of the QCD gluon field. These sources of CP violation are, however, not sufficient
to account for the observed asymmetry between matter and anti-matter in our
universe. Thus additional sources of CP violation are required and provide a strong
motivation to search for new physics beyond the Standard Model.
1.1.2 The Standard Model
The Standard Model of particle physics does predict the existence of non-zero
particle EDMs through δ CKM and θ QCD . However, these EDMs are many orders of
magnitude smaller than current experimental sensitivity (see Figure 1.2). On the
other hand, models beyond the Standard Model, such as multiple-Higgs theories,
left-right symmetry and supersymmetry (SUSY), generally include additional CPviolating
complex phases and predict EDMs within current experimental reach [1].
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