Geant4 Simulations for the Radon Electric Dipole Moment Search at

ˆP
ր
ˆT
ց
Figure 1.1: An illustration of the parity and time-reversal transformations operating
on a quantum system with a charge distribution and non-zero spin. Acting with the
parity (ˆP) operator on this system leaves the spin invariant, but changes the sign of
the electric dipole moment. Conversely, acting with the time-reversal (ˆT) operator
on this system changes the direction of the spin and leaves the electric dipole moment
invariant. The resulting states on the right-hand side are equivalent to each other
under a rotation of 180 ◦ . Note that in both cases, the constant of proportionality
between ⃗ S and ⃗ d has changed sign under the ˆP or ˆT transformations.
to find all particle and atomic EDMs to be zero. The measurement of a permanent
non-zero EDM would represent a violation of both of these symmetries. The violation
of parity symmetry by the weak nuclear force is well known. The direct violation of
time-reversal symmetry, however, hasnotbeendetected inanyofthecurrently known
fundamental interactions of nature.
Figure 1.1 illustrates the effect of the ˆP and ˆT transformations on a quantum
system (particle or atom) with a charge distribution and non-zero spin. Acting with
theparityoperator(ˆP)onthequantumsystem flipsthepositionsofthecharges. This
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