R. Garisto et Jd. Wells, CONSTRAINTS ON SUPERSYMMETRIC SOFT PHASES FROM RENORMALIZATION-GROUP RELATIONS, Physical review. D. Particles and fields, 55(3), 1997, pp. 1611-1622
By using relations derived from renormalization group equations (RGEs)
, we find that strnog indirect constraints can be placed on the top sq
uark mixing phase in A(t) from the electric dipole moment of the neutr
on (d(n)). Since m(t) is large, any GUT-scale phase in A(t) feeds into
other weak scale phases through RGEs, which in turn contribute to d(n
). Thus CP-violating effects due to a weak-scale A(t) are strongly con
strained. We find that \Im A(t)(EW)\ must be smaller than or of order
\Im B-EW\, making the electric dipole moment of the top quark unobserv
ably small in most models. Quantitative estimates of the contributions
to d(n) from A(u), A(d), and B show that substantial fine-tuning is s
till required to satisfy the experimental bound on d(n). While the low
energy phases of the A's are not as strongly constrained as the phase
of B-EW, we note that the phase of a universal A(GUT) induces large c
ontributions in the phase of B-EW through RGEs, and is thus still stro
ngly constrained in most models with squark masses below a TeV.