PaXSubstituteEpsilon is an option for PaXEvaluate. For
brevity, Package-X normally abbreviates
1/Epsilon - EulerGamma + Log[4Pi] with
1/Epsilon (see DimRegEpsilon in the
Documentation of Package-X).
When SubstituteEpsilon is set to True,
PaXEvaluate will undo this abbreviation to obtain the full
result.