Changes
- The estimate of the non-logarithmic contributions to the quartic
Higgs coupling λ due to the hierarchy expansion has been changed:
Xt^5 and Xt^6 terms are no longer taken into account in the
uncertainty estimate, because they do not appear at 3-loop
O(αt*αs^2). Only the Xt^4 term is used in the uncertainty
estimate, if it is absent from the selected hierarchy. As a
result, the uncertainty estimate is now symmetric in Xt.