Speaker
Vincenzo Branchina
(Catania U. & INFN)
Description
According to the standard analysis, the stability condition of the
EW vacuum mainly depends on the values of the Higgs and top masses,
MH and Mt. For this reason, it has been believed and strongly
stressed in the last years that a precision measurement of Mt will
provide an answer to the crucial question of whether our universe
is in a stable or metastable vacuum, or at the edge of stability.
Needless to say, the top quark mass is one of the fundamental
parameters of the Standard Model: the top cross sections, the size
of quantum corrections to different processes, the value of the top
Yukawa coupling, just to mention few examples, all crucially depend
on Mt. Obviously, a precision measurement of Mt is of the greatest
importance. However, it will not be able to tell us anything on the
"fate of our universe" (contrary to what is often stated).
The reason is that new physics interactions, even if they show up
only at very high scales (Planck scale), can strongly affect the
stability condition of the EW vacuum. In the past, it was argued that
new physics at very high energies cannot have impact on the vacuum
stability properties, and this led to the believe that a precision
measurement of Mt could "solve" the crucial stability problem.
