Anomalous Higgs Yukawa Couplings

Abstract

In the standard model, the Higgs boson $h$ couples to the quarks and charged leptons according to the well-known formula $(m_\psi/v) h \bar{\psi}\psi$, where $\psi$ = quark (q) or lepton (l) and $v$ = 246 GeV is its vacuum expectation value. Suppose $m_\psi$ is of radiative origin instead, then the effective $h \bar{\psi}\psi$ Yukawa coupling will not be exactly $m_\psi/v$. We show for the first time quantitatively how this may shift the observed branching fraction of $h \to \bar{b}b$ and $h \to \tau^+ \tau^-$ upward or downward. Thus the precision measurements of Higgs decay to fermions at the Large Hadron Collider, due to resume operation in 2015, could be the key to possible new physics.