Lance Labun, Johann Rafelski
We consider the effect of the magnetic moment of the top quark on the Higgs $h\to \gamma \gamma$ two photon decays and we evaluate this decay amplitude allowing for an arbitrary top gyromagnetic factor $g_t$ value. We show that for any $g_t\ne 2$ the $h\to \gamma \gamma$ decay rate is always enhanced: the negative interference between W-loop and top loop is reduced and even reversed. For $g_t\to 0, \pm 4, ...$ the enhancement of the $h\to \gamma \gamma$ decay rate is up to a factor two. Standard model interactions' 1st order perturbative effect on $g_t$ amounts to a 2% enhancement of the $h\to \gamma\gamma$. Nonperturbative and BSM contributions to $g_t$, and the lack of other sensitive experimental constraints are noted; $h\to\gamma\gamma$ seems to be the most sensitive presently available probe of the top gyromagnetic factor.
View original:
http://arxiv.org/abs/1209.1046
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