Two mass scales for the Higgs field?

Abstract

In the original version of the theory, the driving mechanism for spontaneous symmetry breaking was identified in the pure scalar sector. However, this old idea requires a heavy Higgs particle that, after the discovery of the 125 GeV resonance, seems to be ruled out. We argue that this is not necessarily true. If the phase transition is weakly first order, as indicated by most recent lattice simulations, one should consider those approximation schemes that are in agreement with this scenario. Then, even in a simple one-component theory, it becomes natural to introduce two mass scales, say $M_h$ and $m_h$ with $m_h \ll M_h$. This resembles the coexistence of phonons and rotons in superfluid helium-4, which is the non-relativistic analogue of the scalar condensate, and is potentially relevant for the Standard Model. In fact, vacuum stability would depend on $M_h$ and not on $m_h$ and be nearly insensitive to the other parameters of the theory (e.g. the top quark mass). By identifying $m_h=125$ GeV, and with our previous estimate from lattice simulations $M_h= 754 \pm 20 ~\rm{(stat)} \pm 20 ~\rm{(syst)}$ GeV, we thus get in touch with a recent, independent analysis of the ATLAS + CMS data which claims experimental evidence for a scalar resonance around $700$ GeV.