Implications of a new light scalar near the bottomonium regime

Abstract

We study the decay modes of a new, light spin-0 particle, arguing that if the mass of the (pseudo)scalar is ∼ 11 − 15 GeV, it can have an appreciable branching ratio into bottomonium, in particular the rare η b s. Using non-relativistic QCD (NRQCD), we calculate its decay rate to bottomonia for mass splittings greater than the typical momentum transfer within the bound state. It can exceed that of decays to other Standard Model fermions under the assumption of couplings proportional to those of the Standard Model. At smaller splittings, where our computational methods break down, we estimate the rate into bottomonia using data-driven methods. When the spin-0 state decays to bottomonia whose mass is too light to produce B-meson pairs, we get a qualitatively new experimental signature, decays to b-quarks invisible to b-tagging. Such a light, spinless particle can arise in extended Higgs sectors, making this channel potentially observable in decay chains initiated by the subdominant decay of a Standard Model-like Higgs to a pair of them.

Exotic decays of the 125 GeV Higgs boson

“…First, as the mass of a is getting close to the ϒ mass, the branching ratio a → bb can be significantly reduced in favor of a → η þ X, leading effectively to a τ þ τ − j event topology and opening up additional possible backgrounds from bottomonium decays [281] (see [124] for a detailed discussion and calculation of the branching ratios). In addition, the τ's tend to merge in this region of parameter space, failing isolated reconstruction criteria and yielding effectively a single τ-like jet instead of two.…”

“…As mentioned in Sec. I C 1, perturbative QCD can be used for pseudoscalar masses above ∼1 GeV, though the calculation breaks down near quarkonium states [124]. A detailed investigation of this is beyond the scope of this paper.…”

“…The final state consists of two opposite-sign muons and two b-tagged jets and is simulated for m h ¼ 125 GeV and m a ∈ ð15; 60Þ GeV. (Lower masses involve complicated decays to quarkonia [124], which are beyond the scope of this study.) The main background is Drell-Yan (DY) production with associated jets, Z=γ Ã þ 2j=2c=2b, where the Z-decay=γ Ã produces two muons.…”

Cosmological signals of a mirror twin Higgs

“…In particular, the prescription of [45] has been followed for approximating the bottom partial width close to the open flavour threshold. Resonant decay into gluons from bottomonia mixing has been neglected, although these resonant mass ranges are expected to be only ∼ MeV wide at the CP-even, spin-0 bottomonia masses m X = m χ bi (see [45] and [46]). It should be noted, however, that at temperatures above that of the QCD phase transition, the quark decay products behave differently compared to that expected in a low temperature environment.…”

“…The larger couplings then imply potentially stronger constraints from invisible mesonic decays. See [46][47][48] for further discussion and recent analysis of the pertinent experimental constraints.…”