Search for a CP-odd Higgs boson decaying to $Zh$ in $pp$ collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

TL;DR

This paper reports a search for a heavy CP-odd Higgs boson decaying into a Z boson and a 125 GeV Higgs, using 8 TeV proton-proton collision data from ATLAS, setting upper limits on production cross sections.

Contribution

First search for a CP-odd Higgs decaying to Zh in ATLAS data at 8 TeV, providing limits within two-Higgs doublet models.

Findings

No evidence for the A boson was observed.

Upper limits on cross section times branching ratio were set.

Results constrain parameter space of two-Higgs doublet models.

Abstract

A search for a heavy, CP-odd Higgs boson, $A$, decaying into a $Z$ boson and a 125 GeV Higgs boson, $h$, with the ATLAS detector at the LHC is presented. The search uses proton--proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb$^{-1}$. Decays of CP-even $h$ bosons to $\tau\tau$ or $bb$ pairs with the $Z$ boson decaying to electron or muon pairs are considered, as well as $h \rightarrow bb$ decays with the $Z$ boson decaying to neutrinos. No evidence for the production of an $A$ boson in these channels is found and the 95% confidence level upper limits derived for $\sigma (gg\rightarrow A) \times \mbox{BR}(A \rightarrow Zh) \times \mbox{BR}(h \rightarrow f\bar{f})$ are 0.098--0.013 pb for $f=\tau$ and 0.57--0.014 pb for $f=b$ in a range of $m_A =$ 220--1000 GeV. The results are combined and interpreted in the context of two-Higgs doublet models.