Study of the mass and spin-parity of the Higgs boson candidate via its decays to Z boson pairs

TL;DR

The present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis.

Abstract

A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17.3 inverse femtobarns, collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the ZZ channel, where both Z bosons decay to e or mu pairs, is 126.2 +/- 0.6 (stat.) +/- 0.2 (syst.) GeV. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis.

Figures (3)

• Figure 1: a) Distribution of four-lepton invariant mass in the range near the 126 GeV resonance. Points represent the observed data, shaded histograms represent the backgrounds, and the open histograms represent the signal expectation. The inset shows the $m_{4\ell}$ distribution for events with high values of kinematic discriminant $K_D$. b) Scan of $-2\Delta\ln \mathcal{L}$ versus $m_{{H}\xspace}$ with and without the effect of systematic uncertainties included.
• Figure 2: a) Observed distribution of the $D_{SB}$ (SM Higgs boson versus background) discriminant compared with the background and signal expectations. b) Observed distribution of $D_{PS}$ ($J^P=0^-$ versus $J^P=0^+$) compared with expectation, for $D_{SB} > 0.5$. c) Observed distribution of $D_{GS}$ ($J^P=2^+$ versus $J^P=0^+$) compared with expectation, for $D_{SB} > 0.5$. Points represent the observed data, shaded histograms represent the background, and the open histogram represent the expectation for a 126 GeV boson with the indicated spin-parity, produced at the SM Higgs boson rate.
• Figure 3: Expected distribution of $-2\ln\mathcal{L}_{0^-}/\mathcal{L}_{0^+}$ under the pure pseudoscalar and pure scalar hypotheses (histograms). The arrow indicates the value determined from the observed data.