Constraints on Models of the Higgs Boson with Exotic Spin and Parity using Decays to Bottom-Antibottom Quarks in the Full CDF Data Set

A search for particles with the same mass and couplings as those of the standard model Higgs boson but different spin and parity quantum numbers is presented. We test two specific alternative Higgs boson hypotheses: a pseudoscalar Higgs boson with spin-parity $J^P=0^{-}$ and a gravitonlike Higgs boson with $J^P=2^{+}$, assuming for both a mass of $125\mathrm{GeV}/c^2$. We search for these exotic states produced in association with a vector boson and decaying into a bottom-antibottom quark pair. The vector boson is reconstructed through its decay into an electron or muon pair, or an electron or muon and a neutrino, or it is inferred from an imbalance in total transverse momentum. We use expected kinematic differences between events containing exotic Higgs bosons and those containing standard model Higgs bosons. The data were collected by the CDF experiment at the Tevatron proton-antiproton collider, operating at a center-of-mass energy of $\sqrt{s}=1.96\mathrm{TeV}$, and correspond to an integrated luminosity of $9.45{\mathrm{fb}}^{-1}$. We exclude deviations from the predictions of the standard model with a Higgs boson of mass $125\mathrm{GeV}/c^2$ at the level of 5 standard deviations, assuming signal strengths for exotic boson production equal to the prediction for the standard model Higgs boson, and set upper limits of approximately 30% relative to the standard model rate on the possible rate of production of each exotic state.

Figure 1

Distributions of ${\log }_{10}(s/b)$ for the data from all contributing Higgs boson search channels for a boson mass of $125\mathrm{GeV}/c^2$ for (a) the $0^{-}$ search and (b) the $2^{+}$ search. The observed numbers of events are represented by the points, and the expected exotic signals are shown as histograms with ${\mu }_{\text{exotic}}=1$ stacked on top of the backgrounds, which are fit to the data within their systematic uncertainties. The expected $s/b$ ratios of the exotic signal over the background yield are used to rank analysis bins. The background predictions do not include the contributions from the SM Higgs boson, which are shown as separate histograms, not stacked. The error bars shown on the data correspond to the square root of the observed data count. Underflows and overflows are collected into the leftmost and rightmost bins, respectively.

Figure 2

Combined two-dimensional posterior density of the measured (a) $0^{-}$-vs-$0^{+}$ and (b) $2^{+}$-vs-$0^{+}$ cross sections, normalized to the SM predictions.