Can the 126 GeV boson be a pseudoscalar

We test the possibility that the newly discovered 126 GeV boson is a pseudoscalar by examining the correlations among the loop-induced pseudoscalar decay branching fractions to $\ensuremath{\gamma}\ensuremath{\gamma}$, $Z{Z}^{*}$, $Z\ensuremath{\gamma}$, and $W{W}^{*}$ final states in a model-independent way. These four decays are controlled by only two effective operators, so that the rates in $Z\ensuremath{\gamma}$ and $W{W}^{*}$ are predicted now that the rates in $\ensuremath{\gamma}\ensuremath{\gamma}$ and $Z{Z}^{*}$, $Z{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}4\ensuremath{\ell}$ have been measured. We find that the pseudoscalar possibility is disfavored but not conclusively excluded. Experimental exclusion of the $Z\ensuremath{\gamma}$ decay to well below $\ensuremath{\sigma}/{\ensuremath{\sigma}}_{\mathrm{SM}}\ensuremath{\sim}170$ or conclusive observation of the $W{W}^{*}$ decay near the Standard Model rate would eliminate the pseudoscalar possibility. The $Z\ensuremath{\gamma}$ exclusion should be possible using existing data. The only loophole in our argument is the possibility that the $4\ensuremath{\ell}$ signal comes from pseudoscalar decays to a pair of new neutral gauge bosons with mass near the $Z$ pole.