Associated Production Evidence against Higgs Impostors and Anomalous Couplings

Abstract

There is still no proof that the new particle $X$ recently discovered by the ATLAS and CMS Collaborations indeed has spin zero and positive parity, as confidently expected. We show here that the energy dependence of associated $W/Z + X$ production would be much less for a $J^P = 0^+$ boson with minimal couplings, such as the Higgs boson of the Standard Model, than for a spin-two particle with graviton-like couplings or a spin-zero boson with non-minimal couplings. The $W/Z + (X \to {\bar b}b)$ signal apparently observed by the CDF and D0 Collaborations can be used to predict the cross section for the same signal at the LHC that should be measured under the spin-two and different spin-zero hypotheses. The spin-two prediction exceeds by an order of magnitude the upper limits established by the ATLAS and CMS Collaborations, which are consistent with the minimal $0^+$ prediction, thereby providing {\it secunda facie} evidence against spin-two Higgs impostors. Similar analyses of energy dependences provide evidence against $0^-$ impostors, non-minimal scalar boson couplings, including the best LHC limits on dimension-six operators. Comparing the LHC vector boson fusion cross sections at 7 and 8 TeV in the centre of mass provides additional but weaker evidence in favour of the identification of the $X$ particle as a $J^P = 0^+$ boson with minimal couplings.