Vector-like quark interpretation of excess in Higgs signal strength

摘要

There is a+2σdeviation in the average Higgs-signal strength for all the7+8+13TeV data up to Summer 2018. We find that a slight reduction of the bottom-Yukawa coupling can fit the data better than the standard model. We suggest an extension with a vector-like quark doublet, of which the right-handed component ofb′mixes nonnegligibly with the standard modelbquark. We show that the mixing would induce a reduction of the bottom Yukawa coupling. Simultaneously, the coupling of theZboson to the right-handedbquark increases, which could reduce the forward-backward asymmetry of bottom production at LEP and bring it closer to the experimental value. However, such a mixing is in tension with the ratioRbof the partial widthZ→bbˉto the total hadronic width, and with the total hadronic width of theZboson.