Measuring properties of a Heavy Higgs boson in the $H\to t\bar{t}\to b{W}^{+}\bar{b}{W}^{-}$ decay

Abstract

Suppose a heavy neutral Higgs or scalar boson $H$ is discovered at the LHC, it is important to investigate its couplings to the standard model particles as much as possible. Here in this work we attempt to probe the CP-even and CP-odd couplings of the heavy Higgs boson to a pair of top quarks, through the decay $H\to t\bar{t}\to b{W}^{+}\bar{b}{W}^{-}$. We use the helicity-amplitude method to write down the most general form for the angular distributions of the final-state $b$ quarks and $W$ bosons. We figure out that there are 6 types of angular observables and, under CP$\tilde{\mathrm{T}}$ conservation, one-dimensional angular distributions can only reveal two of them. Nevertheless, the $H$ couplings to the $t\bar{t}$ pair can be fully determined by exploiting the one-dimensional angular distributions. A Higgs-boson mass of 380 GeV not too far above the $t\bar{t}$ threshold is illustrated with full details. With a total of $10^4$ events of $H\to t\bar{t}\to b{W}^{+}\bar{b}{W}^{+}$, one can determine the couplings up to 10-20 % uncertainties.

Comments: 23 pages, 4 figures, 3 tables. arXiv admin note: text overlap with arXiv:1708.05583, to appear in JHEP, A reference added