Measuring properties of a Heavy Higgs boson in the H→tt¯→bW+b¯W− $$ H\to t\overline{t}\to b{W}^{+}\overline{b}{W}^{-} $$ 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→tt¯→bW+b¯W− $$ H\to t\overline{t}\to b{W}^{+}\overline{b}{W}^{-} $$. 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 CPT˜ $$ \mathrm{C}\mathrm{P}\tilde{\mathrm{T}} $$ conservation, one-dimensional angular distributions can only reveal two of them. Nevertheless, the H couplings to the tt¯ $$ t\overline{t} $$ pair can be fully determined by exploiting the one-dimensional angular distributions. A Higgs-boson mass of 380 GeV not too far above the tt¯ $$ t\overline{t} $$ threshold is illustrated with full details. With a total of 104 events of H→tt¯→bW+b¯W+ $$ H\to t\overline{t}\to b{W}^{+}\overline{b}{W}^{+} $$, one can determine the couplings up to 10-20% uncertainties