Use of the [formula omitted] or [formula omitted] decay mode to distinguish an intermediate mass Higgs boson from a technipion

Abstract

A technipion and an elementary Higgs particle with a mass greater than about 10 GeV can always be distinguished by a 10–20% accuracy measurement of the full sequential decay correlation function I( E 1, E 2, cos ψ 12) = S + γ CP D in the Higgs/technipion rest frame for a decay mode such as ττ with τ ± → ℓ ±ν ν or t t with t → b μ + ν, t → b μ − ν , where E 1,2 are the charged lepton energies and ψ 12 is the angle between the charged lepton momenta. For the charged leptons back-to-back, in the extreme relativistic scaling limit D/ S ≅ 21% for E 1 = E 2 ≅ ( E max/2), whereas for M H = 70 GeV already D/ S ≅ 19% so the scaling limit is rapidly reached. If for the t t mode the b jets′ momenta are also measured, then a correlation function in t quark rest frames′ helicity angles and energies can be used instead to determine γ CP but from a much smaller number of events. This procedure is possible because the standard ν ν correlation function is symmetric in the azimuthal angle φ ν ν , so cos φ ν ν and the helicity polar angles θ ν and θ ν of the missing and antineutrino are measurable in spite of a two-fold kinematic ambiguity in the t and t momenta directions. If the top quark has a mass m t ≥ 100 GeV, the t t mode with t → bW +, t → b W − can be used to determine γ CP by measuring the two b jets′ momenta.