Charged Higgs Boson Search at the Tevatron Upgrade Using Tau(6)

We explore the prospect of charged Higgs boson search in top quark decay at the Tevatron collider upgrade, taking advantage of the opposite states of $\tau$ polarization resulting from the $H^\pm$ and $W^\pm$ decays. Methods of distinguishing the two contr

Nonetheless the method of enhancing the signal to background ratio by theτpolarization e?ect discussed below can be extended to this channel,provided one can identify theττevents from the QCD background.

3TAU POLARIZATION EFFECT

We shall concentrate on the1-prong hadronic decay channel ofτ,which is best suited forτidenti?cation.It accounts for80%of hadronicτdecays and50% of overallτdecays.The main contributors to the1-prong hadronicτdecay are [1]

τ±→π±ντ(12.5%)(20)

τ±→ρ±ντ→π±π0ντ(24%)(21)

τ±→a±1ν→π±π0π0ντ(7.5%)(22) where the branching fractions for theπandρchannels include the small con-tributions from the K and K?channels respectively,since they have identical polarization e?ects.Note that only half the a1decay channel contributes to the 1-prong con?guration.The masses and widths ofρand a1are[1]

mρ(Γρ)=770(150)MeV,m a

1(Γa

1

)=1260(400)MeV.(23)

One sees that the three decay processes(20,21,22)account for about90%of the1-prong hadronic decay ofτ.Thus the inclusion ofτpolarization e?ect in these processes will account for its e?ect in the inclusive1-prong hadronic decay channel to a good approximation.

The formalism relatingτpolarization to the momentum distribution of its decay particles in(20,21,22)has been widely discussed in the literature[5,6, 12,13].We shall only discuss the main formulae relevant for our analysis.A more detailed account can be found in a recent paper by Bullock,Hagiwara and Martin[6],which we shall closely follow.Forτdecay intoπor a vector meson (ρ,a1),one has

1

d cosθ=

1

Γv

dΓvL2m2τ

Γv dΓvT

m2τ+2m2v

(1?Pτcosθ)(26)

5

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