Charged Higgs and Scalar Couplings in Semileptonic Meson Decay


We present a new charged Higgs search technique using the effects of scalar dynamics in semileptonic meson decay. Applying this method to a modest sample of B meson decays yields sensitivity to the high tan β region well beyond existing charged Higgs searches. Past searches for charged Higgs can be put into four categories: 1) direct production in colliders, 2) measurement of anomalously large branching ratios for top, bottom and τ lepton decays, 3) lepton polarization measurements in meson decay and 4) precision measurements of well known quantities such as K–K0 mixing, Z width, etc. [1]. Category 1 represent direct searches while categories 2–4 are indirect search techniques. Of the indirect searches, only the lepton polarization technique makes use of the scalar nature of the charged Higgs. Requiring scalar dynamics in a process which may be mediated by a charged Higgs provides an extra constraint and narrows the number of possible interpretations of indirect searches. In this Letter, we review a method to identify scalar dynamics or couplings in semileptonic decays of pseudoscalar mesons. By identifying the scalar coupling as a charged Higgs mediating the decay, one may extract the relative H±/W± coupling strengths. We apply the relative coupling strength information to a two Higgs doublet model and evaluate the possible sensitivities of precision measurements in B meson decay dynamics to charged Higgs searches. 1 General Phenomenology We begin by considering a general semileptonic meson decay. M → mlν, (1) where M and m denote the parent and offspring pseudoscalar mesons and l and ν refer to the charged lepton and its neutrino. The general amplitude describing a pseudoscalar to pseudoscalar transition, consistent with the Dirac equation and left handed, massless neutrinos, is M = GF √ 2 Viju(pν)(1 + γ ) { MfS − 12 [(P + p)αf+ + (P − p)αf−] γ + iT M σαβP p } v(pl), (2) where GF is the Fermi coupling constant, Vij is the appropriate CabibboKobayashi-Maskawa [2] (CKM) matrix element and P , M and p, m are the 4-momenta and masses of the parent and offspring mesons, respectively. This transition amplitude contains four form factors, fS, f+, f−, and fT , which parameterize the M → m transition and provide a measure of the admixture of different dynamics or couplings occurring in the decay. In general, the form factors depend on the 4-momentum transferred to the leptons, Q = (P−p)2. Two of the form factors, f+ and f−, arise from a vector particle mediating the decay while the remaining form factors, fS and fT , come from scalar and tensor exchange. The term in equation 2 involving f− may be collapsed, using the Dirac equation, to give an induced scalar coupling. The tensor term may be similarly collapsed into induced vector and scalar components. To calculate the decay rate, we use the notation of Chizhov [3] and define parameters for effective vector and scalar terms: V = f+ + ml M fT S = fS + ml 2M f− + { (Eν−El) M + m l 2M }

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Cite this paper

@inproceedings{Tesarek1999ChargedHA, title={Charged Higgs and Scalar Couplings in Semileptonic Meson Decay}, author={Richard J. Tesarek}, year={1999} }