Title

Leptonic decays of charged D and Ds mesons

Date of Award

2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Advisor(s)

Sheldon Stone

Keywords

Leptonic decays, D mesons

Subject Categories

Physical Sciences and Mathematics | Physics

Abstract

Using 281 pb -1 of data taken on the ψ(3770) resonance and 314 pb -1 of data near or at 4170 MeV collected with the CLEO-c detector, we present two analyses to study the purely leptonic decays of charmed and charmed strange charged mesons.

In the first analysis, we extract a relatively precise value for the decay constant of the D + meson by measuring [Special characters omitted.] ( D + [arrow right] μ + ν) = (4.40 ± [Special characters omitted.] ) × 10 -4 . We find f D + = (222.6 ± [Special characters omitted.] ) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on [Special characters omitted.] ( D + [arrow right] e + ν) < 2.4 × 10 -5 which constrains new physics models. Finally with this data sample, we test whether or not the τ lepton manifests the same couplings as the μ lepton by investigating the relative decay rates in purely leptonic D + meson decays. We limit [Special characters omitted.] ( D + [arrow right] τ + ν) < 2.1 × 10 -3 at 90% confidence level (C. L.), thus allowing us to place the first upper limit on the ratio R = Γ ( D + [arrow right] τ + ν)/Γ( D + [arrow right] μ + ν). The ratio of R to the Standard Model expectation of 2.65 then is <1.8 at 90% C. L., consistent with the prediction of lepton universality.

In the second analysis, we examine e + e - [arrow right] [Special characters omitted.] and [Special characters omitted.] interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant [Special characters omitted.] . We use the [Special characters omitted.] [arrow right] [cursive l] + ν channel, where the [cursive l] + designates either a μ + or a τ + , when the τ + [arrow right] π + ν. Analyzing both modes independently, we determine [Special characters omitted.] ([Special characters omitted.] [arrow right] μ + ν) = (0.594 ± 0.066 ± 0.031)%, [Special characters omitted.] ([Special characters omitted.] [arrow right] τ + ν) = (8.0 ± 1.3 ± 0.4)%. We also analyze them simultaneously to find an effective value of [Special characters omitted.] ([Special characters omitted.] [arrow right] μ + ν) = (0.621 ± 0.058 ± 0.032)% and extract [Special characters omitted.] = 270 ± 13 ± 7 MeV. Combining with our previous determination of [Special characters omitted.] ( D + [arrow right] μ + ν), we also find the ratio [Special characters omitted.] = 1.21 ± 0.11 ± 0.04. We compare with current theoretical estimates. Finally, we limit [Special characters omitted.] ([Special characters omitted.] [arrow right] e + ν) < 1.3 × 10 -4 at 90% confidence level.

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