Measurement of the pseudoscalar decay constantfDsusingDs+→τ+ν,

Abstract

Analyzing 600 pb À1 of e þ e À collisions at 4170 MeV center-of-mass energy with the CLEO-c detector, we measure the branching fraction BðD þ s ! þ Þ ¼ ð5:52 AE 0:57 AE 0:21Þ% using the þ ! þ " decay mode. Combining with other CLEO measurements of BðD þ s ! þ Þ we determine the pseudoscalar decay constant f D s ¼ ð259:7 AE 7:8 AE 3:4Þ MeV consistent with the value obtained from our D þ s ! þ measurement of ð257:6 AE 10:3 AE 4:3Þ MeV. Combining these measurements we find a value of f D s ¼ ð259:0 AE 6:2 AE 3:0Þ MeV, that differs from the most accurate prediction based on unquenched lattice gauge theory of ð241 AE 3Þ MeV by 2.4 standard deviations. We also present the first measurements of BðD þ s ! K 0 þ 0 Þ ¼ ð1:00 AE 0:18 AE 0:04Þ%, and BðD þ s ! þ 0 0 Þ ¼ ð0:65 AE 0:13 AE 0:03Þ%, and measure a new value for BðD þ s ! þ Þ ¼ ð8:9 AE 0:6 AE 0:5Þ%.

Sterile neutrinos in leptonic and semileptonic decays

“…Both these observables present a deviation from the theoretical expectation: 2.4 σ using the QCD sum rules estimation for the decay constant f Ds , or a 2.8 σ deviation using the lattice determination (see [66] and references therein).…”

“…Nominal SM expectations on D and D S leptonic decays, as well as the experimental results from CLEO-c and BES III, can be found in [65]. In our study we focus in particular on D s observables, which have recently been well measured by CLEO-c [66]:…”

Measuring V ub and probing SUSY with double ratios of purely leptonic decays of B and D mesons

“…On the experimental side, D s → τ ν has been measured at CLEO-c for three decay modes of τ (eνν, πν, ρν) [30,33,34]. These are absolute branching ratio measurements.…”

“…The decays D → µν [29], D s → µν [30][31][32] and D s → τ ν [30,[33][34][35] have been measured with ∼ 10% precision at CLEO-c and the B factories, and the ongoing BES-III experiment will reduce the error in all these decays to maybe 3% [36,37]. The current measurements of B u → τ ν, D → µν, D s → µν and D s → τ ν are in agreement with the SM prediction, within the errors of the decay constants.…”

Impact of sterile neutrinos on nuclear-assisted cLFV processes

“…Further constraints arise from leptonic and semileptonic decays of pseudoscalar mesons K, D, D s , B (see [72,73] for kaon decays, [74,75] for D and D S decay rates, and [76,77] for B-meson observations). Recent studies suggest that in the framework of the SM extended by sterile neutrinos the most severe bounds arise from the violation of lepton universality in leptonic kaon decays (parametrised by the observable ∆r K ) [58,78].…”