Measurement ofB(Ds+→l+ν)and the decay constantf

Abstract

We examine e + e − → D − s D * + s and D * − s D + s interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant f D + s with good precision. Previously our measurements were substantially higher than the most precise lattice based QCD calculation of (241±3) MeV. Here we use the D + s → ℓ + ν channel, where the ℓ + designates either a µ + or a τ + , when the τ + → π + ν.

Measurements of branching fractions of leptonic and hadronic $ D_s^{+} $ meson decays and extraction of the $ D_s^{+} $ meson decay constant

“…Measurements of f Ds have been made previously by several groups: CLEO [11][12][13], Belle [14] and BaBar [15]. The current world average is f exp Ds = (260.0 ± 5.4) MeV [2].…”

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

“…Unlike the CLEO-c measurements above, this measurement is normalized to the branching ratio of the decay D s → K ± K 0 . The decay D s → µν has been measured at CLEO-c [30], BELLE [31] and BABAR [32]. Both the CLEO-c and BELLE measurements are of the absolute branching ratio, while the BABAR measurement is normalized to the decay D s → φ 0 π ± (note that this differs from the decay D s → K ± K 0 which is used in the BABAR measurement of D s → τ ν).…”

“…Due to the sizeable uncertainty in the branching ratio of D s → φ 0 π ± , the BABAR measurement [32] is not included in the averages given in [71]. The average of the six measurements [30,31,[33][34][35] results in a world average of f Ds = 257.5± 6.1 MeV (derived in [71] and is dominated by the average of the four CLEO-c measurements). The world average given in [68] is lower (f Ds = 254.6 ± 5.9 MeV) because it includes the BABAR measurement of f Ds in [32] (although with a reinterpreted value, as explained in [77]).…”

“…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.…”