Decay Constants fD Research Articles

C,b quark masses and f,f decay constants from pseudoscalar sum rules in full QCD to order α2

Abstract The pseudoscalar sum rules of the heavy–light quark systems are used for extracting simultaneously the c,b quark masses and the decay constants fD(s),fB(s) of the D(s),B(s) mesons. To order αs2, one obtains the running quark masses: m c (m c )=(1.10±0.04) GeV, m b (m b )=(4.05±0.06) GeV implying m b (M Z )=(2.65±0.05) GeV; the perturbative pole masses: Mc=(1.46±0.04) GeV, Mb=(4.69±0.06) GeV; and the decay constants: fD=(205±20) MeV, fB=(203±23) MeV and fDs=(235±24) MeV, fBs=(236±30) MeV, in the normalization where fπ=130.56 MeV. The fitted values of the pole and running masses satisfy quite well their three-loop perturbative relation. The value fD≃fB confirms earlier findings from the sum rule that the 1/ M P heavy quark symmetry scaling law is affected by large 1/MP corrections.

Ds decay constant and D0D̄0 mixing from CLEO

The pseudoscalar decay constant fDs has been measured by CLEO tobe (280±19±28±34) MeV. A search for D0D̄0mixing based on 9.0 fb-1 of e+e- collision data at s≈5.5 GeV is summarized.

Purely leptonic decays of bottom and charm mesons

Recent measurements of leptonic decays of D S mesons and searches for leptonic decays of B mesons are presented. The average D S leptonic branching fraction is used extract the decay constant fD S = 246 ± 27 MeV. No evidence for leptonic B decays is observed, and the limit on the branching fraction is interpreted in the context of type II Higgs doublet models.

Evidence for the leptonic decay D→μν

Abstract Purely leptonic decays of the charged D meson have been studied using the reaction e + e − →D ∗+ D − at a center of mass energy of 4.03 GeV. A search was performed for D→μνμ recoiling against a D0 or D+ which had been reconstructed from its hadronic decay products. A single event candidate was found in the reaction e + e − →D ∗+ D − , where D ∗+ →π + D 0 with the D0→K−π+, and the recoiling D− decaying via D − →μ − ν μ . This yields a branching fraction value B(D→μνμ)=0.08−0.05−0.02+0.16+0.05%, and a corresponding value of the pseudoscalar decay constant fD=300−150−40+180+80 MeV.

Measurement of [formula omitted] and determination of the decay constant fDs

We have observed 23.2 ± 6.0 −0.9 +1.0 purely-leptonic decays of D s + → μ + ν μ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the D s + → φμ + ν μ yield measured previously in this experiment, we obtain B(D s + → μ +ν μ) B(D s + → φμ +ν μ) = 0.16 ± 0.06 ± 0.03 . In addition, we extract the decay constant f D s = 194 ± 35 ± 20 ± 14 MeV.

Production ofD S + mesons inB decays and determination of $$f_{D_S } $$

The production ofDS+ mesons inB meson decays, and inq\(\bar q\) continuum events, has been studied with the ARGUS detector at thee+e− storage ring DORIS II. In addition to the measurement of inclusiveDS+ production in γ(4S)→B\(\bar B\) decays, all eight two-body decay modesB→DS(*)D(*) have been measured with branching ratios between 1% and 3%. By comparing our inclusive and exclusive results to predictions of heavy quark effective theory, a value of (267±28) MeV × [2.7%/BR(Ds+→φπ+)]1/2 is obtained for the weak decay constant fDS(*), averaged overDS+ andDS*+ mesons.

Search for the decay D+--> micro+ nu micro and an upper limit on the pseudoscalar decay constant.

We report the results of a search for the leptonic decay D+→μ+νμ using the Mark III detector at the SLAC e+e− storage ring SPEAR. A data sample of 9.3 pb−1 collected at the ψ(3770) resonance yields no signal events, corresponding to a 90%-confidence-level upper limit of 7.2×10−4 on the branching ratio B(D+→μ+νμ). This represents an upper limit on the pseudoscalar decay constant fD of 290 MeV/c2.Received 13 October 1987DOI:https://doi.org/10.1103/PhysRevLett.60.1375©1988 American Physical Society