Decay Constants fD Research Articles

(Semi-) leptonic D(s) decays at BESIII

BESIII has collected 2.93fb−1 and 6.32fb−1 of e+e− collision data samples at the center-of-mass energies 3.773 and 4.178–4.226 GeV, respectively. We report recent measurements of the (semi-) leptonic decays Ds→ℓ+νℓ (ℓ=μ,τ) and D(s)→Xℓ+νℓ [X=η,K1(1270) or denotes generic decays, and ℓ=e,μ]. The decay constant fDs+, the semileptonic form factor f+η(0) and the CKM matrix elements |Vcd(s)| are determined precisely. These results are important to verify the theoretical calculations of fDs+ and f+η(0), and the unitarity of the CKM matrix. Precision tests of lepton-flavor universality with (semi-) leptonic D(s) decays are also performed.

Initial charm program on direct measurements of weak decay constant fDs and branching fraction B(Ds → μνμ) and prospect with high-precision

First direct measurements of the weak decay constant [Formula: see text] and the [Formula: see text] branching fractions to [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] at the BES experiments in 1990s are reviewed. Referring to the BESIII results of [Formula: see text] and branching fraction [Formula: see text] with best precision1 to date, prospect for challenge on precision measurements of [Formula: see text] and [Formula: see text] at BESIII is presented.

Heavy Domain Wall Fermions: The RBC and UKQCD charm physics program

We review the domain wall charm physics program of the RBC and UKQCD collaborations based on simulations including ensembles with physical pion mass. We summarise our current set-up and present a status update on the decay constants fD, fDs, the charm quark mass, heavy-light and heavy-strange bag parameters and the ratio ξ

The decay constants fD and {f}_{D_s} in the continuum limit of Nf = 2 + 1 domain wall lattice QCD

We present results for the decay constants of the D and Ds mesons computed in lattice QCD with Nf = 2 + 1 dynamical flavours. The simulations are based on RBC/UKQCD’s domain wall ensembles with both physical and unphysical light-quark masses and lattice spacings in the range 0.11-0.07 fm. We employ the domain wall discretisation for all valence quarks.The results in the continuum limit are fD = 208.7(2.8)stat(− 1.8+ 2.1)sysMeV and {f}_{D_s}=246.4{(1.3)}_{mathrm{stat}}{left({}_{-1.9}^{+1.3}right)}_{mathrm{sys}}mathrm{M}mathrm{e}mathrm{V} and {f}_{D_s}={f}_D=1.667{(77)}_{mathrm{stat}}{left({}_{-43}^{+57}right)}_{mathrm{sys}} . Using these results in a Standard Model analysis we compute the predictions |Vcd| = 0.2185(50)exp(− 37+ 35)lat and |Vcs| = 1.011(16)exp(− 9+ 4)lat for the CKM matrix elements.

CHARM PHYSICS AT BESIII

We present a selection of recent charm results from the BESIII Collaboration. The topics include measurements of strong phase in D0 → Kπ decay and yCP, decay constant fD+ measurement from D+ → μ+ν, form-factors measurement in D0 → K−e+ν, π−e+ν, Dalitz plot analysis of [Formula: see text], search for D0 → γγ rare decay and Ds decays.

Recent results from BESIII

Selected results of BESIII are reported, including the observation of charged, charmonium-like states, the Zc(3900), Zc(4020), and Zc(4025); observation of e+e- → γX(3872); study of ηη system in J/ψ → γηη; baryon excited study in [Formula: see text]; precise measurements of the decay constant fD from D+ → μ+ν and form-factors in D0 → K-e+ν,π-e+ν.

Recent charm physics results from BABAR

In this proceeding, recent charm physics results from the BABAR experiment are discussed. The studies include a Dalitz plot and partial-wave analysis of the decay Ds → K+ K− π+, a recent measurement of the leptonic decay constant fDs, the precision mass and width measurements of the Ds1(2535) meson, searches for new resonances in inclusive e+e− collisions, searches for flavor changing neutral currents, lepton-flavor and lepton-number violating decays, and searches for CP violation.

Uncertainty study of D−S(D−)→γlν̄(l = e, μ) decays determined by wave function

Wave function is important for determining decay constants fD−S and fD−. Using the 5 types of D meson wave functions in the heavy quark limit, we studied the uncertainties of radiative pure-leptonic decays of D−S(D−) mesons. The branching ratios are (1.025390−1.706812)×10−5 and (0.953498−1.576725)×10−6 for D−S and D− decays, respectively, which are sensitive to the type of wave function.

LEPTONIC D AND DS DECAYS FROM CLEO-c AND PROSPECTS FOR BESIII

We first review recent measurements of D → μν and Ds → μν, τν from CLEO-c. These decays are used to determine leptonic decay constants fD and fDs which may be compared to modern Lattice QCD (LQCD) calculations. Such cross-checks can provide confidence in Lattice results for B(s) meson decay constants which are needed to fully exploit data used to extract the CKM matrix elements Vub and Vcb. We also comment briefly on the outlook for further progress at BESIII.

ABSOLUTE MEASUREMENTS OF PURE LEPTONIC Ds DECAYS AND fDs DECAY CONSTANT FROM BABAR

I present the measurements and limits of the branching fractions of leptonic decays of the Ds meson, and the subsequent estimation of the decay constant fDs, using the complete BaBar dataset (530 fb-1). we measure [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and fDs = (258.6±6.4±7.5)MeV, where the first uncertainties are statistical and the second uncertainties are systematic.

Measurement of the pseudoscalar decay constantfDsusingDs+→τ+ν,τ+→ρ+ν¯decays

Analyzing 600/pb of e+e- collisions at 4170 MeV center-of-mass energy with the CLEO-c detector, we measure the branching fraction B(Ds+ -> tau+ nu)=(5.52\pm 0.57\pm 0.21)% using the tau+ -> rho^+ anti-nu decay mode. Combining with other CLEO measurements of B(Ds+ -> tau+ nu) we determine the pseudoscalar decay constant fDs = (259.7\pm 7.8\pm 3.4) MeV consistent with the value obtained from our Ds+ -> mu+ nu measurement of (257.6\pm 10.3\pm 4.3) MeV. Combining these measurements we find a value of fDs=(259.0 \pm 6.2\pm 3.0) MeV, that differs from the most accurate prediction based on unquenched lattice gauge theory of (241\pm 3) MeV by 2.4 standard deviations. We also present the first measurements of B(Ds+ -> K0 pi+ pi0)=(1.00\pm0.18\pm 0.04)%, and B(Ds+ -> pi+ pi0 pi0)=(0.65\pm0.13\pm 0.03)%, and measure a new value for B(Ds+ -> eta rho+)=(8.9\pm0.6\pm0.5)%.

Measurement ofB(Ds+→l+ν)and the decay constantfDs+from600 pb−1ofe+e−annihilation data near 4170 MeV

We examine e+e- --> Ds^-D_s^{*+} and Ds^{*-}Ds^{+} interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs 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^+ --> ell^+ nu channel, where the ell^+ designates either a mu^+ or a tau^+, when the tau^+ --> pi^+ anti-nu. Analyzing both modes independently, we determine B(D_s^+ --> mu^+ nu)= 0.565 +/- 0.045 +/- 0.017)%, and B(D_s^+ --> mu^+ nu)= (6.42 +/- 0.81 +/- 0.18)%. We also analyze them simultaneously to find an effective value of B^{eff}(D_s^+ --> mu^+ nu)= (0.591 +/- 0.037 +/- 0.018)% and fDs=(263.3 +/- 8.2 +/- 3.9) MeV. Combining with the CLEO-c value determined independently using D_s^+ --> tau^+ nu, tau^+ --> e^+ nu anti-nu decays, we extract fDs=(259.5 +/- 6.6 +/- 3.1) MeV. Combining with our previous determination of B(D^+ --> mu^+ nu), we extract the ratio fDs/fD+=1.26 +/- 0.06 +/- 0.02. No evidence is found for a CP asymmetry between Gamma(D_s^+ --> mu^+\nu) and \Gamma(D_s^- --> mu^- nu); specifically the fractional difference in rates is measured to be (4.8 +/- 6.1)%. Finally, we find B(D_s^+ --> e^+ nu) < 1.2x10^{-4} at 90% confidence level.

A possible signature of new physics at BES-III

The recent observations of the purely leptonic decay D+s → μ+ νμ and τ+ ντ at CLEO-c and B factory may allow a possible contribution from a charged Higgs boson. One such measurement of the decay constant fDS differs from the most precise unquenched lattice QCD calculation by a level of 4 σ. Meanwhile, the measured ratio, , is larger than the standard model prediction at a 2.0σ level. We discuss that the precise measurement of the ratio ) at BES-III will shed light on the presence of new intermediate particles by comparing the data with the theoretical predictions, especially, the predictions of high precise unquenched lattice QCD calculations.

Precision measurement ofB(D+→μ+ν)and the pseudoscalar decay constantfD+

We measure the branching ratio of the purely leptonic decay of the D+ meson with unprecedented precision as B(D+ -> mu+ nu) = (3.82 +/- 0.32 +/- 0.09)x10^(-4), using 818/pb of data taken on the psi(3770) resonance with the CLEO-c detector at the CESR collider. We use this determination to derive a value for the pseudoscalar decay constant fD+, combining with measurements of the D+ lifetime and assuming |Vcd| = |Vus|. We find fD+ = (205.8 +/- 8.5 +/- 2.5) MeV. The decay rate asymmetry [B(D+ -> mu+ nu)-B(D- -> mu- nu)]/[B(D+ -> mu+ nu)+B(D- -> mu- nu)] = 0.08 +/- 0.08, consistent with no CP violation. We also set 90% confidence level upper limits on B(D+ -> tau+ nu) < 1.2x10^(-3) and B(D+ -> e+ nu) < 8.8x10^(-6).

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

We examine e+e−→Ds−Ds*+ and Ds*−Ds+ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs+. We use the Ds+→ℓ+ν channel, where the ℓ+ designates either a μ+ or a τ+, when the τ+→π+ν¯. Analyzing both modes independently, we determine B(Ds+→μ+ν)=(0.594±0.066±0.031)%, and B(Ds+→τ+ν)=(8.0±1.3±0.4)%. We also analyze them simultaneously to find an effective value of Beff(Ds+→μ+ν)=(0.638±0.059±0.033)% and extract fDs+=274±13±7 MeV. Combining with our previous determination of B(D+→μ+ν), we also find the ratio fDs+/fD+=1.23±0.11±0.04. We compare to current theoretical estimates. Finally, we find B(Ds+→e+ν)<1.3×10−4 at 90% confidence level.4 MoreReceived 2 April 2007DOI:https://doi.org/10.1103/PhysRevD.76.072002©2007 American Physical Society

Direct measurement of the pseudoscalar decay constant [formula omitted

The absolute branching fraction for the decay D+→μ+ν has been directly measured based on a data sample of about 33 pb−1 collected around s=3.773 GeV with the BES-II detector at the BEPC collider. A total of 5321±149±160D− mesons are reconstructed in nine hadronic decay modes. In the system recoiling against these singly tagged D− mesons, 2.67±1.74 purely leptonic decay events of D+→μ+νμ are observed. Those yield the branching fraction of BF(D+→μ+νμ)=(0.122−0.053+0.111±0.010)%, and a corresponding value of the pseudoscalar decay constant fD+=(371−119+129±25) MeV.

Measurement of ℬ(D+ → μ+νμ) and the pseudoscalar decay constant fD at CLEO

The analysis of 60 pb−1 data collected on the ψ(3770) resonance with the CLEO-c detector has produced the first statistically significant signal for D+ → μ+ν decay and led to the measurement of the decay branching fraction β(D+→μ+νμ) = (3.5 ± 1.4 ± 0.6) × 10−4 and the pseudoscalar decay constant fD = (202 ± 41 ± 17) MeV.

A precise determination of the decay constant of the Ds-meson in quenched QCD

We present a precise determination of the leptonic decay constant FDs of the DS-meson in quenched lattice QCD. This work is particularly focused on the analysis and discussion of all sources of systematic errors. We simulate directly at the physical quark masses for five different lattice spacings between 0.1 fm and 0.03 fm using O(a)-improvement. The finest lattice is still work in progress. After taking the continuum limit and setting the scale with the Kaon decay constant FK = 160 MeV we arrive at a value of Ds, = 252(9) MeV. Setting the scale with the nucleon mass instead leads to a decrease of about 20 MeV of FDins.

Radiative leptonic decays of Ds± and D± mesons

In this Letter, we investigate the radiative leptonic decays D−(s)→γℓν̄ (ℓ=e,μ) at tree level within the non-relativistic constituent quark model and the effective Lagrangian for the heavy flavor decays. We find that the contributions from the three Feynman diagrams are all important. With the full calculation, the decay branching ratios are of the order of 10−5 for Ds−→γℓν̄ (ℓ=e,μ) and 10−6 for D−→γℓν̄ (ℓ=e,μ), respectively. These decays can be measured at B factories and future CLEO-C experiments to determine the decay constants fDs and fD.

A precise determination of the decay constant of the Ds-meson in quenched QCD

We present a lattice determination of the leptonic decay constant FDs of the Ds-meson using its mass and FK as experimental input. Setting the scale with FK=160 MeV, our final result is FDs=252(9) MeV. The error contains all uncertainties apart from the quenched approximation. Setting the scale with the nucleon mass instead leads to an decrease of 20(1) MeV of the leptonic decay constant.