D-meson Decay Research Articles

Formula omitted] correction to ƒ B

The 1/ m corrections to the B-meson decay constant ƒ B (and the D-meson decay constant ƒ D) of the heavy quark effective theory are calculated in the Green function approach. The corrections are found to be sensitive to the difference of the meson mass m B and the heavy quark mass m b. For m b=4.8 1 GeV we obtain a 100% correction to the heavy quark limit m b= m B. The scaling law of the ratio ƒ B/ƒ D is, however, quite well satisfied because of cancellations. For reasonable values of quark masses we obtain ƒ B = (130±20) MeV and ƒ D = (170±10) MeV .

A lattice study of semileptonic decays of d-mesons

We present the results of a computation of the matrix elements of the vector current which are relevant for the semileptonic decays of D-mesons. The computations are performed on a 20×10 2×40 lattice at β=6.0 using Wilson fermions in the quenched approximation. From the study of the matrix element 〈K −| J μ |D 0〉 we find that the form factor at zero momentum transfer is given by ƒ + (0) = 0.74±0.17 , in excellent agreement with the experimental measurement. From a computation of the matrix element 〈 π −| J μ |D 0〉 we find that the corresponding form factor at zero momentum transfer is given by ƒ + (0)=0.70±0.20 . Within our statistical errors vector dominance gives a good description of the form factor at the values of the momentum transfers accessible on our lattice.

Derivation ofv ?/v ? and the spectra of neutrinos from pions and kaons produced by primary cosmic rays throughp-nucleus collisions

The muon neutrino-antineutrino flux ratios, viz.,vμ/vμ generated from the decays of charged pions and kaons in atmosphere have been derived from the latest primary spectrum and the CERN ISRpp-collision data modified forp-nucleus interactions. The dynamical method of Allkoferet al. (1978) has been used in the present investigation. The estimated result forvμ/vμ yields 1.39 and 1.70 asE→0 and ∞, respectively. The neutrino fluxes from pion- and kaon-decay spectra have been calculated. Attention has been paid on prompt neutrino spectrum calculation from the decays ofD mesons. A rough estimate on the prompt muon spectrum has been given. The calculated results have been compared with the previous available results.

Effective lagrangian analysis of new interactions and flavour conservation

New interactions with a scale Λ larger than the Fermi scale G F − 1 2 will manifest themselves at energies below Λ through small deviations from the standard model, which can be described by an effective lagrangian containing non-renormalizable SU(3) × SU(2) × U(1) invariant operators. We construct the first two terms of this lagrangian in an expansion in powers of 1/Λ and study systematically possible effects of new interactions such as anomalous magnetic moments, deviations from universality in weak interactions and rare processes. Among the flavour conserving processes the universality of the charged current weak interactions yields the strongest bound on the new interaction scale, Λ > 5 TeV, whereas flavour non-conserving processes imply the bound Λ > 3000 TeV. We derive conditions for natural flavour conservation. Although it cannot be excluded that all flavour changing operators are dynamically suppressed, this appears difficult to understand without a symmetry for which the standard electroweak theory seems to provide no hint. We emphasize the importance of searching for rare decays of D-mesons.

Phenomenological Lagrangian for nonleptonic charmed-meson decays.

A gauged chiral-Lagrangian model for charmed-meson decays is proposed. The 0/sup +/ uncharmed mesons are included in the model to account for S-wave hadronic final-state interactions. All the hadron fields are incorporated into the phenomenological Lagrangian through the general framework proposed by Coleman, Wess, and Zumino. The model correctly predicts the branching ratios of various two-body D-meson decay modes in both Cabibbo-angle-favored and Cabibbo-angle-suppressed channels, with the only exception of B(D-bar /sup 0/..-->..K/sup +/K/sup -/)/B(D /sup 0/..--> pi../sup +/..pi../sup -/). We have also shown that the prediction of S-wave threshold parameters in ..pi pi.. scattering can be in good agreement with data, if the SU(3)-symmetry-breaking effect in 0/sup +/ uncharmed-meson decay vertices is suitably adjusted.

The annihilation diagram in three-body D-meson decay

We discuss some features of three-body decays of the D meson which are puzzling from the standpoint of the annihilation diagram. As a result, we (1) provide an upper bound on the lifetime ratio of D's, τ + D/ τ 0 D < 2.5 ± 3.4 and (2) argue that the puzzles are resolved, even if somewhat inelegantly, if final state interactions generate the annihilation diagram.

Evidence for "Total Number" Conservation of Quarks in the D-Meson Decay?

Evidence for "Total Number" Conservation of Quarks in the D-Meson Decay?

Cabibbo suppressed two-body hadronic decays of D-mesons

The contribution of Penguin diagrams to the Cabibbo-suppressed decays D 0→π +π −, D 0→K +K − are estimated and found to be significant. The inclusion of these diagrams is therefore necessary in any attempt to extract information on the Kobayashi-Maskawa mixing angles from the above decay processes.

Charmed «current quark» mass and D-meson semi-leptonic decays

The size of the charmed «current” quark massm c is estimated from the treatment of D-meson semi-leptonic decays in the current algebra framework. One findsm c≈1200 to 1400 MeV, in agreement with previous determinations.

Rare Formula* - and Strong K- +-Signals in D-Meson Decays and Some Evidence for (Formulas)R Current

It is discussed that a quark-diagram approach is suitable for describing nonleptonic decays of charmed mesons which seem to have no sharp enhancement in contrast to the case of kaon decays. The present experiment shows some characteristic features such as Br(D0→K-ρ+(→π+π0)) ≫Br(D0→K-π+) ≫Br(D0→K*-(→K0π-)π+)+Br(D0→K0ρ0(→π+π-)). In the framework of such an approach, Br(D0→K-ρ+(→π+π0)) ≫Br(D0→K-π+) as well as the other features are shown to be well explained by introducing (cs)R current. The possibility of existence of such a current is shown to be tested also in F-meson decays.

Comments on the D-Meson Decays

Comments on the D-Meson Decays