Decays Of Charmed Mesons Research Articles

Hadronic charm decays

I summarize recent data on the decay of charmed mesons into hadronic final states which can be used to test factorization models and help elucidate the important role of final-state interactions. I will emphasize recent results on the resonant substructure in charmed-meson decays.

Inclusive decay B--> eta X.

Using data samples taken at the ϒ(4S) resonance and nearby continuum e + e - annihilation with the CLEO-II detector at CESR, we have measured the inclusive branching fraction B(B→ηX)=(17.6±1.1±1.2)%, and the momentum distribution of the η mesons from B meson decay. The η yield cannot be explained as arising solely from the decay of intermediate charmed mesons.

Super-high-energy neutrino spectra in the atmosphere derived from the latest JACEE, MSU, SOKOL and CRN primary spectrum usingZ-factors for p-air collisions estimated from Fermi national accelerator data

The absolute spectra of atmospheric neutrinos in the vertical direction and at large zenith angle have been estimated directly from the primary cosmic-ray nucleon spectrum based on the latest JACEE, MSU, SOKOL and CRN data surveyed by Swordy. The Fermi National Accelerator Laboratory results for pp→K±X, pp→K±X and pp→pX inclusive reactions have been used for theZ-factor calculations for meson production and these were modified for p-air and A-A collisions. The derived muon and electron neutrino spectra at 0° and 89° from non-prompt meson decay are found comparable with the results of Volkova and Zatsepin, and Butkevichet al. An estimate of the prompt muon neutrino spectra at 0° and 89° fromtthe charmed-meson decay has been given along with the earlier results of different authors. The present result for muon neutrino spectra at zenith angles 0° and 89° is found in approximate agreement with the EAS-TOP results of the Gran Sasso group.

Enhancement of charm signal significance in hadroproduction

Given several sets of candidate charm decay events, where some candidates are true decays but most are random background coincidences, it is shown that signal significance can be maximized by assigning to the candidates in each set a weight equal to the ratio of signal to variance in that set. This method improves on the traditional analysis which assigns unit weight to selected candidate events and zero weight to the others. When the sets are defined along a range of some parameter the assigned weights constitute a smooth function of the value of the parameter. The technique is generalized to a multiplicity of parameters, and the utility of the method is demonstrated by application to the charmed meson decay D0 → K−π+ (plus charge conjugate) signal in Fermilab Experiment E769.

Radiative weak decays of charm mesons.

We address Standard Model predictions for flavor-changing radiative transitions of the pseudoscalar charm mesons. Short-distance contributions in $D$ radiative transitions are contrasted with those in B decays. A full analysis is presented of the $c\to u+\gamma$ electromagnetic penguin amplitude with QCD radiative corrections included. Given the importance of long-range effects for the charm sector, special attention is paid to such contributions as the vector dominance and pole amplitudes. A number of two-body final states in exclusive charm radiative decays is considered and the corresponding branching ratio predictions are given.

QUASI TWO-BODY DECAYS OF CHARM MESONS

Quasi two-body decays of charm mesons are studied by using a hard-meson approximation in which the amplitude M is given by M≃METC+MS. The surface term MS is given by a sum of all possible pole amplitudes involving contributions of four-quark and hybrid mesons in addition to ground-state [Formula: see text] mesons. Contributions of multihadron intermediate states are taken in the form of METC. The spectator type of decays can have significant contributions of s-channel poles of four-quark mesons. In the annihilation type of decays, s-channel hybrid-meson poles can play an important role. The mixed type of decays can have all the pole contributions of the ground-state [Formula: see text], possible hybrid and four-quark mesons in the s-channel. The estimated branching ratios, [Formula: see text] and [Formula: see text] are of ordinary size, in contrast with the factorization which predicts very large rates for these decays. The [Formula: see text] and [Formula: see text] decays can be suppressed in consistency with the other decays.

Cabibbo-favoured decays of charm mesons to pseudoscalar and axial-vector mesons

In this paper we study weak decays of D and Ds mesons emitting pseudoscalar and axial-vector mesons in the ISGW (Isgur-Scora-Grinstein-Wise) quark model using a factorization scheme. Branching ratios for the Cabibbo-angle-favoured decays are calculated. Like the BSW model, here also the calculated branching ratios are smaller than the observed values by a factor of 2-5. We discuss the missing physics that may bridge the gap between theory and experiment.

Charm meson decay into the final states Ks0K+ and [formula omitted

We have made a new measurement of the branching ratio Γ(D + → K 0 K +) Γ(D + → K 0 π +) and the first measurement of Γ(D + → K 0 K ∗+) Γ(D + → K 0 π +) . The data were accumulated in the 1990–1991 fixed target running period of Fermilab high energy photoproduction experiment E687. We measure Γ(D + → K 0 K +) Γ(D + → K 0 π +) = 0.25 ± 0.04 ± 0.02 and Γ(D + → K 0 K ∗+) Γ(D + → K 0 π +) = 1.1 ± 0.3 ± 0.4 .

Results on charmed meson decay from the WA82 experiment at the CERN omega spectrometer

The WA82 experiment has collected data with the Ω′ spectrometer at the CERN SPS. Its aim was a high-statistics study of charm hadroproduction, using a silicon microstrip vertex detector and a trigger on impact parameter. WA82 is also studying rare decay modes for charm. Latest results on non-leptonic charmed meson decay branching ratios are presented here, including the study of doubly Cabibbo-suppressed modes for D+. This analysis, using the particle identification provided by a Ring Imaging CHerenkov detector (RICH), gives an indication for a new decay mode, D+→K-K+K+. An upper limit for the D+→K+π-π+ mode branching ratio is also obtained.

SU(3) breaking effects in charmed meson decays

The decay rates of D + → π + π 0 and D 0 → K + π − recently measured by CLEO give the ratios R 1 = 2¦ V cs V cd ¦ 2γ (D + → π +π 0) γ(D + → K 0π +) = 3.29±1.16 and R 2 = ¦ V cs ∗V ud (V cd ∗V us) ¦ 2γ (D 0 → K +π −) γ(D 0 → K −π +) = 2.92±1.34 . Both are about three times of those expected from SU(3) symmetry. We show that, in the large- N c factorization approach, such large SU(3) violations can be accounted for by the accumulations of several small SU(3)-breaking effects. An important requirement is the relative magnitude of the form factors, ƒ + Dπ(0) > ƒ + DK(0) .

RECENT RESULTS ON SEMIMUONIC DECAYS OF CHARM MESONS FROM FERMILAB EXPERIMENT E653

Fermilab experiment E653 has recently reported several results on the semimuonic decays of charm mesons. In this paper we review these results, which include the measurement of form factor ratios in [Formula: see text], the first measurement of form factor ratios in [Formula: see text], the first observations of [Formula: see text], and of the Cabibbo disfavored channel D+ → ρ0μ+ν, and an upper limit for rare D0 decays.

Limits for four- and five-prong semimuonic charm meson decays

Upper limits at the 90% confidence level are presented for four- and five-prong semimuonic decays of charm mesons. From a study of four-prong vertices we find B(D0 → K−π+π−μ+ν)/B(D0 → K−μ+ν) < 0.037 and B (D0 → (K∗ (892)π)−μ+ν)/B(D0 → K−μ+ν) < 0.043. The five-prong vertices yield the result B(DS+ → η′μ+ν) / B(DS+ → φμ+ν) < 1.6.

Ds+--> pi + eta and pi + eta ' decays.

From a perspective in which the dynamical contribution of hadrons is manifested, Cabibbo-angle-favored two-body decays of charm mesons into final states involving η or η' are studied in consistency with the other charm meson decays

Two-body decays of charm mesons and the role of exotic mesons.

Two-body decays of charm mesons (except for decays into the final states involving [eta] or [eta][prime]) are studied from a perspective in which dynamical contributions of hadrons are explicitly taken into account. All the observed values of branching ratios for the two-body decays of charm mesons are reproduced well. In particular, a solution to the well-known puzzle, [Gamma]([ital D][sup 0][r arrow][ital K][sup +][ital K[minus]])/[Gamma]([ital D][sup 0][r arrow][pi][sup +][pi][sup [minus]])[congruent]2--3, is presented. Contributions of exotic ([ital QQ])([ital [bar Q][bar Q]]) mesons can explain the large violation of the charm counterpart of the [vert bar][Delta][ital I][vert bar]=1/2 rule in consistency with the small violation of the [vert bar][Delta][ital I][vert bar]=1/2 rule in the [ital K][r arrow][pi][pi] decays.

Ways to measure the hairpin diagram in charmed meson decays

The possible presence of hairpin diagrams is analyzed in th model-independent quark-diagram scheme for two-body decays of charmed mesons. Current experimental data do not require the presence of hairpin diagrams in D --> VP (V: vector meson, P: pseudoscalar meson), in accordance with the OZI rule. However, there is a possible indication that they are important in the decay of D --> PP. The measurement of D(s)-+ --> pi+ eta' is crucial to test the mechanism of hairpin diagrams.

Numerical analysis of vector symmetry breaking in charmed meson decays

We analyze hadronic D-decays involving two mesons in the final states based on vector symmetry. We perform multiparameter χ 2-fits to the data and find that while vector symmetry breaking is not overwhelming for the best fit, higher-order corrections are required to reproduce data.

Lattice study of semileptonic decays of charm mesons into vector mesons.

We present our lattice calculation of the semileptonic form factors for the decays {ital D}{r arrow}{ital K}{sup *}, {ital D}{sub {ital s}}{r arrow}{phi}, and {ital D}{r arrow}{rho} using Wilson fermions on a 24{sup 3}{times}39 lattice at {beta}=6.0 with 8 quenched configurations. For {ital D}{r arrow}{ital K}{sup *}, we find for the ratio of axial form factors {ital A}{sub 2}(0)/{ital A}{sub 1}(0)=0.70{plus minus}0.16{sub {minus}0.15}{sup +0.20}. Results for other form factors and ratios are also given.

Analyses of the hadronic matrix elements of the B meson decays

The weak hadronic matrix elements are analyzed in the non-leptonic charmed meson decays of the B meson based on the factorization assumption. The relevant form-factors are derived from the new experimental data of ARGUS and CLEO. The factorization with the large N limit works successfully for the single charmed meson decays. For the double charmed meson decays, it may be consistent with the CLEO data if the large final state phase shift is taken in the B → D ∗π decay.

Strange charmed meson decays of [formula omitted] in the factorized hadron currents approximation

Strange charmed meson decays of [formula omitted] in the factorized hadron currents approximation

A lattice study of charmed meson decays

Results of the recent computations of the hadronic matrix elements relevant for semi-leptonic and non-leptonic decays of charmed mesons are presented.