Wave functions and decay constants of <Emphasis Type="Italic">B</Emphasis> and <Emphasis Type="Italic">D</Emphasis> mesons in the relativistic potential model

With the decay constants of D and D _s mesons measured in experiment recently, we revisit the study of the bound states of quark and antiquark in B and D mesons in the relativistic potential model. The relativistic bound state wave equation is solved numerically. The masses, decay constants and wave functions of B and D mesons are obtained. Both the masses and decay constants obtained here can be seen as consistent with the experimental data. The wave functions can be used in the study of B and D meson decays.     

Phenomenology of neutral D-meson decays and double-flavour oscillations

Decays of neutral D-mesons are considered phenomenologically without invoking any particular models. Special attention is given to cascade decays with intermediate neutral kaons where coherent double-flavour oscillations (CDFO) become possible. We show necessity and unique possibilities of experiments on CDFO. They allow to relate with each other widths and masses of D-meson eigenstates, to separate interference effects due to D ⁰-ˉD ⁰ mixing and/or Cabibbo-favoured vs. doubly-suppressed transitions. Such experiments provide the only known ways to unambiguous model-independent measurements of all CP-violating parameters and of Cabibbo-doubly-suppressed amplitudes, where the New Physics may have more prominent manifestations. Similar experiments would be useful and interesting also for charged D-meson decays to neutral kaons. Received: 13 August 1998     

Weak nonleptonic decays of 3/2+ isobars in SU(3)

Weak transitions of decuplet isobars are expanded in terms of eigen-amplitudes of the direct channel in the framework of SU(3). Starting with the most general weak Hamiltonian and assuming intermediate states to be non-exotic, we obtain ΔI=1/2 rule for Ω⁻ decays. Invoking of the CP invariance forbids all thepv weak processesD(10)→D(10) +P(8). Decays of the charmed multiplets are also discussed in these dynamical considerations. We obtain triplet dominance of charm changing weak Hamiltonian for Ω*⁺⁺ ₃ decays.     

A detailed analysis ofD-,D s - andB-meson transition form factors and the determination of |V cb |

We study various transition form factors in semi-leptonic decays ofD-,D _s -,B- andB _s -mesons using the pole dominance assumption. The vector current form factor is found to have only a negligible contribution to the decay rates involving pseudoscalar to vector transitions. In view of this fact we evaluate the form factors from present experimental data on the exclusive semi-leptonic decay rateΓ and the ratioΓ _l /Γ _T of the longitudinal and transverse partial decay rates. Some non-leptonic two-body decay rates are also investigated using the factorization ansatz. Consistency with the semi-leptonic decays is found. The transition form factors of theD- andD _s -mesons are found to contradict the predictions of quark model. In contrast, the experimental data on the transition form factors ofB-mesons are found to be consistent with the quark model predictions. The KM matrix element |V _cb | is determined to be |V _cb |=0.040±0.010, a value somewhat smaller than is usually chosen.     

Production properties ofD 0,D +,D *+ andD s + in 230 GeV/cπ − andK −-Cu interactions

We have studied the hadronic production of charmed mesons in the NA 32 experiment at CERN. A special trigger together with a high resolution vertex detector consisting of charge coupled devices and silicon microstrip detectors allowed the selection of very clean samples of charmed mesons. We have collected 852 fully reconstructed decays: 60D _s ⁺ →K ⁺ K ^?π⁺, 543D°→K ^?π⁺ andK ^?π⁺π^?π⁺ as well as 249D ⁺→K ^?π⁺π⁺ (or charge conjugate). 147 mesons out of our \({{D^0 } \mathord{\left/ {\vphantom {{D^0 } {\bar D^0 }}} \right. \kern-0em} {\bar D^0 }}\) sample were produced via chargedD ^* state. For all charmed mesons we determine the total production cross-section and study thex _F andp _t ² distributions.     

Nonfactorizable contributions to charm meson (D→ PP) decays

Two-body weak decays of charm mesons into two pseudoscalar mesons are examined employing SU(3) flavor symmetry for the non-factorizable matrix elements. Using certain measured Cabibbo-favored modes, we fix the reduced matrix elements and predict the branching ratios of the Cabibbo-angle suppressed and doubly-suppressed decays of D and D _s mesons.     

Weak annihilation and the effective parameters <Emphasis Type="Italic">a</Emphasis><Subscript>1</Subscript> and <Emphasis Type="Italic">a</Emphasis><Subscript>2</Subscript> in non-leptonic <Emphasis Type="Italic">D</Emphasis> decays

Based on SU(3) flavor symmetry, many of the quark-graph amplitudes in two-body non-leptonic decays of charmed mesons can be extracted from experiment, which enable us to see the relevance and importance of weak annihilation topologies and to determine the complex parameters a₁ and a₂ to test the factorization approach. It is found that a ₂ /a ₁ in and can be different by a factor of 2, indicating that non-factorizable corrections to the latter are far more important than the former. The relative phase between a₁ and a₂ is about 150°. Weak annihilation topologies induced by nearby resonances via final-state rescattering can be described in a model-independent manner. Although the W-exchange contribution in decays is dominated by resonant final-state interactions (FSIs), its amplitude in VP decays (V: vector meson, P: pseudoscalar meson) receives little contributions from FSIs in the quark-antiquark resonance formation. As a consequence, the sign flip of the W-exchange amplitude in and decays, which is needed to explain the relatively real decay amplitudes of , remains unexplained. SU(3) symmetry is badly broken in some Cabibbo-suppressed modes and this can be accounted for by the accumulation of some modest SU(3) violation in individual quark-graph amplitudes. Received: 19 July 2002 / Published online: 20 November 2002     

Chiral SU(4) × SU(4) breaking: masses and decay constants of charmed hadrons

The (4, 4*) ⊕ (4*, 4) model of broken chiral SU (4) × SU (4) symmetry has been used to calculate the third-order coupling constants involving charmed and ordinary pseudoscalar mesons. These coupling constants are exploited to derive some interesting new relations among the masses and decay constants of these charmed particles. Using the known masses and decay constants as inputs, we exploit these relations to predict:F _D = −1·41F _π ,F _F = −1·13F _π ,F _D/F_F = 1·25,m(D _s) = 1·43 GeV,m(F _s) = 1·39 GeV andm(K _s) = 1·02 GeV.     

Measurement of D0, D+, Ds+ and D*+ production in fixed target 920?GeV proton–nucleus collisions

The inclusive production cross sections of the charmed mesons D⁰,D⁺,D_s ⁺ and D^*+ have been measured in interactions of 920 GeV protons on C, Ti, and W targets with the HERA-B detector at the HERA storage ring. Differential cross sections as a function of transverse momentum and Feynman’s x variable are given for the central rapidity region and for transverse momenta up to p_T=3.5 GeV/c. The atomic mass number dependence and the leading to non-leading particle production asymmetries are presented as well. PACS 13.85.Ni; 24.85.+p; 13.20.Fc     

Charm Hadrons in Dense Matter

The properties of the D and D _s charmed mesons in normal nuclear matter density are studied within a coupled channel approach using a t-channel vector-meson exchange mechanism as driving force. The in-medium scattering amplitudes are obtained by solving the Lippmann?CSchwinger equation including Pauli blocking effects and medium self-energies in a self-consistent way.     

Some comments on selection rules for nonleptonic decays of charmed particles

We show that even if only the decays of charmed mesons into two body final states are concerned, the Δn _t=0 rule is stillnot equivalent to sextet dominance. We also isolate the significant contribution of each quark diagram to non-leptonic decays of charmed particles. Thereby pointing out that the recent SLAC observation of Λ _c ⁺ →K ^?Δ⁺⁺ has already given evidence that theW-exchange diagram may be important in charmed baryon decays.     

Gluonic penguin contribution to B \rightarrow \pi \pi decays

We use the light-cone sum rule technique to calculate the contribution of the gluonic penguin operator O _8g to the decay of the B-meson to two pions. Leading-order perturbative and non-perturbative corrections are included, corresponding to hard and soft exchanged gluons, respectively. While the overall contribution of this operator to the decay is small as expected before, we find that the so-called soft-gluon part of this contribution is of the order of the hard-gluon one. This implies that the inclusion of soft gluons in the calculation of matrix elements may be important.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.25.Hw Hadronic decays of mesons: Decays of bottom mesons - 11.55.Hx Sum rules     

Detection of charged charmed D ± mesons in proton-nucleus interactions at 70 GeV with the SVD-2 setup

The results of processing the data of the SERP-E-184 experiment that studied mechanisms of the production of charmed particles in proton-nucleus interactions at 70 GeV and their decays are presented. The data were obtained in irradiating the SVD-2 active target consisting of carbon, silicon, and lead plates with a 70-GeV proton beam. A detailed simulation based on the FRITIOF7.02 and GEANT3.21 packages made it possible to optimize event-selection criteria and to calculate the detection efficiencies for D ^± mesons. After the selection of a signal from the three-body decay of charged charmed D ^± mesons, the inclusive cross sections for their production at threshold energies were measured along with respective lifetimes and parameters of the A dependence of the cross sections. The yields of D mesons and their ratios are compiled in a table along with data fromother experiments and the respective theoretical predictions.     

Probing the interactions of charmed mesons with nuclei in ¯p-induced reactions

We study the perspectives of resonant and nonresonant charmed-meson production in ˉp + A reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances Ψ(3770),Ψ(4040) and Ψ(4160) on various nuclei, their propagation and decay to D,ˉD, D ^*,ˉD^*, D _s,ˉD_s in the medium and vacuum, respectively. The modifications of the open charm vector mesons in the nuclear medium are found to be rather moderate or even small such that dilepton spectroscopy will require an invariant mass resolution of a few MeV. Furthermore, the elastic and inelastic interactions of the open charm mesons in the medium are taken into account, which can be related to (u, d )-, s- or c-quark exchange with nucleons. It is found that by studying the D/ˉD ratio for low momenta in the laboratory ( ? 2 - 2.2 GeV/c) as a function of the target mass A stringent constraints on the c-quark exchange cross-section can be obtained. On the other hand, the ratios D ^- _s/D ⁺ _s as well as D/D ^- _s and D/D ⁺ _s at low momenta as a function of A will permit to fix independently the strength of the s-quark exchange reaction in D ^- _s N scattering. Received: 1 March 2002 / Accepted: 21 March 2002     

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 inDVP (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 ofDPP. The measurement ofD _s ^{+ +} is crucial to test the mechanism of hairpin diagrams.     

Improved search for $B_{s}^{0} - \overline{B}_{s}^{0}$ oscillations

An improved search for B _s ⁰ oscillations is performed in the ALEPH data sample collected during the first phase of LEP, and reprocessed in 1998. Three analyses based on complementary event selections are presented. First, decays of B _s ⁰ mesons into hadronic flavour eigenstates are fully reconstructed. This selection yields a small sample of candidates with excellent decay length and momentum resolution and hi gh average B _s ⁰ purity. Semileptonic decays with a reconstructed D _s ^- meson provide a second sample with larger statistics, high average B _s ⁰ purity, but a poorer momentum and decay length resolution due to the partial decay reconstruction. Finally, semileptonic b-hadron decays are inclusively selected and yield the data sample with the highest sensitivity to B _s ⁰ oscillations, as the much higher statistics compensate for the low average B _s ⁰ purity and poorer time resolution. A lower limit is set atps^-1 at 95% C.L., significantly lower than the expected limit of 15.2 ps^-1. Received: 21 February 2003 / Published online: 11 June 2003     

Quark loop model of radiative meson decays

Radiative meson decays are computed from quark loop anomalies, taking into account the SU(3) splitting of the quark masses. Predicted rates for ?→ηγ,K ^*→Kγ, and η→ππγ are brought into satisfactory agreement with experiment. Formulas are given for the radiative decay rates of charmed las are given for the radiative decay rates of charmed mesons, and a mechanism suggested for suppression of the radiative decays of mesons containing a charmed quark.