Effective meson lagrangian with chiral and heavy quark symmetries from quark flavor dynamics

By bosonization of an extended NJL model we derive an effective meson theory which describes the interplay between chiral symmetry and heavy quark dynamics. This effective theory is worked out in the low-energy regime using the gradient expansion. The resulting effective lagrangian describes strong and weak interactions of heavy B and D mesons with pseudoscalar Goldstone bosons and light vector and axial-vector mesons. Heavy meson weak decay constants, coupling constants and the Isgur-Wise function are predicted in terms of the model parameters partially fixed from the light quark sector. Explicit SU(3)_F symmetry breaking effects are estimated and, if possible, confronted with experiment.     

Radiative leptonic decays of heavy mesons in heavy quark limit

We study the radiative leptonic decays of heavy mesons within the covariant light-front model. Using this model, both the form factors F_V and F_A have the same form when the heavy quark limit is taken. In addition, the relation between the form factor F_V and the decay constant of a heavy meson F_H is obtained. The hadronic parameter β can be determined by the parameters appearing in the wave function of the heavy meson. We find that the value of β is not only quite smaller than the one in the non-relativistic case, but also insensitive to the value of the light quark mass m_q. These results mean that the relativistic effects are very important in this work. We also obtain that the branching ratio of B→lν_lγ is about (1.40–1.67)×10^-6, in agreement with the general estimates in the literature. PACS 12.39.Hg; 13.40.Gp     

Weak radiative decay Λ b →Λγ in the heavy quark effective theory

The weak radiative decay Λ _b →Λγ is studied in the heavy quark effective theory treatings-quark as heavy. This rare decay is induced by the short distance electromagnetic penguins. Including corrections of the order of (1/m _Q), we obtain the transition matrix element and the corresponding decay width. The Isgur-Wise function is evaluated in the largeN _c limit and the branching ratio obtained is 1.48×10⁻⁵.     

Properties of<Emphasis Type="Italic">B</Emphasis><Subscript>c</Subscript> meson

The mass spectrum ofcb meson is investigated with an effective quark-antiquark potential of the form -α_c/r +Ar ^νwith ν varying from 0.5 to 2.0. TheS andP-wave masses, pseudoscalar decay constant, weak decay partial widths in spectator model and the lifetime ofB _cmeson are computed. The properties calculated here are found to be in good agreement with other theoretical and experimental values at potential index,ν = 1     

Semileptonic B<Subscript>s</Subscript>→D<Subscript>sJ</Subscript>(2460)lν decay in QCD

Using three point QCD sum rule methods, the form factors relevant to semileptonic B_s→D_sJ(2460)ℓν decay are calculated. The q² dependences of these form factors are evaluated and compared with the heavy quark effective theory predictions. The dependence of the asymmetry parameter α, characterizing the polarization of the D_sJ meson, on q² is studied. The branching ratio of this decay is also estimated, and it is shown that it can easily be detected at LHC.     

Unified QCD determination of all pseudoscalar leptonic decay constants

Leptonic decay constants of all pseudoscalar mesons are determined in QCD by means of a new QCD sum-rule method. In the light meson and heavy quark limit the results are very similar and also agree with the well-known PCAC and scaling predictions respectively. The corrections to light meson pole dominance are generally small while those to the heavy quark limit are found to be sensitive to the binding energy (i.e. meson and quark mass differences). For standard values of quark masses we obtainf =132 MeV,f _k=161 MeV,f _B=128±28 MeV,f _D=175±13 MeV,f _Bs=144±30 MeV andf _Ds=193±12 MeV.Work supported by Bundesministerium für Forschung und Technologie (BMFT) under contract No. 06MZ758     

Heavy quark 1/m Q expansion of meson weak decay form factors in the relativistic quark model

The method of systematical expansion in the inverse powers of the heavy quark masses of the weak current matrix elements between heavy meson states is developed in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. The comparison of the first and second order terms of this expansion with the structure predicted by the heavy quark effective theory imposes strong constraints on the form of the long-range confining potential of quark-antiquark interaction. It is found that the confinig $q\bar q$ potential is effectively vector, while scalar potential is anticonfining and helps to reproduce the correct nonrelativistic limit. At large distances quarks have nonperturbative anomalous chromomagnetic moments. The obtained values of the potential parameters are in accord with the ones found in our previous consideration of meson masses and decay rates. We calculate the Isgur-Wise function. The first and the second order form factors within 1/m _Q expansion.     

Two body non-leptonic decaysB →Dπ with heavy quark and chiral symmetry

We have analysed the two body non-leptonic charmed-meson decays of heavyB meson based on the factorization assumption. The transition matrix elements and the corresponding decay widths are calculated in the heavy quark and chiral symmetry limit and the Isgur-Wise function present in the expression is determined by the wave function model of Aliet al. The results obtained are quite interesting and agree reasonably well with the experimental data.     

Heavy-to-Light Form Factors in the Quark Model with Infrared Heavy-Quark Propagators

We calculate the heavy-to-light form factors in a relativistic quark model with infrared heavy-quark propagators. Their -dependence in the physical region is defined by two parameters: the “infrared” parameter characterizing the infrared behaviour of the heavy quark and the mass difference of the heavy meson and the heavy quark . It is found that the values of the and form factors at are in excellent agreement with the available experimental data and other approaches whereas for transitions these values are found to be larger than those of several other models. The obtained form factors are used to calculate the widths of the semileptonic decays of and mesons. A comparison of our results with available experimental data and other approaches is presented. Received January 31, 1997; revised July 15, 1997; accepted for publication January 20, 1998     

Some two body non-leptonicB decays and estimation off D in the heavy quark effective theory

We have studied some of the two body nonleptonic decays ofB meson in the context of heavy quark effective theory using factorization hypothesis. Treatinga ₁ as a free parameter, we have obtained its value asa ₁=0.822±0.045, by correlating the experimental and predicted branching ratio for process. With this value ofa ₁ the branching ratios obtained for other decay channels are in good agreement with the experiment. The decay constant ofD meson is extracted to be 280.82 MeV. Heavy quark spin symmetry has also been tested.     

Leading logarithms of heavy quark masses in processes with light and heavy quarks

The matrix elements of operators containing both heavy quark (Q) and light quark (q) fields can contain large logarithms of the type ln(m_Q²/μ²), where μ is a typical QCD mass scale and m_Q is the heavy quark mass. We outline a method for summing leading logarithms of this type. We apply it to the decay constant f_M of a low lying pseudoscalar meson M with Q̄q flavor quantum numbers and predict the ratios of decay constants for mesons with different heavy flavors. We also apply it to a matrix element of a four-quark operator which is relevant for B⁰−B̄⁰ mixing.     

Hadronic decays of N and Δ resonances in a chiral quark model

π and η decay modes of light baryon resonances are investigated within a chiral quark model whose hyperfine interaction is based on Goldstone-boson exchange. For the decay mechanism a modified version of the ³ P ₀ model is employed. Our primary aim is to provide a further test of the recently proposed Goldstone-boson exchange constituent quark model. We compare the predictions for π and η decay widths with experiment and also with results from a traditional one-gluon exchange constituent quark model. The differences between nonrelativistic and semirelativistic versions of the constituent quark models are outlined. We also discuss the sensitivity of the results on the parameterization of the meson wave function entering the ³ P ₀ model. Received: 11 May 2001 / Accepted: 17 September 2001     

A relativistic quark model for mesons with an instanton-induced interaction

We present new results of a relativistic quark model based on the Bethe-Salpeter equation in its instantaneous approximation. Assuming a linearly rising confinement potential with an appropriate spinorial structure in Dirac space and adopting a residual interaction based on instanton effects, we can compute masses of the light mesons up to highest observed angular momenta with a natural solution of the U _A(1) problem. The calculated ground states masses and the radial excitations describe the experimental results well. In this paper, we will also discuss our results concerning numerous meson decay properties. For processes like π⁺/K ⁺↦e ⁺υ_eγ and 0^-↦γγ at various photon virtualities, we find a good agreement with experimental data. We will also comment on the form factors of the K _?3 decay and on the decay constants of the π, K and η mesons. For the sake of completeness, we will furthermore present the electromagnetic form factors of the charged π and K mesons as well as a comparison of the radiative meson decay widths with the most recent experimental data. Received: 28 August 2000 / Accepted: 12 September 2000     

Current non-conservation effects in ultra-high energy neutrino interactions

The overall hardness scale of the ultra-high energy neutrino-nucleon interactions is usually estimated as Q ² ∼ m _w ² The effect of non-conservation of weak currents pushes this scale up to the top quark mass squared and changes dynamics of the scattering process. The Double Leading Log Approximation provides simple and numerically accurate formula for the top-bottom contribution to the total cross section σ^νN . Corresponding correction to σ^νN appears to be numerically large. It is comparable with the leading contribution evaluated in the massless quark approximation.     

Two body non-leptonic Λ b decays in the largeN c limit

The two body non-leptonic Λ _b decays are analysed in the HQET with factorization approximation and largeN _c limit. In this limit, Λ _b and Λ _c baryons can be treated as the bound states of chiral soliton and heavy meson, and consequently the Isgur-Wise function comes out in a straight forward manner. The results obtained remain well below their previously predicted upper limit.     

DsJ (2317) meson production at RHIC

We study the production of D _sJ (2317) mesons in relativistic heavy ion collisions using the quark coalescence model. The predicted D _sJ (2317) abundance depends sensitively on the quark structure of the D _sJ (2317) meson. We have also evaluated the absorption cross sections of the D _sJ (2317) meson by π, ρ, kaon and K* in a phenomenological hadronic model. We find that the final yield of D _sJ (2317) mesons remains sensitive to its initial number produced from the quark-gluon plasma, providing thus the possibility of studying the quark structure of the D _sJ (2317) meson and its production mechanism in relativistic heavy ion collisions.     

Constraint on three-Higgs-doublet model parameters by b → sγ decay considering possibility of the fourth generation in quark sector

Weak radiative B-meson decay has been studied to find plausible constraints on the complex coupling constants that arise from the diagonalization of the charged scalar mixing matrix in Weinberg three-Higgs-doublet model considering possibility of the fourth generation in quark sector. We examined the range of these complex coupling constants taking in to account corrections up to leading QCD logarithms, using evolution of fourth-generation CKM matrix with CP violation phase approximately equal to zero. Range of the mass of fourth generation down-type quark b′ and that of fourth-generation uptype quark t′ have been taken with due consideration of the constraint imposed by the present experimental value of theρ parameter keeping in view the mass difference of the fourth-generation quark doublet.     

Dispersion approach to quark-binding effects in weak decays of heavy mesons

The dispersion approach based on the constituent quark picture and its applications to weak decays of heavy mesons are reviewed. Meson interaction amplitudes are represented within this approach as relativistic spectral integrals over the mass variables in terms of the meson wave functions and spectral densities of the corresponding Feynman diagrams. Various applications of this approach are discussed:Relativistic spectral representations for meson elastic and transition form factors at spacelike momentum transfers are constructed. Form factors at q² > 0 are obtained by the analytical continuation. As a result of this procedure, form factors are given in the full q² range of the weak decay in terms of the wave functions of the participating mesons.The 1/m_Q expansion of the obtained spectral representations for the form factors for the particular limits of the heavy-to-heavy and heavy-to-light transitions are analysed. Their full consistency with the constraints provided by QCD for these limits is demonstrated.Predictions for form factors for B_(s) and D_(s) decays to light mesons are given.The B → γℓν decay and the weak annihilation in rare radiative decays are considered. Nonfactorizable corrections to the B⁰ mixing are calculated.Inclusive weak B decays are analysed and the differential distributions are obtained in terms of the B meson wave function.