18648204
Decay Constants and Semileptonic Form Factors of Pseudoscalar Mesons 1
AbstractA relativistic constituent quark model is adopted to give an uniﬁed description of the leptonic andsemileptonic decays of pseudoscalar mesons (π, K, D, D s , B, B s ). The calculated leptonic decayconstants and form factors are found to be in good agreement with available experimental data andthe results of other approaches. Eventually, the model is found to reproduce the scaling behavioursof spin-ﬂavor symmetry in the heavy-quark limit. 1 Introduction Semileptonic decays of pseudoscalar mesons allow to evaluate the elements of the Cabibbo–Kobayashi–Maskawa (CKM) matrix, which are fundamental parameters of the Standard Model. The decay K → πeνprovides the most accurate determination of V us , the semileptonic decays of D and B mesons, D →K(K ∗ )lν, B → D(D ∗ )lν and B → π(ρ)lν, can be used to determine |V cs |, |V cb | and |V ub |, respectively.This program can be performed if the non-perturbative QCD eﬀects, which are parameterized by theform factors, are known. Up to now, these form factors cannot be evaluated from ﬁrst principles, thusmodels, more or less connected with QCD, are usually considered for this purpose. Here we discuss arelativistic quark model [1], previously used to study the baryon form factors [2].This model is based on an eﬀective Lagrangiandescribingthe coupling ofmesons with their constituentquarks. The physical processes are described by the one-loop quark diagrams and meson-quark verticesrelated to the Bethe-Salpeter amplitudes. In principle, the vertex functions and quark propagatorsshouldbe given by the Bethe-Salpeter and Dyson-Schwinger equations, respectively. This kind of analysis isprovided by the Dyson-Schwinger Equation (DSE) studies [3] and an uniﬁed description of light andheavy meson observables was carried out in [4, 5]. Here, instead, we use free propagators for constituentquarks and consider a Gaussian vertex function as Bethe-Salpeter conﬁning function. The adjustableparameters, the widths of Bethe-Salpeter amplitudes in momentum space, and the constituent quarkmasses, are determined from the best ﬁt of available experimental data and some lattice simulations.Our results are in good agreement with experimental data and other approaches. We also reproduce thespin-ﬂavor symmetry relations and scaling for leptonic decay constants and semileptonic form factors inthe heavy-quark limit [6].An approach similar to the one presented here, can be found in [7]. That model is based on meson-quark interactions, so the mesonic transition amplitudes are described by diagrams with heavy mesonsattached to quark loops. The free propagator has been used for light quarks, while the quark propagatorobtained in the heavy-quark limit has been adopted for heavy quarks.
198488906
The Box anomaly and radiative decays of eta(eta-prime) mesons
We report on a confined quark model calculation of the transition form factors for the radiative decays of \eta(\eta')->\gamma l^+l^- and \eta(\eta')->\gamma\pi^+\pi^-. The \eta-\eta' mixing angle \theta_P is determined from the set of data on the electromagnetic \eta(\eta') decays. It is found that \theta_P\sim -16.5. The analysis of the dipionic mass distribution in the decay \eta'->\gamma\pi^+\pi^- confirms the existence of a non-resonant contribution which is the box anomaly.
117141257
Multiquark states in the covariant quark confinement model
This talk reviews the last applications of the covariant quark model for studying the properties of the multiquark states: B_s-meson (quark-antiquark state), light baryons (three-quark states) and tetraquark (four-quark state). The form factors of the B(B_s)-> P(V)-transitions are evaluated in the full kinematical region of momentum transfer squared. The widths of some B_s-nonleptonic decays are calculated. The static properties of the proton and neutron, and the \Lambda-hyperon (magnetic moments and charge radii) and the behavior of the nucleon form factors at low momentum transfers are described. The consequences of treating the X(3872) meson as a tetraquark bound state are explored. The decay widths of the observed channels X->J/\psi+2\pi (3\pi) and X-> \bar D^0 + D^0+\pi^0 via the intermediate off--shell states X-> J/\psi+\rho(\omega) and X-> \bar D + D^* are calculated. Its one-photon decay X-> \gamma+ J/\psi is also analyzed.
995629
The Semileptonic decays of the $B_c$ meson
We study the semileptonic transitionsBc → �c, J/ , D, D ∗ , B, B ∗ , Bs, B ∗ s in the framework of a relativistic constituent quark model. We use experimental data on leptonic J/ decay, lattice and QCD sum rule results on leptonic Bc decay, and experimental data on radiativec transitions to adjust the quark model parameters. We compute all form factors of the above semileptonic Bc-transitions and give predictions for various semileptonic Bc decay modes including their �-modes when they are kinematically accessible. The impli- cations of heavy quark symmetry for the semileptonic decays are discussed and are shown to be manifest in our explicit relativistic quark model calcu- lation. A comparison of our results with the results of other calculations is performed.
117870749
On the mesonic Lagrangian of order p^6 in chiral SU(2)
We show that the number of operators in the presently known mesonic chiral Lagrangian of order p^6 in the two-flavour sector can be reduced by at least one from 57 to 56 by providing an explicit relation among the operators. We briefly discuss the relevance of this new relation.
6599022
LEPTONIC AND SEMILEPTONIC DECAYS OF PSEUDOSCALAR MESONS
Abstract We employ the relativistic constituent quark model to give a unified description of the leptonic and semileptonic decays of pseudoscalar mesons ( π , K , D , D s , B , B s ). The calculated leptonic decay constants and form factors are found to be in good agreement with available experimental data and other approaches. We reproduce the results of spin-flavor symmetry in the heavy quark limit.
7790135
Primary postulates of the standard model as consequences of the composite nature of the fundamental fermions
SummaryA field model of two-component fermions is described, the consequences of which coincide in the main with primary postulates of the standard model. Such a model can be constructed for 4 generations at the minium. Peculiarities of the relative coordinate space, determining in general an internal symmetry group, are considered. Analogues of the Higgs fields appear in the model naturally after transition to the Grassmannian extra coordinates.
18867033
A quantum gravitational model of redshifts
The main features of an alternative model of redshifts are described here. The model is based on conjectures about an existence of the graviton background with the Planckian spectrum and a super-strong character of quantum gravitational interaction. This model is connected with the assumed quantum mechanism of gravity. A behavior of two theoretical functions of a redshift $z$ in this model - the geometrical distance $r(z)$ and the luminosity distance $D_{L}(z)$ - and an existence of two different cosmological horizons for any observer are discussed.
13058665
Galaxy number counts in a presence of the graviton background
In the model of low-energy quantum gravity by the author, cosmological redshifts are caused by interactions of photons with gravitons. Non-forehead collisions with gravitons will lead to an additional relaxation of any photonic flux. Using only the luminosity distance and a geometrical one as functions of a redshift in this model, theoretical predictions for galaxy number counts are considered here. The Schechter luminosity function with $\alpha =-2.43$ is used. The considered model provides a good fit to galaxy observations by Yasuda et al. (AJ, 122 (2001) 1104) if the same K-corrections are added. It is shown that observations of $N(z)$ for different magnitudes $m$ are a lot more informative than the ones of $N(m).$
118722197
Testing Lorentz invariance of dark matter
We study the possibility to constrain deviations from Lorentz invariance in dark matter (DM) with cosmological observations. Breaking of Lorentz invariance generically introduces new light gravitational degrees of freedom, which we represent through a dynamical timelike vector field. If DM does not obey Lorentz invariance, it couples to this vector field. We find that this coupling affects the inertial mass of small DM halos which no longer satisfy the equivalence principle. For large enough lumps of DM we identify a (chameleon) mechanism that restores the inertial mass to its standard value. As a consequence, the dynamics of gravitational clustering are modified. Two prominent effects are a scale dependent enhancement in the growth of large scale structure and a scale dependent bias between DM and baryon density perturbations. The comparison with the measured linear matter power spectrum in principle allows to bound the departure from Lorentz invariance of DM at the per cent level.
16422963
May gravitons be super-strong interacting particles?
A scheme, in which gravitons are super-strong interacting, is described. The graviton background with the Planckian spectrum and a small effective temperature is considered as a reservoir of gravitons. A cross-section of interaction of a graviton with any particle is assumed to be a bilinear function of its energies. Any pair of bodies are attracting not due to an exchange with its own gravitons, but due to a pressure of external gravitons of this background. A graviton pairing is necessary to obtain classical gravity. Any divergencies are not possible in such the model because of natural smooth cut-offs of the graviton spectrum from both sides. Some cosmological consequences of this scheme are discussed, too. Also it is shown here that the main conjecture of this approach may be verified at present on the Earth.