Covariant Oscillator Quark Model Research Articles

RADIATIVE π-γ TRANSITIONS OF EXCITED LIGHT-QUARK MESONS IN THE COVARIANT OSCILLATOR QUARK MODEL

A study of the light-meson couplings to the single photon in the framework of the covariant oscillator quark model (COQM) is reported. The transition rates of {ρ(770), b1(1235), a1(1260), a2(1320), π2(1670), ρ3(1690), ρ(1700)}± into π±γ, being expected to be measured by the COMPASS collaboration in their Primakoff-reaction experiments, are calculated. It could be useful not only for understanding the internal structures of observed light-quark mesons and their quark-model classification but also for the ongoing experimental studies by COMPASS.

Radiative decays of charmed mesons in the covariant oscillator quark model

We report on a study of the radiative decays for the ground S -wave and the excited P -wave charmed ( c u ¯ , c d ¯ ) mesons applying the covariant oscillator quark model. The obtained results are compared with experimental data including a recently reported D 1 ( 2420 ) 0 → D 0 γ , and other quark-model predictions. These predictions could provide a useful clue as to search for the radiative decays of excited D mesons in the foreseeable future experiments at the B-factories.

Strong Decays of sc Mesons in the Covariant Oscillator Quark Model with the \widetildeU(4)DS ×O(3,1)L-Classification Scheme

Strong Decays of sc Mesons in the Covariant Oscillator Quark Model with the \widetildeU(4)DS ×O(3,1)L-Classification Scheme

Two-photon and one-photon–one-vector meson decay widths of thef0(1370),f2(1270),f0(1710),f2′(1525), andK2*(1430)

We calculate the radiative decay widths, two-photon ($\gamma\gamma$) and one photon-one vector meson ($V\gamma$), of the dynamically generated resonances from vector meson-vector meson interaction in a unitary approach based on the hidden-gauge Lagrangians. In the present paper we consider the following dynamically generated resonances: $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^*_2(1430)$, two strangeness=0 and isospin=1 states, and two strangeness=1 and isospin=1/2 states. For the $f_0(1370)$ and $f_2(1270)$ we reproduce the previous results for the two-photon decay widths and further calculate their one photon-one vector decay widths. For the $f_0(1710)$ and $f_2'(1525)$ the calculated two-photon decay widths are found to be consistent with data. The $\rho^0\gamma$, $\omega\gamma$ and $\phi\gamma$ decay widths of the $f_0(1370)$, $f_2(1270)$, $f_0(1710)$, $f'_2(1525)$ are compared with the results predicted by other approaches. The $K^{*+}\gamma$ and $K^{*0}\gamma$ decay rates of the $K^*_2(1430)$ are also calculated and compared with the results obtained in the framework of the covariant oscillator quark model. The results for the two states with strangeness=0, isospin=1 and two states with strangeness=1, isospin=1/2 are predictions that need to be tested by future experiments.

Covariant oscillator quark model for glueballs and baryons

An analytic resolution of the covariant oscillator quark model for a three-body system is presented. Our harmonic potential is a general quadratic potential which can simulate both a {delta}-shape configuration or a simplified Y-configuration where the junction is located at the center of mass. The mass formulas obtained are used to compute glueball and baryon spectra. We show that the agreement with lattice and experimental data is correct if the Casimir scaling hypothesis is assumed. It is also argued that our model is compatible with pomeron and odderon approaches.

Retardation effects in the rotating string model

A new method to study the retardation effects in mesons is presented. Inspired from the covariant oscillator quark model, it is applied to the rotating string model in which a non zero value is allowed for the relative time between the quark and the antiquark. This approach leads to a retardation term which behaves as a perturbation of the meson mass operator. It is shown that this term preserves the Regge trajectories for light mesons, and that a satisfactory agreement with the experimental data can be obtained if the quark self-energy contribution is added. The consequences of the retardation on the Coulomb interaction and the wave function are also analyzed.

Weak Radiative Decay Width B ->K* in COQM Including Long-Range Contributions

The study of the weak radiative decay B → K∗γ has attracted considerable attention as a test of the Standard Model (SM) since the CLEO experiment 1) gave the preliminary value of the branching ratio Br(B → K∗γ) = (4.0±1.7±0.8)×10−5. This decay mode arises from the quark level process b → sγ via flavor changing neutral current (FCNC). There are two essential contributions to the amplitude of the weak radiative decay b → sγ, the short distance (SD) contribution due to the electromagnetic penguin and the long distance (LD) contribution due to strong interactions. The LD contribution is calculated using the vector meson dominance (VMD) method 2) at the quark level as b → s[cc], followed by the conversion [cc] → γ. In order to obtain the relevant ratio Br(B → K∗γ), it is necessary to take into account the quark confined effect. The estimation of this effect is a problem of non-perturbative QCD, and we must use some models presently. In a previous work 3) we studied the problem of determining the width of this decay by using the covariant oscillator quark model (COQM), 4) where we have taken into account only the leading SD contribution. In the present work we improve our calculation by adding the LD contribution.

Semi-Leptonic B Meson Decays to Excited D Mesons in the Covariant Oscillator Quark Model

The spectra and branching ratios of the weak semi-leptonic B meson decays to the first excited D mesons are predicted, taking into account the confined effects of quarks using the covariant oscillator quark model (COQM). In the COQM the same relation between general weak transition form factors as that in HQET is derived, and the concrete form of the Isgur-Wise function is given with no free parameters. Our results are somewhat different from those of other models. The present experimental data are not sufficient for comparison.

Weak Radiative Decay b -> and Quark-Confined Effects in the Covariant Oscillator Quark Model

Motivated by the observation of the decay B to K* gamma by the CLEO collaboration, we have systematically analyzed the weak radiative decay Lambda_b to Lambda gamma, evaluating the confined effects of quarks in the covariant oscillator quark model. This decay process receives both short distance (electromagnetic penguins at the one loop level) the long distance contributions in the quark level. The long distance contributions are analyzed using the vector meson dominance (VMD) method. The estimated branching ratio is found to be 0.23 times 10^-5.

Mass Spectra and Wave Functions of Meson Systems and the Covariant Oscillator Quark Model as an Expansion Basis

n, cand bb meson systems within the framework of the covariant oscillator quark model with the boosted LS-coupling scheme. We solve nonperturbatively an eigenvalue problem for the squared-mass operator, which in- corporates the four-dimensional color-Coulomb-type interaction, by taking a set of covariant oscillator wave functions as an expansion basis. We obtain mass spectra of these meson systems, which reproduce quite well their experimental behavior. The resultant manifestly covariant wave functions, which are applicable to analyses of various reaction phenomena, are given. Our results seem to suggest that the present model may be considered effectively as a covariant version of the nonrelativistic linear-plus-Coulomb potential quark model.

Exclusive Semi-Leptonic Decays of Heavy Mesons in the Covariant Oscillator Quark Model

The spectra of exclusive semi-leptonic decays of heavy b-quark and c-quark mesons are derived, taking account of confined effects of quarks in the covariant oscillator quark model (COQM). The respective partial widths are also calculated using the standard values of KM-matrix elements. In COQM all kinematics and effective interactions are expressed in a manifestly covariant and unified way. The effective weak currents are given as overlapping integrals between initial and final hadron “wave functions” and lead to the many relations among the form factors, including those derived by HQET in the case of heavy-light quark meson systems. On the other hand, for reference the values of the relevant KM-matrix elements, estimated in COQM directly from each experimental decay width, are also given.

Exclusive Weak Radiative Decays of B Mesons in the Covariant Oscillator Quark Model

Exclusive weak radiative B meson decays are studied using the covariant oscillator quark model. The branching ratios for the processes B0 to K*0 gamma and B to K* gamma have been estimated. These are in reasonable agreement with the available experimental data. The calculation has been extended to the CKM-suppressed decay processes B- to rho- gamma and Bs to K*0 gamma .

Non-Leptonic Two-Meson Decays of B Mesons in the Covariant Oscillator Quark Model with Factorization Ansatz

Exclusive nonleptonic bottom meson decays are studied in the covariant osillator quark model using the factorization assumption. The main feature of this model is that it can simultaniously be applied to both heavy to heavy and heavy to light transitions, satisfying the constraints of the heavy quark effective theory (HQET) in the appropriate limit. The results obtained are in overall agreement with the present experimental data for various B decays.

Hadronic Weak Decays of b Baryon in the Covariant Oscillator Quark Model

Cabibbo allowed two-body hadronic weak decays of Lambda b baryons are analyzed in the factorization approximation. We use the covariant oscillator quark model to evaluate the heavy to heavy and heavy to light form factors. When applied in the heavy quark limit, our form factors satisfy all the constraints imposed by heavy quark symmetry. The decay rates and up-down asymmetries for Lambda b baryon decaying into Lambda c +P(V) are calculated. It is found that the up-down asymmetry is negative in all these decay modes. Furthermore, the prediction Br(Lambda b to Lambda+J/psi)=2.49 times 10^-4 is consistent with the recent experimental data. Finally it is pointed out that the CKM-Wolfenstein parameter rho^2+eta^2, where eta is the CP phase, can be determined from the ratio of the widths Lambda b to Lambda bar D^0 and Lambda b to Lambda J/psi, independent of the QCD parameter. The value of (rho^2 +eta^2)^1/2 calculated in our model agrees very well with the value recently predicted by Rosner.

Spectra of Exclusive Semi-Leptonic Decays of B-Meson in the Covariant Oscillator Quark Model

The spectra and form factors of exclusive semi-leptonic decays of B-meson are analyzed, taking account of confined effects of quarks by the Covariant Oscillator Quark Model. The predicted B --> (D*,D)l nubar_l spectra with the conventional value of V_cb are fit well to the high-precision experiment. It is also shown the values of V_cb and V_ub obtained through decay widths for the B --> (D,D*,rho)l nubar_l processes are consistent with the presently accepted ones.

Spin-Independent Confining Force and a Boosted LS-Coupling Scheme for Covariant Description of Hadron World

The essential kinematical framework and physical backgrounds of the covariant oscillator quark model are reviewed in the light of its recent progress, obtained through a universal treatment of hadron mass spectra and of weak transition form factors in the light-through-heavy quark meson and baryon systems. Recently the heavy quark effective theory 0 (HQET) has aroused wide interests among high energy physicists as a promising effective theory describing strong interactions of heavy quarks in the framework of QCD. Especially it is interesting that HQET, resorting to the heavy quark symmetry (HQS), is able to derive the relations 2 > among weak transition form factors (FF's) in the heavy-light-quark system and to evaluate the genuine (without the binding effects of heavy hadrons) of relevant Kobayashi-Maskawa (KM) matrix element, Vcb, in the limit of infinite heavy quark mass mQ=oo. It may be interesting and quite desirable if there is any means to estimate similarly the other elements of KM-matrix, although the straight extension of HQET seems to be almost impossible. Here we should like to mention that the same FF relations and a similar value 3 > of Vcb are also obtained in the covariant oscillator quark model*>,ts> (COQM), where all meson and baryon systems with any flavor­

Spin-Independent Confining Force and a Boosted LS-Coupling Scheme for Covariant Description of Hadron World

The essential kinematical framework and physical backgrounds of the covariant oscillator quark model are reviewed in the light of its recent progress, obtained through a universal treatment of hadron mass spectra and of weak transition form factors in the light-through-heavy quark meson and baryon systems.

Effective Weak Transition Currents of Light-through-Heavy-Quark Meson and Baryon Systems in the Covariant Oscillator Quark Model

Effective weak transition currents for meson and baryon systems with light-through-heavy flavors are derived unifiedly in COQM. From these we can deduce many relations among relevant form factors which concern mesons and baryons of all possible flavor-configurations; including those in heavy-light-quark systems, generally believed to be due to the heavy-quark symmetry.

Effective Weak Transition Currents of Light-through-Heavy-Quark Meson and Baryon Systems in the Covariant Oscillator Quark Model

Effective Weak Transition Currents of Light-through-Heavy-Quark Meson and Baryon Systems in the Covariant Oscillator Quark Model

Weak Transition Form Factor of heavy-light mesons in the Covariant Oscillator Quark Model

Weak Transition Form Factor of heavy-light mesons in the Covariant Oscillator Quark Model