Masuho Oda

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

Cabibbo allowed two-body hadronic weak decays of Λb baryons are analyzed in the factorization approximation. We use the covariant oscillator quark model to evaluate the heavy → heavy and heavy → 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 Λb baryon decaying into Λc + P (V ) are calculated. It is found that the up-down asymmetry is negative in all these decay modes. Furthermore, the prediction Br(Λb → Λ + J/ψ )=2 .49 × 10 −4 is consistent with the recent experimental data. Finally it is pointed out that the CKM-Wolfenstein parameter ρ 2 + η 2 , where η is the CP phase, can be determined from the ratio of the widths Λb → Λ ¯ D 0 and Λb → ΛJ/ψ, independent of the QCD parameter. The value of (ρ 2 + η 2 ) 1/2 calculated in our model agrees very well with the value recently predicted by Rosner.

A universal spring and meson orbital regge trajectories

SummaryIn this paper we report on the essential results of our recent work (S. Ishida andM. Oda:Prog. Theor. Phys.,89, 1033 (1993)) Spectroscopy of light- to heavy-quark confined meson systems, in the limit of no perturbative-QCD effects, is well described by a simple covariant-oscillator quark model (COQM) with a universal spring constant independent of quark flavour.

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

The spectra and form factors of exclusive semi-Ieptonic decays of B-mesons are analyzed, taking account of confined effects of quarks using the covariant oscillator quark model. The predicted B --+ (D*, D)W! spectra with the conventional value of Vcb are fit well to the high-precision experiment. It is also shown the values of Vcb and Vub obtained through decay widths for the B --+ (D, D*, p)W, processes are consistent with the presently accepted values.

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.

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.

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 oscillator quark model using the factorization assumption. The main feature of this model is that it can simultaniously be applied to both heavy → heavy and heavy → 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. The description of exclusive nonleptonic decays of B mesons represents an important and complicated theoretical problem. These decays are nonperturbative in nature and cannot be calculated reliably from the QCD Lagrangian. In contrast to exclusive semileptonic decays, where the weak current matrix elements between meson states are involved, nonleptonic decays require the evaluation of hadronic matrix elements of four local quark operators. To simplify the analysis it is usually assumed that the matrix element of the current-current weak interaction factorizes into the product of two single current matrix elements. Thus the problem reduces to the calculation of the meson form factors, which are contained in the hadronic matrix elements of weak currents as in the case of semileptonic decays, and of the meson decay constants, describing the leptonic decays. This makes the factorization hypothesis 1) a very appealing assumption. Although it is very difficult to prove the factorization hypothesis theoretically within our present understanding of QCD nonperturbative effects, this hypothesis is expected to be valid to a rather good approximation in the case of transitions with large energy release, such as heavy B decays, since the finalmesons carrying l arge momenta escape from the region of interaction, thereby minimizing the effects of a finalstate interaction. Severaltests have been made to prove its validity phenomenologically, 2) and, it has been shown to work well for the description of B meson decays into a D or D ∗ and a light meson. Once the factorization assumption is made, nonleptonic decays are related to the corresponding semileptonic decays.

Strong decays of excited 1D charmed(-strange) mesons in the covariant oscillator quark model

Recently observed charmed mesons, D1*(2760), D3*(2760) and charmed-strange mesons, Ds1*(2860), Ds3*(2860), by BaBar and LHCb collaborations are considered to be plausible candidates for cq¯ 13 DJ (q = u, d, s) states. We calculate the strong decays with one pion (kaon) emission of these states including well-established 1S and 1P charmed(-strange) mesons within the framework of the covariant oscillator quark model. The results obtained are compared with the experimental data and the typical nonrelativistic quark-model calculations. Concerning the results for 1S and 1P states, we find that, thanks to the relativistic effects of decay form factors, our model parameters take reasonable values, though our relativistic approach and the nonrelativistic quark model give similar decay widths in agreement with experiment. While the results obtained for 13 DJ=1,3 states are roughly consistent with the present data, they should be checked by the future precise measurement.Recently observed charmed mesons, D1*(2760), D3*(2760) and charmed-strange mesons, Ds1*(2860), Ds3*(2860), by BaBar and LHCb collaborations are considered to be plausible candidates for cq¯ 13 DJ (q = u, d, s) states. We calculate the strong decays with one pion (kaon) emission of these states including well-established 1S and 1P charmed(-strange) mesons within the framework of the covariant oscillator quark model. The results obtained are compared with the experimental data and the typical nonrelativistic quark-model calculations. Concerning the results for 1S and 1P states, we find that, thanks to the relativistic effects of decay form factors, our model parameters take reasonable values, though our relativistic approach and the nonrelativistic quark model give similar decay widths in agreement with experiment. While the results obtained for 13 DJ=1,3 states are roughly consistent with the present data, they should be checked by the future precise measurement.

Ds1*(2710) and Dsj*(2860) in the Ũ(12)×O(3,1)‐scheme

In order to classify the charmed‐strange mesons, including puzzling Ds0*(2317) and Ds1(2460), and recently observed Ds1*(2710) ans Dsj*(2860), we employ the Ũ(12)×O(3,1) level‐classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2)ρ, which leads to a number of extra states out of conventional SU(6)‐scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S‐ and P‐wave cs mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that Ds0*(2317) and Ds1(2460) are described as 1S0χ and 3S1χ chiralons, forming the SU(2)ρ doublet with the ground‐state Ds and Ds*, respectively. Furthermore, the observed decay properties of Ds1*(2710) is consistently explained as the vector chiralon 1P1χ. On the other hand, it is also found that the controversial narrow state, Dsj*(2860), does not fit as predicted properties of our P‐wave vector chiralon.In order to classify the charmed-strange mesons, including puzzling D{sub s0}*(2317) and D{sub s1}(2460), and recently observed D{sub s1}*(2710) ans D{sub sj}*(2860), we employ the U-tilde(12)xO(3,1) level-classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2){sub {rho}}, which leads to a number of extra states out of conventional SU(6)-scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S- and P-wave cs-bar mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that D{sub s0}*(2317) and D{sub s1}(2460) are described as {sup 1}S{sub 0}{sup {chi}}and {sup 3}S{sub 1}{sup {chi}}chiralons, forming the SU(2){sub {rho}}doublet with the ground-state D{sub s} and D{sub s}*, respectively. Furthermore, the observed decay properties of D{sub s1}*(2710) is consistently explained as the vector chiralon {sup 1}P{sub 1}{sup {chi}}. On the other hand, it is also found that the controversial narrow state, D{sub sj}*(2860), does not fit as predicted properties of our P-wave vector chiralon.

D[sub s1]∗](2710) and [sub D[sub sj]]∗](2860) in the Ũ(12)×O(3,1)-scheme

In order to classify the charmed‐strange mesons, including puzzling Ds0*(2317) and Ds1(2460), and recently observed Ds1*(2710) ans Dsj*(2860), we employ the Ũ(12)×O(3,1) level‐classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2)ρ, which leads to a number of extra states out of conventional SU(6)‐scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S‐ and P‐wave cs mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that Ds0*(2317) and Ds1(2460) are described as 1S0χ and 3S1χ chiralons, forming the SU(2)ρ doublet with the ground‐state Ds and Ds*, respectively. Furthermore, the observed decay properties of Ds1*(2710) is consistently explained as the vector chiralon 1P1χ. On the other hand, it is also found that the controversial narrow state, Dsj*(2860), does not fit as predicted properties of our P‐wave vector chiralon.In order to classify the charmed-strange mesons, including puzzling D{sub s0}*(2317) and D{sub s1}(2460), and recently observed D{sub s1}*(2710) ans D{sub sj}*(2860), we employ the U-tilde(12)xO(3,1) level-classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2){sub {rho}}, which leads to a number of extra states out of conventional SU(6)-scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S- and P-wave cs-bar mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that D{sub s0}*(2317) and D{sub s1}(2460) are described as {sup 1}S{sub 0}{sup {chi}}and {sup 3}S{sub 1}{sup {chi}}chiralons, forming the SU(2){sub {rho}}doublet with the ground-state D{sub s} and D{sub s}*, respectively. Furthermore, the observed decay properties of D{sub s1}*(2710) is consistently explained as the vector chiralon {sup 1}P{sub 1}{sup {chi}}. On the other hand, it is also found that the controversial narrow state, D{sub sj}*(2860), does not fit as predicted properties of our P-wave vector chiralon.

D{sub s1}*(2710) and {sub D{sub s{sub j}}}*(2860) in the U-tilde(12)xO(3,1)-scheme

In order to classify the charmed‐strange mesons, including puzzling Ds0*(2317) and Ds1(2460), and recently observed Ds1*(2710) ans Dsj*(2860), we employ the Ũ(12)×O(3,1) level‐classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2)ρ, which leads to a number of extra states out of conventional SU(6)‐scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S‐ and P‐wave cs mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that Ds0*(2317) and Ds1(2460) are described as 1S0χ and 3S1χ chiralons, forming the SU(2)ρ doublet with the ground‐state Ds and Ds*, respectively. Furthermore, the observed decay properties of Ds1*(2710) is consistently explained as the vector chiralon 1P1χ. On the other hand, it is also found that the controversial narrow state, Dsj*(2860), does not fit as predicted properties of our P‐wave vector chiralon.In order to classify the charmed-strange mesons, including puzzling D{sub s0}*(2317) and D{sub s1}(2460), and recently observed D{sub s1}*(2710) ans D{sub sj}*(2860), we employ the U-tilde(12)xO(3,1) level-classification scheme of hadrons proposed and developed by us in recent years. The scheme has a new degree of freedom, SU(2){sub {rho}}, which leads to a number of extra states out of conventional SU(6)-scheme, named chiralons. Applying this novel classification scheme, we investigate the strong decays of S- and P-wave cs-bar mesons with one pseudoscalar emission by using the covariant oscillator quark model. As a result it is shown that D{sub s0}*(2317) and D{sub s1}(2460) are described as {sup 1}S{sub 0}{sup {chi}}and {sup 3}S{sub 1}{sup {chi}}chiralons, forming the SU(2){sub {rho}}doublet with the ground-state D{sub s} and D{sub s}*, respectively. Furthermore, the observed decay properties of D{sub s1}*(2710) is consistently explained as the vector chiralon {sup 1}P{sub 1}{sup {chi}}. On the other hand, it is also found that the controversial narrow state, D{sub sj}*(2860), does not fit as predicted properties of our P-wave vector chiralon.