Tomohito Maeda

Covariant Quark Representation of Composite Meson Systems and Chiral Symmetry

Assuming spin-independence of the confining force, we give a covariant quark representation of general composite meson systems with definite Lorentz transformation properties. With this representation we are able to deduce automatically the transformation rules of composite mesons for general symmetry operations from those of constituent (exciton)quarks. Applying this, we investigate in particular physical implications of chiral symmetry for meson systems, and point out the possibility of the existence of new meson multiplets.

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.

Chiral Mass Splitting for cs̄ and cn̄ Mesons in the Ũ(12)‐Classification Scheme of Hadrons

We investigate the chiral mass splitting of parity‐doubled J = 0, 1 states for cs and cn meson systems in the Ũ(12)SF‐classification scheme of hadrons, using the linear sigma model to describe the light‐quark pseudoscalar and scalar mesons together with the spontaneous breaking of chiral symmetry, and consequently predict the masses of as‐yet‐unobserved (0+, 1+) cn mesons. We also mention some indications of their existence in the recent published data from the Belle and BABAR Collaborations.

Indications for the Existence of Chiral Particles: the Axial-Vector D1χ and the Scalar B0χ

In a covariant level-classification scheme of hadrons proposed recently, the existence of “chiral particles”, scalar and axial-vector mesons as the partners of the ground-state pseudo-scalar and vector mesons, respectively, were predicted in D and B meson systems, realizing a linear representation of chiral symmetry concerning the light quark. In this work we reanalyze the D^*π mass spectra obtained through Υ(4S) and Z^0 decay and the Bπ spectra obtained through Z^0 decay to show the possibility of the existence of D_1^χ and B_0^χ, respectively.

Radiative decays of light-quark mesons to a pion revisited in the covariant oscillator quark model

The present talk consists of two parts. The first one is allocated for consideration of the dimension of bilocal meson fields for quark-antiquark meson systems, which have been so far treated as the bosonic fields independent of constituent quark flavors, in the covariant oscillator quark model. Revisiting the electromagnetic currents of quark-antiquark meson systems, we show that the bilocal meson fields should be bosonic for light-quark meson systems, while fermionic for heavy-light and heavy-heavy meson systems. In the second part we apply the effective electromagnetic interactions of meson systems derived in the first part to radiative decay processes for the excited states of light-quark mesons. The calculated results for the

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

\pi \gamma

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

decay widths of the

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

a_1(1260)

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

,

Covariant description of composite meson systems and chiral symmetry

a_2(1320)