ar X iv : h ep - p h / 01 02 25 8 v 1 2 1 Fe b 20 01 1 Property of Chiral Scalar and Axial - Vector Mesons in Heavy - Light Quark System Muneyuki

We investigate the properties of new scalar XB, XD and axial-vector XB * , XD * mesons, which are recently predicted, in the covariant meson-classification scheme, to exist as the partners of ground-state pseudoscalar B, D and vector B * , D * mesons, respectively, realizing a linear representation of chiral symmetry for the light quark component in heavy-light-quark meson system. The mass splittings between the respective chiral partners are shown to be equal, and the decay widths of one pion emission of XB, XD, XB * and XD * become to have a common value, due to chiral and heavy quark symmetry. The property of heavy-light quark meson systems is one of the important topics of high energy physics. Until recently the mass spectra and weak transitions of B and D meson systems have been analyzed mainly by using the heavy quark effective theory (HQET). 1) The HQET is based on heavy quark symmetry (HQS), which represent a spin-flavor symmetry of QCD in the heavy quark sector. The QCD has another symmetry, chiral symmetry, in the light quark sector. Thus far for many years, the chiral symmetry had been applied in hadron physics mainly to describe the properties of π-meson octet through non-linear representation. Recently the existence of light σ-meson, σ(500–600), is suggested strongly by the several groups, 2) including ours. 3) The observed properties of σ-meson are consistent 4) with the relation between mass and width predicted by the linear σ model (LσM), 5) and this fact seems to suggest that the linear representation of chiral symmetry is also realized 6) in nature. In a previous paper 7) we have proposed a new covariant framework for me-son level-classification and considered chiral transformation for the q ¯ q wave function (WF) directly in the framework of covariant oscillator quark model (COQM). 8) The σ is argued to be discriminated from the (q ¯ q) 3 P 0-state appearing in the non-relativistic quark model (NRQM), and to be classified into, so to speak, the " rela-tivistic S-wave " state of the (q ¯ q) system, which has never been appeared in NRQM. This type of new covariant state is called " chiralons. " We assume the chiral symmetry for light quark component in the heavy-light quark systems is also effective, where the possible existence of this new type of mesons is suggested as chiral partners of the ground S-wave state …