Property of Chiral Scalar and Axial-Vector Mesons in Heavy-Light Quark Systems

Abstract

Recently we have proposed a new level-classification scheme of hadrons with a manifestly covariant framework. In this scheme the requirement of chiral symmetry on the light quark leads to a prediction of existence of new type of scalars XB, XD and axial-vectors XB * , XD * as the chiral partners of ground state pseudoscalar B, D and vector B * , D * mesons, respectively. They belong to "relativistic S-wave states," and are discriminated from the conventional P -wave mesons with jq = 1/2 appearing in the heavy quark effective theory. In this talk we examine the properties of these chiral mesons: The mass-splittings between the respective chiral partners are predicted to be equal, and the decay widths of one pion emission of XB, XD, XB * and XD * are to take the same value due to both chiral and heavy quark symmetries. Some experimental indications for existence of XB and XD * are also given, which are consistent with the above prediction. §1. IntroductionRecently, we have proposed a covariant level classification scheme of hadrons 1) , unifying the seemingly contradictory two viewpoints, non-relativistic one with LScoupling scheme and relativistic one with chiral symmetry. In this scheme, it is expected that the hadron spectra are to show, concerning light quark constituents, the approximateŨ (12) SF symmetry (including static SU (6) SF as a subgroup) around the lower mass region, and is predicted the existence of many relativistic states, called "chiralons," which are out of the framework of conventional LS coupling scheme in NRQM. Recently, the existence of a light scalar σ meson with the property as partner of π meson in the linear representation of chiral symmetry seems to be confirmed 2), 3) . In our classification scheme, this σ is naturally classified into the relativistic S-wave qq state, which is to be discriminated from the 3 P 0 -state appearing in NRQM.In heavy-light quark nb(= ub, db) systems, the existence of chiralons, new scalar and axial-vector mesons, denoted as X B = t (X B + , X B 0 ) and X B * = t (X B * + , X B * 0 ), is expected to exist as the chiral partners of the pseudoscalar B = t (B + , B 0 ) and the vector B * = t (B * + , B * 0 ) mesons, respectively. Similarly, in the nc = t (uc, dc) system, the scalar XD = t (XD0, X D − ) and the axial-vector XD * = t (XD * 0, X D * − ) mesons, is expected to exist as the chiral partners of the pseudoscalarD = t (D 0 , D − ) and the vectorD * = t (D * 0 , D * − ) mesons, respectively. These chiral scalar and axialvector mesons are classified to the relativistic S-wave states, which are discriminated from the P -wave mesons appearing in NRQM, or the scalars B * 0 , D * 0 and axial-vectors * ) Here the normalization of states |B(0) ≡ a † B(0) |0 , etc. are used, where [a B(p) , a † B(p ′ ) ] = δ (3) (p − p ′ ).