U(2)L×U(2)Rchiral theory of mesons

Abstract

A u ( 2 )~ x U ( 2 )~ chiral theory of pseudoscalar, vector, and axial-vector mesons is proposed and studied at the tree level. VMD is a natural result of this theory. The physical processes of normal parity and abnormal parity have been studied by using the same Lagrangian leading to a universality of coupling. Two new mass relations between vector and axial-vector mesons have been found. Weinberg's first sum rule and new relations about the amplitude of a1 decay are satisfied. The KSFR sum rule is satisfied reasonably well. The p pole in the pion form factor has been achieved.The theoretical results for the processes p + nn, w + nn, a1 -+ pn, and ny, T -+ pv, T -+ alv, no -+ 77, w --+ ~7 , p -+ a7, fl -+ pmr, fl -+ ~mr, p -+ qy, w -+ qy are in good agreement with the data. The nrr scattering lengths and slopes have been found to be the same as obtained by Weinberg. In particular, the p resonance in the amplitude T : of .rrn scattering has been obtained from this theory. Two coefficients of chiral perturbation theory have been determined and they are close to the values used in chiral perturbation theory. This theory has dynamical chiral symmetry breaking.PACS number(s): 13.75.Lb, Chiral symmetry is one of the most important features revealed from quantum chromodynamics (QCD). Chiral perturbation theory (CPT) is successful in describing many aspects of pseudoscalar meson physics [1,2]. It has been well known for a long time that vector meson dominance (VMD) [3] provides a buitful mechanism in understanding the electromagnetic properties of hadrons.

Dilepton emission rates from hot hadronic matter

“…The matrix element M f i has contributions from the channels ω → ρπ → 3π (described by Eq. (10) and the direct decay ω → 3π resulting from the contact interaction (second term in (12)) [32,33,34]. After fitting g ωρπ from the ω → πγ decay width, the point interaction coupling g ω3π is determined by fitting the partial decay width ω → 3π in vacuum (7.49 MeV) to be 0.24 [22].…”

“…To calculate the decay width for the ω-meson, we write down the effective Lagrangian for the ω meson as [31,32] …”

Decay of axial-vector mesons into VP andPγ

“…With these problems in mind, it becomes more useful to have at hand a Lagrangian which combines simplicity, wide applicability and accuracy. At the same time, most of the work done, for instance those derived in a chiral formalism [3][4][5][6][7][8][9][10][11], pay attention to the a 1 (1260) meson, while the b 1 (1235) has received much less attention. However, both the a 1 and the b 1 mesons and their SU(3) partners appear on an equal footing in the physical processes which we mentioned before.…”

“…Much of the work have been done in SU(2) [3,6,[8][9][10] and general structures have been developed. In particular, an interesting formulation develops starting from chiral Lagrangians of pseudoscalar mesons assuming a gauge nature for the vector fields and introducing them through covariant derivatives [4][5][6][7][8][9].…”

“…The decay of axial-vector mesons of J P C = 1 +− , 1 ++ (nonets associated to the b 1 (1235) and a 1 (1260) and partners respectively, (see table 1)), into a pseudoscalar (P) and a vector meson (V) has received some attention from the perspective of quark models [1,2] as well as using effective Lagrangians of the strong interaction [3][4][5][6][7][8][9][10][11]. Much of the work have been done in SU(2) [3,6,[8][9][10] and general structures have been developed.…”