The a0(980), a0(1450) and scalar decay constants and the isovector scalar spectrum

Abstract

The scalar correlator Π(q 2 ) = i d 4 x e iq·x 0|T J(x)J † (0) |0 (with J = ∂ µ d γ µ u ) is studied using a class of finite energy sum rules shown recently to be very well satisfied in the vector isovector channel. The values of the a 0 scalar decay constants extracted in this analysis, which describe the couplings of the a 0 (980) and a 0 (1450) to the current J, are shown to be comparable, strongly disfavoring any scenario in which the a 0 (980) is interpreted as a loosely bound KK molecule and the a 0 (1450) is assigned to the same flavor multiplet as the K * 0 (1430). The a 0 decay constants are also compared to the analogous decay constant describing the coupling of the K * 0 (1430) to the divergence of the strange vector current, J s = ∂ µ (sγ µ u) (which may be obtained from experimental K e3 and Kπ phase shift data) and implications of the relative magnitudes for the interpretation of the nature of the a 0 states discussed.

HadronicBdecays involving even-parity charmed mesons

“…Consequently, the decay constant of the charged a 0 (980) is very small, while the one for K * 0 (1430) is less suppressed. A calculation based on the finite-energy sum rules [26] yields…”

HadronicDdecays involving scalar mesons

“…obtained from the finite-energy sum rules [43]. (A different calculation of the scalar meson decay constants based on the generalized NLJ model is given in [44].)…”

“…(A different calculation of the scalar meson decay constants based on the generalized NLJ model is given in [44].) Since they are derived using the qq quark model, it is not clear if the a ± 0 decay constant remains the same in the q 2q2 picture, though it is generally expected that the decay constant is suppressed in the latter scenario because a four-quark state is larger than a two-quark state [43].…”

Coupled channel study of a0 resonances

“…The presence of two distinct poles related to the a 0 (980) meson means that in principle one has two options while fixing the model parameters using Eq. (12). At first we shall discuss a case when the a 0 (980) pole is located on sheet II at M 1 −i Γ 1 /2 = (1005−24.5 i) MeV.…”

“…Many conflicting view-points in which scalars are treated as qq or qqqq states, two-meson quasi-bound states and mixed states including glueballs coexist (see, for example, [8][9][10][11][12][13]). …”