Constraint onKK¯compositeness of thea0(980)and

Takayasu Sekihara

¹

,

S. Kumano

²

Abstract

Constraint on KK compositeness of the a 0 (980) and f 0 (980) resonances from their mixing intensity Structure of the a0(980) and f0 (980) resonances is investigated with the a0(980)-f0(980) mixing intensity from the viewpoint of compositeness, which corresponds to the amount of two-body states composing resonances as well as bound states. For this purpose we first formulate the a0(980)-f0(980) mixing intensity as the ratio of two partial decay widths of a parent particle, in the same manner as the recent analysis in BES experiments. Calculating the a0(980)-f0(980) mixing intensity with the existing Flatte parameters from experiments, we find that many combinations of the a0(980) and f0(980) Flatte parameters can reproduce the experimental value of the a0(980)-f0(980) mixing intensity by BES. Next, from the same Flatte parameters we also calculate the KK compositeness for a0(980) and f0(980). Although the compositeness with the correct normalization becomes complex in general for resonance states, we find that the Flatte parameters for f0(980) imply large absolute value of the KK compositeness and the parameters for a0(980) lead to small but nonnegligible absolute value of the KK compositeness. Then, connecting the mixing intensity and the KK compositeness via the a0(980)-and f0(980)-KK coupling constants, we establish a relation between them. As a result, a small mixing intensity indicates a small value of the product of the KK compositeness for the a0(980) and f0 (980) resonances. Moreover, the experimental value of the a0(980)-f0(980) mixing intensity implies that the a0(980) and f0 (980) resonances cannot be simultaneously KK molecular states.

Structure of near-threshold quasibound states

“…[25,49] with explicit model calculations, which are in good agreement with the present model-independent results. TheKN composite dominance of Λ(1405) is supported by the recent lattice QCD calculation [15] and the realisticKN potential [16].…”

“…[53] (see Ref. [49]), we conclude that the structure of a 0 (980) is dominated by the non-KK component. On the other hand, the results of f 0 (980) are scattered and not conclusive, as a consequence of the uncertainties of the Flatte parameters.…”

“…As summarized in Ref. [49], recent experimental data around theKK threshold has been analyzed by Flatte parametrization [50][51][52][53][54][55][56][57][58][59][60], from which E QB and a 0 can be determined. Except for Ref.…”

The $$D_s^+ \rightarrow a_0(980) e^+ \nu _e$$ reaction and the $$a_0(980)-f_0(980)$$ mixing

“…This occurs in reactions where the production of one of the states is allowed by isospin conservation and the other meson is observed in an isospin violating mode. The topic has been studied in numerous works and the relevant ingredient in the mixing lies in the mass difference between the neutral and charged kaons [16,21,23,24,31,34,[36][37][38][39]41,42] which is responsible for the lack of cancellation in loops involving kaons. This idea was first discussed in Ref.…”

Isovector scalar a0(980) and a0(1450) resonances in the

“…Amongst them, two important low-lying scalar resonances, namely, isoscalar f 0 ð980Þ and isovector a 0 ð980Þ, are of special interest. Their almost degenerate masses would lead to a mixing with each other through isospin violating effects [2][3][4][5]. As their masses proximity to the KK threshold, both can strong coupling to KK.…”