Possible signatures for tetraquarks from the decays of $$a_0(980)$$ a 0 ( 980 )

Abstract

Based on the recent proposal for the tetraquarks with the mixing scheme, we investigate fall-apart decays of a 0 (980), a 0 (1450) into two lowest-lying mesons. This mixing scheme suggests that a 0 (980) and a 0 (1450) are the tetraquarks with the mixtures of two spin configurations of diquark and antidiquark. Due to the relative sign differences in the mixtures, the couplings of fall-apart decays into two mesons are strongly enhanced for a 0 (980) but suppressed for a 0 (1450). We report that this expectation is supported by their experimental decays. In particular, the ratios of the associated partial decay widths, which depend on some kinematical factors and the couplings, are found to be around.52 − 0.89, which seems to agree with the experimental ratios reasonably well. This agreement can be interpreted as the tetraquark signatures for a 0 (980), a 0 (1450).

Tetraquark mixing framework for isoscalar resonances in light mesons

“…This tetraquark mixing framework seems to work for the isovector and isodoublet resonances, a 0 (980), a 0 (1450), K * 0 (800), K * 0 (1430). Their hyperfine mass splitting matches relatively well with their experimental mass splitting [21] and the fall-apart modes of a 0 (980), a 0 (1450) seem to be consistent with their experimental decay modes [22].…”

Further signatures to support the tetraquark mixing framework for the two light-meson nonets

“…Even in the light meson system composed of u, d, s quarks, one can introduce a different diquark, namely the spin-1 diquark with (6 c ;3 f ), and construct the second type of tetraquarks [36][37][38] in addition to the first type constructed from the most common spin-0 diquark discussed above. The spin-1 diquark can be used as a building block also because it forms a bound state even though it is less attractive than the spin-0 diquark above [30].…”

“…The main aspect of Refs. [36][37][38] is that the two tetraquark types, one type constructed from the spin-0 diquark and the other type from the spin-1 diquark, mix strongly through the color-spin interaction. So the physical resonances can be identified by the eigenstates that diagonalize the hyperfine color-spin interaction.…”

“…This tetraquark mixing framework is very promising as a possible structure for the two nonets in the review of the Particle Data Group (PDG) [40], a 0 ð980Þ, K Ã 0 ð800Þ, f 0 ð500Þ, and f 0 ð980Þ in the light nonet and a 0 ð1450Þ, K Ã 0 ð1430Þ, f 0 ð1370Þ, and f 0 ð1500Þ in the heavy nonet. Indeed, this structure has been tested relatively well in reproducing the mass splittings between the two nonets as well as the partial decay widths into two pseudoscalar mesons [36][37][38].…”

“…In this work, we investigate additional signatures to support the tetraquark mixing framework [36][37][38] as a plausible structure for the two nonets in PDG, the light and heavy nonets. First, we point out that the two nonets satisfy the Gell-Mann-Okubo mass relation approximately, which may indicate that the two nonets form the flavor nonets.…”