Production of $$a_1$$ a 1 in heavy meson decays

Abstract

In this work, we study various decays of heavy B/D mesons into the a 1 (1260), based on the form factors derived in different nonperturbative or factorization approaches. These decay modes are helpful to explore the dynamics in the heavy to light transitions. Meanwhile they can also provide insights to a newly discovered state, the a 1 (1420) withAvailable theoretical explanations include tetraquark or rescattering effects due to a 1 (1260) decays. If the a 1 (1420) were induced by the rescattering, its production rates are completely determined by those of the a 1 (1260). Our numerical results for decays into the a 1 (1260) indicate that there is a promising prospect to study these decays on experiments including BES-III, LHCb, Babar, Belle, and CLEO-c, the forthcoming Super-KEKB factory and the under-design Circular Electron-Positron Collider.

The decay width of the $$Z_c(3900)$$Zc(3900) as an axialvector tetraquark state in solid quark–hadron duality

“…where t = log [37], and evolve all the input parameters to the optimal energy scale μ = 1.4 GeV to extract hadronic coupling constants [12,38].…”

“…As far as the X (5568) is concerned, if we take the scenario of tetraquark states, the width can also be reproduced based on the connected Feynman diagrams alone [26] or the connected plus disconnected Feynman diagrams [27,28]. We should prove that the contributions of the disconnected Feynman diagrams can be neglected safely.…”

The magnetic moment of the $$Z_c(3900)$$ Z c ( 3900 ) as an axialvector tetraquark state with QCD sum rules

“…the physical width of the ground state (M 2 Z ) = Z c (3900) = (28.1 ± 2.6) MeV is small enough [36], while the effect of the large width of the first radial excited state (M 2 Z ) = Z (4430) = 181 ± 31 MeV can be absorbed into the continuum states (the Z (4430) can be tentatively assigned to be the first radial excitation of the Z c (3900) based on the QCD sum rules [37]), the zero width approximation in the hadronic spectral density works, the contaminations of the intermediate meson-loops are expected to be small and can be neglected safely [38]. In fact, even the effect of the large width of the Z c (4200) ( Z c (4200) = 370 ± 70 +70 −132 MeV) can be safely absorbed into the pole residue [39].…”

“…where [36,42,46,47], and evolve all the input parameters to the optimal energy scale μ = 1.4 GeV to extract the form-factor G 2 (0) [10,24,48].…”

“…The hadronic parameters are taken as s 0 Z = 4.4 GeV, M Z = 3.899 GeV, λ Z = 2.1 × 10 −2 GeV 5 [10,48]. In the scenario of tetraquark states, the QCD sum rules indicate that the Z c (3900) and Z (4430) can be tentatively assigned to be the ground state and the first radial excited state of the axialvector tetraquark states, respectively [37].…”