Radiative and Meson Decays of Y(4230) in Flavor SU(3)

Luciano Maiani,Antonio Davide Polosa,Verónica Riquer

doi:10.3390/sym13050751

Abstract

The charmonium-like exotic states Y(4230) and the less known Y(4320), produced in e+e− collisions, are sources of positive parity exotic hadrons in association with photons or pseudoscalar mesons. We analyze the radiative and pion decay channels in the compact tetraquark scheme, with a method that proves to work equally well in the most studied D∗→γ/π+D decays. The decay of the vector Y into a pion and a Zc state requires a flip of charge conjugation and isospin that is described appropriately in the formalism used. Rates are found to depend on the fifth power of pion momentum, which would make the final states πZc(4020) strongly suppressed with respect to πZc(3900). The agreement with BES III data would be improved considering the πZc(4020) events to be fed by the tail of the Y(4320) resonance under the Y(4230). These results should renovate the interest in further clarifying the emerging experimental picture in this mass region.

Highlights

The so-called Y states, unexpected charmonium-like states created by the initial lepton pair, are efficient sources of positive parity exotic hadrons produced in association with one photon, pion or K meson
Decays of the lightest Y states, such as Y (4230) into γ/π/K + X/Z, extensively studied by the BES III collaboration, have provided precious information on properties and quantum numbers of the lightest, J P = 1+ exotic states, the latest result being the observation of the first, hidden charm, open strangeness Zcs (3985), produced in association with a charged K meson in [2]
We assume D ∗+ decay to be dominated by πD final states and use the D ∗+ total width [32] to estimate the value of g, obtaining g ∼ 0.56

Summary

Introduction

The study of final states in e+ e− high energy annihilation, with the pioneering contributions by BaBar, Belle and BES collaborations, has opened the way to the new spectroscopy of exotic hadrons. Arises from a Y-like resonance with [cu][cū] or [cs][cs] valence quark composition that decays to the final K + Zcs state by the elementary processes u → s K+. Valence quark composition is [cq][cq], diquark and antidiquark spin are indicated in parenthesis and L is the orbital angular momentum. It was noted in [13] that the mass difference of Y1,2 arises from two contrasting contributions: the hyperfine interaction, which pushes Y1 down, and the spin–orbit interaction, which pushes Y2 down. The first term corresponds to the well known electric dipole transition that changes by one unit the orbital angular momentum, leaving the spin wave function unchanged [29].

Charge Conjugation in Y and Other Tetraquark Nonets

Transition Radius

Summary