Studies of xi (2230) in J/ psi radiative decays

Evidence for a New Structure in the J/ψp and J/ψp[over ¯] Systems in B_{s}^{0}→J/ψpp[over ¯] Decays

An amplitude analysis of flavor-untagged B_{s}^{0}→J/ψpp[over ¯] decays is performed using a sample of 797±31 decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9  fb^{-1}. Evidence for a new structure in the J/ψp and J/ψp[over ¯] systems with a mass of 4337_{-4}^{+7} _{-2}^{+2}  MeV and a width of 29_{-12}^{+26} _{-14}^{+14}  MeV is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7σ, depending on the assigned J^{P} hypothesis.

Highlights of light meson spectroscopy at the BESIII experiment

Hadron spectroscopy provides a way to understand the dynamics of the strong interaction. For light hadron systems, only phenomenological models or lattice quantum chromodynamics (QCD) are applicable, because of the failure of perturbation expansions for QCD at low energy. Experimental data on light hadron spectroscopy are therefore crucial to provide necessary constraints on various theoretical models. Light meson spectroscopy has been studied using charmonium decays with the Beijing Spectrometer Experiment (BES) at the Beijing Electron-Positron Collider, operating at 2.0-4.6 GeV center-of-mass energy, for nearly three decades. Charmonium data with unprecedented statistics and well-defined initial and final states provide BESIII with unique opportunities to search for glueballs, hybrids and multi-quark states, as well as perform systematic studies of the properties of conventional light mesons. In this article, we review BESIII results that address these issues.

Observation of the Radiative Decays of ϒ(1S) to χ_{c1}

We report the first observation of the radiative decay of the ϒ(1S) into a charmonium state. The significance of the observed signal of ϒ(1S)→γχ_{c1} is 6.3 standard deviations including systematics. The branching fraction is calculated to be B[ϒ(1S)→γχ_{c1}]=[4.7_{-1.8}^{+2.4}(stat)_{-0.5}^{+0.4}(sys)×10^{-5}]. We also searched for ϒ(1S) radiative decays into χ_{c0,2} and η_{c}(1S,2S), and set upper limits on their branching fractions. These results are obtained from a 24.9  fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider at a center-of-mass energy equal to the ϒ(2S) mass using ϒ(1S) tagging by the ϒ(2S)→ϒ(1S)π^{+}π^{-} transitions.

Lattice study of radiative J/ψ decay to a tensor glueball

The radiative decay of J/ψ into a pure gauge tensor glueball is studied in the quenched lattice QCD formalism. With two anisotropic lattices, the multipole amplitudes E1(0), M2(0), and E3(0) are obtained to be 0.114(12)(6) GeV, -0.011(5)(1)  GeV, and 0.023(8)(1) GeV, respectively. The first error comes from the statistics, the Q2 interpolation, and the continuum extrapolation, while the second is due to the uncertainty of the scale parameter r0(-1)=410(20)  MeV. Thus, the partial decay width Γ(J/ψ→γG(2++)) is estimated to be 1.01(22)(10) keV, which corresponds to a large branch ratio 1.1(2)(1)×10(-2). The phenomenological implication of this result is also discussed.

Search for f(J)(2220) in radiative J/ψ decays

We present a search for f(J)(2220) production in radiative J/ψ→γf(J)(2220) decays using 460  fb⁻¹ of data collected with the BABAR detector at the SLAC PEP-II e(+)e⁻ collider. The f(J)(2220) is searched for in the decays to K(+)K⁻ and K(S)⁰K(S)⁰. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/ψ→γf(J)(2220) and f(J)(2220)→K(+)K⁻(K(S)⁰K(S)⁰) as a function of spin and helicity are set at the level of 10⁻⁵, below the central values reported by the Mark III experiment.