Extraction of the light quark mass ratio from the decays psi'-->J/psipi0(eta)

Light quark mass dependence in heavy quarkonium physics

The issue of chiral extrapolations in heavy quarkonium systems is discussed. We show that the light quark mass dependence of the properties of heavy quarkonia is not always suppressed. For quarkonia close to an open flavor threshold, even a nonanalytic chiral extrapolation is needed. Both these nontrivial facts are demonstrated to appear in the decay widths of the hindered M1 transitions between the first radially excited and ground state P-wave charmonia. The results at a pion mass of about 500 MeV could deviate from the value at the physical pion mass by a factor of two. Our findings show the necessity of performing chiral extrapolations for lattice simulations of heavy quarkonium systems. Furthermore, lattice calculations of these transitions would also provide a definite answer to the role of coupled-channel effects in heavy quarkonium physics due to virtual heavy mesons.

Examining coupled-channel effects in radiative charmonium transitions

Coupled-channel effects due to coupling of charmonia to the charmed and anticharmed mesons are of current interest in heavy quarkonium physics. However, the effects have not been unambiguously established. In this Letter, a clean method is proposed in order to examine the coupled-channel effects in charmonium transitions. We show that the hindered M1 radiative transitions from the 2P to 1P charmonia are suitable for this purpose. We suggest to measure one or more of the ratios Γ(h(c)'→χ(cJ)γ)/Γ(χ(cJ)'→χ(cJ)π(0)) and Γ(χ(cJ)'→h(c)γ)/Γ(χ(cJ)'→χ(cJ)π(0)), for which highly nontrivial and parameter-free predictions are given. The picture can also be tested using both unquenched and quenched lattice calculations.

Extracting the light quark mass ratio m(u)/m(d) from bottomonia transitions

We propose a new method to extract the light quark mass ratio m(u)/m(d) using the Υ(4S)→h(b)π⁰(η) bottomonia transitions. The decay amplitudes are dominated by the light quark mass differences, and the corrections from other effects are rather small, allowing for a precise extraction. We also discuss how to reduce the theoretical uncertainty with the help of future experiments. As a by-product, we show that the decay Υ(4S)→h(b)η is expected to be a nice channel for searching for the h(b) state.