We present calculations of radiative transitions between vector and pseudoscalar quarkonia in the light-front Hamiltonian approach. The valence sector light-front wave functions of heavy quarkonia are obtained from the Basis Light-Front Quantization approach in a holographic basis. We study the transition form factor with both the traditional "good current" J+ and the transverse current J→ (in particular, JR=Jx+iJy). This allows us to investigate the role of rotational symmetry by considering vector mesons with different magnetic projections (mj=0,±1). We use the mj=0 state of the vector meson to obtain the transition form factor, since this procedure employs the dominant spin components of the light-front wave functions and is more robust in practical calculations. While the mj=±1 states are also examined, transition form factors depend on subdominant components of the light-front wave functions and are less robust. Transitions between states below the open-flavor thresholds are computed, including those for excited states. Comparisons are made with the experimental measurements, as well as with lattice QCD and quark model results. In addition, we apply the transverse current to calculate the decay constant of vector mesons where we obtain consistent results using either mj=0 or mj=1 light-front wave functions. This consistency provides evidence for features of rotational symmetry within the model.
Bibliographical noteFunding Information:
We wish to thank Lekha Adhikari, Guangyao Chen, Shaoyang Jia, V. A. Karmanov, Sofia Leitão, Wayne N. Polyzou, Wenyang Qian, Shuo Tang, Anji Yu, and Xingbo Zhao for valuable discussions. We thank R. M. Woloshyn for his communications regarding his calculation on the three-point matrix elements. This work was supported in part by the U.S. Department of Energy (DOE) under Grants No. DE-FG02-87ER40371, No. DE-SC0018223 (SciDAC-4/NUCLEI), No. DE-SC0015376 (DOE Topical Collaboration in Nuclear Theory for Double-Beta Decay and Fundamental Symmetries), and No. DE-FG02-04ER41302. A portion of the computational resources was provided by the National Energy Research Scientific Computing Center, which is supported by the U.S. DOE Office of Science.