Corrections to / + Production at Factories
Wen-Long Sang (School of Physical Science and Technology, Southwest University, Chongqing, China, College of Physics, Chongqing University, Chongqing, China)
; Feng Feng (China University of Mining and Technology, Beijing, China, Institute of High Energy Physics, Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing, China); Yu Jia (School of Physics, University of Chinese Academy of Sciences, Beijing, China, Institute of High Energy Physics, Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing, China); Zhewen Mo (School of Physics, University of Chinese Academy of Sciences, Beijing, China, Institute of High Energy Physics, Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing, China)
; Jia-Yue Zhang (School of Physics, University of Chinese Academy of Sciences, Beijing, China, Institute of High Energy Physics, Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing, China)
We compute the corrections to the exclusive channels () at GeV within the nonrelativistic QCD (NRQCD) factorization framework. The validity of NRQCD factorization at has been confirmed for these double-charmonium exclusive production processes. We analyze the impact of the corrections on the polarized and unpolarized cross sections, as well as the angular distributions, which largely reduce the renormalization scale dependence but increase the NRQCD predictions to some extent for . With high numerical accuracy, our predictions for through are compatible with the upper limit of the Belle measurement. Although the theoretical prediction for is consistent with both Belle and BaBar measurements within uncertainties, there still exists serious tension between the predicted and the measured profiles for the angular distribution. Regarding the bright observation prospect of the channels in Belle 2 experiment, it is interesting to compare the future measurements with our NRQCD predictions. The more accurate measurement of at Belle 2 will also help to clarify the long-standing puzzle of angular distribution.