2022.02.04
In this study, the research team of Professor Seong Chan Park, Department of Physics, Yonsei University, proposed several explorations using the process by which J/psi particles are generated in lepton colliders such as BESIII and Belle II.
It is expected that this search will allow the search of light gauge particle X, which explains anomalies such as Be8 proposed in the ATOMKI experiment.
BESIII confirmed that J/psi -> eta_c + X -> eta_c e+ e - can give a constraint on the coupling constant of the X gauge particle and charm quark by considering the decay channel of e + e -. Currently, it is expected that the J/psi decay event of N_J/psi = 10^10 collected in BESIII will give eps_c > 5*10-3 constraints, and it is expected that the X particle model can be tested from the final data amount N_J/psi = 10^11 to eps_c ~ 3 * 10^-3 parameters in the BESIII experiment to be collected in the future. If the X particles combine equally for all quark generations, the parameters for the explanation of the ATOMKI anomaly are considered to be fully testable.
On the other hand, in Belle II, due to the higher CM energy, the generation of J/psi particles accompanied by lepton pairs can be a more effective channel, and this study showed that the search of the channel( l^-l^+ J/psi -> eta_c X -> eta_c e^+ e^-)can also test the coupling constant of charm quarks and X particles. Considering the data of 50 ab^{-1}, the interaction seems to be testable up to eps_c > 1.8 * 10^-2.
In addition, in Belle II(e^- e^+ -> X J/psi -> e^- e^+ l^+ l^-) it is expected that the interaction of X particles and electrons can be explored through the channel, in which case the X particles are significantly accelerated, and the decay distance to the electron pair is expected to be given as O (mm-cm). In this case, it was confirmed that if the transverse flight length of the X particle is given within the category of 2mm < d_xy < 8mm, the background incident can be considered a virtually non-existent displaced vertex signal, and by analyzing in detail the statistical validity given from this particular signal incident, the interaction coupling constant of the X particle and the electron (IF 5.875).
Author Kayoung Ban, Yongsoo Jho, Youngjoon Kwon, Seong Chan Park, Seokhee Park & Po-Yan Tseng
Journal Journal of High Energy Physics
DOI doi.org/10.1007/JHEP04(2021)091
publish 2021 Apr 12