Precise Measurement of Chromoelectric Dipole Moment of the Charm Quark

Abstract

The combined symmetry of charge conjugation and parity ($CP$) is tested in the hadronic transition $\ddot{I}ˆ(3686)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$, using a dataset of $(2712.4\pm 14.3)\times 10^6$ $\ddot{I}ˆ(3686)$ events collected by the BESIII detector at the BEPCII collider. The resulting asymmetry observable is $A_{cp}=(0.6\pm 1.8\pm 0.1)\times 10^{-4}$, which is determined by combining the two channels $J/\ddot{I}ˆ\to e^{+}{e}^{-}$ and $J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}$. Additionally, by considering the relationship between the chromoelectric dipole moment (CEDM) and the $A_{cp}$ observable derived from the quantum chromodynamics multipole expansion theory based on the Chen-Kuang model and the Cornell potential model, we obtain the results of charm quark's CEDM with $d_c^{\prime }=(2.6\pm 7.8\pm 0.4\pm 0.6)\times 10^{-16}$ $e$cm, and $d_c^{\prime }=(3.5\pm 10.5\pm 0.6\pm 0.5)\times 10^{-16}$ $e$cm, respectively. The uncertainties are statistical, systematic, and theoretical, respectively. These results correspond to an upper limit of $|d_c^{\prime }|<2.1\times 10^{-15}$ $e$ cm at 90\% confidence level, representing an order of magnitude improvement in sensitivity compared to the previous direct bound using the same decay process.

9 pages, 3 figures, 1 End Matter, consistent with the publication in Physical Review Letters