Speaker
Description
Quantum correlations in pairs of neutral $D$ mesons are induced by charge-conjugation symmetry in the decay of charmonia and charmonia-like states such as the $C=-1$ $\psi(3770)$ charmonium state decaying to $D\overline{D}$. Such systems are currently used to measure $D$ decay strong phases, which serve as an input to measurements of $D^{0}-\overline{D}^{0}$ mixing as well as measurements of the CKM angle $\gamma$. Additionally, correlated pairs of $D$ mesons could also potentially enable direct measurements of $T$ and $CPT$ symmetries in the neutral charm system, and constrain the properties of observed resonances in spectroscopy studies.
To date, all studies involving quantum-correlated $D\overline{D}$ pairs have been carried out at $e^{+}e^{-}$ experiments, with the most notable examples being BESIII and CLEO-c. Prompt production of correlated $D\overline{D}$ pairs from the decays of charmonia and charmonia-like states, including the $\chi_{c1}(3872)$ exotic hadron, with its subsequent decay to the $D\overline{D}\pi^{0}$ and $D\overline{D}\gamma$ final states, provides us with an opportunity to study such systems at a hadron collider for the first time. The presence of boosted $D$ mesons at LHCb also presents a unique opportunity for time-dependent measurements of $T$ and $CPT$ symmetries.
This talk presents work on an ongoing analysis to make the first confirmation of quantum-correlated $D\overline{D}$ pairs at a hadron collider, using $16.8\ \mbox{fb}^{-1}$ of $pp$ collision data collected in 2024 and 2025 by the LHCb experiment at CERN. $C$-even and $C$-odd $D\overline{D}$ contributions from the $\chi_{c1}(3872)$ decay are studied with the goal of measuring the branching fraction of the non-resonant $\chi_{c1}(3872) \to D^{0}\overline{D}^{0}\pi^{0}$ relative to the $\chi_{c1}(3872) \to D^{0}\overline{D}^{*0}$ decay and the relative strong phase $\delta^{D}_{K\pi}$ between the $D^{0} \to K^{-}\pi^{+}$ and $\overline{D}^{0} \to K^{+}\pi^{-}$ decays.