Charming synergies: the role of charm-threshold studies in the search for physics beyond the Standard Model

Abstract

Measurements performed with pairs of charm mesons produced at threshold from the decay of the $\psi (3770)$ resonance are of great value in flavour physics. The quantum correlation that exists between the two mesons allows unique access to strong-phase information, which is essential input to flavour-physics studies conducted in other environments. An excellent example from the BESIII collaboration is a recent determination of the strong-phase difference between $D^0$ and ${\bar{D}}^0$ mesons in the decay $D^0\to K_S^0{\pi }^{+}{\pi }^{-}$, which has enabled recent measurements to be performed of the $CP$-violating phase $\gamma$ and $D^0-{\bar{D}}^0$ oscillations by the LHCb experiment at CERN. These $\psi (3770)$ data, and also those collected just above the thresholds for $D_s^{+}$ and ${\Lambda }_c^{+}$ production, can also be exploited in many other ways that are of benefit to flavour-physics studies. These synergies are reviewed, and the need for larger threshold data samples in the near future is emphasised.

Comments: `News and Views' article to be published in Science Bulletin. Minor typos fixed in this version