${\Xi }_{cc}^{++}-{\Xi }_{cc}^{+}$ Transitions as a Two-Charm-Selective Portal to Ultra-Low-$Q$ Charged Currents

Yong Du

The recent LHCb observation of ${\Xi }_{cc}^{+}$ opens the ultra-low-$Q$ transition ${\Xi }_{cc}^{++}\to {\Xi }_{cc}^{+}$ as an experimentally motivated null test of charged-current new physics. O…