Speaker
Description
$Z$-pole operation at FCC-ee represents an unprecedented opportunity for heavy flavour physics, as the production of $5 \times 10^{12}$ $Z$ bosons will result in a sample of $8 \times 10^{11}$ $b$-quark pairs. All species of $B$ hadron will be produced at FCC-ee, including the doubly heavy $B_c^+$ meson. The purely leptonic decays of this meson, which proceed in the Standard Model via annihilation of the $\bar{b}$ and $c$ quarks, have not yet been observed experimentally. The $B_c^+ \to \tau^+ \nu_\tau$ decay is of particular interest, as its decay rate is highly sensitive to potential New Physics contributions from mediators such as charged Higgs bosons or leptoquarks. A measurement of the $B_c^+ \to \tau^+ \nu_\tau$ branching fraction at FCC-ee has the potential to rule out large regions of New Physics parameter space, and either confirm or refute the indications of New Physics in $b \to c \tau \nu_\tau$ transitions. This talk describes a complete feasibility study for the measurement of $\mathcal{B}(B_c^+ \to \tau^+ \nu_\tau)$ at FCC-ee, where precision estimates are given as a function of the number of $Z$ bosons produced. This work represents the first FCC-ee analysis to use common software tools from EDM4hep through to final analysis.
