Probing the B+ and Bc+ meson substructure with the LHCb experiment

by Dr Fabian Christoph Glaser (Heidelberg University)

Thursday 3 Sept 2026, 15:30 → 16:30 Europe/Berlin

CP-03-123 - E5a Seminarraum (TUDortmund)

Precision measurements of B meson decays provide powerful tests of the Standard Model and sensitive probes for physics beyond it. Their interpretation, however, often relies on the ability to calculate the underlying non-perturbative QCD effects. Thus, a detailed understanding of hadronic structure is essential for fully exploiting the precision of experimental measurements.

The $B^+\to\mu^+\nu_\mu\gamma$ decay is often considered the golden mode to probe the internal structure of the $B^+$ meson. Its decay rate is sensitive to the $B$-meson light-cone distribution amplitude, and in particular to its first inverse moment, $\lambda_B$, which is the most important parameter for exclusive $B$-meson decay. While it is extremely difficult to obtain the value of $\lambda_B$ from theoretical models, experimental input on the $B^+\to\mu^+\nu_\mu\gamma$ branching fraction is crucial to constrain the value of $\lambda_B$ and thus reduce the theoretical uncertainty on a wide range of $B$ meson decays. In this context, I will present the search for radiative leptonic $B^+_{(c)}\to\mu^+\nu_\mu\gamma$ decays with the LHCb experiment, the first of its kind at a hadron collider, discuss its impact on the current understanding of the $B^+$-meson substructure and future prospects of the analysis.

For the doubly-heavy $B^+_c$ meson, composed of a bottom and charm quark, two-body non-leptonic decays offer a complementary laboratory for studying the non-perturbative QCD description of the $B^+_c$ meson. I will present the first search for the Cabibbo-suppressed $B^+_c \to J/\psi D^{*+}$ decay and discuss its potential to probe the validity and limitations of factorisation-based models.