Prospects for |V$_{ub}$| measurements at LHCb

Precise measurements of the quark coupling strength, $|V_{ub}|$, the least well known CKM element, allow a strong test of the unitarity of the CKM matrix. Previous measurements using exclusive and inclusive methods have resulted in values of $|V_{ub}|$ which are 3$\sigma$ apart. The first measurement of $|V_{ub}|$ at LHCb confirmed this tension using the $\Lambda^{0}_{b} \rightarrow p \mu^{-} \overline{\nu}$ decay. This strengthens the motivation to measure this quantity using different channels, one of them being purely leptonic decay $B^{+} \rightarrow \mu^{+} \mu^{-} \mu^{+} \nu$, which benefits from LHCb's very good muon identification ability. This mode had never been observed before. With recent lattice QCD calculations, LHCb can also constrain $|V_{ub}|$ using the $B^{0}_s \rightarrow K^{+} \mu^{-} \overline{\nu}$ decay where the theoretical uncertainty is significantly smaller.