Towards the First Measurement of: $\Lambda _{b}^{0}\to \Lambda _{c}^{*+}D_{s}^{(*)-}$

The Standard Model states that all three lepton flavours (electron e −, muon µ, tau τ ) have the same electroweak coupling with the gauge bosons Z and W+−. This implies that for decays involving different lepton families, the branching fractions are not affected by the type of lepton but vary only due to differences in phase space and contributions suppressed by helicity. This principle is known as Lepton Flavour Universality (LFU). LFU tests involves comparing the ratios of branching fractions in leptonic and semi-leptonic decays. If these ratios are consistent with the predictions of the Standard Model, it supports the validity of LFU. However, if discrepancies are observed, it could indicate new physics beyond the Standard Model (BSM). Testing LFU with semileptonic Λb → Λ ∗ c decays can help verify current anomalies observed in decays involving charmed mesons. This can be achieved by measuring the ratio R(Λ∗ c ), where R(Λ∗ c ) = B(Λb → Λ ∗+ c τν¯τ )/B(Λb → Λ∗+ c µν¯µ). We can evaluate the Λb → Λ ∗+ c τν¯τ decay by studying its dominant background, which is the Λ0 b → Λ ∗+ c D (∗)− s channel. In particular, we are interested in processes where Ds decays to κ +κ −π −. This process is something that has never been measured before, and is also a good opportunity to study the nature of the Λ+ c resonances, as we have that Λ∗+ c → Λ + c π +π − and Λ+ c = Λc (2595, 2625)+ .