Abstract
AbstractThe prospects are presented for precise measurements of the branching ratios of the purely leptonic $$B_c^+ \rightarrow \tau ^+ \nu _\tau $$
B
c
+
→
τ
+
ν
τ
and $$B^+ \rightarrow \tau ^+ \nu _\tau $$
B
+
→
τ
+
ν
τ
decays at the Future Circular Collider (FCC). This work is focused on the hadronic $$\tau ^{+} \rightarrow \pi ^+ \pi ^+ \pi ^- {\bar{\nu }}_\tau $$
τ
+
→
π
+
π
+
π
-
ν
¯
τ
decay in both $$B_c^+ \rightarrow \tau ^+ \nu _\tau $$
B
c
+
→
τ
+
ν
τ
and $$B^+ \rightarrow \tau ^+ \nu _\tau $$
B
+
→
τ
+
ν
τ
processes. Events are selected with two Boosted Decision Tree algorithms to optimise the separation between the two signal processes as well as the generic hadronic Z decay backgrounds. The range of the expected precision for both signals are evaluated in different scenarios of non-ideal background modelling. This paper demonstrates, for the first time, that the $$B^+ \rightarrow \tau ^+ \nu _\tau $$
B
+
→
τ
+
ν
τ
decay can be well separated from both $$B_c^+ \rightarrow \tau ^+ \nu _\tau $$
B
c
+
→
τ
+
ν
τ
and generic $$Z\rightarrow b{\bar{b}}$$
Z
→
b
b
¯
processes in the FCC-ee collision environment and proposes the corresponding branching ratio measurement as a novel way to determine the CKM matrix element $$|V_{ub}|$$
|
V
ub
|
. The theoretical impacts of both $$B^+ \rightarrow \tau ^+ \nu _\tau $$
B
+
→
τ
+
ν
τ
and $$B_c^+ \rightarrow \tau ^+ \nu _\tau $$
B
c
+
→
τ
+
ν
τ
measurements on New Physics cases are discussed for interpretations in the generic Two-Higgs-doublet model and leptoquark models.
Funder
Deutsche Forschungsgemeinschaft
Horizon 2020 Framework Programme
Publisher
Springer Science and Business Media LLC
Subject
Physics and Astronomy (miscellaneous),Engineering (miscellaneous)