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The 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.

Since 2015, with the restart of the LHC for its second run of data taking, the LHCb experiment has been empowered with a dedicated computing model to select and analyse calibration samples to measure the performance of the particle identification (PID) detectors and algorithms. The novel technique was developed within the framework of the innovative trigger model of the LHCb experiment, which relies on online event reconstruction for most of the datasets, reserving offline reconstruction to special physics cases. The strategy to select and process the calibration samples, which includes a dedicated data-processing scheme combining online and offline reconstruction, is discussed. The use of the calibration samples to measure the detector PID performance, and the efficiency of PID requirements across a large range of decay channels, is described. Applications of the calibration samples in data-quality monitoring and validation procedures are also detailed.

Reconstruction of the B0→ D∗−τ+ντ angular distribution is complicated by the strongly biasing effect of losing the neutrino information from both the B and τ decays. In this work, a novel method for making unbiased measurements of the angular coefficients while preserving the model independence of the angular technique is demonstrated. The twelve angular functions that describe the signal decay, in addition to background terms, are modelled in a multidimensional fit, using template probability density functions that encapsulate all resolution and acceptance effects. Sensitivities at the LHCb and Belle II experiments are estimated, and sources of systematic uncertainty are discussed, notably in the extrapolation to a measurement of R(D∗).

A bstract This paper presents the prospects for a precise measurement of the branching fraction of the leptonic B c + → τ + ν τ decay at the Future Circular Collider (FCC-ee) running at the Z -pole. A detailed description of the simulation and analysis framework is provided. To select signal candidates, two Boosted Decision Tree algorithms are employed and optimised. The first stage suppresses inclusive b b ¯ , c c ¯ , and q q ¯ backgrounds using event-based topological information. A second stage utilises the properties of the hadronic τ + → π + π + π − ν ¯ τ decay to further suppress these backgrounds, and is also found to achieve high rejection for the B + → τ + ν τ background. The number of B c + → τ + ν τ candidates is estimated for various Tera- Z scenarios, and the potential precision of signal yield and branching fraction measurements evaluated. The phenomenological impact of such measurements on various New Physics scenarios is also explored.

The prospects are presented for precise measurements of the branching ratios of the purely leptonic B c + → τ + ν τ and B + → τ + ν τ decays at the Future Circular Collider (FCC). This work is focused on the hadronic τ + → π + π + π - ν ¯ τ decay in both B c + → τ + ν τ and 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 + → τ + ν τ decay can be well separated from both B c + → τ + ν τ and generic 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 | . The theoretical impacts of both B + → τ + ν τ and B c + → τ + ν τ measurements on New Physics cases are discussed for interpretations in the generic Two-Higgs-doublet model and leptoquark models.

This paper presents the prospects for a precise measurement of the branching fraction of the leptonic$$ {B}_c^{+} $$B c + → τ + ν τ decay at the Future Circular Collider (FCC-ee) running at the Z -pole. A detailed description of the simulation and analysis framework is provided. To select signal candidates, two Boosted Decision Tree algorithms are employed and optimised. The first stage suppresses inclusive$$ b\\overline{b} $$b b ¯ ,$$ c\\overline{c} $$c c ¯ , and$$ q\\overline{q} $$q q ¯ backgrounds using event-based topological information. A second stage utilises the properties of the hadronic τ + → π + π + π −$$ \\overline{\\nu} $$ν ¯ τ decay to further suppress these backgrounds, and is also found to achieve high rejection for the B + → τ + ν τ background. The number of$$ {B}_c^{+} $$B c + → τ + ν τ candidates is estimated for various Tera- Z scenarios, and the potential precision of signal yield and branching fraction measurements evaluated. The phenomenological impact of such measurements on various New Physics scenarios is also explored.

The prospects are presented for precise measurements of the branching ratios of the purely leptonic [Formula omitted] and [Formula omitted] decays at the Future Circular Collider (FCC). This work is focused on the hadronic [Formula omitted] decay in both [Formula omitted] and [Formula omitted] 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 [Formula omitted] decay can be well separated from both [Formula omitted] and generic [Formula omitted] processes in the FCC-ee collision environment and proposes the corresponding branching ratio measurement as a novel way to determine the CKM matrix element [Formula omitted]. The theoretical impacts of both [Formula omitted] and [Formula omitted] measurements on New Physics cases are discussed for interpretations in the generic Two-Higgs-doublet model and leptoquark models.

This paper presents the prospects for a precise measurement of the branching fraction of the leptonic B_(c)⁺ → τ ⁺ ν _(τ)decay at the Future Circular Collider (FCC-ee) running at the Z -pole. A detailed description of the simulation and analysis framework is provided. To select signal candidates, two Boosted Decision Tree algorithms are employed and optimised. The first stage suppresses inclusive bb̅ , cc̅ , and qq̅ backgrounds using event-based topological information. A second stage utilises the properties of the hadronic τ ⁺ → π ⁺ π ⁺ π ⁻ ν̅ _(τ)decay to further suppress these backgrounds, and is also found to achieve high rejection for the B ⁺ → τ ⁺ ν _(τ)background. The number of B_(c)⁺ → τ ⁺ ν _(τ)candidates is estimated for various Tera-Z scenarios, and the potential precision of signal yield and branching fraction measurements evaluated. The phenomenological impact of such measurements on various New Physics scenarios is also explored.

A bstract Reconstruction of the B 0 → D ∗− τ + ν τ angular distribution is complicated by the strongly biasing effect of losing the neutrino information from both the B and τ decays. In this work, a novel method for making unbiased measurements of the angular coefficients while preserving the model independence of the angular technique is demonstrated. The twelve angular functions that describe the signal decay, in addition to background terms, are modelled in a multidimensional fit, using template probability density functions that encapsulate all resolution and acceptance effects. Sensitivities at the LHCb and Belle II experiments are estimated, and sources of systematic uncertainty are discussed, notably in the extrapolation to a measurement of R ( D ∗ ).

Reconstruction of the B ⁰ → D ^(∗−) τ ⁺ ν _(τ)angular distribution is complicated by the strongly biasing effect of losing the neutrino information from both the B and τ decays. In this work, a novel method for making unbiased measurements of the angular coefficients while preserving the model independence of the angular technique is demonstrated. The twelve angular functions that describe the signal decay, in addition to background terms, are modelled in a multidimensional fit, using template probability density functions that encapsulate all resolution and acceptance effects. Sensitivities at the LHCb and Belle II experiments are estimated, and sources of systematic uncertainty are discussed, notably in the extrapolation to a measurement of R(D ^(∗) ).