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A bstract A future high-luminosity Z -factory will offer the possibility to study rare Z decays, as those leading to lepton flavour violating final states. Processes such as Z  →  ℓ 1 ∓ ℓ 2 ± are potentially complementary to low-energy (high-intensity) observables of lepton flavour violation. In this work we address the impact of new sterile fermions on lepton flavour violating Z decays, focusing on potential searches at FCC-ee (TLEP), and taking into account experimental and observational constraints on the sterile states. We consider a minimal extension of the Standard Model by one sterile fermion state, and two well-motivated frameworks of neutrino mass generation, the Inverse Seesaw embedded into the Standard Model, and the ν MSM. Our study shows that sterile neutrinos can give rise to contributions to BR( Z  →  ℓ 1 ∓ ℓ 2 ± ) within reach of the FCC-ee. We also discuss the complementarity between a high-luminosity Z -factory and low-energy charged lepton flavour violation facilities.

We consider measurements of exclusive rare semi-tauonic b -hadron decays, mediated by the b → s τ + τ - transition, at a future high-energy circular electron–positron collider (FCC- ee ). We argue that the high boosts of b -hadrons originating from on-shell Z boson decays allow for a full reconstruction of the decay kinematics in hadronic τ decay modes (up to discrete ambiguities). This, together with the potentially large statistics of Z → b b ¯ , opens the door for the experimental determination of τ polarizations in these rare b -hadron decays. In the light of the current experimental situation on lepton flavor universality in rare semileptonic B decays, we discuss the complementary short-distance physics information carried by the τ polarizations and suggest suitable theoretically clean observables in the form of single- and double- τ polarization asymmetries.

We consider measurements of exclusive rare semi-tauonic b-hadron decays, mediated by the [Formula omitted] transition, at a future high-energy circular electron-positron collider (FCC-ee). We argue that the high boosts of b-hadrons originating from on-shell Z boson decays allow for a full reconstruction of the decay kinematics in hadronic [Formula omitted] decay modes (up to discrete ambiguities). This, together with the potentially large statistics of [Formula omitted], opens the door for the experimental determination of [Formula omitted] polarizations in these rare b-hadron decays. In the light of the current experimental situation on lepton flavor universality in rare semileptonic B decays, we discuss the complementary short-distance physics information carried by the [Formula omitted] polarizations and suggest suitable theoretically clean observables in the form of single- and double- [Formula omitted] polarization asymmetries.

Abstract We consider measurements of exclusive rare semi-tauonic b-hadron decays, mediated by theb → s τ ⁺ τ ⁻b→sτ+τ- transition, at a future high-energy circular electron–positron collider (FCC-ee). We argue that the high boosts of b-hadrons originating from on-shell Z boson decays allow for a full reconstruction of the decay kinematics in hadronicτ τ decay modes (up to discrete ambiguities). This, together with the potentially large statistics ofZ→ bb̄Z→bb¯ , opens the door for the experimental determination ofτ τ polarizations in these rare b-hadron decays. In the light of the current experimental situation on lepton flavor universality in rare semileptonic B decays, we discuss the complementary short-distance physics information carried by theτ τ polarizations and suggest suitable theoretically clean observables in the form of single- and double- τ τ polarization asymmetries.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract A measurement of the Z([arrow right] [mu] ^sup +^ [mu] ^sup -^) + jet production cross-section in pp collisions at a centre-of-mass energy ... = 7 TeV is presented. The analysis is based on an integrated luminosity of 1.0 fb^sup -1^ recorded by the LHCb experiment. Results are shown with two jet transverse momentum thresholds, 10 and 20 GeV, for both the overall cross-section within the fiducial volume, and for six differential cross-section measurements. The fiducial volume requires that both the jet and the muons from the Z boson decay are produced in the forward direction (2.0 < [eta] < 4.5). The results show good agreement with theoretical predictions at the second-order expansion in the coupling of the strong interaction. [Figure not available: see fulltext.]

The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of s√=13TeV, corresponding to an integrated luminosity of 279±11pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10GeV/c in the rapidity range 2.0

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