A new paradigm for data-driven, model-agnostic new physics searches at colliders is emerging, and aims to leverage recent breakthroughs in anomaly detection and machine learning. In order to develop and benchmark new anomaly detection methods within this framework, it is essential to have standard datasets. To this end, we have created the LHC Olympics 2020, a community challenge accompanied by a set of simulated collider events. Participants in these Olympics have developed their methods using an R&D dataset and then tested them on black boxes: datasets with an unknown anomaly (or not). Methods made use of modern machine learning tools and were based on unsupervised learning (autoencoders, generative adversarial networks, normalizing flows), weakly supervised learning, and semi-supervised learning. This paper will review the LHC Olympics 2020 challenge, including an overview of the competition, a description of methods deployed in the competition, lessons learned from the experience, and implications for data analyses with future datasets as well as future colliders.

We introduce two anomaly free versions of Froggatt-Nielsen (FN) models, based on either G FN = U (1) 3 or G FN = U (1) horizontal symmetries, that generate the SM quark and lepton flavor structures. The structure of these "inverted" FN models is motivated by the clockwork mechanism: the chiral fields, singlets under G FN , are supplemented by chains of vector-like fermions charged under G FN . Unlike the traditional FN models the hierarchy of quark and lepton masses is obtained as an expansion in M/ φ , where M is the typical vector-like fermion mass, and φ the flavon vacuum expectation value. The models can be searched for through deviations in flavor observables such as K −K mixing, µ → e conversion, etc., where the present bounds restrict the masses of vector-like fermions to be above O(10 7 GeV). If G FN is gauged, the models can also be probed by searching for the flavorful Z gauge bosons. In principle, the Z s can be very light, and can be searched for using precision flavor, astrophysics, and beam dump experiments.

We analyze the prospects of probing the CP -odd iκtγ 5 th interaction at the LHC and its projected upgrades, the high-luminosity and high-energy LHC, directly using associated on-shell Higgs boson and top quark or top quark pair production. To this end we first construct a CP -odd observable based on top quark polarization in W b → th scattering with optimal linear sensitivity toκ. For the corresponding hadronic process pp → thj we present a method of extracting the phase-space dependent weight function that allows to retain close to optimal sensitivity toκ. We project future sensitivity to the signal in pp → t(→ νb)h(→ bb)j. Based on these insights we propose novel CP -odd observables for top quark pair production in association with the Higgs, pp → tth, with semileptonically decaying tops and h →bb, that rely solely on measuring the momenta of leptons and b-jets from the decaying tops without having to distinguish the charge of the b-jets. Among the many possibilities we single out an observable that can potentially probeκ ∼ 0.1 at the high-energy LHC with 2σ confidence.

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Rare b hadron decays are considered excellent probes of new semileptonic four-fermion interactions of microscopic origin. However, the same interactions also correct the high-mass Drell-Yan tails. In this work, we revisit the first statement in the context of this complementarity and chart the space of short-distance new physics that could show up in rare b decays. We analyze the latest b → qℓ+ℓ− measurements, where q = d or s and ℓ = e or μ, including the most recent LHCb $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ update, together with the latest charged and neutral current high-mass Drell-Yan data, pp → ℓν and pp → ℓ+ℓ−. We implement a sophisticated interpretation pipeline within the flavio framework, allowing us to investigate the multidimensional SMEFT parameter space thoroughly and efficiently. To showcase the new functionalities of flavio, we construct several explicit models featuring either a Z′ or a leptoquark, which can explain the tension in b → sμ+μ− angular distributions and branching fractions while predicting lepton flavor universality (LFU) ratios to be SM-like, $$ {R}_{K^{\left(\ast \right)}}\approx {R}_{K^{\left(\ast \right)}}^{\textrm{SM}} $$ R K ∗ ≈ R K ∗ SM , as indicated by the recent data. Those models are then confronted against the global likelihood, including the high-mass Drell-Yan, either finding tensions or compatibility.