Search

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 compute all of the one-loop corrections that are enhanced, $O(\lambda_i\lambda_j / 16 \pi^2)$, in the limit $s \gg |\lambda_i | v^2 \gg M_{W}^2$, $s\gg m_{12}^2$ to all the $2 \to 2$ longitudinal vector boson and Higgs bosonscattering amplitudes in the $CP$-conserving two-Higgs doublet model with asoftly broken $\mathbb{Z}_2$ symmetry. In the two simplified scenarios westudy, the typical bound we find is $|\lambda_i(s)| \lessapprox 4$.

We compute all of the one-loop corrections that are enhanced, $O(\lambda_i\lambda_j / 16 \pi^2)$, in the limit $s \gg |\lambda_i | v^2 \gg M_{W}^2$, $s\gg m_{12}^2$ to all the $2 \to 2$ longitudinal vector boson and Higgs bosonscattering amplitudes in the $CP$-conserving two-Higgs doublet model with asoftly broken $\mathbb{Z}_2$ symmetry. In the two simplified scenarios westudy, the typical bound we find is $|\lambda_i(s)| \lessapprox 4$.

Abstract: We derive the decay rate of an unstable phase of a quantum field theory in the presence of an impurity in the thin-wall approximation. This derivation is based on the how the impurity changes the (flat spacetime) geometry relative to case of pure false vacuum. Two examples are given that show how to estimate some of the additional parameters that enter into this heterogeneous decay rate. This formalism is then applied to the Higgs vacuum of the Standard Model (SM), where baryonic matter acts as an impurity in the electroweak Higgs vacuum. We find that the probability for heterogeneous vacuum decay to occur is suppressed with respect to the homogeneous case. That is to say, the conclusions drawn from the homogeneous case are not modified by the inclusion of baryonic matter in the calculation. On the other hand, we show that Beyond the Standard Model physics with a characteristic scale comparable to the scale that governs the homogeneous decay rate in the SM, can in principle lead to an enhanced decay rate.

We present a sum rule for Higgs fields in general representations under SU(2) L × U(1) Y that follows from the connection between the Higgs couplings and the mechanism that gives the electroweak bosons their masses, and at the same time restricts these couplings. Sum rules that follow from perturbative unitarity will require us to include singly and doubly charged Higgses in our analysis. We examine the consequences of these sum rules for Higgs phenomenology in both model independent and model specific ways. The relation between our sum rules and other works, based on dispersion relations, is also clarified. © 2014 The Author(s).

We show that the three-body decays of the resonance recently discovered at the LHC are potentially sensitive to efects of new physics. Even if the fully integrated partial decay widths are consistent with the minimal Standard Model there is information that is lost upon integration, which can be uncovered in the diferential decay widths. oncentrating on the decay h→Zll, we identify the regions in the three-body phase space in which these efects become especially pronounced and could be detected in future experiments. © SISSA 2013.

We computed the bottom-quark forward-backward asymmetry at the Tevatron in the standard model (SM) and for several new physics scenarios. Near the Z pole, the SM bottom asymmetry is dominated by tree level exchanges of electroweak gauge bosons. While above the Z pole, next-to-leading order QCD dominates the SM asymmetry as was the case with the top-quark forward-backward asymmetry. Light new physics, M(NP)≲150  GeV, can cause significant deviations from the SM prediction for the bottom asymmetry. The bottom asymmetry can be used to distinguish between competing new physics (NP) explanations of the top asymmetry based on how the NP interferes with s-channel gluon and Z exchange.

We computed the bottom-quark forward-backward asymmetry at the Tevatron in the standard model (SM) and for several new physics scenarios. Near the Z pole, the SM bottom asymmetry is dominated by tree level exchanges of electroweak gauge bosons. While above the Z pole, next-to-leading order QCD dominates the SM asymmetry as was the case with the top-quark forward-backward asymmetry. Light new physics, M(NP)≲150  GeV, can cause significant deviations from the SM prediction for the bottom asymmetry. The bottom asymmetry can be used to distinguish between competing new physics (NP) explanations of the top asymmetry based on how the NP interferes with s-channel gluon and Z exchange.

Contrary to popular belief conformality does not require zero beta functions. This follows from the work of Jack and Osborn, and examples in non-supersymmetric theories were recently found by some of us. In this Letter we show that such examples are absent in unitary N=1 supersymmetric four-dimensional field theories. More specifically, we show to all orders in perturbation theory that the beta-function vector field of such theories does not admit limit cycles. A corollary of our result is that unitary N=1 supersymmetric four-dimensional theories cannot be superscale-invariant without being superconformal. © 2012.

We show that the anomalously large top quark forward-backward asymmetry observed by CDF and DØ can naturally be accommodated in models with flavor-violating couplings of a new massive spin-2 state to quarks. Regardless of its origin, the lowest-order couplings of a spin-2 boson to fermions are analogous to the coupling of the graviton to energy/momentum, leading to strong sensitivity of the effects associated with its virtual exchange to the energy scales at hand. Precisely due to this fact, the observed dependence of the asymmetry on the tt invariant mass fits nicely into the proposed framework. In particular, we find a vast parameter space which can lead to the central value for the observed forward-backward asymmetry in the high mass bin. © 2012 SISSA.

Electroweak precision data constraints on avor symmetric vector fields are determined. The avor multiplets of spin one that we examine are the complete set of fields that couple to quark bi-linears at tree level while not initially breaking the quark global avor symmetry group. Flavor safe vector masses proximate to, and in some cases below, the electroweak symmetry breaking scale are found to be allowed. Many of these fields provide a avor safe mechanism to explain the tt forward backward anomaly, and can simultaneously significantly raise the allowed values of the Standard Model Higgs mass consistent with electroweak precision data. © SISSA 2011.