The boundary of a 3+1-dimensional topological superconductor carries a ℤ_16-valued global (Dai-Freed) anomaly, famously matched by the 16 fermions of a Standard Model generation once a certain ℤ_4 symmetry is gauged. In a supergravity completion, though, a gravitino contributes -7/16 rather than ±1/16, obstructing this ℤ_4 in the Minimal Supersymmetric Standard Model. We observe that four-dimensional 𝒩=8 supergravity evades this fate. Its fermions, eight gravitini in the 8 and fifty-six spin-12 states in the 56=Λ^38 of the SU(8) R-symmetry, saturate the anomaly. The cancellation holds for every admissible ℤ_4 structure, is consistent with the vanishing of the continuous SU(8) anomaly, and follows from a Smith homomorphism identifying the supergravity anomaly with that of the topological superconductor. In maximal supergravity this ℤ_4 stays anomaly-free and gaugeable despite its eight gravitini. All numbers are reproduced by an open-source library described in the Supplemental Material.

Abstract Lorentz invariant quantum field theories (QFTs) with fermions in four spacetime dimensions (4D) have a ℤ 4 symmetry provided there exists a basis of operators in the QFT where all operators have even operator dimension, d, including those with d > 4. The ℤ 4 symmetry is the extension of operator dimension parity by fermion number parity. If the ℤ 4 is anomaly-free, such QFTs can be related to 3D topological superconductors. Additionally, imposing the ℤ 4 symmetry on the Standard Model effective field theory severely restricts the allowed processes that violate baryon and lepton numbers.

The wealth of experimental data collected at laboratory experiments suggests that there is some scale separation between the Standard Model (SM) and phenomena beyond the SM (BSM). New phenomena can manifest itself as small corrections to SM predictions, or as signals in processes where the SM predictions vanish or are exceedingly small. This makes precise calculations of the SM expectations essential, in order to maximize the sensitivity of current and forthcoming experiments to BSM physics. This topical group report highlights some past and forthcoming theory developments critical for maximizing the sensitivity of the experimental program to understanding Nature at the shortest distances.

In this contribution to the Snowmass 2021 process we review theoretical developments in the Standard Model Effective Field Theory (SMEFT) with a focus on effects at the dimension-8 level and beyond. We review the theoretical advances that led to the complete construction of the operator bases for the dimension-8 and dimension-9 SMEFT Lagrangians. We discuss the possibility of obtaining all-orders results in the $1/\Lambda$ expansion for certain SMEFT observables as well as the current status of renormalization group running and implications for positivity, and briefly present the on-shell approach to constructing SMEFT amplitudes. Finally we present several new phenomenological effects that first arise at dimension-8 and discuss the impact of these terms on experimental analyses.

We construct a complete basis of dimension-8 operators in the Low-Energy Effective Field Theory below the Electroweak Scale (LEFT). We find there are 35058 dimension-8 operators in the LEFT for two generations of up-type quarks and three generations of down-type quarks, charged leptons, and left-handed neutrinos. The existence of this operator basis is a necessary prerequisite for matching to the Standard Model Effective Field Theory at the dimension-8 level.

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.

Abstract We present a complete basis of dimension-8 operators in the Standard Model Effective Field Theory. Attention is paid to operators that vanish in the absence of flavor structure. The 44,807 operators are encoded in 1,031 Lagrangian terms. We also briefly discuss a few aspects of phenomenology involving dimension-8 operators, including light-by-light scattering and electroweak precision data.

Introduction Condition-based monitoring (CbM) involves monitoring of machines or assets using sensors to measure the current state of health. Predictive maintenance (PdM) involves a combination of techniques such as CbM, machine learning, and analytics to predict upcoming machine or asset failures. When monitoring the health of a machine, it is critically important to select the most suitable sensors to ensure faults can be detected, diagnosed, and even predicted. There are many sensors currently used to sense and detect faults, in rotating machinery and their loads, with the end goal of avoiding unplanned downtime. Ranking each sensor is difficult as PdM techniques are applied to a multitude of rotating machines (motors, gears, pumps, and turbines) and nonrotating machines (valves, circuit breakers, and cables).

Effective Field Theories (EFTs) capture effects from heavy dynamics at low energy and represent an essential ingredient in the context of Standard Model (SM) precision tests. This document gathers a number of relevant scenarios for heavy physics beyond the SM and presents explicit expressions for the Wilson coefficients in their low-energy EFT. It includes i) weakly coupled scenarios in which one or a few particles of different spins and quantum numbers interact linearly with the SM and generate EFT effects at tree-level, ii) scenarios where heavy particles interact quadratically whereupon the resulting EFT arises only at loop-level and iii) strongly coupled scenarios where the size of Wilson coefficients is controlled by symmetry arguments. This review aims at motivating experimental EFT studies in which only a subset of all possible EFT interactions is used, as well as facilitating the theoretical interpretation of EFT fits.

We study the theoretical constraints on a model whose scalar sector contains one color octet and one or two color singlet SU(2)(L) doublets. To ensure unitarity of the theory, we constrain the parameters of the scalar potential for the first time at the next-to-leading order in perturbation theory. Moreover, we derive new conditions guaranteeing the stability of the potential. We employ the HEPfit package to extract viable parameter regions at the electroweak scale and test the stability of the renormalization group evolution up to the multi-TeV region. Furthermore, we set upper limits on the scalar mass splittings. All results are given for both cases with and without a second scalar color singlet.

Measurements from the Gaia satellite have greatly increased our knowledge of the dark matter velocity distributions in the Solar neighborhood. There is evidence for multiple cold structures nearby, including a high-velocity stream counterrotating relative to the Sun. This stream could significantly alter the spectrum of recoil energies and increase the annual modulation of dark matter in direct detection experiments such as DAMA/Libra. We reanalyze the experimental limits from Xenon1T, CDMSlite, PICO-60 and COSINE-100, and compare them to the results of the DAMA/Libra experiment. While we find that this new component of the dark matter velocity distribution can greatly improve the fit to the DAMA/Libra data, both spin-independent and spin-dependent interpretations of the DAMA/Libra signal with elastic and inelastic scattering continue to be ruled out by the null results of other experiments, in particular Xenon1T.

The acceleration gradients generated in a laser- or beam-driven plasma wakefield accelerator are typically three orders of magnitude greater than those produced by a conventional accelerator, and hence plasma accelerators can open a route to a new generation of very compact machines. In addition, plasma-based accelerators can generate beams with unique properties, such as tens of kiloamp peak currents, attosecond bunch duration, ultrahigh brightness and intrinsic particle beam-laser pulse synchronization. In this roadmap we review the status of plasma accelerator research in the UK. We outline potential applications, describe the research and development required to enable those applications, and discuss synergies with related areas of research. We also set-out the resources required to realise these ambitions and provide a timeline for advances in the key areas.

This report comprises the outcome of five working groups that have studied the physics potential of the high-luminosity phase of the LHC (HL-LHC) and the perspectives for a possible future high-energy LHC (HE-LHC).The working groups covered a broad range of topics: Standard Model measurements, studies of the properties ofthe Higgs boson, searches for phenomena beyond the Standard Model, flavor physics of heavy quarks and leptonsand studies of QCD matter at high density and temperature.The work is prepared as an input to the ongoing process of updating the European Strategy for Particle Physics,a process that will be concluded in May 2020.

A common problem in a high energy physics experiment is extracting a signal from a much larger background. Posed as a classification task, there is said to be an imbalance in the number of samples belonging to the signal class versus the number of samples from the background class. In this work we provide a brief overview of class imbalance techniques in a high energy physics setting. Two case studies are presented: (1) the measurement of the longitudinal polarization fraction in same-sign $WW$ scattering, and (2) the decay of the Higgs boson to charm-quark pairs.

We derive model-independent bounds on the form factors for the decay B-c(+) -> eta(c)l+. including full mass effects, i. e., l = e; mu, and tau. The bounds are obtained by using the Boyd-Grinstein-Lebed parametrization for the form factors, and fitting to the preliminary lattice data of the HPQCD Collaboration. Our main result after bounding the form factors is the Standard Model prediction for the ratio of branching fractions R(eta(c)) = B(B-c(+) -> eta c tau(+)nu(tau))/B(B-c(+) -> eta(c)mu(+)nu mu). We find R(eta(c))+jSM = 0.31(-0.02)(+0.04), and argue that a measurement ofRo.c+ is within the reach of LHCb during the high-luminosity run of the LHC. In addition, using the heavyquark spin symmetry of the Bc meson we relate our results for B-c(+) -> eta(c)l(+)nu. to those for B-c(+) -> J/psi l(+)nu yielding the estimate Ro(J/psi)|(SM) = 0.26 +/- 0.02 in good agreement with other determinations.

Abstract The ATLAS and CMS collaborations have recently released significant new data on Higgs and diboson production in LHC Run 2. Measurements of Higgs properties have improved in many channels, while kinematic information for h → γγ and h → ZZ can now be more accurately incorporated in fits using the STXS method, and W + W − diboson production at high p T gives new sensitivity to deviations from the Standard Model. We have performed an updated global fit to precision electroweak data, W + W − measurements at LEP, and Higgs and diboson data from Runs 1 and 2 of the LHC in the framework of the Standard Model Effective Field Theory (SMEFT), allowing all coefficients to vary the combined dataset, and present the results in both the Warsaw and SILH operator bases. We exhibit the improvement in the constraints on operator coefficients provided by the LHC Run 2 data, and discuss the correlations between them. We also explore the constraints our fit results impose on several models of physics beyond the Standard Model, including models that contribute to the operator coefficients at the tree level and stops in the MSSM that contribute via loops.

We derive model-independent bounds on the form factors for the decay ${B}_{c}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ including full mass effects, i.e., $\ensuremath{\ell}=e,\ensuremath{\mu}$, and $\ensuremath{\tau}$. The bounds are obtained by using the Boyd-Grinstein-Lebed parametrization for the form factors, and fitting to the preliminary lattice data of the HPQCD Collaboration. Our main result after bounding the form factors is the Standard Model prediction for the ratio of branching fractions $R({\ensuremath{\eta}}_{c})=\mathcal{B}({B}_{c}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{\ensuremath{\tau}}^{+}{\ensuremath{\nu}}_{\ensuremath{\tau}})/\mathcal{B}({B}_{c}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}})$. We find $R({\ensuremath{\eta}}_{c}){|}_{\mathrm{SM}}=0.3{1}_{\ensuremath{-}0.02}^{+0.04}$, and argue that a measurement of $R({\ensuremath{\eta}}_{c})$ is within the reach of LHCb during the high-luminosity run of the LHC. In addition, using the heavy-quark spin symmetry of the ${B}_{c}$ meson we relate our results for ${B}_{c}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ to those for ${B}_{c}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ yielding the estimate $R(J/\ensuremath{\psi}){|}_{\mathrm{SM}}=0.26\ifmmode\pm\else\textpm\fi{}0.02$ in good agreement with other determinations.

We perform a parameter fit in the Standard Model Effective Field Theory (SMEFT) with an emphasis on using regularized linear regression to tackle the issue of the large number of parameters in the SMEFT. In regularized linear regression a positive definite function of the parameters of interest is added to the usual cost function. A cross-validation is performed to try to determine the optimal value of the regularization parameter to use, but it selects the Standard Model (SM) as the best model to explain the measurements. Nevertheless as proof of principle of this technique we apply it to fitting Higgs boson signal strengths in SMEFT, including the latest Run-2 results. Results are presented in terms of the eigensystem of the covariance matrix of the least squares estimators as it has a degree model-independent to it. We find several results in this initial work: the SMEFT predicts the total width of the Higgs boson to be consistent with the SM prediction; the ATLAS and CMS experiments at the LHC are currently sensitive to non-resonant double Higgs boson production. Constraints are derived on the viable parameter space for electroweak baryogenesis in the SMEFT, reinforcing the notion that a first order phase transition requires fairly low scale Beyond the SM physics. Finally, we study which future experimental measurements would give the most improvement on the global constraints on the Higgs sector of the SMEFT.

The collection of a few anomalies in semileptonic B -decays, especially in b→ c τν̅ , invites to speculate about the emergence of some striking new phenomena, perhaps interpretable in terms of a weakly broken U(2)^n flavor symmetry and of leptoquark mediators. Here we aim at a partial UV completion of this interpretation by generalizing the minimal composite Higgs model to include a composite vector leptoquark as well.