Lepton (electron and muon) scattering experiments are excellent tools to gain insight into the nucleon structure. Elastic electron-proton scattering probes the spatial distribution of charge and magnetization inside the proton, and comparing electron-proton and muon-proton scattering data tests lepton universality. The availability of a plethora of scattering data with increased precision and observed discrepancies such as the proton form factor puzzle and the proton radius puzzle motivated a renewed effort to improve the theoretical framework. Realizing that the one-photon-exchange approximation (OPE), i.e. the Born approximation, is not sufficient, radiative corrections in QED, especially the two-photon-exchange (TPE) diagrams, are under investigation. The TPE diagrams are of special interest among the radiative corrections, since they depend on the proton structure. In this work, we present a complete calculation of QED radiative corrections to elastic electron-proton and muon-proton scattering at next-to-leading order, taking into account loop-momentum-dependent form factors. In the discussion of their numerical impact on lepton-proton scattering cross sections, we pay special attention to the TPE diagrams and compare them with existing theoretical predictions and lepton-proton scattering data.

We present the application of the ACOT and S-ACOT general mass variable flavor number schemes to proton-proton collisions with particular attention to the production of final states with at least one heavy quark. Subtraction and residual heavy-quark parton distribution functions are introduced to facilitate the implementation of this scheme at higher orders in perturbative QCD. The calculation of Z-boson hadronic production with at least one b jet beyond the lowest order in QCD is considered for illustration purposes.

We present an implementation of tt??t'+t'??? (t' = e, ??) hadronic production at next-to-leading order in QCD matched to parton-shower event generators in the POWHEG BOX framework. The program we developed includes all leading-order contributions of order ??2s ??2 for the specified final state, as well as the corresponding first-order QCD corrections. Decays of the top quarks have been simulated retaining spin-correlations in all tree-level matrix elements. We consider the case of the Large Hadron Collider at p = 13 TeV and compare results for tt??t'+t'??? production in the fiducial volume where the invariant mass ffiffis of the lepton pairs is centered around the Z-boson mass to corresponding predictions for tt??Z on-shell production with Z ??? t'+t'???. We find that off-shell effects in tt??t'+t'??? are in general small at the level of the total cross section, but can decrease the tail of the leptons??? transverse momentum distributions by 10%???20% and, in these regions, they are visible beyond the scale uncertainty due to renormalization and factorization scale variation. Moreover, we find that accounting for top-quark decays in the narrow-width approximation with tree-level spin correlations also gives origin to 10%???20% effects in specific regions of the kinematic distributions of the tt??t'+t'??? decayed final state.

This report, as part of the 2021 Snowmass Process, summarizes the current status of collider physics at the Energy Frontier, the broad and exciting future prospects identified for the Energy Frontier, the challenges and needs of future experiments, and indicates high priority research areas.

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.

Electroweak (EW) triboson production processes with at least one heavy gauge boson are of increasing interest at the Large Hadron Collider (LHC) as direct precision probes of one of the least-tested sectors of the Standard Model (SM), the quartic couplings of the EW gauge bosons. These processes therefore offer promising opportunities for searches for indirect signals of beyond the SM physics. In this paper, we present results for fiducial cross sections at next-to-leading-order (NLO) EW and NLO QCD to pp -> e thorn ve mu thorn mu-gamma at the 13 TeV LHC. This signature includes the triboson production process pp -> W thorn Z gamma with leptonic decays, W thorn -> e thorn ve and Z -> mu thorn mu-. The computation is based on the complete set of LO and thus off shell effects, spin correlations and nonresonance contributions are fully taken into account. We construct a Monte Carlo framework that provides total and differential cross sections for a chosen set of basic analysis cuts. We find that while NLO EW corrections enhance the fiducial LO total cross section by only 1%, they can significantly change some distributions in certain kinematic regions. For example, the relative NLO EW corrections to the muon transverse momentum distribution at 500 GeV amounts to -20%. To illustrate how missing NLO EW corrections could masquerade as beyond the SM physics, we show examples for the impact of dimension-eight operators in the SM effective field theory framework on selected kinematic distributions.

This report summarizes the work of the Energy Frontier Topical Group on EW Physics: Heavy flavor and top quark physics (EF03) of the 2021 Community Summer Study (Snowmass). It aims to highlight the physics potential of top-quark studies and heavy-flavor production processes (bottom and charm) at the HL-LHC and possible future hadron and lepton colliders and running scenarios.

Highlights of recent theory developments are summarized relevant to precision Standard Model (SM) studies and searches for Beyond-the-SM (BSM) phenomena at present and future high-energy pp and e+ e- colliders, and B-factories, as well as to selected topics in heavy ion collisions.

We compute the O(alpha(s)alpha(2)) and O(alpha(2)(s)alpha) contributions to the production cross section of a Z boson with one b jet at the Large Hadron Collider (LHC) and study their phenomenological relevance for LHC physics. The accurate prediction of hadronic Z + b-jet production is needed to control a background that greatly affects both the measurement of Higgs-boson properties and the searches of new physics at the LHC. At the same time it could enable the first precise measurement of the b-quark parton distribution function. In this context b-quark mass effects become relevant and need to be studied with care, both at the level of the hard process and at the level of the initial- and final-state parton evolution. It is the aim of this paper to explore some of these issues in the framework of a massive five-flavor scheme and to assess the need for the inclusion of both electroweak corrections, in addition to QCD corrections, and b-quark mass effects in the prediction of total and differential cross sections for hadronic Z + b-jet production.

After a brief introduction to the state of the art of theoretical predictions for electroweak vector-boson production with both top and bottom quarks at the LHC, we review the case of Z-boson production with b jets, and discuss the impact of NLO QCD+EW corrections and finite b-quark mass effects on the theoretical prediction for Z+b jet production.

This report was prepared in the context of the LPCC Electroweak Precision Measurements at the LHC WG ( https://lpcc.web.cern.ch/lpcc/index.php?page=electroweak_wg ) and summarizes the activity of a subgroup dedicated to the systematic comparison of public Monte Carlo codes, which describe the Drell–Yan processes at hadron colliders, in particular at the CERN Large Hadron Collider (LHC). This work represents an important step towards the definition of an accurate simulation framework necessary for very high-precision measurements of electroweak (EW) observables such as the W boson mass and the weak mixing angle. All the codes considered in this report share at least next-to-leading-order (NLO) accuracy in the prediction of the total cross sections in an expansion either in the strong or in the EW coupling constant. The NLO fixed-order predictions have been scrutinized at the technical level, using exactly the same inputs, setup and perturbative accuracy, in order to quantify the level of agreement of different implementations of the same calculation. A dedicated comparison, again at the technical level, of three codes that reach next-to-next-to-leading-order (NNLO) accuracy in quantum chromodynamics (QCD) for the total cross section has also been performed. These fixed-order results are a well-defined reference that allows a classification of the impact of higher-order sets of radiative corrections. Several examples of higher-order effects due to the strong or the EW interaction are discussed in this common framework. Also the combination of QCD and EW corrections is discussed, together with the ambiguities that affect the final result, due to the choice of a specific combination recipe. All the codes considered in this report have been run by the respective authors, and the results presented here constitute a benchmark that should be always checked/reproduced before any high-precision analysis is conducted based on these codes. In order to simplify these benchmarking procedures, the codes used in this report, together with the relevant input files and running instructions, can be found in a repository at https://twiki.cern.ch/twiki/bin/view/Main/DrellYanComparison .

Electroweak (EW) corrections can be enhanced at high energies due to the soft or collinear radiation of virtual and real W and Z bosons that result in Sudakov-like corrections of the form alpha(l)(W) log(n)(Q(/)(2)M(W,Z)(2)), where alpha(W) = alpha/(4 pi sin(2)theta(W)) and n <= 2l - 1. The inclusion of EW corrections in predictions for hadron colliders is therefore especially important when searching for signals of possible new physics in distributions probing the kinematic regime Q(2) >> M-V(2). Next-to-leading order (NLO) EW corrections should also be taken into account when their size [O(alpha)] is comparable to that of QCD corrections at next-to-next-to-leading order (NNLO) [O(alpha(2)(s))]. To this end we have implemented the NLO weak corrections to the Neutral-Current Drell-Yan process, top-quark pair production and dijet production in the parton-level Monte-Carlo program MCFM. This enables a combined study with the corresponding QCD corrections at NLO and NNLO. We provide both the full NLO weak corrections and their Sudakov approximation since the latter is often used for a fast evaluation of weak effects at high energies and can be extended to higher orders. With both the exact and approximate results at hand, the validity of the Sudakov approximation can be readily quantified.

Electroweak (EW) corrections at the LHC can be enhanced at high energies due to soft/collinear radiation of W and Z bosons, being dominated by Sudakov-like corrections in the form of $\alpha_W^l\log^n(Q^2/M_W^2)$ $(n \le 2l, \alpha_W = \alpha/(4\pi\sin\theta_W^2))$ when the energy scale $Q$ enters the TeV regime. Thus, the inclusion of EW corrections in LHC predictions is important for the search of possible signals of new physics in tails of kinematic distributions. EW corrections should also be taken into account in virtue of their comparable size ($\mathcal{O}(\alpha)$) to that of higher order QCD corrections ($\mathcal{O}(\alpha_s^2)$). We calculated the next-to-leading-order (NLO) weak corrections to the neutral-current (NC) Drell-Yan process, top-quark pair production and di-jet producion, and implemented them in the Monte-Carlo program MCFM. This enables a combined study with the corresponding NLO QCD corrections. We provide both the full NLO weak corrections and their weak Sudakov approximation valid at high energies. The latter is often used for a fast evaluation of weak effects, and having the exact result available as well allows to quantify the validity of the Sudakov approximation.

The hadronic production of a Higgs boson (H) in association with b jets will play an important role in investigating the Higgs-boson couplings to Standard Model particles during Run II of the CERN Large Hadron Collider, and could in particular reveal the presence of anomalies in the assumed hierarchy of Yukawa couplings to the third-generation quarks. A very high degree of accuracy in the theoretical description of this process is crucial to implement the rich physics program that could lead to either direct or indirect evidence of new physics from Higgs-boson measurements. Aiming for accuracy in the theoretical modeling of H+b-jet production, we have interfaced the analytic Next-to-Leading-Order QCD calculation of H-bottom-antibottom production with parton-shower Monte Carlo event generators in the POWHEG BOX framework. In this paper we describe the most relevant aspects of the implementation and present results for the production of H+1 b jet, H+2 b jets, and $H$ with no tagged b jets, in the form of kinematic distributions of the Higgs boson, of the b jets, and of the non-b jets, at the 13 TeV Large Hadron Collider. The corresponding code is part of the public release of the POWHEG BOX.

The addition of the QCD axion to the Minimal Supersymmetric Standard Model (MSSM) not only solves the strong CP problem but also modifies the dark sector with new dark matter candidates. While SUSY axion phenomenology is usually restricted to searches for the axion itself or searches for the ordinary SUSY particles, this work focuses on scenarios where the axion's superpartner, the axino, may be detectable at the Large Hadron Collider (LHC) in the decays of neutralinos displaced from the primary vertex. In particular, we focus on the KSVZ axino within the hadronic axion window. The decay length of neutralinos in this scenario easily fits the ATLAS detector for SUSY spectra expected to be testable at the 14 TeV LHC. We compare this signature of displaced decays to axinos to other well motivated scenarios containing a long lived neutralino which decays inside the detector. These alternative scenarios can in some cases very closely mimic the expected axino signature, and the degree to which they are distinguishable is discussed. We also briefly comment on the cosmological viability of such a scenario.

We study possible CP violating effects due to the one loop corrections to the top quark pair production in the Complex MSSM with minimal flavor violation (MFV) at hadron colliders. We calculate the complete SUSY Electroweak and SUSY QCD corrections to the two main production mechanisms, namely: the quark-antiquark annihilation and the gluon fusion processes. At the top quark level, we study the spin-spin correlating observables that may be sensitive to the CP violating phases presented in the Complex MFV-MSSM. We present here the main results at the parton level, in particular the SUSY QCD contributions, which are the most important ones.

We present results from the analytic calculation of top+antitop+Higgs hadronic production at Next-to-Leading Order in QCD interfaced with parton-shower Monte Carlo event generators in the POWHEG BOX framework. We consider kinematic distributions of the top quark and Higgs boson at the 8 TeV Large Hadron Collider and study the theoretical uncertainties due to specific choices of renormalization/factorization scales and parton-showering algorithms, namely PYTHIA and HERWIG. The importance of spin-correlations in the production and decay stages of a top/antitop quark is discussed on the example of kinematic distributions of leptons originating from the top/antitop decays. The corresponding code is now part of the public release of the POWHEG BOX.

A comprehensive review of physics at an [Formula: see text] linear collider in the energy range of [Formula: see text] GeV-3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well as astroparticle physics. The report focusses in particular on Higgs-boson, top-quark and electroweak precision physics, but also discusses several models of beyond the standard model physics such as supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analysed as well.

A comprehensive review of physics at an \(e^+e^-\) linear collider in the energy range of \(\sqrt{s}=92\) GeV–3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well as astroparticle physics. The report focusses in particular on Higgs-boson, top-quark and electroweak precision physics, but also discusses several models of beyond the standard model physics such as supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analysed as well.