Fully automated precision predictions for heavy neutrino production mechanisms at hadron colliders

Motivated by TeV-scale neutrino mass models, we propose a systematic treatment of heavy neutrino (N) production at hadron colliders. Our simple and efficient modeling of the vector boson fusion (VBF) Wγ → Nl and Nl þ nj signal definitions resolve collinear and soft divergences that have plagued past studies, and is applicable to other color-singlet processes, e.g., associated Higgs ðWhÞ, sparticle ðl~ ν~ lÞ, and charged Higgs ðhh∓Þ production. We present, for the first time, a comparison of all leading N production modes, including both gluon fusion (GF) gg → Z=h → Nνl ð−Þ and VBF. We obtain fully differential results up to next-to-leading order (NLO) in QCD accuracy using a Monte Carlo tool chain linking FEYNRULES, NLOCT, and MADGRAPH5_AMC@NLO. Associated model files are publicly available. At the 14 TeV LHC, the leading order GF rate is small and comparable to the NLO Nl þ 1j rate; at a future 100 TeV Very Large Hadron Collider, GF dominates for mN ¼ 300–1500 GeV, beyond which VBF takes the lead

Global fit of pseudo-Nambu-Goldstone Dark Matter

We perform a global fit within the pseudo-Nambu-Goldstone dark matter (DM) model emerging from an additional complex scalar singlet with a softly broken global U(1) symmetry. Leading to a momentum-suppressed DM-nucleon cross section at tree level, the model provides a natural explanation for the null results from direct detection experiments. Our global fit combines constraints from perturbative unitarity, DM relic abundance, Higgs invisible decay, electroweak precision observables and latest Higgs searches at colliders. The results are presented in both frequentist and Bayesian statistical frameworks. Furthermore, post-processing our samples, we include the likelihood from gamma-ray observations of $\mathit{Fermi}$-LAT dwarf spheroidal galaxies and compute the one-loop DM-nucleon cross section. We find two favoured regions characterised by their dominant annihilation channel: the Higgs funnel and annihilation into Higgs pairs. Both are compatible with current $\mathit{Fermi}$-LAT observations, and furthermore, can fit the slight excess observed in four dwarfs in a mass range between about 30-300 GeV. While the former region is hard to probe experimentally, the latter can partly be tested by current observations of cosmic-ray antiprotons as well as future gamma-ray observations.Comment: 35 pages, 10 figures, 2 tables; v2: Matches version published in JHE

Effective Field Theory: A Modern Approach to Anomalous Couplings

We advocate an effective field theory approach to anomalous couplings. The effective field theory approach is the natural way to extend the standard model such that the gauge symmetries are respected. It is general enough to capture any physics beyond the standard model, yet also provides guidance as to the most likely place to see the effects of new physics. The effective field theory approach also clarifies that one need not be concerned with the violation of unitarity in scattering processes at high energy. We apply these ideas to pair production of electroweak vector bosons.Comment: 16 pages, 1 figur

UFO 2.0: the ‘Universal Feynman Output’ format

We present an update of the Universal FeynRules Output model format, commonly known as the UFO format, that is used by several automated matrix-element generators and high-energy physics software. We detail different features that have been proposed as extensions of the initial format during the last ten years, and collect them in the current second version of the model format that we coin the Universal Feynman Output format. Following the initial philosophy of the UFO, they consist of flexible and modular additions to address particle decays, custom propagators, form factors, the renormalisation group running of parameters and masses, and higher-order quantum corrections

Electroweak Higgs boson production in the standard model effective field theory beyond leading order in QCD

We study the impact of dimension-six operators of the standard model effective field theory relevant for vector-boson fusion and associated Higgs boson production at the LHC. We present predictions at the next-to-leading order accuracy in QCD that include matching to parton showers and that rely on fully automated simulations. We show the importance of the subsequent reduction of the theoretical uncertainties in improving the possible discrimination between effective field theory and standard model results, and we demonstrate that the range of the Wilson coefficient values allowed by a global fit to LEP and LHC Run I data can be further constrained by LHC Run II future results

Understanding the roles of forests and tree-based systems in food provision

Forests and other tree-based systems such as agroforestry contribute to food and nutritional security in myriad ways. Directly, trees provide a variety of healthy foods including fruits, leafy vegetables, nuts, seeds and edible oils that can diversify diets and address seasonal food and nutritional gaps. Forests are also sources of a wider range of edible plants and fungi, as well as bushmeat, fish and insects. Treebased systems also support the provision of fodder for meat and dairy animals, of “green fertiliser” to support crop production and of woodfuel, crucial in many communities for cooking food. Indirectly, forests and tree-based systems are a source of income to support communities to purchase foods and they also provide environmental services that support crop production. There are, however, complexities in quantifying the relative benefits and costs of tree-based systems in food provision. These complexities mean that the roles of tree-based systems are often not well understood. A greater understanding focuses on systematic methods for characterising effects across different landscapes and on key indicators, such as dietary diversity measures. This chapter provides a number of case studies to highlight the relevance of forests and tree-based systems for food security and nutrition, and indicates where there is a need to further quantify the roles of these systems, allowing proper integration of their contribution into national and international developmental policies

New physics signals in top physics

Effective Field Theory (EFT) provides a model-independent way to search for new physics if the new degrees of freedom are heavy. The new physics appears then as new interactions between the known particles including modification of the SM vertices. In the Lagrangian, they are written as new operators built from the SM fields and invariant under its symmetries. These operators have dimension higher than four and are suppressed by negative powers of the new physics scale Λ to get the required dimension for the Lagrangian. Only the operators with the lower dimension, i.e. dimension-six, can be kept in good approximation since the new physics scale is well above the energies probed by the experiments. Consequently, EFT is valid only below the scale of the new physics. In this region, the unitary bound is never reached and no form factors are needed unlike for anomalous couplings (see [1] for a complete discussion of the advantages of EFT compared to anomalous couplings). EFT is also more predictive due to the symmetries. For example, an operator often contains several vertices with different numbers of legs all depending on its coefficient only. The symmetries also make the EFT Lagrangian renormalizable and allow loop computation. Despite that the number of dimension-six operators that can be added to the SM Lagrangian is large, only a few contribute to a particular process and they can usually be distinguished using several observables. This will be illustrated in the following for top pair production. The complete discussion and list of references can be found in ref. [2]. The only references hereafter are new measurements or computations that have been used to update the results from ref. [2]