@article{DennerLangPellenetal.2017, author = {Denner, Ansgar and Lang, Jean-Nicolas and Pellen, Mathieu and Uccirati, Sandro}, title = {Higgs production in association with off-shell top-antitop pairs at NLO EW and QCD at the LHC}, series = {Journal of High Energy Physics}, journal = {Journal of High Energy Physics}, number = {2}, doi = {10.1007/JHEP02(2017)053}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171871}, year = {2017}, abstract = {We present NLO electroweak corrections to Higgs production in association with off-shell top-antitop quark pairs. The full process pp → e +νeµ -ν¯µbb¯H is considered, and hence all interference, off-shell, and non-resonant contributions are taken into account. The electroweak corrections turn out to be below one per cent for the integrated cross section but can exceed 10\% in certain phase-space regions. In addition to its phenomenological relevance, the computation constitutes a major technical achievement as the full NLO virtual corrections involving up to 9-point functions have been computed exactly. The results of the full computation are supported by two calculations in the double-pole approximation. These also allow to infer the effect of off-shell contributions and emphasise their importance especially for the run II of the LHC. Finally, we present combined predictions featuring both NLO electroweak and QCD corrections in a common set-up that will help the experimental collaborations in their quest of precisely measuring the aforementioned process.}, language = {en} } @phdthesis{Lang2017, author = {Lang, Jean-Nicolas Olivier}, title = {Automation of electroweak NLO corrections in general models}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-154426}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2017}, abstract = {The thesis deals with the automated generation and efficient evaluation of scattering amplitudes in general relativistic quantum field theories at one-loop order in perturbation theory. At the present time we lack signals beyond the Standard Model which, in the past, have guided the high-energy physics community, and ultimately led to the discovery of new physics phenomena. In the future, precision tests could acquire this guiding role by systematically probing the Standard Model and constraining Beyond the Standard Model theories. As current experimental constraints strongly favour Standard Model-like theories, only small deviations with respect to the Standard Model are expected which need to be studied in detail. The required precision demands one-loop corrections in all future analyses, ideally in a fully automated way, allowing to test a variety of observables in different models and in an effective field theory approach. In the process of achieving this goal we have developed an enhanced version of the tool Recola and on this basis the generalization Recola2. These tools represent fully automated tree- and one-loop-amplitude providers for the Standard Model, or in the case of Recola2 for general models. Concerning the algorithm, we use a purely numerical and fully recursive approach allowing for extreme calculations of yet unmatched complexity. Recola has led to the first computation involving 9-point functions. Beyond the Standard Model theories and Effective Field theories are integrated into the Recola2 framework as model files. Renormalized model files are produced with the newly developed tool Rept1l, which can perform the renormalization in a fully automated way, starting from nothing but Feynman rules. In view of validation, we have extended Recola2 to new gauges such as the Background-Field Method and the class of Rxi gauges. In particular, the Background-Field Method formulation for new theories serves as an automated validation, and is very useful in practical calculations and the formulation of renormalization conditions. We have applied the system to produce the first results for Higgs-boson production in Higgs strahlung and vector-boson fusion in the Two-Higgs-Doublet Model and the Higgs-Singlet Extension of the Standard Model. All in all, we have laid the foundation for an automated generation and computation of one-loop amplitudes within a large class of phenomenologically interesting theories. Furthermore, we enable the use of our system via a very flexible and dynamic control which does not require any intermediate intervention.}, subject = {Standardmodell }, language = {en} } @article{DennerLangUccirati2017, author = {Denner, Ansgar and Lang, Jean-Nicolas and Uccirati, Sandro}, title = {NLO electroweak corrections in extended Higgs sectors with RECOLA2}, series = {Journal of High Energy Physics}, volume = {7}, journal = {Journal of High Energy Physics}, number = {87}, doi = {10.1007/JHEP07(2017)087}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170673}, year = {2017}, abstract = {We present the computer code RECOLA2 along with the first NLO electroweak corrections to Higgs production in vector-boson fusion and updated results for Higgs strahlung in the Two-Higgs-Doublet Model and Higgs-Singlet extension of the Standard Model. A fully automated procedure for the generation of tree-level and one-loop matrix elements in general models, including renormalization, is presented. We discuss the application of the Background-Field Method to the extended models. Numerical results for NLO electroweak cross sections are presented for different renormalization schemes in the Two-Higgs-Doublet Model and the Higgs-Singlet extension of the Standard Model. Finally, we present distributions for the production of a heavy Higgs boson.}, language = {en} } @article{DennerJennichesLangetal.2016, author = {Denner, Ansgar and Jenniches, Laura and Lang, Jean-Nicolas and Sturm, Christian}, title = {Gauge-independent (MS)over-bar renormalization in the 2HDM}, series = {Journal of High Energy Physics}, volume = {09}, journal = {Journal of High Energy Physics}, number = {115}, doi = {10.1007/JHEP09(2016)115}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-166402}, year = {2016}, abstract = {We present a consistent renormalization scheme for the CP-conserving Two-Higgs-Doublet Model based on (MS)over-bar renormalization of the mixing angles and the soft-Z 2-symmetry-breaking scale M sb in the Higgs sector. This scheme requires to treat tadpoles fully consistently in all steps of the calculation in order to provide gauge-independent S-matrix elements. We show how bare physical parameters have to be defined and verify the gauge independence of physical quantities by explicit calculations in a general R ξ -gauge. The procedure is straightforward and applicable to other models with extended Higgs sectors. In contrast to the proposed scheme, the (MS)over-bar renormalization of the mixing angles combined with popular on-shell renormalization schemes gives rise to gauge-dependent results already at the one-loop level. We present explicit results for electroweak NLO corrections to selected processes in the appropriately renormalized Two-Higgs-Doublet Model and in particular discuss their scale dependence.}, language = {en} }