Track 3: Computations in theoretical physics -- techniques and methods

Here, we attempt to summarize the activities of Track 3 of the 17th International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT 2016).Comment: 10 pages, 3 figures, to appear in the proceedings of ACAT 201

Wbbj production at NLO with POWHEG+MiNLO

We present a next-to-leading order plus parton-shower event generator for the production of a W boson plus two bottom quarks and a jet at hadron colliders, implemented in the POWHEG BOX framework. Bottom-mass effects and spin correlations of the decay products of the W boson are fully taken into account. The code has been automatically generated using the two available interfaces to MadGraph4 and GoSam, the last one updated to a new version. We have applied the MiNLO prescription to our Wbbj calculation, obtaining a finite differential cross section also in the limit of vanishing jet transverse momentum. Furthermore, we have compared several key distributions for Wbbj production with those generated with a next-to-leading order plus parton-shower event generator for Wbb production, and studied their factorization- and renormalization-scale dependence. Finally, we have compared our results with recent experimental data from the ATLAS and CMS Collaborations.Comment: Version as accepted for publication. Added references, one table and one figure. All the rest is the same as version

NNLO Antenna Subtraction with One Hadronic Initial State

In this talk we present the extension of the antenna subtraction method to include initial states containing one hadron at NNLO. We sketch the requirements for the different necessary subtraction terms, and we explain how the antenna functions are integrated over the appropriate phase space by reducing the integrals to a small set of master integrals. Where applicable, our results for the integrated antennae were cross-checked against the known NNLO coefficient functions for deep inelastic scattering processes.Comment: 6 pages, 1 figure. Talk given at RADCOR 2009 - 9th International Symposium on Radiative Corrections (Applications of Quantum Field Theory to Phenomenology) October 25 - 30 200

HW/HZ + 0 and 1 jet at NLO with the POWHEG BOX interfaced to GoSam and their merging within MiNLO

We present a generator for the production of a Higgs boson H in association with a vector boson V=W or Z (including subsequent V decay) plus zero and one jet, that can be used in conjunction with general-purpose shower Monte Carlo generators, according to the POWHEG method, as implemented within the POWHEG BOX framework. We have computed the virtual corrections using GoSam, a program for the automatic construction of virtual amplitudes. In order to do so, we have built a general interface of the POWHEG BOX to the GoSam package. With this addition, the construction of a POWHEG generator within the POWHEG BOX is now fully automatized, except for the construction of the Born phase space. Our HV + 1 jet generators can be run with the recently proposed MiNLO method for the choice of scales and the inclusion of Sudakov form factors. Since the HV production is very similar to V production, we were able to apply an improved MiNLO procedure, that was recently used in H and V production, also in the present case. This procedure is such that the resulting generator achieves NLO accuracy not only for inclusive distributions in HV + 1 jet production but also in HV production, i.e. when the associated jet is not resolved, yielding a further example of matched calculation with no matching scale.Comment: 22 pages, 18 figures. Version accepted for publication on JHE

Multi-leg One-loop Massive Amplitudes from Integrand Reduction via Laurent Expansion

We present the application of a novel reduction technique for one-loop scattering amplitudes based on the combination of the integrand reduction and Laurent expansion. We describe the general features of its implementation in the computer code NINJA, and its interface to GoSam. We apply the new reduction to a series of selected processes involving massive particles, from six to eight legs.Comment: v3: 39 pages, minor typos and one benchmark point correcte

Quel sens de futurs enseignants attribuent-ils à l’évaluation par tâche complexe ?

L'approche par compétence développée dans le cadre de la formation professionnelle des enseignants a entraîné une modification importante des dispositifs d'évaluation. A la Haute Ecole pédagogique de Fribourg, des tâches complexes réparties sur les trois années de formation permettent de certifier le niveau d’acquisition des compétences. Après des travaux antérieurs consacrés à la question de la validité des tâches et à leur évolution analysée du point de vue des formateurs ainsi qu’à la compréhension des critères par les étudiants, cette recherche questionne les étudiants sur le sens qu’ils construisent autour de cette forme d’évaluation. Le rapport des fonctions sommative et formative au regard de l’évaluation des compétences est ainsi questionné à partir des témoignages de futurs enseignants. Cette recherche inscrite dans une visée exploratoire analyse une vingtaine d'entretiens réalisés auprès d'étudiants aborde plusieurs thématiques : la compréhension de l’évaluation réalisée par les formateurs et des différents critères, les mécanismes d'autorégulation mis en oeuvre ainsi que le sens attribué à cette forme d’évaluation. Les résultats montrent la faible compréhension des différents critères utilisés et le caractère hautement formatif associé par les étudiants à ces tâches qui ont pourtant une visée certificative. Cette communication met en évidence les liens étroits entre l’évaluation du développement de compétences professionnelles et le sens que les étudiants voient dans ce type de tâche