Diphoton production in association with two bottom jets

We study the production of a photon pair in association with two bottom jets at the LHC. This process constitutes an important background to double Higgs production with the subsequent decay of the two Higgs bosons into a pair of photons and b-quarks respectively. We calculate this process at next-to-leading order accuracy in QCD and find that QCD corrections lead to a substantial increase of the production cross section due to new channels opening up at next-to-leading order and their inclusion is therefore inevitable for a reliable prediction. Furthermore, the approximation of massless b-quarks is scrutinized by calculating the process with both massless and massive b-quarks. We find that the massive bottom quark leads to a substantial reduction of the cross section where the biggest effect is however due to the use of a four flavor PDF set and the corresponding smaller values for the strong coupling constant.Comment: 19 pages, 10 figure

Automation of the Dipole Subtraction Method in MadGraph/MadEvent

We present the implementation of the dipole subtraction formalism for the real radiation contributions to any next-to-leading order QCD process in the MadGraph/MadEvent framework. Both massless and massive dipoles are considered. Starting from a specific (n+1)-particle process the package provides a Fortran code for all possible dipoles to all Born processes that constitute the subtraction term to the (n+1)-particle process. The output files are given in the usual "MadGraph StandAlone" style using helicity amplitudes.Comment: 14 pages, 4 figure

Interference contributions to gluon initiated heavy Higgs production in the Two-Higgs-Doublet Model

We discuss the production of a heavy neutral Higgs boson of a CP-conserving Two-Higgs-Doublet Model in gluon fusion and its decay into a four-fermion final state, $gg (\rightarrow VV) \rightarrow e^+e^-\mu^+\mu^-/e^+e^-\nu_l\bar\nu_l$. We investigate the interference contributions to invariant mass distributions of the four-fermion final state and other relevant kinematical observables. The relative importance of the different contributions is quantified for the process in the on-shell approximation, $gg\rightarrow ZZ$. We show that interferences of the heavy Higgs with the light Higgs boson and background contributions are essential for a correct description of the differential cross section. Even though they contribute below $\mathcal{O}(10\%)$ to those heavy Higgs signal cross sections, to which the experiments at the Large Hadron Collider were sensitive in its first run, we find that they are sizeable in certain regions of the parameter space that are relevant for future heavy Higgs boson searches. In fact, the interference contributions can significantly enhance the experimental sensitivity to the heavy Higgs boson.Comment: 24 pages, 13 figures; minor clarifications, updated references, matches published versio

Integrated dipoles with MadDipole in the MadGraph framework

Heading towards a full automation of next-to-leading order (NLO) QCD corrections, one important ingredient is the analytical integration over the one-particle phase space of the unresolved particle that is necessary when adding the subtraction terms to the virtual corrections. We present the implementation of these integrated dipoles in the MadGraph framework. The result is a package that allows an automated calculation for the NLO real emission parts of an arbitrary process.Comment: 22 pages, 1 figure. Published version: few reference updates and a couple of minor corrections to the tex

Automation of electroweak corrections for LHC processes

For the Run 2 of the LHC next-to-leading order electroweak corrections will play an important role. Even though they are typically moderate at the level of total cross sections they can lead to substantial deviations in the shapes of distributions. In particular for new physics searches but also for a precise determination of Standard Model observables their inclusion in the theoretical predictions is mandatory for a reliable estimation of the Standard Model contribution. In this article we review the status and recent developments in electroweak calculations and their automation for LHC processes. We discuss general issues and properties of NLO electroweak corrections and present some examples, including the full calculation of the NLO corrections to the production of a W boson in association with two jets computed using GoSaM interfaced to MadDipole.Comment: LaTex, 60 pages, 8 Figure

GoSam 2.0: Automated one loop calculations within and beyond the Standard Model

We present GoSam 2.0, a fully automated framework for the generation and evaluation of one loop amplitudes in multi leg processes. The new version offers numerous improvements both on generational aspects as well as on the reduction side. This leads to a faster and more stable code for calculations within and beyond the Standard Model. Furthermore it contains the extended version of the standardized interface to Monte Carlo programs which allows for an easy combination with other existing tools. We briefly describe the conceptual innovations and present some phenomenological results.Comment: 7 pages, 3 figures, Contribution to the Proceeedings of the 37th International Conference on High Energy Physics (ICHEP) 2014, Valencia, Spai

Constraints on Electroweak Effective Operators at One Loop

We derive bounds on nine dimension-six operators involving electroweak gauge bosons and the Higgs boson from precision electroweak data. Four of these operators contribute at tree level, and five contribute only at one loop. Using the full power of effective field theory, we show that the bounds on the five loop-level operators are much weaker than previously claimed, and thus much weaker than bounds from tree-level processes at high-energy colliders.Comment: 15 page