In this work, a new Monte-Carlo simulation of double parton scattering (DPS) at parton level is presented. The simulation is based on the QCD framework developed recently by M. Diehl, J. R. Gaunt and K. Schönwald. With this framework, the dynamics of the 1 → 2 perturbative splittings is consistently included inside the simulation, with the impact-parameter dependence taken into account. The simulation evolves simultaneously two hard systems from a common hard scale down to the hadronic scale. The evolution is performed using an angular-ordered parton shower which is combined with a set of double parton distributions that depend explicitly on the inter-parton distance. An illustrative study is performed in the context of same-sign WW production at the LHC, with the quark content of the proton being limited to three flavours. In several distributions we see differences compared to DPS models in Herwig, Pythia, and the DPS "pocket formula". 6 Summary 39 A Evolution equations for valence and sea components 41 B Initial conditions and number sum rules 42 C Validation plots and scale variations 43

In this paper we will describe two new optimisations implemented in MadGraph5_aMC@NLO, both of which are designed to speed-up the computation of leading-order processes (for any model). First we implement a new method to evaluate the squared matrix element, dubbed helicity recycling, which results in factor of two speed-up. Second, we have modified the multi-channel handling of the phase-space integrator providing tremendous speed-up for VBF-like processes (up to thousands times faster).

In this paper, we calculate the inclusive rate of W + W − pair production through leptonic decay channels W + W − → l + ν l + l − ν l in the k t -factorization framework. We also consider the exclusive W + W − pair production through the one-loop induced gg → H → W + W − channel that is important for the study of new physics beyond the Standard Model. The results are compared with predictions from the Herwig 7 event generator in the collinear factorization framework and with the experimental data from the ATLAS and the CMS collaborations. It will be shown that our predictions for the W + W − boson pair production signals are in agreement with the experimental data as well as the collinear results. a neda.darvishi@manchester.ac.uk

We present here two separate projects. The first is a phase-space generator, dubbed SingularPhasespace. It is designed to help probe the singular limits of NLO simulations. It is hoped this will prove to be a useful tool for developers. The user (or SingularPhasespace) chooses an initial momentum configuration for the hard process and then new events are generated that are successively more and more singular. This is done whilst trying to keep as close to the initial event as possible. This allows for a clear understanding of how the simulation behaves in the singular limit. The second project is our implementation of 'helicity recycling' within M G _ MC@NLO. This is a restructuring of the code that allows the program to recycle parts of the matrix-element calculation when summing it over helicities. This optimisation is applicable to all LO processes. For complex processes we can see a speed up of a factor of ∼2×.