We propose a novel method for the elimination of negative Monte Carlo event weights. The method is process-agnostic, independent of any analysis, and preserves all physical observables. We demonstrate the overall performance and systematic improvemen
t with increasing event sample size, based on predictions for the production of a W boson with two jets calculated at next-to-leading order perturbation theory.
We describe the calculation of the QCD contribution to same-sign $W$-pair production, $ppto e^pm u_e mu^pm u_mu jj$, resumming all contributions scaling as $alpha_W^4 alpha_s^{2+k}log^k(hat s/p_perp^2)$ [arXiv:2107.06818]. These leading logarithmic
contributions are enhanced by typical cuts used for Vector Boson Scattering (VBS) studies. We show that while the cross sections are little affected by these corrections, other more exclusive observables relevant for experimental studies are affected more significantly.
We present the results of the first calculation of the logarithmic corrections to the QCD contribution to same-sign $W$-pair production, $ppto e^pm u_e mu^pm u_mu jj$, for same-sign charged leptons. This includes all leading logarithmic contributio
ns which scale as $alpha_W^4 alpha_s^{2+k}log^k(hat s/p_perp^2)$. This process is important for the study of electroweak couplings and hence the QCD contributions are usually suppressed through a choice of Vector Boson Scattering (VBS) cuts. These select regions of phase space where logarithms in $hat s/p_perp^2$ are enhanced. While the logarithmic corrections lead to a small change for the cross sections, several distributions relevant for experimental studies are affected more significantly.
Large logarithmic corrections in $hat s/p_t^2$ lead to substantial variations in the perturbative predictions for inclusive $W$-plus-dijet processes at the Large Hadron Collider. This instability can be cured by summing the leading-logarithmic contri
butions in $hat s/p_t^2$ to all orders in $alpha_s$. As expected though, leading logarithmic accuracy is insufficient to guarantee a suitable description in regions of phase space away from the high energy limit. We present (i) the first calculation of all partonic channels contributing at next-to-leading logarithmic order in $W$-boson production in association with at least two jets, and (ii) bin-by-bin matching to next-to-leading fixed-order accuracy. This new perturbative input is implemented in emph{High Energy Jets}, and systematically improves the description of available experimental data in regions of phase space which are formally subleading with respect to $hat s/p_t^2$.
We propose the Positive Resampler to solve the problem associated with event samples from state-of-the-art predictions for scattering processes at hadron colliders typically involving a sizeable number of events contributing with negative weight. The
proposed method guarantees positive weights for all physical distributions, and a correct description of all observables. A desirable side product of the method is the possibility to reduce the size of event samples produced by General Purpose Event Generators, thus lowering the resource demands for subsequent computing-intensive event processing steps. We demonstrate the viability and efficiency of our approach by considering its application to a next-to-leading order + parton shower merged prediction for the production of a $W$ boson in association with multiple jets.
We present HEJ 2, a new implementation of the High Energy Jets formalism for high-energy resummation in hadron-collider processes as a flexible Monte Carlo event generator. In combination with a conventional fixed-order event generator, HEJ 2 can be
used to obtain greatly improved predictions for a number of phenomenologically important processes by adding all-order logarithmic corrections in $hat{s}/p_perp^2$. A prime example for such a process is the gluon-fusion production of a Higgs boson in association with widely separated jets, which constitutes the dominant background to Higgs boson production in weak-boson fusion.
