People interested (add your name): Francesco Riva, Ken Mimasu, Benjamin Fuks, Julia Harz, Kristin Lohwasser, Fabio Maltoni, Jorge de Blas, Daniele Barducci, Minho Son, Haiying Cai

Investigate the impact of higher order corrections or additional radiation on high energy 2→2 processes involving dimension 6 EFT operators that have been shown not to interfere at leading order.

A simple test case may be $W^+ W^-$ production at a lepton collider. Here the EW corrections including dimension 6 operators have not been calculated but an extra photon (or any extra vector) emission would alter the helicity structure and is part of the higher order contribution.

References:

• “Helicity selection rules and noninterference for BSM amplitudes” (arXiv)

Helicity amplitude from madgraph (2 to 2 and 2 to 3):

1. https://phystev.cnrs.fr/wiki/_media/2017:groups:np:ee_ww_sm_only.tgz
2. https://phystev.cnrs.fr/wiki/_media/2017:groups:np:ee_ww_int_only.tgz
3. https://phystev.cnrs.fr/wiki/_media/2017:groups:np:ee_ww_sm_dim6.tgz

Benchmark parameters from CLIC [https://arxiv.org/abs/1608.07537 – Updated baseline for a staged Compact Linear Collider]

accelerator design foresees 80% electron polarisation.

stages running with different CME and luminosity: