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--- 2017:groups:np:eftinterference [2017/06/16 17:42]
ken.mimasu created
+++ 2017:groups:np:eftinterference [2017/08/15 13:46]
francesco.riva
@@ Line 1: / Line 1: @@
-Non-interference theorem in dimension 6 EFT beyond LO & 2->2 processes
+====== Non-interference in dimension 6 EFT: beyond LO & 2 to 2 processes ======
+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, Olivier Mattelaer, Adam Falkowski
+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.
+We focus on the operator that generates transverse helicity, schematically O_{3W}= W_{\mu\nu}^3
+References:
+  * "Helicity selection rules and noninterference for BSM amplitudes" [[https://arxiv.org/abs/1607.05236| (arXiv)]]
+  * "Testing gluon selfinteractions in three jet events at hadron colliders" [[https://arxiv.org/abs/hep-ph/9312363| (arXiv)]]
+Helicity amplitude from madgraph (2 to 2 and 2 to 3):
+  - https://phystev.cnrs.fr/wiki/_media/2017:groups:np:ee_ww_sm_only.tgz
+  - https://phystev.cnrs.fr/wiki/_media/2017:groups:np:ee_ww_int_only.tgz
+  - 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:
+{{:2017:groups:np:clic.jpg?direct&400|}}
+To Do:
+) Read References (in particular Dixon&Shadmi)
+) Compute Amplitude for e^+ e^- -> W^+ W^- and e^+ e^- -> W^+ W^- \gamma or Z in the SM first and with the above dimension-6 operator
+) Expand in m_W/Energy and in g^'->0 to have simpler expressions
+) Check with MG5 the analog of the angular distributions of Dixon/Shadmi
+) Asses, as function of the collision energy, luminosity and systematic errors, wheter the best reach on c_{3W} is given by processes with 3 final states or two
+Further Questions
+Also loop effects generate interference. Yet this is small compared with the tree-level SM^2 contribution to the same amplitude. Instead for real emission both the leading SM^2 and interference are suppressed. Do Sudakov effects play a role here? can they enhance virtual loops?

Les Houches

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