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The effective field theory of low scale see-saw at colliders.

Biekötter, Anke and Chala, Mikael and Spannowsky, Michael (2020) 'The effective field theory of low scale see-saw at colliders.', European physical journal C., 80 (8). p. 743.


We study the Standard Model effective field theory (νSMEFT) extended with operators involving right-handed neutrinos, focussing on the regime where the right-handed neutrinos decay promptly on collider scales to a photon and a Standard Model neutrino. This scenario arises naturally for right-handed neutrinos with masses of the order mN∼0.1…10GeV. We limit the relevant dimension-six operator coefficients using LEP and LHC searches with photons and missing energy in the final state as well as pion and tau decays. While bounds on new physics contributions are generally in the TeV scale for order one operator coefficients, some coefficients, however, remain very poorly constrained or even entirely evade bounds from current data. Consequently, we identify such weakly constrained scenarios and propose new searches for rare top and tau decays involving photons to probe potential new physics in the νSMEFT parameter space. Our analysis highlights the importance of performing dedicated searches for new rare tau and top decays.

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Publisher statement:This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit
Date accepted:09 August 2020
Date deposited:18 August 2020
Date of first online publication:14 August 2020
Date first made open access:18 August 2020

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