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CP violation at ATLAS in effective field theory

Das Bakshi, Supratim; Chakrabortty, Joydeep; Englert, Christoph; Spannowsky, Michael; Stylianou, Panagiotis

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Supratim Das Bakshi

Joydeep Chakrabortty

Christoph Englert

Panagiotis Stylianou


CP violation beyond the Standard Model (SM) is a crucial missing piece for explaining the observed matter-antimatter asymmetry in the Universe. Recently, the ATLAS experiment at the Large Hadron Collider performed an analysis of electroweak Zjj production, thereby excluding the SM locally at 95% confidence level in the measurement of CP-sensitive observables. We take the excess interpretation in terms of anomalous gauge-Higgs interactions at face value and discuss further steps that are required to scrutinize its origin. In particular, we discuss the relevance of multiboson production using adapted angular observables to show how they can be used to directly tension the reported Zjj excess in a more comprehensive analysis. To connect the excess to a concrete UV scenario for which the underlying assumptions of the Zjj analysis are valid, we identify vectorlike leptons as a candidate theory consistent with the observed CP-odd Wilson coefficient hierarchy observed by ATLAS. We perform a complete one-loop matching calculation to motivate further model-specific and correlated new physics searches. In parallel, we provide estimates of the sensitivity reach of the LHC’s high luminosity phase for this particular scenario of CP violation in light of electroweak precision and Run-2 Higgs data. These provide strong constraints on the model’s CP-even low-energy phenomenology, but also inform the size of the CP-odd SM deformation indirectly via our model hypothesis.


Das Bakshi, S., Chakrabortty, J., Englert, C., Spannowsky, M., & Stylianou, P. (2021). CP violation at ATLAS in effective field theory. Physical Review D, 103(5), Article 055008.

Journal Article Type Article
Acceptance Date Feb 3, 2021
Online Publication Date Mar 15, 2021
Publication Date Mar 1, 2021
Deposit Date Sep 21, 2021
Publicly Available Date Sep 21, 2021
Journal Physical Review D
Print ISSN 2470-0010
Electronic ISSN 2470-0029
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 103
Issue 5
Article Number 055008


Published Journal Article (Advance online version) (2 Mb)

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Copyright Statement
Advance online version Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP.

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