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LHC EFT WG Note: Basis for Anomalous Quartic Gauge Couplings
by Gauthier Durieux, Grant N. Remmen, Nicholas L. Rodd, Oscar J. P. Éboli, Maria C. Gonzalez-Garcia, Dan Kondo, Hitoshi Murayama, Risshin Okabe
This Submission thread is now published as
Submission summary
Authors (as registered SciPost users): | Gauthier Durieux · Grant Remmen · Nicholas Rodd |
Submission information | |
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Preprint Link: | https://arxiv.org/abs/2411.02483v1 (pdf) |
Date accepted: | 2025-02-10 |
Date submitted: | 2024-11-06 18:27 |
Submitted by: | Rodd, Nicholas |
Submitted to: | SciPost Physics Community Reports |
Ontological classification | |
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Academic field: | Physics |
Specialties: |
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Approaches: | Theoretical, Experimental, Phenomenological |
Abstract
In this note, we give a definitive basis for the dimension-eight operators leading to quartic -- but no cubic -- interactions among electroweak gauge bosons. These are often called anomalous quartic gauge couplings, or aQGCs. We distinguish in particular the CP-even ones from their CP-odd counterparts.
Published as SciPost Phys. Comm. Rep. 6 (2025)
Reports on this Submission
Report #2 by Anonymous (Referee 2) on 2025-1-2 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2411.02483v1, delivered 2025-01-02, doi: 10.21468/SciPost.Report.10415
Report
In this article, the authors present the first complete basis of the dimension-eight SMEFT operators that induce anomalous quartic gauge couplings (aQGC) in the electroweak sector. This corrects several previous, albeit incomplete, efforts by various groups (including some of the authors) to establish such a basis. The article also provides the relations of the presented basis to the ones previously used in the literature. Thus, this paper establishes a valuable foundation for the community to explore aQGC.
The paper is well written and clearly formulated. I only have a few suggestions for improvements:
1) I believe the introduction would benefit from a brief discussion of why aQGC are interesting to study.
2) It is very useful, that the authors also provide a FeynRules implementation of their operator basis in a public GitHub repository that is linked in section 4. The relations of the corresponding operator coefficients are given in Eq. (5). The notation and naming convention are, however, not fully clear when only looking at the paper itself. I would therefore suggest to either properly define the notation and give a few more detail on what FS0,… and cS1,… exactly correspond to, or to possibly move this equation entirely to the GitHub repository, where all coefficients are defined in the FeynRules file. In its current form, Eq. (5) is difficult to understand if one is not looking at the repository in parallel.
3) The notation chosen for the Wilson coefficients in Eq. (6) is rather confusing. While cH2B21 is the coefficient of OH2B21 and c(1)B2H2D2 is the coefficient of O(1)B2H2D2, it appears that the coefficient of OM3 is not given by cM3 but instead by −cM1, and similar naming issues for the other operators.
I would thus suggest using a different notation for the coefficients appearing on the left-hand side of Eq. (6), or to at least clearly state the issues associated with the chosen notation.
4) There is a typo in the acknowledgements: “the the”.
Recommendation
Ask for minor revision
Report #1 by Anonymous (Referee 1) on 2024-12-13 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2411.02483v1, delivered 2024-12-13, doi: 10.21468/SciPost.Report.10325
Report
The report presents a community effort to clarify - once and for all - the composition and properties of the basis of dimension 8 SMEFT operators that generate anomalous Quartic Gauge Couplings (aQGC), but no anomalous Triple Gauge Couplings (aTGC).
The phenomenology of such operators has been studied for a long time, and the ATLAS and CMS collaborations have been long using this formalism to search for anomalies in their measurements, in particular of Vector Boson Scattering processes.
The basis employed was corrected several times in the past years, and the CP properties were never established in a fully correct way, leading to multiple inconvenient changes of notation and updates of the corresponding Monte Carlo tools.
The results of this report, which is co-authored by members of all groups who have previously attempted to close the deal on the operator set, are therefore very welcome.
There is no doubt that this report fulfills all requirements for publication in this journal.
I did my best to cross-check the formulas presented, as the value of the report clearly hinges on them being correct and free from typesetting errors.
I only found a few minor points, that I kindly ask the authors to look into (hopefully one last time) before recommending the report for publication.
1- is a factor 1/2 missing in the definition of OM4,OM5?
ref [3] uses ˆWμν=Wiμντi2.
in OM1, for instance, the 1/4 coming from the two W partially cancels with a 2 from tr(τiτj)=2δij, but in OM4,OM5 there are no traces of the pauli matrices, so I'm not seeing how the 1/2 could go away
2- for the same reason, is a 1/4 missing in the definition of OM7?
3- of all operators, I couldn't understand the conversion of OM7 to the notation of refs [4,6].
using the pauli matrix relation τiτj=δij+iϵijkτk and keeping the current normalization in the definition of OM7, I find:
OM7=OH2W21−OH2W23
where the minus sign in the second term comes from relabeling ijk→kji and then taking ϵkji=−ϵijk.
I'm not sure where the relative factor 2 could come from.
4- as a minor comment, for the sake of having all conventions spelled out, it would be useful to indicate the conventions adopted for the definition of dual field strength and for the covariant derivative sign in the monte carlo codes.
Recommendation
Ask for minor revision
Author: Nicholas Rodd on 2024-12-29 [id 5071]
(in reply to Report 1 on 2024-12-13)
We thank the referee for going over our work so carefully and double checking even fine details of the bases. Let us respond to the comments raised.
We believe there is actually a common issue that resolves the first three of the referee's queries. In particular, we did not define our convention for the basis of the generators. Following our Ref. [4], we took τI=σI/2, with σI the Pauli matrices. That therefore means we have in the notation defined below Eq. (3) of our Ref. [3],
With that convention, our operator definitions exactly match Ref. [3] for OM4,5. This is of course a key point, however, and we will add an explicit definition of τI to the end of section 1.
We believe the factor of 1/4 the referee asked about in OM7 is resolved identically to the 1/2 discussed above.
We evaluated the mapping between the two bases as follows.
This appears to be the exact same manipulation made by the referee up to the factors of 1/4 and 1/2 which again arise from τI=σI/2.
We will explicitly define the dual field strengths and our convention for the covariant derivative in section 1 also.
Anonymous on 2025-01-03 [id 5079]
(in reply to Nicholas Rodd on 2024-12-29 [id 5071])
I thank the authors for their reply.
Indeed, the conventions on the definition of τI were unclear, and taking τI=σI/2 solves all my queries about basis conversion.
There is only one issue left, which is that Ref [6] (Murphy, see below their Eq. 2.2) defines τI=σI, which means there should be factors 2 between the definitions in [4] and [6] for all operators with explicit τ's.
Would the authors agree?
Anonymous on 2025-01-07 [id 5093]
(in reply to Anonymous Comment on 2025-01-03 [id 5079])We had completely missed this different use of τI in the Murphy basis and thank the referee for bringing it to our attention. This will introduce additional factors of 1/2 in the mapping we employ for several of the CP-even and odd mixed type operators, but we will implement these carefully in the updated manuscript. In particular, the operators Q4,5,6W2H2D2 and Q1−6WBH2D2 in the Murphy notation will be updated with an additional factor of 1/2.
Author: Nicholas Rodd on 2025-01-07 [id 5094]
(in reply to Report 2 on 2025-01-02)We thank the referee for their careful reading of the manuscript and FeynRules implementation. We respond to their four comments below.