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Status of leptoquark models after LHC Run-2 and discovery prospects at future colliders
by Dr. Nishita Desai, Amartya Sengupta
Submission summary
| Authors (as registered SciPost users): | Amartya Sengupta |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202406_00034v1 (pdf) |
| Date submitted: | June 15, 2024, 2:54 p.m. |
| Submitted by: | Amartya Sengupta |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational, Phenomenological |
Abstract
We study limits from dilepton searches on leptoquark completions to the Stan- dard Model in the parameter space motivated by anomalies in the b → s sector. After a full Run-2 analysis by LHCb, the disparity in lepton flavour universality violation has disappeared. However, the mismatch in angular distributions as well as in Bs → μ+μ− partial width is still unresolved and still implies a possible new physics contribution. We probe three models of leptoquarks — scalar models S3 and R2 as well as vector leptoquark model U1 using non-resonant dilepton searches to place limit on both the mass and couplings to SM fermions. Current limits on lepto- quarks with both non-uniform or uniform coupling to lepton flavours are calculated. Interestingly, if leptoquark couplings to electrons and muons are indeed universal, then the U1 model parameter space that corresponds to the anomalous contribution should already be accessible with Run-2 data in the non-resonant eμ channel. In the non-universal case, there is a significant exclusion in couplings, but not enough to reach regions that explain observed anomalies. We, therefore, examine the prospec- tive sensitivity at the HL-LHC as well as of a 3 TeV future muon collider. For the vector leptoquark model, we find that a muon collider can probe all of the relevant parameter space at 95% confidence with just 1 fb^{-1} data whereas R2 and S3 models can be excluded at 95% with 5 fb^{−1} and 6.5 fb^{−1} luminosity respectively.
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Furthermore, there is no discussion provided of what is already known in the literature regarding the impact of the 2022 LHCb measurement on the validity of leptoquark models and the values of the relevant Wilson coefficients. Such analysis have been done by multiple groups, not only Ref.7, but also e.g. 2212.10497, 2304.07330, 2310.05585. Given the amount of information available, the authors should justify why they pick a result from just one paper and how the results of other analyses might impact they conclusions.
Also, as the idea behind the presented studies is not very original (similar ideas, just differently realised, have been explored), I would expect that the authors would make an effort to make detailed studies, taking into account how the end results can be affected. In contrast, the presented analysis is very arbitrary: assumptions are made without discussing their validity or their effects on the conclusions, higher-order effects are only sometimes included, sometimes not, the limitations of or uncertainties on the derived bounds are not discussed, etc.
Altogether, the paper gives an impression of an outdated draft (also manifesting through the lack of any references to 2023 or 2024 papers), instead of a high-quality final product.
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Another main point concerns the bounds themselves: the analysis is a simple leading order comparison with data. More refined analyses exist in the literature. As an example see the NLO one for scalar leptoquarks at LHC in 2108.11404
In my opinion the paper does not provide an accurate present status of leptoquark models and misses existing work in the field which is more advanced and more up to date.
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