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Global LHC constraints on electroweak-inos with SModelS v2.3

by Mohammad Mahdi Altakach, Sabine Kraml, Andre Lessa, Sahana Narasimha, Timothée Pascal, Théo Reymermier, Wolfgang Waltenberger

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Submission summary

Authors (as registered SciPost users): Sabine Kraml · Timothée Pascal · Wolfgang Waltenberger
Submission information
Preprint Link:  (pdf)
Code repository:
Data repository:
Date submitted: 2024-01-10 01:07
Submitted by: Pascal, Timothée
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • High-Energy Physics - Experiment
  • High-Energy Physics - Phenomenology
Approach: Phenomenological


Electroweak-inos, superpartners of the electroweak gauge and Higgs bosons, play a special role in supersymmetric theories. Their intricate mixing into chargino and neutralino mass eigenstates leads to a rich phenomenology, which makes it difficult to derive generic limits from LHC data. In this paper, we present a global analysis of LHC constraints for promptly decaying electroweak-inos in the context of the minimal supersymmetric standard model, exploiting the SModelS software package. Combining up to 16 ATLAS and CMS searches for which electroweak-ino efficiency maps are available in SModelS, we study which combinations maximise the sensitivity in different regions of the parameter space, how fluctuations in the data in individual analyses influence the global likelihood, and what is the resulting exclusion power of the combination compared to the analysis-by-analysis approach.

Current status:
Has been resubmitted

Reports on this Submission

Anonymous Report 3 on 2024-3-4 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:2312.16635v1, delivered 2024-03-04, doi: 10.21468/SciPost.Report.8659


In this work, the authors performed a global analysis of LHC constraints for the promptly decaying Electroweakinos using the public tool SModelsv2.3. The relevant Electroweakino searches at ATLAS and CMS experiments are incorporated into the SModels v2.3 database. The combined likelihood has been calculated for a particular signal process considering combinability based on approximate correlation among different experimental analyses. One of the main findings of this study is that the exclusion effect of the most sensitive analyses can be diminished if a combination of analyses is considered. The results have been exemplified with various gaugino compositions of the lightest supersymmetric particle (LSP), i.e. the neutralino. The production cross-sections are analyzed at NLO with the newly added Resummino interface.
The study is rigorous and comprehensive and the paper warrants publication.

Minor comments:
1. The sleptons are considered decoupled in this study. However, the authors may wish to comment on including searches where chargino decays via slepton which is a part of the 2lepton plus mET searches (e.g. Ref. [39]), whether this will be included in the future version or not.

2. The decay branching ratio for the lightest chargino is missing in Fig. 15 and 16.

  • validity: high
  • significance: high
  • originality: high
  • clarity: top
  • formatting: excellent
  • grammar: excellent

Author:  Sabine Kraml  on 2024-03-09  [id 4352]

(in reply to Report 3 on 2024-03-04)

Thank you for the concise and very positive evaluation of our work. I wish to briefly reply to point 1. and the question whether chargino decays via sleptons will be included in a future version:

The results for slepton/sneutrino-mediated chargino decays in, e.g., Ref. [39] are given for a fixed slepton/sneutrino mass only (relative to the chargino and neutrino masses). This corresponds to a 2-dimensional slice of a 3-dimensional parameter space and cannot reliably be used for the general case, where the slepton/sneutrino mass may take any value in-between the chargino and the neutrino mass. Without at least two more 2-dimensional slices (a.k.a. mass plane), allowing us to interpolate the results to general mass patterns, or a full 3-dimensional parametrisation, these results are simply not useful for reinterpretation with SModelS and we therefore do not include them in the database. The issue has been discussed in previous publications, including the RiF report from Run2. Since it is of no direct relevance to the present study, we do not wish to re-iterate on it in this paper.

Anonymous Report 2 on 2024-2-23 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:2312.16635v1, delivered 2024-02-23, doi: 10.21468/SciPost.Report.8610


Report attached in PDF


  • validity: -
  • significance: -
  • originality: -
  • clarity: -
  • formatting: -
  • grammar: -

Author:  Sabine Kraml  on 2024-03-09  [id 4353]

(in reply to Report 2 on 2024-02-23)
answer to question

We thank the referee for the careful assessment and the detailed comments on our work. Most points raised by the referee have been accommodated in the revised version of the manuscript. We here supplement some additional information:

  1. Regarding the usage of the full statistical model for the ATLAS-SUSY-2018-41 analysis : Indeed a set of statistical models for the analysis ATLAS-SUSY-2018-41 has been available for a while. However, the version that we need has been uploaded on HEPData as “version 3” only in mid-November 2023, when our numerical study (which was highly CPU intensive) was basically completed. Moreover, using this full statistical model is less straightforward as it seems, as the relevant efficiency maps have to be extracted from the pyhf patchsets, and their validation turns out to be quite difficult for some of the simplified models. In particular the differences w.r.t. the official ATLAS results noted by the referee seem to remain. Likely, this is more due to the accuracy of the efficiency maps than the statistical modelling. We are investigating this in detail, but, for this study, we do not go beyond what is implemented in the v2.3 database.

  2. Regarding the impact of the NLO cross sections computed with Resummino: First of all we confirm that, for speed reasons, we computed the cross sections at NLO, not NLO+NLL, in the scan (section 4.1). Going from LO to NLO is indeed quite relevant: about 15% less points would be flagged as excluded when using only the LO cross sections. This corresponds roughly to the relative difference between LO and NLO cross sections. We have added a sentence at the end of the second paragraph of section 5 (page 21) quantifying the relevance of the NLO cross sections. However, in order not to disrupt the flow of the discussion in section 5, we refrain from adding any plots.

  3. In the minor issues, on referring to the higgsino-like states as a triplet: By triplet we mean three non-degenerate masses. This is rather common in the literature, and we like to stick to this phrasing.

For everything else, please see the "list of changes" which accompanies the revised version of the manuscript.

Anonymous Report 1 on 2024-2-22 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:2312.16635v1, delivered 2024-02-22, doi: 10.21468/SciPost.Report.8604


Strong paper


Any substantial theory discussion beyond pmssm is avoided


Report on Altakach et al., Global LHC constraints...

The paper by Altakach et al. presents a global analysis of
electroweakino pair production using 11 ATLAS and 5 CMS simplified model
seach channels. They provide a solid review of these various experimental
analyses, and then perform a scan over EWino weak scale parameter space
M1, M2, mu and tanb to present global exclusion results in the various
parameter space planes.
This paper straddles a middle ground trying to be more theoretical than
simplified models but then ignoring theory motivations such as naturalness
which is violated by too large a mu parameter. They remark at the end that
their analysis doesn't address the ATLAS and CMS soft dilepton excesses
that can arise from light higgsino pair production,
but they promise to address this case using a future version of SMODELS v3.
It may be worth noting the connection of these signals to naturalness
in the discussion of Sec. 6 since this an important motivation.
This appears to be a solid piece of work and thus I recommend publication.

  • validity: high
  • significance: high
  • originality: good
  • clarity: high
  • formatting: excellent
  • grammar: excellent

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