SciPost Submission Page

Constraining Electroweakinos in the Minimal Dirac Gaugino Model

by Mark D. Goodsell, Sabine Kraml, Humberto Reyes-González, Sophie L. Williamson

Submission summary

As Contributors: Sabine Kraml
Preprint link: scipost_202009_00011v1
Code repository:
Data repository:
Date accepted: 2020-09-17
Date submitted: 2020-09-13 22:12
Submitted by: Kraml, Sabine
Submitted to: SciPost Physics
Discipline: Physics
Subject area: High-Energy Physics - Phenomenology
Approaches: Theoretical, Computational, Phenomenological


Supersymmetric models with Dirac instead of Majorana gaugino masses have distinct phenomenological consequences. In this paper, we investigate the electroweakino sector of the Minimal Dirac Gaugino Supersymmetric Standard Model (MDGSSM) with regards to dark matter (DM) and collider constraints. We delineate the parameter space where the lightest neutralino of the MDGSSM is a viable DM candidate, that makes for at least part of the observed relic abundance while evading constraints from DM direct detection, LEP and lowenergy data, and LHC Higgs measurements. The collider phenomenology of the thus emerging scenarios is characterised by the richer electroweakino spectrum as compared to the Minimal Supersymmetric Standard Model (MSSM) -- 6 neutralinos and 3 charginos instead of 4 and 2 in the MSSM, naturally small mass splittings, and the frequent presence of long-lived particles, both charginos and/or neutralinos. Reinterpreting ATLAS and CMS analyses with the help of SModelS and MadAnalysis 5, we discuss the sensitivity of existing LHC searches for new physics to these scenarios and show which cases can be constrained and which escape detection. Finally, we propose a set of benchmark points which can be useful for further studies, designing dedicated experimental analyses and/or investigating the potential of future experiments.

Current status:
Publication decision taken: accept

Editorial decision: For Journal SciPost Physics: Publish
(status: Editorial decision fixed and (if required) accepted by authors)

Author comments upon resubmission

We thank the first referee for recommending our paper for publication. To the remaining concerns of the second referee we reply as follows:

Regarding the question about the meaning of the Ward identity: Apologies for not understanding the source of confusion. Yes it should not matter whether equation (17) or (18) is used. Perhaps the text does not correctly convey that prior to version 4.14.3 the spin structure summation was simply completely wrong for fermionic two-body decays to massless gluons/photons. In correcting the routines, there was a choice of whether to use equation (17) or (18), and it was decided to use the simpler and manifestly non-negative result from equation (18), which is therefore also more stable numerically. We have modified the text for clarity.
For earlier versions of SARAH, instead of one of these expressions above, an incorrect formula was used. As of SARAH version 4.14.3 we implemented the spin summation.

Regarding Fig. 3, we have changed the colour scheme (in both panels of Fig. 3) to make the wino-like point in Fig. 3(b) better visible.

Regarding the benchmark points, we obviously have disagreeing views. We have made our point in the previous reply and can only repeat it. We also want to point out the opinion of the other referee, who stated "The manuscript is well written and provides useful information including the benchmark points that they proposed, in terms of investigating the MDGSSM at colliders."

To clarify the referee's earlier question about the differences in points 7 and 9: they have very different masses! As a consequence, point 7 saturates the dark matter density (so has a p-value in Xenon of only 0.2, raising the prospect of discovery/exclusion within some time) while point 9 is very much underdense: the strategy for searching for these points is then very different, when one considers collider-dark matter complementarity. Perhaps we can further add that, since the spectrum files for our benchmarks are available online, they can prove useful examples for future simulations (for example, further recasting studies) or starting points for further parameter scans. We agree that there can be benefit in a minimalistic approach, but usually at the price of simplification and loss of information. Here, we opted for a different way, that also conveys the complexity of the different scenarios that arise, and we find the 10 points a reasonable choice to this end.

In any case, we think we should be free to present the [number of] sample points we find illustrative and useful, just as the reader is free to use those which suit his or her purpose.

List of changes

- Added "For earlier versions of SARAH, instead of one of these expressions above, an incorrect formula was used." in the paragraph following eq. (18).

- Changed the colour scheme in Fig. 3, to make the wino-like point in Fig. 3(b) better visible.

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