Motivated by dark-matter considerations in supersymmetric theories, we investigate in a fairly model-independent way the detection at the LHC of nearly degenerate gauginos with mass differences between a few GeV and about 30 GeV. Due to the degeneracy of gaugino states, the conventional leptonic signals are likely lost. We first consider the leading signal from gluino production and decay. We find that it is quite conceivable to reach a large statistical significance for the multi-jet plus missing energy signal with an integrated luminosity about 50 pb^-1 (50 fb^-1) for a gluino mass of 500 GeV (1 TeV). If gluinos are not too heavy, less than about 1.5 TeV, this channel can typically probe gaugino masses up to about 100 GeV below the gluino mass. We then study the Drell-Yan type of gaugino pair production in association with a hard QCD jet, for gaugino masses in the range of 100-150 GeV. The signal observation may be statistically feasible with about 10 fb^-1, but systematically challenging due to the lack of distinctive features for the signal distributions. By exploiting gaugino pair production through weak boson fusion, signals of large missing energy plus two forward-backward jets may be observable at a 4-6σlevel above the large SM backgrounds with an integrated luminosity of 100-300 fb^-1. Finally, we point out that searching for additional isolated soft muons in the range p_T ~3-10 GeV in the data samples discussed above may help to enrich the signal and to control the systematics. Significant efforts are made to explore the connection between the signal kinematics and the relevant masses for the gluino and gauginos, to probe the mass scales of the superpartners, in particular the LSP dark matter.
We perform a threshold resummation calculation for the associated production of gluinos and gauginos at the LHC to the next-to-leading logarithmic accuracy. Analytical results are presented for the process-dependent soft anomalous dimension and the hard function. The resummed results are matched to a full next-to-leading order calculation, for which we have generalised the previously known results to the case of supersymmetric scenarios featuring non-universal squark masses. Numerically, the next-to-leading logarithmic contributions increase the total next-to-leading order cross section by 7 t…
Most SUSY searches at the LHC are optimised for the MSSM, where gauginos are Majorana particles. By introducing Dirac gauginos, we obtain an enriched phenomenology, from which considerable differences in the LHC signatures and limits are expected as compared to the MSSM. Concretely, in the minimal Dirac gaugino model (MDGSSM) we have six neutralino and three chargino states. Moreover, production cross sections are enhanced for gluinos, while for squarks they are suppressed. In this contribution, we explore the consequences of the current LHC limits on gluinos and squarks in this model.
We present a calculation of higgsino and gaugino pair production at the LHC at next-to-next-to-leading logarithmic (NNLL) accuracy, matched to approximate next-to-next-to-leading order (aNNLO) QCD corrections. We briefly review the formalism for the resummation of large threshold logarithms and highlight the analytical results required at aNNLO+NNLO accuracy. Our numerical results are found to depend on the mass and nature of the produced charginos and neutralinos. The differential and total cross sections for light higgsinos, which like sleptons are produced mostly at small x and in the s-cha…
Dirac gauginos are a well-motivated extension of the MSSM, leading to interesting phenomenological consequences. At the LHC, gluino-pair production is enhanced while squark production is suppressed as compared to the MSSM, and the decay signatures are altered by a more complex chargino and neutralino spectrum. We investigate how this impacts current gluino and squark mass limits from Run~2 of the LHC. Concretely, we compare different assumptions about the electroweak-ino spectrum through four benchmark models paying particular attention to the effect of the trilinear $λ_S$ coupling, which indu…
We investigate exclusion limits on the the non-universal gaugino mass scenario in the Minimal Supersymmetric Standard Model (MSSM), according the the latest results of the super-particle search at the LHC8 and the LHC13. In this scenario, suitable ratios of wino to gluino mass can realize the observed value of the Higgs boson mass, while keeping a small $μ$ parameter. Such a small $μ$ parameter corresponds to the mass of higgsino, so that lightest neutralino and chargino are higgsino-like and their masses are almost degenerate. Besides, we find that the right-handed top squark tends to be ligh…
Now that the mass limits for gluinos have been pushed to the few-TeV range, they might only be visible at the LHC in associated production with lighter gauginos. We compute the corresponding cross section at next-to-leading logarithmic (NLL) and next-to-leading order (NLO) precision in the QCD coupling constant. The resulting expressions are implemented in the public code RESUMMINO and can be directly used in the corresponding experimental searches.
Many supersymmetry models feature gauginos and also sleptons with masses below a few hundred GeV. These can give rise to direct pair production rates at the LHC that can be observed in the data sample recorded by the ATLAS detector. The talk presents results from searches for gaugino and slepton pair production in final states with leptons.
In this letter, we study collider phenomenology in the supersymmetric Standard Model with a certain type of non-universal gaugino masses at the gauge coupling unification scale, motivated by the little hierarchy problem. In this scenario, especially the wino mass is relatively large compared to the gluino mass at the unification scale, and the heavy wino can relax the fine-tuning of the higgsino mass parameter, so-called $μ$-parameter. Besides, it will enhance the lightest Higgs boson mass due to the relatively large left-right mixing of top squarks through the renormalization group (RG) effec…
We argue that in order to account for the muon anomalous magnetic moment $g-2$, dark matter and LHC data, non-universal gaugino masses $M_i$ at the high scale are required in the framework of the Minimal Supersymmetric Standard Model (MSSM). We also need a right-handed smuon $\tildeμ_R$ with a mass around 100 GeV, evading LHC searches due to the proximity of a neutralino $\tildeχ^0_1$ several GeV lighter which allows successful dark matter. We discuss such a scenario in the framework of an $SU(5)$ Grand Unified Theory (GUT) combined with $A_4$ family symmetry, where the three $\overline{5}$ re…
We revisit the existing limits on the gaugino masses in various Supersymmetric (SUSY) scenarios derived from Run-I data of the LHC. These limits obtained from the various final states rely heavily on the simplified assumptions regarding the masses, compositions and decay branching ratios of the gauginos. The most promising exclusion limits on the gaugino masses are obtained from trilepton final states while the second lightest neutralino ($\widetilde χ_2^0$) decaying into the SM-like Higgs and lightest SUSY particle (LSP) results in the weakest bounds. Our aim is to assess the extent of deviat…
The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light higgsinos with mass $\sim 100-300$\,GeV, the lighter the better. While such light compressed spectra may be challenging to observe at LHC, the International Linear $e^+e^-$ Collider (ILC) with $\sqrt{s}>2m_{\rm higgsino}$ would serve as both a SUSY discovery machine and a precision microscope. We study higgsino pair production signatures at the ILC based on full, \texttt{Geant4-}based simulation of the ILD detector concept. We examine several benchmark scenarios that may …
Higgsino in supersymmetric standard models is known to be a promising candidate for dark matter in the Universe. Its phenomenological property is strongly affected by the gaugino fraction in the Higgsino-like state. If this is sizable, in other words, if gaugino masses are less than ${\cal O}(10)$ TeV, we may probe the Higgsino dark matter in future non-accelerator experiments such as dark matter direct searches and measurements of electric dipole moments. On the other hand, if gauginos are much heavier, then it is hard to search for Higgsino in these experiments. In this case, due to a lack o…
The 750 GeV diphoton excess reported by ATLAS and CMS indicates the presence of several pairs of the vector-like matter multiplets around TeV scale. If that is the case, radiative corrections from the $SU(3)$ gauge interaction significantly change from those of MSSM, and the infrared-free nature of the gauge interaction leads to characteristic SUSY mass spectra: a ratio of a squark mass to the gluino mass, and scalar trilinear couplings are enhanced at the low-energy scale. Consequently, even in gaugino mediation models, the Higgs boson mass of 125 GeV is explained with the fairly light gluino…
We study two simple and well motivated nonuniversal gaugino mass models, which predict higgsino dark matter. One can account for the observed dark matter relic density along with the observed Higgs boson mass of ~ 125 GeV over a large region of the parameter space of each model, corresponding to higgsino mass of ~ 1 TeV. In each case this parameter region covers the gluino mass range of 2-3 TeV, parts of which can be probed by the 14 TeV LHC experiments. We study these model predictions for LHC in brief and for dark matter detection experiments in greater detail.
The heavy sfermion scenario is naturally realized when supersymmetry breaking fields are charged under some symmetry or are composite fields. There, scalar partners of standard model fermions and the gravitino are as heavy as O(10-1000) TeV while gauginos are as heavy as O(1) TeV. The scenario is not only consistent with the observed higgs mass, but also is free from cosmological problems such as the Polonyi problem and the gravitino problem. In the scenario, gauginos are primary targets of experimental searches. In this thesis, we discuss gaugino masses in the heavy sfermion scenario. First, …
