We investigate the sensitivity of existing LHC searches to the charginos and neutralinos of the MSSM when all the other superpartners are decoupled. In this limit, the underlying parameter space reduces to a simple four-dimensional set $\{M_1,\,M_2,\,μ,\,\tanβ\}$. We examine the constraints placed on this parameter space by a broad range of LHC searches taking into account the full set of relevant production and decay channels. We find that the exclusions implied by these searches exceed existing limits from LEP only for smaller values of the Bino mass $M_1 \lesssim 150$ GeV. Our results have implications for MSSM dark matter and electroweak baryogenesis.
We investigate the heavier electroweakino sectors in several versions of the MSSM, which has not been explored so far in the light of the LHC data, and obtain new bounds using the ATLAS Run I constraints in the $3l + {E\!\!\!\!/_T}$ channel. We also venture beyond the trilepton events and predict several novel multilepton + ${E\!\!\!\!/_T}$ signatures of these electroweakinos which may show up before the next shutdown of the LHC.
The aim of this paper is to showcase the novel multilepton ($nl + E\!\!\!\!/_T$, n = 3 - 5) signals, hitherto unexplored at the LHC, arising from the heavier electroweakinos, in several generic pMSSMs at the upcoming LHC experiments. We first briefly review our old constraints on the full electroweakino sector of these models, containing both lighter and heavier sparticles, using the ATLAS trilepton data from the LHC Run I. Next we derive new stronger constraints on this sector for the first time using the ATLAS Run II data. We identify some benchmark points and explore the prospect of observi…
As sequel to a recent paper we examine the phenomenology of the full electroweakino sector of the pMSSM without invoking the adhoc but often employed assumption that the heavier ones are decoupled. We identify several generic models which illustrate the importance of the heavier electroweakinos and constrain them with the LHC $3l$ + ${E\!\!\!\!/_T}$ data. The constraints are usually stronger than that for decoupled heavier electroweakinos indicating that the LHC data is already sensitive to their presence. We also take into account the constraints from the observed dark matter relic density of…
We consider pair-production of electroweakinos promptly decaying to light gravitinos in general gauge mediation scenarios within the minimal supersymmetric standard model. Typically the presence of photons and missing transverse momentum is the key signature for this kind of scenarios. We highlight where LHC analyses which have originally been designed to probe different scenarios provide complementary constraints with respect to the dedicated searches and we present the constraints on the parameter space.
We investigate multi-lepton signals produced by ElectroWeakino (EWino) decays in the MSSM and the TMSSM scenarios with sfermions, gluinos and non Standard Model Higgses at the TeV scale, being the Bino electroweak-scale dark matter. We recast the present LHC constraints on EWinos for these models and we find that wide MSSM and TMSSM parameter regions prove to be allowed. We forecast the number of events expected in the signal regions of the experimental multi-lepton analyses in the next LHC runs. The correlations among these numbers will help to determine whether future deviations in multi-lep…
In this work, we analyse and demonstrate possible strategies to explore extended Higgs sector of the Minimal Supersymmetric Standard Model (MSSM). In particular we concentrate on heavy Higgs decays to electroweakinos. We analyse the Higgs to electroweakino decays in the allowed MSSM parameter space after taking into account 13 TeV LHC searches for supersymmetric particles and phenomenological constraints such as flavour physics, Higgs measurements and dark matter constraints. We explore some novel aspects of these Higgs decays. The final states resulting from Higgs to electroweakino decays wil…
Motivated by the increased precision expected from LHC Run 3, equally accurate theory predictions are mandatory. As supersymmetry mass limits increase, predictions can be improved by threshold resummation. We examine the effects of including next-to-leading logarithms on associated squark-electroweakino production at the LHC and find a significant reduction in the uncertainty of factorisation and renormalisation scale dependence and a modest increase in the total cross section.
Using parton density functions (PDFs) with threshold-resummation improvement, we consistently calculate higgsino/gaugino and slepton pair production at next-to-leading order and next-to-leading logarithmic accuracy at the LHC. The smaller PDF uncertainty of the global PDF sets is exploited with a factorisation method, which also avoids complications arising in the refitting of threshold-resummation improved PDF replicas in Mellin space. We explicitly take into account the reduction of the scale uncertainty due to the resummation. We show that the resummation contributions in the PDF fits parti…
The multi-sector SUSY breaking predicts pseudo-goldstino which can couple to the visible sector more strongly than the ordinary gavitino and thus induce the decays of the lightest neutralino and chargino (collectively called electroweakinos) inside the detector. In this note we study the electroweakino pair productions via vector boson fusion (VBF) processes followed by decays to pseudo-goldstino at the LHC. Our Monte Carlo simulations show that at the 14 TeV LHC with 3000 fb^{-1} luminosity the dominant production channel pp->chargino+neutralino+2 jets can have a statistical significance abov…
In the Minimal Supersymmetric Standard Model light neutralinos can satisfy the dark matter (DM) abundance constraint by resonant annihilation via a $Z$ or a light Higgs ($h$) boson. In this work we study the current and future status of this scenario by investigating relevant experimental constraints, including DM direct detection, measurements of $Z$ and Higgs invisible decays, and direct searches at the Large Hadron Collider (LHC). To take full advantage of the LHC data, we combine the results of all relevant electroweakino searches performed by the Compact Muon Solenoid (CMS) Collaboration.…
The level of experimental precision that will be achieved with LHC Run-III data and in the forthcoming High Luminosity stage calls for equally accurate theoretical predictions to compare with. Here we present updated cross section calculations for the electroweak production of SUSY particles at the LHC with aNNLO+NNLL (approximate next-to-next-to-leading-order plus next-to-next-to-leading-logarithmic) accuracy. Results are shown for slepton pair production and for electroweakinos pair production in their mostly higgsino or gaugino configuration, finding a further significant reduction of the f…
We make a systematic and comparative study for the LHC and ILC for the electroweakino searches in the Minimal Supersymmetric Standard Model. We adopt a general bottom-up approach and scan over the parameter regions for all the three cases of the lightest supersymmetric particle being Bino-, Wino-, and Higgsino-like. The electroweakino signal from pair production and subsequent decay to Wh (h to b\bar b) final state may yield a sensitivity of 95% C.L. exclusion (5sigma discovery) to the mass scale M_2, mu ~ 250-400 GeV (200-250 GeV) at the 14 TeV LHC with an luminosity of 300 fb^{-1}. Combining…
In this work, we examine the sensitivity of monojet searches at the LHC to directly produced charginos and neutralinos (electroweakinos) in the limit of small mass splitting, where the traditional multilepton plus missing energy searches loose their sensitivity. We first recast the existing 8 TeV monojet search at CMS in terms of a SUSY simplified model with only light gauginos (winos and binos) or only light higgsinos. The current searches are not sensitive to MSSM like production cross sections, but would be sensitive to models with 2-20 times enhanced production cross section, for particle …
The projected reach of direct electroweakino searches at the HL-LHC ($\sqrt{s}=14~{\rm TeV}, ~3000~{\rm fb^{-1}}$ LHC) in the framework of simplified models with R-parity violating (RPV) operators: $λ_{112}^{\prime \prime}u^{c}d^{c}s^{c}$ and $λ_{113}^{\prime\prime}u^{c}d^{c}b^{c}$, is studied. Four different analysis channels are chosen: $Wh$ mediated $1l+2b+jets+\rm E{\!\!\!/}_T$, $Wh$ mediated $1l+2γ+jets+\rm E{\!\!\!/}_T$, $WZ$ mediated $3l+jets+\rm E{\!\!\!/}_T$ and $WZ$ mediated $3l+2b+jets+\rm E{\!\!\!/}_T$ and the projected exclusion/discovery reach of direct wino searches in these cha…
Searches for weakly interacting particles is one of the main goals of the high luminosity LHC run. In this work we study the well motivated cases of electroweakinos with mostly Wino and Bino components. We show the relevance of squark induced t-channel production in defining the production cross section and hence the LHC reach. Moreover, a realistic evaluation of the decay branching ratios show a strong dependence on the sign of $μ$ and, for negative values of $μ$, on the relative size of the ratio of $μ$ to the gaugino masses compared with tan$β$. Overall, unless it is kinematically suppresse…
What has the LHC told us about the electroweakino sector of the Minimal Supersymmetric Standard Model?
Nanjing Normal University（南京师范大学）；Monash University（蒙纳士大学）；University of Glasgow（格拉斯哥大学）；University College London（伦敦大学学院）；University of Oslo（奥斯陆大学）；Xi’an Jiaotong-Liverpool University（西交利物浦大学）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；European Organisation for the Exploitation of Meteorological Satellites（欧洲气象卫星应用组织）；CERN（欧洲核子研究中心）；Gridsight（网格视野）
Direct production of electroweakly charged states may not produce the high energy jets or the significant missing energy required in many new physics searches at the LHC. However, because these states produce leptons, they are still potentially detectable over the sizeable Standard Model backgrounds. We show that current LHC Higgs searches, particularly in the WW* and ZZ* channels, are sensitive to new electroweak states, such as supersymmetric charginos or neutralinos. Indeed, the 1.7 fb^{-1} Higgs searches can provide the strongest limits in certain regions of parameter space, extending the …
We perform a threshold resummation calculation for the associated production of squarks and electroweakinos at the LHC to the next-to-leading logarithmic (NLL) accuracy. Analytical results for the process-dependent soft anomalous dimension and the hard matching coefficient are presented. The resummed results are matched to fixed-order predictions at next-to-leading order (NLO) in QCD, which are generalised to scenarios with non-universal squark masses and mixings. Numerically, the NLL contributions increase the total NLO cross section by $2\%$ to $6\%$ for squark masses ranging from 1 TeV to 3…
Using the GAMBIT global fitting framework, we constrain the MSSM with an eV-scale gravitino as the lightest supersymmetric particle, and the six electroweakinos (neutralinos and charginos) as the only other light new states. We combine 15 ATLAS and 12 CMS searches at 13\,TeV, along with a large collection of ATLAS and CMS measurements of Standard Model signatures. This model, which we refer to as the $\tilde G$-EWMSSM, exhibits quite varied collider phenomenology due to its many permitted electroweakino production processes and decay modes. Characteristic $\tilde G$-EWMSSM signal events have t…
We present a set of NLO SUSY-QCD calculations for the pair production of neutralinos and charginos at the LHC, and their matching to parton-shower programs in the framework of the POWHEG-BOX program package. The code we have developed provides a SUSY Les Houches Accord interface for setting supersymmetric input parameters. Decays of the neutralinos and charginos and parton-shower effects can be simulated with PYTHIA. To illustrate the capabilities of our program, we present phenomenological results for a representative SUSY parameter point. We find that NLO-QCD corrections increase the product…
Squeezed supersymmetric spectra are challenging for the LHC searches based on a sizable missing energy and hard visible particles. One such scenario consists of chargino/second-lightest neutralino NLSPs and a lightest neutralino LSP with a relatively small mass gap (10-50GeV). In this note, we explore search strategies to better probe this parameter space. We focus on the three-lepton plus missing energy channel arising from the chargino/second-lightest neutralino associated production, and we investigate the role of a relatively hard initial state radiation (ISR) jet. In addition to typical k…
We present the full NLO SUSY-QCD corrections to the pair production of neutralinos and charginos at the LHC in association with a jet and their matching to parton-shower programs in the framework of the POWHEG-BOX package. The code we have developed provides a SUSY Les Houches Accord interface for setting electroweak and supersymmetric input parameters. Decays of the neutralinos and charginos and parton-shower effects can be simulated with multi-purpose programs such as PYTHIA. The capabilities of the code are illustrated by phenomenological results for a parameter point in the framework of pM…
We extend the formalism developed in Ref. [20] for the renormalisation of the chargino-neutralino sector to the most general case of the MSSM with complex parameters. We show that products of imaginary parts arising from MSSM parameters and from absorptive parts of loop integrals can already contribute to predictions for physical observables at the one-loop level, and demonstrate that the consistent treatment of such contributions gives rise to non-trivial structure, either in the field renormalisation constants or the corrections associated with the external legs of the considered diagrams. W…
Given the increasingly more stringent bounds on Supersymmetry (SUSY) from the LHC searches, we are motivated to explore the situation in which the only accessible SUSY states are the electroweakinos (charginos and neutralinos). In the minimal SUSY framework, we systematically study the three general scenarios classified by the relative size of the gaugino mass parameters M_1, M_2 and the Higgsino mass parameter μ, with six distinctive cases, four of which would naturally result in a compressed spectrum of nearly degenerate LSPs. We present the relevant decay branching fractions and provide ins…
Supersymmetry is one of the most popular extensions of the Standard Model of particle physics, as it offers solutions to several shortcomings of the Standard Model. Natural supersymmetric models favor masses for the new particles which are predicted by supersymmetry in the range of hundreds of GeV, well within the reach of the Large Hadron Collider at CERN. If squarks and gluinos are much heavier, the production of charginos and neutralinos may be the dominant production mode for supersymmetric particles. These proceedings present results from new searches for the production of charginos and n…
We test the impact of the ATLAS and CMS multi-lepton searches performed at the LHC with 8 as well as 13 TeV center-of-mass energy (using only the pre-2018 results) on the chargino and neutralino sector of the NMSSM. Our purpose consists in analyzing the actual reach of these searches for a full model and in emphasizing effects beyond the MSSM that affect the performance of current (MSSM-inspired) electroweakino searches. To this end, we consider several scenarios characterizing specific features of the NMSSM electroweakino sector. We then perform a detailed collider study, generating Monte-Car…
In this review, we consider a general theoretical framework for fermionic color-singlet states, including a singlet, a doublet and a triplet under the standard model SU(2)$_{\rm L}$ gauge symmetry, corresponding to the Bino, Higgsino and Wino in Supersymmetric theories, generically dubbed as "electroweakinos" for their mass eigenstates. Depending on the relations among their three mass parameters and the mixings after the electroweak symmetry breaking, this sector leads to rich phenomenology potentially accessible at the current and near-future experiments. We discuss the decay patterns of the…
As a sequel to our earlier work on wino-dominated $\tilde χ_1^{\pm}$ and $\tilde χ_2^{0}$ (wino models), we focus on the pMSSM models where $\tilde χ_1^{\pm}$ and $\tilde χ_{2,3}^{0}$ are either higgsino dominated (higgsino models) or admixtures of significant amount of higgsino and wino components (mixed models), with or without light sleptons. The LHC constraints in the trilepton channel are significantly weaker even in the presence of light sleptons, especially in the higgsino models, compared to those mostly studied by the LHC collaborations with wino-dominated $\tilde χ_1^{\pm}$ and $\til…
In this paper we present a new search technique for electroweakinos, the superpartners of electroweak gauge and Higgs bosons, based on final states with missing transverse energy, a photon, and a dilepton pair, $\ell^+\,\ell^- + γ+ \displaystyle{\not} E_T$. Unlike traditional electroweakino searches, which perform best when $m_{\widetildeχ^0_{2,3}} - m_{\widetildeχ^0_1}, m_{\widetildeχ^{\pm}} - m_{\widetildeχ^0_1} > m_Z$, our search favors nearly degenerate spectra; degenerate electroweakinos typically have a larger branching ratio to photons, and the cut $m_{\ell\ell} \ll m_Z$ effectively rem…
A multitude of searches have already been performed by the ATLAS and CMS collaborations at the LHC to probe the heavy Higgses of the Minimal Supersymmetric Standard Model (MSSM) through their decay to the Standard Model particles. In this paper, we study the decay of the MSSM heavy Higgses into neutralino and chargino pairs and estimate the maximum possible branching ratios for these `ino' modes being consistent with the present LHC data. After performing a random scan of the relevant electroweakino parameters, we impose the SM 125 GeV Higgs constraints, low energy flavour data as well as curr…
The electroweak sector may play a crucial role in discovering supersymmetry. We systematically investigate the patterns of the MSSM-like electroweakinos, when the neutralino relic abundance $Ω_χh^2\leq 0.12$, that is, also admitting for multi-component Dark Matter, in a broad range of the parameter space. We find that for a very large range of parameters the Direct Detection experiments are/will be sensitive to underabundant neutralinos, in spite of the strong rescaling of the flux factor. The second general conclusion is that the bound $Ω_χh^2\leq 0.12$ together with the LUX (XENON1T) limits …
The hallmark way to search for electroweakinos in natural supersymmetry at the LHC involves the trilepton plus missing energy final state. This approach assumes an electroweakino mass hierarchy that allows for cascade decays leading to a final state of $W^{\pm}Z^0$ plus missing energy. There are, however, situations when that decay pattern may not exist, such as when a chargino is the lightest electroweakino and the lightest supersymmetric particle is the gravitino. In regions of the parameter space where this ordering occurs, the production of any combination of neutralino/chargino leads to a…
The discovery of a Higgs boson with a mass of 126 GeV at the LHC when combined with the non-observation of new physics both in direct and indirect searches imposes strong constraints on supersymmetric models and in particular on the top squark sector. The experiments for direct detection of dark matter have provided with yet more constraints on the neutralino LSP mass and its interactions. After imposing limits from the Higgs, flavour and dark matter sectors, we examine the feasibility for a light stop in the context of the pMSSM, in light of current results for stop and other SUSY searches at…
In the natural realization of the Next-to-minimal Supersymmetric Standard Model, Higgsinos tend to be lighter than about several hundred GeVs, which can induce detectable leptonic signals at the LHC as well as large DM-nucleon scattering cross section. We explore the constraints from the direct searches for electroweakino and slepton at the LHC Run II and the latest DM direct detection experiments on the scenario with low fine tuning indicator $Δ_{Z/h} \leq 50$. We find that these experiments are complementary to each other in excluding the scenario, and as far as each kind of experiment is co…
We scrutinize the parameter space of the SM-like Higgs boson in the minimal supersymmetric standard model (MSSM) under current experimental constraints. The constraints are from (i) the precison electroweak data and various flavor observables; (ii) the direct 22 separate ATLAS searches in Run-1; (iii) the latest LHC Run-2 Higgs data and tri-lepton search of electroweakinos. We perform a scan over the parameter space and find that the Run-2 data can further exclude a part of parameter space. For the property of the SM-like Higgs boson, its gauge couplings further approach to the SM values with …
Light electroweakinos, the neutral and charged fermionic supersymmetric partners of the Standard Model $\mathrm{SU}(2)\times\mathrm{U}(1)$ gauge bosons and of the two $\mathrm{SU}(2)$ Higgs doublets, are an important target for searches for new physics with the Large Hadron Collider (LHC). However, if the lightest neutralino is the dark matter, constraints from direct dark matter detection experiments rule out large swaths of the parameter space accessible to the LHC, including in large part the so-called "well-tempered" neutralinos. We focus on the Minimal Supersymmetric Standard Model (MSSM)…
We analyze in detail the LHC prospects at the center-of-mass energy of 14 TeV for charged electroweakino searches, decaying to leptons, in compressed supersymmetry scenarios, via exclusive photon-initiated pair production. This provides a potentially increased sensitivity in comparison to inclusive channels, where the background is often overwhelming. We pay particular attention to the challenges that such searches would face in the hostile high pile-up environment of the LHC, giving close consideration to the backgrounds that will be present. The signal we focus on is the exclusive production…
Very precise measurements of masses and cross sections are expected to be achievable with a future linear collider. With such an accuracy one must incorporate loop corrections in order to make meaningful predictions for the underlying new physics parameters. For the electroweakino sector, this involves fitting one-loop predictions to expected measurements of the cross section and forward-backward asymmetry for chargino pair production and of the accessible chargino and neutralino masses. We consider two scenarios with characteristic features, chosen taking recent LHC SUSY and Higgs searches in…
We analyze in detail the LHC prospects at the center-of-mass enery of 14 TeV for charged electroweakino searches, decaying to leptons, in compressed supersymmetry scenarios, via exclusive photon-initiated pair production. This provides a potentially increased sensitivity in comparison to inclusive channels, where the background is often overwhelming. We pay particular attention to the challenges that such searches would face in the hostile high pile--up environment of the LHC, giving close consideration to the backgrounds that will be present. The signal we focus on is the exclusive production…
This is a brief overview on the low energy supersymmetry in light of current experiments including the LHC searches, the dark matter (DM) detections, the muon g-2 and the CDF II measurement of the W-boson mass. We focus on the minimal framework of supersymmetry, namely the minimal supersymmetric model (MSSM), and obtain the following conclusions: (i) The MSSM can survive all current experiments, albeit suffering from the little hierarchy problem due to the heavy stops pushed up by the LHC searches; (ii) The DM relic density can be readily achieved by the thermal freeze-out of the lightest neut…
ATLAS and CMS collaborations have reported the results on the Higgs search analyzing $\sim 36$ fb$^{-1}$ data from Run-II of LHC at 13 TeV. In this work, we study the Higgs sector of the phenomenological Minimal Supersymmetric Standard Model, in light of the recent Higgs data, by studying separately the impact of Run-I and Run-II data. One of the major impacts of the new data on the parameter space comes from the direct searches of neutral CP-even and CP-odd heavy Higgses ($H$ and $A$, respectively) in the $H/A \to τ^{+} τ^{-}$ channel which disfavours high $\tanβ$ regions more efficiently tha…
Searches for supersymmetric electroweakinos have entered a crucial phase, as the integrated luminosity of the Large Hadron Collider is now high enough to compensate for their weak production cross-sections. Working in a framework where the neutralinos and charginos are the only light sparticles in the Minimal Supersymmetric Standard Model, we use gambit to perform a detailed likelihood analysis of the electroweakino sector. We focus on the impacts of recent ATLAS and CMS searches with 36 fb$^{-1}$ of 13 TeV proton-proton collision data. We also include constraints from LEP and invisible decays…
We study the constraints on neutralino dark matter in minimal low energy supersymmetry models and the case of heavy lepton and quark scalar superpartners. For values of the Higgsino and gaugino mass parameters of the order of the weak scale, direct detection experiments are already putting strong bounds on models in which the dominant interactions between the dark matter candidates and nuclei are governed by Higgs boson exchange processes, particularly for positive values of the Higgsino mass parameter mu. For negative values of mu, there can be destructive interference between the amplitudes …
We consider the possibility that the muon g-2 anomaly, $δ(g-2)$, finds its origins in low energy supersymmetry (SUSY). In the general MSSM the parameter space consistent with $δ(g-2)$ and correct dark matter relic density of the lightest neutralino easily evades the present direct LHC limits on sparticle masses and also lies to a large extent beyond future LHC sensitivity. The situation is quite different in GUT-defined scenarios where input SUSY parameters are no longer independent. We analyze to what extent the LHC can probe a broad class of GUT-inspired SUSY models with gaugino non-universa…
