Unless otherwise stated, results in this section assume spectra, production rates, decay modes, and branching ratios as evaluated in the MSSM, with gaugino and sfermion mass unification at the GUT scale. These papers generally study production of ${{\widetilde{\mathit \chi}}_{{i}}^{0}}{{\widetilde{\mathit \chi}}_{{j}}^{0}}$ ($\mathit i{}\geq{}$1, $\mathit j{}\geq{}$2), ${{\widetilde{\mathit \chi}}_{{1}}^{+}}{{\widetilde{\mathit \chi}}_{{1}}^{-}}$ , and (in the case of hadronic collisions) ${{\widetilde{\mathit \chi}}_{{1}}^{+}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$ pairs. The mass limits on ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ are either direct, or follow indirectly from the constraints set by the non-observation of ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ and ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ states on the gaugino and higgsino MSSM parameters $\mathit M_{2}$ and $\mu $. In some cases, information is used from the nonobservation of slepton decays.

Obsolete limits obtained from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ collisions up to $\sqrt {\mathit s }$=184 GeV have been removed from this compilation and can be found in the 2000 Edition (The European Physical Journal C15 1 (2000)) of this Review. $\Delta \mathit m={\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}–{\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$.

VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT $> 150$ 95 1 AAD 2022 E ATLS ${{\mathit t}}{{\widetilde{\mathit \mu}}_{{L}}}$ production, RPV, ${{\widetilde{\mathit \mu}}_{{L}}}$ $\rightarrow$ ${{\mathit \mu}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , ${{\mathit \lambda}_{{231}}^{\,'}}$ = 1, 200 GeV $<$ ${\mathit m}_{{{\widetilde{\mathit \mu}}_{{L}}}}$ $<$ 600 GeV. $\text{none 125 - 175}$ 95 2 TUMASYAN 2022 S CMS 2 same-sign ${{\mathit e}}$ or ${{\mathit \mu}}$, 3 or 4 leptons, Tn1n1A, ${\mathit m}_{{{\widetilde{\mathit G}}}}$ = 1 GeV $\text{none 125 - 415}$ 95 2 TUMASYAN 2022 S CMS 2 same-sign ${{\mathit e}}$ or ${{\mathit \mu}}$, 3 or 4 leptons, Tn1n1B, ${\mathit m}_{{{\widetilde{\mathit G}}}}$ = 1 GeV $\text{none 100 - 625}$ 95 2 TUMASYAN 2022 S CMS 2 same-sign ${{\mathit e}}$ or ${{\mathit \mu}}$, 3 or 4 leptons, Tn1n1C, ${\mathit m}_{{{\widetilde{\mathit G}}}}$ = 1 GeV $\text{none 175 - 1025}$ 95 3 TUMASYAN 2022 V CMS 3, 4 ${{\mathit b}}$-tag jets or 2 large-radius jets, $\not E_T$; Tn1n1A; ${\mathit m}_{{{\widetilde{\mathit G}}}}$=1 GeV $\text{none 450 - 930}$ 95 4 AAD 2021 AX ATLS jets + large-R jets + $\not E_T$, Tn1n1C $\text{none 200 - 320}$ 95 5 AAD 2021 BF ATLS ${{\mathit \ell}^{\pm}}$ + ${{\mathit b}}$-jets + many jets, Tn1n1D, RPV, $\lambda $''$_{323}$ electroweakino decay, degenerate Higgsino triplet $\text{ none 200 - 370}$ 95 5 AAD 2021 BF ATLS ${{\mathit \ell}^{\pm}}$ + ${{\mathit b}}$-jets + many jets, Tn1n1E, RPV, $\lambda {}^{''}_{323}$ electroweakino decay, degenerate Wino doublet 6 DREINER 2009 THEO $>40$ 95 7 ABBIENDI 2004 H OPAL all tan $\beta $, $\Delta \mathit m>$5 GeV, ${\mathit m}_{{{\mathit 0}}}>$500~GeV, ${{\mathit A}_{{0}}}$ = 0 $>42.4$ 95 8 HEISTER 2004 ALEP all tan $\beta $, all $\Delta \mathit m$, all ${\mathit m}_{{{\mathit 0}}}$ $>39.2$ 95 9 ABDALLAH 2003 M DLPH all tan $\beta $, ${\mathit m}_{{{\widetilde{\mathit \nu}}}}>$500~GeV $\bf{>46}$ 95 10 ABDALLAH 2003 M DLPH all tan $\beta $, all $\Delta \mathit m$, all ${\mathit m}_{{{\mathit 0}}}$ $>32.5$ 95 11 ACCIARRI 2000 D L3 tan $\beta >0.7$, $\Delta \mathit m>3$ GeV, all $\mathit m_{0}$ • • We do not use the following data for averages, fits, limits, etc. • • 12 AAD 2014 K ATLS $> 24$ 13 CALIBBI 2013 thermal relic abundance, MSSM particle content 1  AAD 2022E searched in 139 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV for supersymmetry by measuring the yield asymmetry between events containing ${{\mathit e}^{-}}{{\mathit \mu}^{+}}$ and those containing ${{\mathit e}^{+}}{{\mathit \mu}^{-}}$ . This was found in agreement with the standard model prediction of 1. Limits are set on the RPV production of ${{\mathit t}}{{\widetilde{\mathit \mu}}_{{L}}}$ events with ${{\widetilde{\mathit \mu}}_{{L}}}$ $\rightarrow$ ${{\mathit \mu}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ for various values of ${{\mathit \lambda}_{{231}}^{\,'}}$, see their figures 6 and 7. 2  TUMASYAN 2022S searched in 137 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV for evidence of electroweakino pair production in events with three or four leptons, with up to two hadronically decaying ${{\mathit \tau}}$ leptons, or two same-sign light leptons (${{\mathit e}}$ or ${{\mathit \mu}}$). No significant excess above the Standard Model expectations is observed. Limits are set on the mass of ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ in the models Tchi1n2B (in flavory-democratic and tau-enriched or -dominated scenarios), Tchi1n2E, Tchi1n2F, see their Figures $16 - 20$, and on the mass of the higgsino-triplet ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$, ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$, and ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ in the models Tn1n1A, Tn1n1B, and Tn1n1C, see their Figure 21. 3  TUMASYAN 2022V searched in 137 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV for evidence of electroweakino pair production with decay to two Higgs bosons ${{\mathit H}}$, with ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ , resulting either in 4 resolved ${{\mathit b}}$-jets or two large-radius jets, and large $\not E_T$. No significant excess above the Standard Model expectations is observed. Limits are set on the mass of ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ in the models Tn1n1A, see their Figures 11 and 12, or in a model where higgsino-like nearly mass degenerate ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{3}}^{0}}$ are pair produced and each decay to ${{\mathit H}}$ and a bino-like ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$, see their Figure 13. Limits are also set on the gluino mass in the model Tglu1I, see their Figure 14. 4  AAD 2021AX searched in 139 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV for pair production of electroweakinos decaying to the LSP via the emission of Standard Model bosons (Higgs, ${{\mathit W}}$, ${{\mathit Z}}$) decaying into hadrons. The final state in all cases characterised by the presence of $\not E_T$, jets, and large-R jets tagged according to the boson of interest. Different assumptions (Higgsino, Wino, Bino) are made for the pair produced electroweakinos and for the LSP multipliet. No significant excess above the Standard Model predictions is observed. Limits are set on the electroweakino masses as a function of the model parameters (in particular ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$). See Fig. 16. 5  AAD 2021BF searched in 139 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV for pair production of gluinos, stops, electroweakinos decaying RPV either directly or indirectly via the LSP. The final state in all cases is one or two leptons, many jets (up to fifteen) and ${{\mathit b}}$-jets. Different models with different branching fractions of the gluino or stop follow from the assumptions on the nature of the electroweakinos. No significant excess above the Standard Model predictions is observed. Limits are set on the , ${{\widetilde{\mathit t}}_{{1}}}$, electroweakino masses as a function of the ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ mass in several scenarios of gluino, stop and electroweakino pair production. 6  DREINER 2009 show that in the general MSSM with non-universal gaugino masses there exists no model-independent laboratory bound on the mass of the lightest neutralino. An essentially massless ${{\mathit \chi}_{{1}}^{0}}$ is allowed by the experimental and observational data, imposing some constraints on other MSSM parameters, including ${{\mathit M}_{{2}}}$, ${{\mathit \mu}}$ and the slepton and squark masses. 7  ABBIENDI 2004H search for charginos and neutralinos in events with acoplanar leptons+jets and multi-jet final states in the $192 - 209$ GeV data, combined with the results on leptonic final states from ABBIENDI 2004 . The results hold for a scan over the parameter space covering the region 0 $<$ ${{\mathit M}_{{2}}}$ $<$ 5000 GeV, $-1000$ $<$ ${{\mathit \mu}}$ $<$ 1000 GeV and tan ${{\mathit \beta}}$ from 1 to 40. This limit supersedes ABBIENDI 2000H. 8  HEISTER 2004 data collected up to 209 GeV. Updates earlier analysis of selectrons from HEISTER 2002E, includes a new analysis of charginos and neutralinos decaying into stau and uses results on charginos with initial state radiation from HEISTER 2002J. The limit is based on the direct search for charginos and neutralinos, the constraints from the slepton search and the Higgs mass limits from HEISTER 02 using a top mass of 175$~$GeV, interpreted in a framework with universal gaugino and sfermion masses. Assuming the mixing in the stau sector to be negligible, the limit improves to 43.1$~$GeV. Under the assumption of MSUGRA with unification of the Higgs and sfermion masses, the limit improves to 50$~$GeV, and reaches 53$~$GeV for ${{\mathit A}_{{0}}}$ = 0. These limits include and update the results of BARATE 2001 . 9  ABDALLAH 2003M uses data from $\sqrt {s }$ = $192 - 208$ GeV. A limit on the mass of ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ is derived from direct searches for neutralinos combined with the chargino search. Neutralinos are searched in the production of ${{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$, ${{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\widetilde{\mathit \chi}}_{{3}}^{0}}$, as well as ${{\widetilde{\mathit \chi}}_{{2}}^{0}}{{\widetilde{\mathit \chi}}_{{3}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{2}}^{0}}{{\widetilde{\mathit \chi}}_{{4}}^{0}}$ giving rise to cascade decays, and ${{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$, followed by the decay ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\widetilde{\mathit \tau}}}{{\mathit \tau}}$ . The results hold for the parameter space defined by values of $\mathit M_{2}<$ 1 TeV, $\vert {{\mathit \mu}}\vert {}\leq{}$2~TeV with the ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ as LSP. The limit is obtained for tan $\beta $ = 1 and large ${\mathit m}_{{{\mathit 0}}}$, where ${{\widetilde{\mathit \chi}}_{{2}}^{0}}{{\widetilde{\mathit \chi}}_{{4}}^{0}}$ and chargino pair production are important. If the constraint from Higgs searches is also imposed, the limit improves to 49.0 GeV in the $\mathit m{}^{{\mathrm {max}}}_{h}$ scenario with ${\mathit m}_{{{\mathit t}}}$=174.3 GeV. These limits update the results of ABREU 2000J. 10  ABDALLAH 2003M uses data from $\sqrt {s }$ = $192 - 208$ GeV. An indirect limit on the mass of ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ is derived by constraining the MSSM parameter space by the results from direct searches for neutralinos (including cascade decays and ${{\widetilde{\mathit \tau}}}{{\mathit \tau}}$ final states), for charginos (for all $\Delta \mathit m_{+}$) and for sleptons, stop and sbottom. The results hold for the full parameter space defined by values of $\mathit M_{2}<$ 1 TeV, $\vert {{\mathit \mu}}\vert {}\leq{}2~$TeV with the ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ as LSP. Constraints from the Higgs search in the $\mathit m{}^{{\mathrm {max}}}_{h}$ scenario assuming ${\mathit m}_{{{\mathit t}}}$=174.3 GeV are included. The limit is obtained for tan $\beta {}\geq{}$ 5 when stau mixing leads to mass degeneracy between ${{\widetilde{\mathit \tau}}_{{1}}}$ and ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ and the limit is based on ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ production followed by its decay to ${{\widetilde{\mathit \tau}}_{{1}}}{{\mathit \tau}}$. In the pathological scenario where ${\mathit m}_{{{\mathit 0}}}$ and $\vert {{\mathit \mu}}\vert $ are large, so that the ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ production cross section is negligible, and where there is mixing in the stau sector but not in stop nor sbottom, the limit is based on charginos with soft decay products and an ISR photon. The limit then degrades to 39 GeV. See Figs. $40 - 42$ for the dependence of the limit on tan $\beta $ and ${\mathit m}_{{{\widetilde{\mathit \nu}}}}$. These limits update the results of ABREU 2000W. 11  ACCIARRI 2000D data collected at $\sqrt {\mathit s }$=189 GeV. The results hold over the full parameter space defined by $0.7{}\leq{}$tan $\beta {}\leq{}60$, 0${}\leq{}\mathit M_{2}{}\leq{}2$ TeV, $\mathit m_{0}{}\leq{}500$ GeV, $\vert \mu \vert {}\leq{}2$ TeV The minimum mass limit is reached for tan $\beta $=1 and large $\mathit m_{0}$. The results of slepton searches from ACCIARRI 1999W are used to help set constraints in the region of small $\mathit m_{0}$. The limit improves to 48 GeV for $\mathit m_{0}{ {}\gtrsim{} }200$ GeV and tan $\beta { {}\gtrsim{} }10$. See their Figs.$~6 - 8$ for the tan $\beta $ and $\mathit m_{0}$ dependence of the limits. Updates ACCIARRI 1998F. 12  AAD 2014K sets limits on the ${{\mathit \chi}}$-nucleon spin-dependent and spin-independent cross sections out to ${\mathit m}_{{{\mathit \chi}}}$ = 10 TeV. 13  CALIBBI 2013 use the fact that if the relic abundance of ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ does not overclose the universe, scalar lepton and Higgsino masses must be relatively small. Using 8 TeV ATLAS constraints on the scalar tau mass and on invisible Higgs decays, they estimate a lower bound for the ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ mass.

References:

AAD 2022E PL B830 137106 A search for an unexpected asymmetry in the production of e+?? and e??+ pairs in proton?proton collisions recorded by the ATLAS detector at $\sqrt{s}=13$ TeV TUMASYAN 2022S JHEP 2204 147 Search for electroweak production of charginos and neutralinos in proton-proton collisions at $ \sqrt{s} $ = 13 TeV TUMASYAN 2022V JHEP 2205 014 Search for higgsinos decaying to two Higgs bosons and missing transverse momentum in proton-proton collisions at $ \sqrt{s} $ = 13 TeV AAD 2021BF EPJ C81 1023 Search for R-parity-violating supersymmetry in a final state containing leptons and many jets with the ATLAS experiment using $\sqrt{s} = 13 { TeV}$ proton?proton collision data AAD 2021AX PR D104 112010 Search for charginos and neutralinos in final states with two boosted hadronically decaying bosons and missing transverse momentum in $pp$ collisions at $\sqrt {s}$ = 13??TeV with the ATLAS detector AAD 2014K PR D90 012004 Search for Dark Matter in Events with a ${{\mathit Z}}$ Boson and Missing Transverse Momentum in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector CALIBBI 2013 JHEP 1310 132 Cornering light Neutralino Dark Matter at the LHC DREINER 2009 EPJ C62 547 Mass Bounds on a Very Light Neutralino ABBIENDI 2004H EPJ C35 1 Search for Chargino and Neutralino Production at $\sqrt {s }$ = 192 to 209 GeV at LEP HEISTER 2004 PL B583 247 Absolute Mass Lower Limit for the Lightest Neutralino of the MSSM from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Data at $\sqrt {s }$ up to 209 GeV ABDALLAH 2003M EPJ C31 421 Searches for Supersymmetric Particles in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions up to 208 GeV and Interpretation of the Results within the MSSM ACCIARRI 2000D PL B472 420 Search for Charginos and Neutralinos in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at $\sqrt {s }$ = 189 GeV