# ${{\widetilde{\boldsymbol \chi}}_{{2}}^{0}}$, ${{\widetilde{\boldsymbol \chi}}_{{3}}^{0}}$, ${{\widetilde{\boldsymbol \chi}}_{{4}}^{0}}$ (Neutralinos) mass limits INSPIRE search

Neutralinos are unknown mixtures of photinos, z-inos, and neutral higgsinos (the supersymmetric partners of photons and of ${{\mathit Z}}$ and Higgs bosons). The limits here apply only to ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$, ${{\widetilde{\mathit \chi}}_{{3}}^{0}}$, and ${{\widetilde{\mathit \chi}}_{{4}}^{0}}$. ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ is the lightest supersymmetric particle (LSP); see ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ Mass Limits. It is not possible to quote rigorous mass limits because they are extremely model dependent; i.e. they depend on branching ratios of various ${{\widetilde{\mathit \chi}}^{0}}$ decay modes, on the masses of decay products (${{\widetilde{\mathit e}}}$, ${{\widetilde{\mathit \gamma}}}$, ${{\widetilde{\mathit q}}}$, ${{\widetilde{\mathit g}}}$), and on the ${{\widetilde{\mathit e}}}$ mass exchanged in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\widetilde{\mathit \chi}}_{{i}}^{0}}{{\widetilde{\mathit \chi}}_{{j}}^{0}}$ . Limits arise either from direct searches, or from the MSSM constraints set on the gaugino and higgsino mass parameters $\mathit M_{2}$ and $\mu$ through searches for lighter charginos and neutralinos. Often limits are given as contour plots in the ${\mathit m}_{{{\widetilde{\mathit \chi}}^{0}}}–{\mathit m}_{{{\widetilde{\mathit e}}}}$ plane vs other parameters. When specific assumptions are made, e.g, the neutralino is a pure photino (${{\widetilde{\mathit \gamma}}}$), pure z-ino (${{\widetilde{\mathit Z}}}$), or pure neutral higgsino (${{\widetilde{\mathit H}}^{0}}$), the neutralinos will be labelled as such.

Limits obtained from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ collisions at energies up to 136 GeV, as well as other limits from different techniques, are now superseded and have not been included in this compilation. They can be found in the 1998 Edition (The European Physical Journal C3 1 (1998)) of this Review. Some later papers are now obsolete and have been omitted. They were last listed in our PDG 2014 edition: K. Olive, $\mathit et~al.$ (Particle Data Group), Chinese Physics C38 070001 (2014) (http://pdg.lbl.gov).

VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT
$\text{none 220 - 490}$ 95 1
 2017 AW
CMS 1${{\mathit \ell}}$+ 2 ${{\mathit b}}$-jets + $\not E_T$, Tchi1n2E, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
$>600$ 95 2
 2016 AA
ATLS 3/4${{\mathit \ell}}$ + $\not E_T$, Tn2n3A, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$=0GeV
$>670$ 95 2
 2016 AA
ATLS 3/4${{\mathit \ell}}+\not E_T$,Tn2n3B,${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}<$ 200GeV
$>250$ 95 3
 2015 BA
ATLS ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{\pm}}}$ = ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}$, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
$> 380$ 95 4
 2014 H
ATLS ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit \tau}^{\pm}}{{\mathit \nu}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\mathit \tau}^{\pm}}{{\mathit \tau}^{\mp}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , simplified model, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{\pm}}}$ = ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}$, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
$> 700$ 95 4
 2014 H
ATLS ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \nu}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\mathit \ell}^{\pm}}{{\mathit \ell}^{\mp}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , simplified model, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{\pm}}}$ = ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}$, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
$> 345$ 95 4
 2014 H
ATLS ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit W}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\mathit Z}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , simplified model, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{\pm}}}$ = ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}$, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
$> 148$ 95 4
 2014 H
ATLS ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit W}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\mathit H}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , simplified model, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{\pm}}}$ = ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}$, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
$\bf{> 620}$ 95 5
 2014 X
ATLS ${}\geq{}4{{\mathit \ell}^{\pm}}$, ${{\widetilde{\mathit \chi}}_{{2,3}}^{0}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \ell}^{\mp}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
6
 2013
ATLS 3${{\mathit \ell}^{\pm}}$ + $\not E_T$, pMSSM, SMS
7
 2012 BJ
CMS ${}\geq{}$2 ${{\mathit \ell}}$, jets + $\not E_T$, ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$
$\bf{>116.0}$ 95 8
 2000 W
DLPH ${{\widetilde{\mathit \chi}}_{{4{}0}}}$, 1${}\leq{}$tan $\beta {}\leq{}$40, all $\Delta \mathit m$, all $\mathit m_{0}$
• • • We do not use the following data for averages, fits, limits, etc. • • •
$\text{none 180 - 355}$ 95 9
 2014 G
ATLS ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit W}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}{{\mathit Z}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ , simplified model, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{\pm}}}$ = ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{2}}^{0}}}$, ${\mathit m}_{{{\widetilde{\mathit \chi}}_{{1}}^{0}}}$ = 0 GeV
10
 2014 I
CMS ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ( ${{\mathit Z}}$ , ${{\mathit H}}$) ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ ${{\widetilde{\mathit \ell}}}{{\mathit \ell}}$ , simplified model
11
 2012 AS
ATLS 3${{\mathit \ell}^{\pm}}$ + $\not E_T$, pMSSM
12
 2012 T
ATLS ${{\mathit \ell}^{\pm}}{{\mathit \ell}^{\pm}}$ + $\not E_T$, ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$
1  SIRUNYAN 2017AW searched in 35.9 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 13 TeV for events with a charged lepton (electron or muon), two jets identified as originating from a ${{\mathit b}}$-quark, and large $\not E_T$. No significant excess above the Standard Model expectations is observed. Limits are set on the mass of the chargino and the next-to-lightest neutralino in the Tchi1n2E simplified model, see their Figure 6.
2  AAD 2016AA summarized and extended ATLAS searches for electroweak supersymmetry in final states containing several charged leptons, $\not E_T$, with or without hadronic jets, in 20 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV. The paper reports the results of new interpretations and statistical combinations of previously published analyses, as well as new analyses. Exclusion limits at 95$\%$ C.L. are set on mass-degenerate ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{3}}^{0}}$ masses in the Tn2n3A and Tn2n3B simplified models. See their Fig. 15.
3  AAD 2015BA searched in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV for electroweak production of charginos and neutralinos decaying to a final state containing a ${{\mathit W}}$ boson and a 125 GeV Higgs boson, plus missing transverse momentum. No excess beyond the Standard Model expectation is observed. Exclusion limits are derived in simplified models of direct chargino and next-to-lightest neutralino production, with the decays ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ $\rightarrow$ ${{\mathit W}^{\pm}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ and ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit H}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ having 100$\%$ branching fraction, see Fig. 8. A combination of the multiple final states for the Higgs decay yields the best limits (Fig. 8d).
4  AAD 2014H searched in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV for electroweak production of charginos and neutralinos decaying to a final sate with three leptons and missing transverse momentum. No excess beyond the Standard Model expectation is observed. Exclusion limits are derived in simplified models of direct chargino and next-to-lightest neutralino production, with decays to the lightest neutralino via either all three generations of leptons, staus only, gauge bosons, or Higgs bosons, see Fig. 7. An interpretation in the pMSSM is also given, see Fig. 8.
5  AAD 2014X searched in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV for events with at least four leptons (electrons, muons, taus) in the final state. No significant excess above the Standard Model expectations is observed. Limits are set on the neutralino mass in an R-parity conserving simplified model where the decay ${{\widetilde{\mathit \chi}}_{{2,3}}^{0}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \ell}^{\mp}}{{\widetilde{\mathit \chi}}_{{1}}^{0}}$ takes place with a branching ratio of 100$\%$, see Fig. 10.
6  AAD 2013 searched in 4.7 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 7 TeV for charginos and neutralinos decaying to a final state with three leptons (${{\mathit e}}$ and ${{\mathit \mu}}$) and missing transverse energy. No excess beyond the Standard Model expectation is observed. Exclusion limits are derived in the phenomenological MSSM, see Fig. 2 and 3, and in simplified models, see Fig. 4. For the simplified models with intermediate slepton decays, degenerate ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}$ and ${{\widetilde{\mathit \chi}}_{{2}}^{0}}$ masses up to 500 GeV are excluded at 95$\%$ C.L. for very large mass differences with the ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$. Supersedes AAD 2012AS.
7  CHATRCHYAN 2012BJ searched in 4.98 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 7 TeV for direct electroweak production of charginos and neutralinos in events with at least two leptons, jets and missing transverse momentum. No significant excesses over the expected SM backgrounds are observed and 95$\%$ C.L. limits on the production cross section of ${{\widetilde{\mathit \chi}}_{{1}}^{\pm}}{{\widetilde{\mathit \chi}}_{{2}}^{0}}$ pair production were set in a number of simplified models, see Figs. 7 to 12. Most limits are for exactly 3 jets.
8  ABREU 2000W combines data collected at $\sqrt {\mathit s }$=189 GeV with results from lower energies. The mass limit is obtained by constraining the MSSM parameter space with gaugino and sfermion mass universality at the GUT scale, using the results of negative direct searches for neutralinos (including cascade decays and ${{\widetilde{\mathit \tau}}}{{\mathit \tau}}$ final states) from ABREU 2001 , for charginos from ABREU 2000J and ABREU 2000T (for all $\Delta \mathit m_{+}$), and for charged sleptons from ABREU 2001B. The results hold for the full parameter space defined by all values of $\mathit M_{2}$ and $\vert \mu \vert {}\leq{}$2 TeV with the ${{\widetilde{\mathit \chi}}_{{1}}^{0}}$ as LSP.
9  AAD 2014G searched in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV for electroweak production of chargino-neutralino pairs, decaying to a final sate with two leptons (${{\mathit e}}$ and ${{\mathit \mu}}$) and missing transverse momentum. No excess beyond the Standard Model expectation is observed. Exclusion limits are derived in simplified models of chargino and next-to-lightest neutralino production, with decays to the lightest neutralino via gauge bosons, see Fig. 7. An interpretation in the pMSSM is also given, see Fig. 10.
10  KHACHATRYAN 2014I searched in 19.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV for electroweak production of charginos and neutralinos decaying to a final state with three leptons (${{\mathit e}}$ or ${{\mathit \mu}}$) and missing transverse momentum, or with a ${{\mathit Z}}$-boson, dijets and missing transverse momentum. No excess beyond the Standard Model expectation is observed. Exclusion limits are derived in simplified models, see Figs. $12 - 16$.
11  AAD 2012AS searched in 2.06 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 7 TeV for charginos and neutralinos decaying to a final state with three leptons (${{\mathit e}}$ and ${{\mathit \mu}}$) and missing transverse energy. No excess beyond the Standard Model expectation is observed. Exclusion limits are derived in the phenomenological MSSM, see Fig. 2 (top), and in simplified models, see Fig. 2 (bottom).
12  AAD 2012T looked in 1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 7 TeV for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons (${{\mathit e}}$ or ${{\mathit \mu}}$). Same-sign dilepton events were separately studied. Additionally, in opposite-sign events, a search was made for an excess of same-flavor over different-flavor lepton pairs. No excess over the expected background is observed and limits are placed on the effective production cross section of opposite-sign dilepton events with $\not E_T$ $>$ 250 GeV and on same-sign dilepton events with $\not E_T$ $>$ 100 GeV. The latter limit is interpreted in a simplified electroweak gaugino production model.
References:
 SIRUNYAN 2017AW
JHEP 1711 029 Search for Electroweak Production of Charginos and Neutralinos in ${{\mathit W}}{{\mathit H}}$ Events in Proton-Proton Collisions at $\sqrt {s }$ = 13 TeV
PR D93 052002 Search for the Electroweak Production of Supersymmetric Particles in $\sqrt {s }$ = 8 TeV ${{\mathit p}}{{\mathit p}}$ Collisions with the ATLAS Detector
EPJ C75 208 Search for Direct Pair Production of a Chargino and a Neutralino Decaying to the 125 GeV Higgs Boson in $\sqrt {s }$ = 8 TeV ${{\mathit p}}{{\mathit p}}$ Collisions with the ATLAS Detector
JHEP 1404 169 Search for Direct Production of Charginos and Neutralinos in Events with Three Leptons and Missing Transverse Momentum in $\sqrt {s }$ = 8 TeV ${{\mathit p}}{{\mathit p}}$ Collisions with the ATLAS Detector
PR D90 052001 Search for Supersymmetry in Events with Four or More Leptons in $\sqrt {s }$ = 8 TeV ${{\mathit p}}{{\mathit p}}$ Collisions with the ATLAS Detector
JHEP 1405 071 Search for Direct Production of charginos, neutralinos and sleptons in Final States with Two Leptons and Missing Transverse Momentum in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector
 KHACHATRYAN 2014I
EPJ C74 3036 Searches for Electroweak Production of charginos, neutralinos, and sleptons Decaying to Leptons and ${{\mathit W}}$, ${{\mathit Z}}$, and Higgs Bosons in ${{\mathit p}}{{\mathit p}}$ Collisions at 8 TeV
PL B718 841 Search for Direct Production of Charginos and Neutralinos in Events with Three Leptons and Missing Transverse Momentum in $\sqrt {s }$ = 7 TeV ${{\mathit p}}{{\mathit p}}$ Collisions with the ATLAS Detector
PL B709 137 Searches for Supersymmetry with the ATLAS Detector using Final States with Two Leptons and Missing Transverse Momentum in $\sqrt {s }$ = 7 TeV Proton$−$Proton Collisions
PRL 108 261804 Search for Supersymmetry in Events with Three Leptons and Missing Transverse Momentum in $\sqrt {s }$ = 7 TeV ${{\mathit p}}{{\mathit p}}$ Collisions with the ATLAS Detector
JHEP 1211 147 Search for Electroweak Production of Charginos and Neutralinos using Leptonic Final States in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 7 TeV
PL B489 38 Limits on the Masses of Supersymmetric Particles at $\sqrt {s }$ = 189-GeV
PL B511 159 Measurement of the Mass and Width of the ${{\mathit W}}$ Boson in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at $\sqrt {s }$ = 189 GeV
JHEP 1310 130 Search for New Phenomena in Final States with Large Jet Multiplicities and Missing Transverse Momentum at $\sqrt {s }$ = 8 TeV Proton$−$Proton Collisions Using the ATLAS Experiment