# MASS LIMITS FOR NEUTRAL HIGGS BOSONS IN EXTENDED HIGGS MODELS

This Section covers models which do not fit into either the Standard Model or its simplest minimal Supersymmetric extension (MSSM), leading to anomalous production rates, or nonstandard final states and branching ratios. In particular, this Section covers limits which may apply to generic two-Higgs-doublet models (2HDM), or to special regions of the MSSM parameter space where decays to invisible particles or to photon pairs are dominant (see the review on Status of Higgs Boson Physics''). Concerning the mass limits for ${{\mathit H}^{0}}$ and ${{\mathit A}^{0}}$ listed below, see the footnotes or the comment lines for details on the nature of the models to which the limits apply.
The observed signal at about 125 GeV, see section ${{\mathit H}^{0}}$'', can be interpreted as one of the neutral Higgs bosons of an extended Higgs sector.

# Mass Limits for ${{\boldsymbol H}^{0}}$ Decaying to Invisible Final States INSPIRE search

These limits are for a neutral scalar ${{\mathit H}^{0}}$ which predominantly decays to invisible final states. Standard Model values are assumed for the couplings of ${{\mathit H}^{0}}$ to ordinary particles unless otherwise stated.
VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT
• • • We do not use the following data for averages, fits, limits, etc. • • •
1
 2019 AI
ATLS ${{\mathit W}}{{\mathit W}}$ / ${{\mathit Z}}{{\mathit Z}}$ fusion
2
 2015 BD
ATLS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit W}}{{\mathit X}}$ , ${{\mathit H}^{0}}{{\mathit Z}}{{\mathit X}}$
3
 2015 BH
ATLS jet + missing $\mathit E_{T}$
4
 2014 BA
ATLS secondary vertex
5
 2014 O
ATLS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}{{\mathit X}}$
6
 2014 B
CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}{{\mathit X}}$ , ${{\mathit q}}{{\mathit q}}{{\mathit H}^{0}}{{\mathit X}}$
7
 2013 AG
ATLS secondary vertex
8
 2013 AT
ATLS electron jets
9
 2013 BJ
CMS
10
 2012 AQ
ATLS secondary vertex
11
 2012 AB
CDF secondary vertex
12
 2012 U
CDF secondary vertex
$> 108.2$ 95 13
 2010
OPAL
14
 2007
OPAL large width
$> 112.3$ 95 15
 2005
L3
$>112.1$ 95 15
 2004 B
DLPH
$>114.1$ 95 15
 2002
ALEP $\mathit E_{{\mathrm {cm}}}{}\leq{}$209 GeV
$>106.4$ 95 15
 2001 C
ALEP $\mathit E_{{\mathrm {cm}}}{}\leq{}$202 GeV
$>89.2$ 95 16
 2000 M
L3
1  AABOUD 2019AI search for ${{\mathit H}_{{{1,2}}}^{0}}$ production by vector boson fusion and decay to invisible final states in 36.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. See their Fig. 6(b) for limits on cross section times branching ratios for ${\mathit m}_{{{\mathit H}_{{{1,2}}}^{0}}}$ = $0.1 - 3$ TeV.
2  AAD 2015BD search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit W}}{{\mathit X}}$ and ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}{{\mathit X}}$ with ${{\mathit W}}$ or ${{\mathit Z}}$ decaying hadronically and ${{\mathit H}^{0}}$ decaying to invisible final states in 20.3 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 8TeV. See their Fig. 6 for a limit on the cross section times branching ratio for ${\mathit m}_{{{\mathit H}^{0}}}$ = $115 - 300$ GeV.
3  AAD 2015BH search for events with a jet and missing $\mathit E_{T}$ in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. Limits on ${\mathit \sigma (}{{\mathit H}^{'0}}{)}$ B( ${{\mathit H}^{'0}}$ $\rightarrow$ invisible) $<$ ($44 - 10$) pb (95$\%$CL) is given for ${\mathit m}_{{{\mathit H}^{'0}}}$ = $115 - 300$ GeV.
4  AAD 2014BA search for ${{\mathit H}^{0}}$ production in the decay mode ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , where ${{\mathit X}^{0}}$ is a long-lived particle which decays to collimated pairs of ${{\mathit e}^{+}}{{\mathit e}^{-}}$ , ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ , or ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ plus invisible particles, in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Figs. 15 and 16 for limits on cross section times branching ratio.
5  AAD 2014O search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}{{\mathit X}}$ , ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \ell}}{{\mathit \ell}}$ , with ${{\mathit H}^{0}}$ decaying to invisible final states in 4.5 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and 20.3 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Fig. 3 for a limit on the cross section times branching ratio for ${\mathit m}_{{{\mathit H}^{0}}}$ = $110 - 400$ GeV.
6  CHATRCHYAN 2014B search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}{{\mathit X}}$ , ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \ell}}{{\mathit \ell}}$ and ${{\mathit Z}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ , and also ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit q}}{{\mathit q}}{{\mathit H}^{0}}{{\mathit X}}$ with ${{\mathit H}^{0}}$ decaying to invisible final states using data at $\mathit E_{{\mathrm {cm}}}$ = 7 and 8 TeV. See their Figs. 10, 11 for limits on the cross section times branching ratio for ${\mathit m}_{{{\mathit H}^{0}}}$ = $100 - 400$ GeV.
7  AAD 2013AG search for ${{\mathit H}^{0}}$ production in the decay mode ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , where ${{\mathit X}^{0}}$ is a long-lived particle which decays to ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}{{\mathit X}^{'0}}$ , in 1.9 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV. See their Fig. 7 for limits on cross section times branching ratio.
8  AAD 2013AT search for ${{\mathit H}^{0}}$ production in the decay ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , where ${{\mathit X}^{0}}$ eventually decays to clusters of collimated ${{\mathit e}^{+}}{{\mathit e}^{-}}$ pairs, in 2.04 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV. See their Fig. 3 for limits on cross section times branching ratio.
9  CHATRCHYAN 2013BJ search for ${{\mathit H}^{0}}$ production in the decay chain ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , ${{\mathit X}^{0}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}{{\mathit X}^{'0}}$ in 5.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV. See their Fig. 2 for limits on cross section times branching ratio.
10  AAD 2012AQ search for ${{\mathit H}^{0}}$ production in the decay mode ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , where ${{\mathit X}^{0}}$ is a long-lived particle which decays mainly to ${{\mathit b}}{{\overline{\mathit b}}}$ in the muon detector, in 1.94 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV. See their Fig. 3 for limits on cross section times branching ratio for ${\mathit m}_{{{\mathit H}^{0}}}$ = 120, 140 GeV, ${\mathit m}_{{{\mathit X}^{0}}}$ = 20, 40 GeV in the ${{\mathit c}}{{\mathit \tau}}$ range of $0.5 - 35$ m.
11  AALTONEN 2012AB search for ${{\mathit H}^{0}}$ production in the decay ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , where ${{\mathit X}^{0}}$ eventually decays to clusters of collimated ${{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ pairs, in 5.1 fb${}^{-1}$ of ${{\mathit p}}{{\overline{\mathit p}}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 1.96 TeV. Cross section limits are provided for a benchmark MSSM model incorporating the parameters given in Table VI.
12  AALTONEN 2012U search for ${{\mathit H}^{0}}$ production in the decay mode ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit X}^{0}}$ , where ${{\mathit X}^{0}}$ is a long-lived particle with $\mathit c{{\mathit \tau}}$ $\approx{}$ 1 cm which decays mainly to ${{\mathit b}}{{\overline{\mathit b}}}$ , in 3.2 fb${}^{-1}$ of ${{\mathit p}}{{\overline{\mathit p}}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 1.96 TeV. See their Figs. 9 and 10 for limits on cross section times branching ratio for ${\mathit m}_{{{\mathit H}^{0}}}$ = ($130 - 170$) GeV, ${\mathit m}_{{{\mathit X}^{0}}}$ = 20, 40 GeV.
13  ABBIENDI 2010 search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}$ with ${{\mathit H}^{0}}$ decaying invisibly. The limit assumes SM production cross section and B( ${{\mathit H}^{0}}$ $\rightarrow$ invisible) = 1.
14  ABBIENDI 2007 search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}$ with ${{\mathit Z}}$ $\rightarrow$ ${{\mathit q}}{{\overline{\mathit q}}}$ and ${{\mathit H}^{0}}$ decaying to invisible final states. The ${{\mathit H}^{0}}$ width is varied between 1 GeV and 3 TeV. A limit $\sigma \cdot{}$B( ${{\mathit H}^{0}}$ $\rightarrow$ invisible) $<$ ($0.07 - 0.57$) pb (95$\%$CL) is obtained at $\mathit E_{{\mathrm {cm}}}$ = 206 GeV for ${\mathit m}_{{{\mathit H}^{0}}}$ = $60 - 114~$GeV.
15  Search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}$ with ${{\mathit H}^{0}}$ decaying invisibly. The limit assumes SM production cross section and B( ${{\mathit H}^{0}}$ $\rightarrow$ invisible) = 1.
16  ACCIARRI 2000M search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit H}^{0}}$ with ${{\mathit H}^{0}}$ decaying invisibly at $\mathit E_{{\mathrm {cm}}}=183 - 189~$GeV. The limit assumes SM production cross section and B( ${{\mathit H}^{0}}$ $\rightarrow$ invisible)=1. See their Fig.$~$ 6 for limits for smaller branching ratios.
References:
 AABOUD 2019AI
PL B793 499 Search for invisible Higgs boson decays in vector boson fusion at $\sqrt{s} = 13$ TeV with the ATLAS detector
EPJ C75 299 Search for New Phenomena in Final States with an Energetic Jet and Large Missing Transverse Momentum in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector
EPJ C75 337 Search for Invisible Decays of the Higgs Boson Produced in Association with a Hadronically Decaying Vector Boson in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector
PRL 112 201802 Search for Invisible Decays of a Higgs Boson Produced in Association with a ${{\mathit Z}}$ Boson in ATLAS
JHEP 1411 088 Search for Long-Lived Neutral Particles Decaying into Lepton Jets in Proton-Proton Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector
 CHATRCHYAN 2014B
EPJ C74 2980 Search for Invisible Decays of Higgs Bosons in the Vector Boson Fusion and Associated ${{\mathit Z}}{{\mathit H}}$ Production Modes
PL B721 32 Search for Displaced Muonic Lepton Jets from Light Higgs Boson Decay in Proton$−$Proton Collisions at $\sqrt {s }$ = 7 TeV with the ATLAS Detector
NJP 15 043009 Search for ${{\mathit W}}{{\mathit H}}$ Production with a Light Higgs Boson Decaying to Prompt Electron-Jets in Proton$−$Proton Collisions at $\sqrt {s }$ = 7 TeV with the ATLAS Detector
 CHATRCHYAN 2013BJ
PL B726 564 Search for a Non-Standard-Model Higgs Boson Decaying to a Pair of New Light Bosons in Four-Muon Final States
PRL 108 251801 Search for a Light Higgs Boson Decaying to Long-Lived Weakly Interacting Particles in Proton$−$Proton Collisions at $\sqrt {s }$ = 7 TeV with the ATLAS Detector
 AALTONEN 2012U
PR D85 012007 Search for Heavy Metastable Particles Decaying to Jet Pairs in ${{\mathit p}}{{\overline{\mathit p}}}$ Collisions at $\sqrt {s }$ = 1.96 TeV
 AALTONEN 2012AB
PR D85 092001 Search for Anomalous Production of Multiple Leptons in Association with ${{\mathit W}}$ and ${{\mathit Z}}$ Bosons at CDF
 ABBIENDI 2010
PL B682 381 Search for Invisibly Decaying Higgs Bosons in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit Z}^{0}}{{\mathit h}^{0}}$ Production at $\sqrt {s }$ = $183 - 209$ GeV
 ABBIENDI 2007
EPJ C49 457 Search for Invisibly Decaying Higgs Bosons with Large Decay Width using the OPAL Detector at LEP
 ACHARD 2005
PL B609 35 Search for an Invisibly-Decaying Higgs Boson at LEP
 ABDALLAH 2004B
EPJ C32 475 Searches for invisibly Decaying Higgs Bosons with the DELPHI Detector at LEP
 HEISTER 2002
PL B526 191 Final Results of the Searches for Neutral Higgs Bosons in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at$\sqrt {s }$ up to 209 GeV
 BARATE 2001C
PL B499 53 Searches for Neutral Higgs Bosons in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at $\mathit E_{{\mathrm {cm}}}$ from 192 to 202 GeV
 ACCIARRI 2000M
PL B485 85 Search for an Invisibly Decaying Higgs Boson in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at $\sqrt {s }$ = 183-189 GeV