# 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 in General two-Higgs-doublet Models INSPIRE search

VALUE (GeV) CL% DOCUMENT ID TECN COMMENT
*** We do not use the following data for averages, fits, limits, etc ***
1
ATLS ${{\mathit H}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit H}^{0}}$
2
ATLS ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit H}^{0}}$
3
 KHACHATRYAN 2015BB
CMS ${{\mathit H}_{{2}}^{0}}$ , ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
4
 KHACHATRYAN 2015N
CMS ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit H}^{0}}$
5
ATLS ${{\mathit H}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit H}^{\pm}}{{\mathit W}^{\mp}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit W}^{\pm}}{{\mathit W}^{\mp}}$ , ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
6
 KHACHATRYAN 2014Q
CMS ${{\mathit H}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit H}^{0}}$ , ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit H}^{0}}$
7
 AALTONEN 2009AR
CDF ${{\mathit p}}$ ${{\overline{\mathit p}}}$ $\rightarrow$ ${{\mathit H}^{0}_{{{1,2}}}}$ $/$ ${{\mathit A}^{0}}{+}$ ${{\mathit X}}$ , ${{\mathit H}^{0}_{{{1,2}}}}$ $/$ ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$
$\text{none 1 - 55}$ 95 8
 ABBIENDI 2005A
OPAL ${{\mathit H}_{{1}}^{0}}$, Type II model
>$110.6$ 95 9
 ABDALLAH 2005D
DLPH ${{\mathit H}^{0}}$ $\rightarrow$ 2 jets
10
 ABDALLAH 2004O
DLPH ${{\mathit Z}}$ $\rightarrow$ ${{\mathit f}}{{\overline{\mathit f}}}{{\mathit H}}$
11
 ABDALLAH 2004O
DLPH ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}$ , ${{\mathit H}^{0}}{{\mathit A}^{0}}$
12
 ABBIENDI 2002D
OPAL ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit H}}$
$\text{none 1 - 44}$ 95 13
 ABBIENDI 2001E
OPAL ${{\mathit H}_{{1}}^{0}}$, Type-II model
>$68.0$ 95 14
 ABBIENDI 1999E
OPAL tan $\beta >1$
15
 ABREU 1995H
DLPH ${{\mathit Z}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}^{*}}$ , ${{\mathit H}^{0}}{{\mathit A}^{0}}$
16
 PICH 1992
RVUE Very light Higgs
1  AAD 2015BK search for production of a heavy ${{\mathit H}_{{2}}^{0}}$ decaying to ${{\mathit H}^{0}}{{\mathit H}^{0}}$ in the final state ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit b}}{{\overline{\mathit b}}}$ in 19.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Figs. $15 - 18$ for excluded regions in the parameter space.
2  AAD 2015S search for production of ${{\mathit A}^{0}}$ decaying to ${{\mathit Z}}$ ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit \ell}^{+}}{{\mathit \ell}^{-}}{{\mathit b}}{{\overline{\mathit b}}}$ , ${{\mathit \nu}}{{\overline{\mathit \nu}}}{{\mathit b}}{{\overline{\mathit b}}}$ and ${{\mathit \ell}^{+}}{{\mathit \ell}^{-}}{{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Figs. 4 and 5 for excluded regions in the parameter space.
3  KHACHATRYAN 2015BB search for ${{\mathit H}_{{2}}^{0}}$ , ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ in 19.7 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Fig. 10 for excluded regions in the two-Higgs-doublet model parameter space.
4  KHACHATRYAN 2015N search for production of ${{\mathit A}^{0}}$ decaying to ${{\mathit Z}}$ ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit \ell}^{+}}{{\mathit \ell}^{-}}{{\mathit b}}{{\overline{\mathit b}}}$ in 19.7 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Fig. 5 for excluded regions in the tan $\beta$ $−$ cos $(\beta −\alpha )$ plane for ${\mathit m}_{{{\mathit A}^{0}}}$ = 300 GeV.
5  AAD 2014M search for the decay cascade ${{\mathit H}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit H}^{\pm}}{{\mathit W}^{\mp}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit W}^{\pm}}{{\mathit W}^{\mp}}$ , ${{\mathit H}^{0}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$ in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Table IV for limits in a two-Higgs-doublet model for ${\mathit m}_{{{\mathit H}_{{2}}^{0}}}$= $325 - 1025$ GeV and ${\mathit m}_{{{\mathit H}^{+}}}$= $225 - 825$ GeV.
6  KHACHATRYAN 2014Q search for ${{\mathit H}_{{2}}^{0}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit H}^{0}}$ and ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit H}^{0}}$ in 19.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. See their Figs. 4 and 5 for limits on cross section times branching ratio for ${{\mathit m}}_{{{\mathit H}_{{2}}},{{\mathit A}^{0}}}$= $260 - 360$ GeV and their Figs. $7 - 9$ for limits in two-Higgs-doublet models.
7  AALTONEN 2009AR search for Higgs bosons decaying to ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ in two doublet models in 1.8 fb${}^{-1}$ of ${{\mathit p}}{{\overline{\mathit p}}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 1.96 TeV. See their Fig. 2 for the limit on $\sigma \cdot{}$B( ${{\mathit H}^{0}_{{{1,2}}}}$ / ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ ) for different Higgs masses, and see their Fig. 3 for the excluded region in the MSSM parameter space.
8  ABBIENDI 2005A search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}_{{1}}^{0}}{{\mathit A}^{0}}$ in general Type-II two-doublet models, with decays ${{\mathit H}_{{1}}^{0}}$, ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit q}}{{\overline{\mathit q}}}$ , ${{\mathit g}}{{\mathit g}}$ , ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ , and ${{\mathit H}_{{1}}^{0}}$ $\rightarrow$ ${{\mathit A}^{0}}{{\mathit A}^{0}}$ .
9  ABDALLAH 2005D search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}$ and ${{\mathit H}^{0}}{{\mathit A}^{0}}$ with ${{\mathit H}^{0}}$, ${{\mathit A}^{0}}$ decaying to two jets of any flavor including ${{\mathit g}}{{\mathit g}}$ . The limit is for SM ${{\mathit H}^{0}}{{\mathit Z}}$ production cross section with B( ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit j}}{{\mathit j}}$ ) = 1.
10  ABDALLAH 2004O search for ${{\mathit Z}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit H}^{0}}$ , ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit A}^{0}}$ , ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}{{\mathit H}^{0}}$ and ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}{{\mathit A}^{0}}$ in the final states 4 ${{\mathit b}}$ , ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ , and 4 ${{\mathit \tau}}$ . See paper for limits on Yukawa couplings.
11  ABDALLAH 2004O search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit Z}}$ and ${{\mathit H}^{0}}{{\mathit A}^{0}}$ , with ${{\mathit H}^{0}}$, ${{\mathit A}^{0}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$ , ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ , or ${{\mathit H}^{0}}$ $\rightarrow$ ${{\mathit A}^{0}}{{\mathit A}^{0}}$ at $\mathit E_{{\mathrm {cm}}}$ = $189 - 208$ GeV. See paper for limits on couplings.
12  ABBIENDI 2002D search for ${{\mathit Z}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit H}_{{1}}^{0}}$ and ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit A}^{0}}$ with ${{\mathit H}_{{1}}^{0}}$ /${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ , in the range 4$<{\mathit m}_{{{\mathit H}}}<$12 GeV. See their Fig.8 for limits on the Yukawa coupling.
13  ABBIENDI 2001E search for neutral Higgs bosons in general Type-II two-doublet models, at $\mathit E_{{\mathrm {cm}}}{}\leq{}$189 GeV. In addition to usual final states, the decays ${{\mathit H}_{{1}}^{0}}$, ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit q}}{{\overline{\mathit q}}}$ , ${{\mathit g}}{{\mathit g}}$ are searched for. See their Figs.15,16 for excluded regions.
14  ABBIENDI 1999E search for ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit H}^{0}}{{\mathit A}^{0}}$ and ${{\mathit H}^{0}}{{\mathit Z}}$ at $\mathit E_{{\mathrm {cm}}}$ = 183 GeV. The limit is with ${\mathit m}_{{{\mathit H}}}={\mathit m}_{{{\mathit A}}}$ in general two Higgs-doublet models. See their Fig.18 for the exclusion limit in the ${\mathit m}_{{{\mathit H}}}-{\mathit m}_{{{\mathit A}}}$ plane. Updates the results of ACKERSTAFF 1998S.
15  See Fig.4 of ABREU 1995H for the excluded region in the ${\mathit m}_{{{\mathit H}^{0}}}–{\mathit m}_{{{\mathit A}^{0}}}$ plane for general two-doublet models. For tan $\beta >$1, the region ${\mathit m}_{{{\mathit H}^{0}}}+{\mathit m}_{{{\mathit A}^{0}}}{ {}\lesssim{} }$87 GeV, ${\mathit m}_{{{\mathit H}^{0}}}<$47 GeV is excluded at 95$\%$ CL.
16  PICH 1992 analyse ${{\mathit H}^{0}}$ with ${\mathit m}_{{{\mathit H}^{0}}}<$ 2${\mathit m}_{{{\mathit \mu}}}$ in general two-doublet models. Excluded regions in the space of mass-mixing angles from LEP, beam dump, and ${{\mathit \pi}^{\pm}}$, ${{\mathit \eta}}$ rare decays are shown in Figs.3,4. The considered mass region is not totally excluded.
References
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