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\begin{document}
\vspace*{4cm}
\title{Searches for non-SM Higgs Bosons at the Tevatron}

\author{ Andrew Haas \it{for the DZero and CDF collaborations}}
\address{Columbia University, New York, NY, USA}

\maketitle\abstracts{ Extensions of the Standard Model (SM) predict
Higgs phenomenology which can be quite different from that expected
within the SM. This contribution discusses the latest results from
searches for Higgs bosons by the DZero and CDF experiments at the
Tevatron in several non-SM scenarios: supersymmetry, left-right
symmetric (Higgs-triplet), and fermiophobic.}

\section{Introduction}

The Tevatron accelerator at Fermilab has performed very well in
recent years, delivering over 3.5 fb$^{-1}$ of data. The DZero and
CDF experiments are using this data to study many questions at the
forefront of high-energy physics. A central goal is the
understanding of electro-weak symmetry breaking, which gives the W
and Z bosons mass while leaving the photon massless. In the SM,
electro-weak symmetry breaking is delivered via the Higgs mechanism,
which predicts a single neutral spin-0 boson - the Higgs boson.
Extensions to the SM, such as supersymmetry, predict different
productions and/or decays of the Higgs boson and often a richer
spectrum of multiple Higgs bosons.

We will discuss first the most anticipated extension to the SM,
supersymmetry. Both DZero and CDF have specifically tuned searches
for the new neutral Higgs boson(s) of supersymmetry, in the
$bh\rightarrow bbb$, $h\rightarrow \tau\tau$, and $bh\rightarrow
b\tau\tau$ channels. Next we show the results for left-right
symmetric or Higgs-triplet models, which predict a doubly-charged
Higgs boson, $H^{++}$. Finally, DZero has considered the case where
the Higgs prefers not to decay to fermions, the so-called
fermiophobic scenario, leaving open the $h\rightarrow \gamma\gamma$
channel as the main decay mode for a low-mass Higgs boson.

\section{Searches in the MSSM at high $tan\beta$}

In two-Higgs-doublet models of electro-weak symmetry breaking, such
as the minimal supersymmetric extension of the standard model
(MSSM)~\cite{2HDM}, there are five physical Higgs bosons: two
neutral $CP$-even scalars, h and H, with H being the heavier state;
a neutral $CP$-odd state, A; and two charged states, H$^\pm$. The
ratio of the vacuum expectation values of the two Higgs fields is
defined as $tan\beta$ = $v_u/v_d$, where $v_u$ and $v_d$ refer to
the fields that couple to the up-type and down-type fermions,
respectively. At tree level, the coupling of the $A$ boson to
down-type quarks, such as the b-quark, is enhanced by a factor of
$tan\beta$ relative to the SM, and the production cross section is
therefore enhanced by $tan^{2}\beta$~\cite{MSSM_Higgs}. At large
$tan\beta$, this is also true either for the $h$ or $H$ boson
depending on their mass. At high $tan\beta$, the h/H and A decay
roughly 90\% to $bb$ and 10\% to $\tau\tau$.

The dominant decay to $bb$ is unfortunately drowned by QCD
background, but due to the enhanced coupling to b-quarks the h/H and
A are also produced in association with one or more b-quarks,
opening the channel $bh\rightarrow bbb$. Both DZero and CDF have
performed searches for an excess in the di-jet invariant mass
spectrum of the bbb final state. CDF's latest results are shown in
Figure \ref{fig:bbb}, using 1.9 $fb^{-1}$ of data. The dijet mass
spectrum of the heavy flavor multi-jet background is derived from
double-tagged data in a manner that accounts for tagging biases and
kinematic differences introduced by the addition of the third tag.
No excess is observed for any di-jet invariant mass window, so
limits are placed in the Higgs mass vs. $tan\beta$ parameter space.

\begin{figure}
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm} \vskip 2.5cm
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm}
\psfig{figure=fit_mh150_m12.eps,height=2in,width=3in}
\psfig{figure=tb-limits-nowidth.eps,height=2in,width=3in}\caption{The
di-jet invariant mass spectrum in bbb events and corresponding
limits in the $m_A$ - $tan\beta$ parameter space of the MSSM from
the CDF $bh\rightarrow bbb$ analysis. \label{fig:bbb}}
\end{figure}

The subdominant decay of the h/H or A to $\tau\tau$ is much cleaner,
so both DZero and CDF have searched for direct $h\rightarrow
\tau\tau$ excesses, see Figures \ref{fig:htautau1} and
\ref{fig:htautau2}. The main background is from
$Z\rightarrow\tau\tau$, which is essentially irreducible.

At DZero, a set of Neural Networks (NN) are trained to identify tau
decays from jet backgrounds, for each of 3 tau types (charged
pion-like, pion + EM shower-like, and 3-prong). One of the taus is
required to decay to a muon, for triggering and to reduce QCD
background. The QCD background is determined by comparing same-sign
vs. opposite-sign candidates. Some loose selection cuts remove W
backgrounds, such as requiring the visible W mass $<$20 GeV.
Finally, a set of NN's (one for each tau type) is used to separate
signal from backgrounds. Good agreement is seen between data and
expected background at high NN output, so limits are placed on the
signals' cross-sections and interpreted in the Higgs mass vs.
$tan\beta$ parameter space. CDF has performed similar analyses, but
using in addition the e+tau and e+mu decay channels, as well as more
data. No NN separation is employed, however.

\begin{figure}
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm} \vskip 2.5cm
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm}
\psfig{figure=D0_htautau_NN.eps,height=3in}
\psfig{figure=fit140_eMu.eps,height=3in}\psfig{figure=fit140_lTau.eps,height=3in}\caption{(top)
NN outputs for all tau types (top left) and each tau type (see text)
individually in the DZero $h\rightarrow\tau\tau$ analysis. (bottom)
Visible mass distributions in the CDF $h\rightarrow\tau\tau$
analysis for the $e\mu$ and $lepton + \tau$ channels.
\label{fig:htautau1}}
\end{figure}

\begin{figure}
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm} \vskip 2.5cm
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm}
\psfig{figure=D0htautaulimits.eps,height=2in}
\psfig{figure=tanBeta_posMu.eps,height=2in}\caption{D0 (left) and
CDF (right) limits in the $m_A$ - $tan\beta$ parameter space of the
MSSM from the $h\rightarrow\tau\tau$ analyses. \label{fig:htautau2}}
\end{figure}

By adding the requirement that there be an associated b-quark in the
production, followed by the clean di-tau decay, $bh\rightarrow
b\tau\tau$ has the highest signal / background of any high
$tan\beta$ MSSM Higgs search. It also suffers from a low
cross-section times branching ratio however. DZero has performed a
search using just 344 $pb^{-1}$ of data in this channel. Di-tau
events are normalized to the $Z\rightarrow\tau\tau$ peak, and then
an additional b-tagged jet is required with $p_T >$15 GeV. For a
Higgs mass of 120 GeV and $tan\beta$=80, there are 5.3 signal events
expected, with just 6.3 expected background events. Only 3 events
are observed in data, and limits are placed in the Higgs mass vs.
$tan\beta$ plane, as seen in Figure \ref{fig:btautau}, competitive
with the other channels.

\begin{figure}
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm} \vskip 2.5cm
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm}
\psfig{figure=H24F02_left.eps,height=2in}
\psfig{figure=H24F02_right.eps,height=2in}\caption{Limits in the
$m_A$ - $tan\beta$ parameter space of the MSSM from the DZero
$bh\rightarrow b\tau\tau$ analysis. \label{fig:btautau}}
\end{figure}

\section{Searches for $H^{++}H^{--}$}

Many models of beyond-SM Higgs physics predict a doubly-charged
Higgs boson, $H^{++}$, such as left-right symmetric models,
Higgs-triplet models, and little-Higgs. DZero has recently updated
its search for pair-produced $H^{++}H^{--}$, using 1.1 $fb^{-1}$ of
data. 3 muons are required, with $p_T >$15 GeV. At least one pair
must have an invariant mass $>$30 GeV and $\Delta\phi <$2.5 radians,
to reduce backgrounds from QCD and Z decays. 3 events are observed
in data, for an expectation of 3.1 events from backgrounds, and thus
limits are set on the $H^{++}$ mass as shown in Figure
\ref{fig:Hpp}. Left-handed doubly-charged Higgs bosons, $H_L^{++}$
have a larger production cross-section than right-handed,
$H_R^{++}$, by about a factor of 2, due to their different coupling
to the intermediate Z boson. Thus, the limit on the mass of
$H_L^{++}$ ($>$150 GeV) are higher than on $H_R^{++}$ ($>$127 GeV).

\begin{figure}
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm} \vskip 2.5cm
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm}
\psfig{figure=H08AF5.eps,height=2in}
\psfig{figure=H08AF7.eps,height=2in}\caption{(left) Di-muon
invariant mass spectrum in events with 3 muons. (right) Limits on
the $H^{++}$ mass for left- or right-handed Higgs bosons from the
latest DZero search. \label{fig:Hpp}}
\end{figure}

\section{Searches for $h\rightarrow\gamma\gamma$}

Although the SM Higgs boson decays to the di-photon final state with
a small branching ratio, this decay channel could be subject to a
large enhancement in models where the Higgs does not couple strongly
to fermions. In this case, fermion masses could arise from some
other source. DZero has recently completed a search using 2.3
$fb^{-1}$ of data for $h\rightarrow\gamma\gamma$. 2 isolated photons
with $p_T>$25 GeV are required. QCD jets faking photons are
estimated by looking at the calorimeter shower-shape correlations
between the two photons in each event, and samples are divided into
QCD di-jet, photon+jet, and di-photon backgrounds. $Z\rightarrow ee$
also contributes near the Z mass. Data agree very well with
estimated backgrounds, and no significant excess is seen at any
di-photon invariant mass range. Limits are therefore set on the
cross-section times branching ratio for $h\rightarrow\gamma\gamma$
and are compared to the expected cross-section times branching ratio
in the SM, as shown in Figure \ref{fig:Hgg}. The current analysis
can exclude down to about 50 times the SM event rate at 120 GeV and
in fact also contributes non-negligibly to the SM Higgs search.

\begin{figure}
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm} \vskip 2.5cm
%\rule{5cm}{0.2mm}\hfill\rule{5cm}{0.2mm}
\psfig{figure=H48F2a.eps,height=2in}
\psfig{figure=H48F3b.eps,height=2in}\caption{(left) Di-photon
invariant mass spectrum and (right) limits on the
$h\rightarrow\gamma\gamma$ cross-section in units of the SM
cross-section from the latest DZero di-photon analysis.
\label{fig:Hgg}}
\end{figure}

\section{Conclusions}

CDF and DZero have searched for Higgs bosons in several models
beyond the SM: the MSSM at high $tan\beta$ in b and $\tau$ channels,
for doubly charged Higgs, and for fermiophobic Higgs. No significant
excesses or deviations indicative of non-SM Higgs signatures have
been seen so far. But the Tevatron experiments expect to more than
double their data samples in the next two years, hone their search
strategies, and enlarge the variety of models considered.

\section*{Acknowledgments}
We would like to thank the Moriond organizers for a wonderful
conference and the EU for their generous funding of young scientists
attending.

\section*{References}
\begin{thebibliography}{99}

\bibitem{2HDM}
H.~P.~Nilles,
%``Supersymmetry, Supergravity And Particle Physics,''
Phys.\ Rept.\  {\bf 110}, 1 (1984); H.~E.~Haber and G.~L.~Kane,
%``The Search For Supersymmetry: Probing Physics Beyond The Standard Model,''
Phys.\ Rept.\  {\bf 117}, 75 (1985).

\bibitem{MSSM_Higgs}
%The Higgs Working Group: Summary Report (2001), hep-ph/0203056,
%D.Cavalli {\sl et al.}, Published in proceedings of ``Workshop on Physics at TeV Colliders'', pages 10-28.
%``Les Houches 2001, Physics at TeV colliders''
J.~F.~Gunion, H.~E.~Haber, G.~L.~Kane, and S.~Dawson, ``The Higgs
Hunter's Guide,'' Addison-Wesley, 1990.
% Addison-Wesley, Redwood City, 1990.
% SCIPP-89/13, 1989.
%\href{http://www.slac.stanford.edu/spires/find/hep/www?r=scipp-89\%2F13}{SPIRES entry}



\end{thebibliography}

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