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\begin{document}


\Title{Search the SM Higgs boson to $bb$, $\tau\tau$, $WW$, $ZZ$ with 4.7 fb$^{-1}$ of CMS data}

\bigskip\bigskip

%+\addtocontents{toc}{{\it D. Reggiano}}
%+\label{ReggianoStart}

\begin{raggedright}  

{\it Lorenzo Bianchini\index{Bianchini, L.}\\
Laboratoires Leprince--Ringuet\\
\'{E}cole Polytechnique\\
91128 Palaiseau, FRANCE}
\bigskip\bigskip
\end{raggedright}



\section{Introduction}

The Standard Model (SM) %\cite{StandardModel1,StandardModel2,StandardModel3}
of particle physics is the theory of the strong and electroweak interactions.
It has been soundly confirmed by a variety of direct and indirect measurements performed over the last decades.
%One of the cornerstone of the model is the invariance (or symmetry) of the theory under local tranformations of the 
%${\rm SU(3)}_{\rm C}\otimes {\rm SU(2)}_{\rm L} \otimes {\rm U(1)}_{\rm Y}$
%gauge group, which prevents both the force mediators (gauge boson) and the matter particles (fermions)
%from acquiring a mass.
%After the introduction of new scalar degrees of freedom,
By introducing a certain number of scalar degrees of freedom, the mass of the gauge bosons and of the fermions
can be generated via the Brout--Englert--Higgs (BEH) mechanism.
%\cite{HiggsMechanism1}--\cite{HiggsMechanism6}.
In its minimal version, the BEH mechanism implies the existence of one physical neutral boson with $J^{\rm CP}=0^{++}$,
the so--called ``Higgs boson'', whose mass ($M_H$) is a free parameter of the theory.
%The Higgs boson couples directly to massive particles, with a strength proportional to the
%mass of the particle (for fermions) or to the mass squared (for gauge bosons). Couplings to massless particles,
%(photons and gluons) are generated at the quantum level.
Theoretical arguments constrain $M_H$ to be bounded from above by about 700 GeV (see e.g. Ref. \cite{Djouadi}).
Assuming the SM predictions of the electroweak observables, the precision measurements
hint at a rather light Higgs boson, $M_H\approx 100$ GeV.
Direct searches at LEP2 measure a 95\% CL lower bound on $M_H$ at $114.4$ GeV \cite{LEPExc}.
%More recently, direct searches carried out at the $p\bar{p}$ Tevatron collider \cite{TevatronExc}
%and at the $pp$ LHC collider have acquired sensitivity to the SM Higgs boson over a significant 
%range of $M_H$.
Depending on its mass, the Higgs boson decays predominanlty to $b$--quarks and $\tau$--leptons
($M_H\lesssim 135$ GeV) or to a pair of massive gauge bosons ($M_H\gtrsim 135$ GeV).
At the LHC, the main production mechanisms, ordered by importance, are gluon--gluon fusion (GGF), vector--boson fusion (VBF), 
and associated production with a gauge boson ($VH$), or heavy quarks ($bbH$, $ttH$).

A detailed description of the CMS apparatus can be found in Ref. \cite{CMS}.
%The central features
%are the solenoidal magnetic field, with an intensity of 3.8 T in the central volume,
%the fully silicon--based inner tracker, immersed in the solenoidal field, and the scintillating electromagnetic
%calorimeter (ECAL), composed of more than $75000$ lead--tungstate crystals.
%The CMS detector features a cylindrical symmetry around the beam axis, and is fully instrumented both in the barrel
%($|\eta|\lesssim1.5$) and endcaps ($1.5\lesssim|\eta|\lesssim2.5$).
%The acceptance in the forward region ($|\eta|<5.0$) is extended by the presence of two forward calorimeters.
A particle--flow technique is deployed for the offline reconstruction of collision events. %\cite{PFT-09-001}. 
The list of reconstructed ``particle--flow particles'' is then used to build higher--level objects,
like jets, $b$--tag discriminators, or the semileptonic decays of tau leptons ($\tau_h$).
%like jets, $b$--taggers, hadronically--decaying taus, missing transerse energy ($\vec{E}_T^{miss}$), or to evaluate
%the isolation of electrons and muons.
%Muon candidates are reconstructed by matching the tracks identified in the inner tracker
%and in the outer muon system.
%The efficiency to reconstruct a muon with transerse momentum ($p_T$)
%in excess of 5 GeV is larger than
%95\%, while the probability to misidentify a hadron as a muon is below 0.1\%.
%The momentum resolution for a muon with $p_T\sim 100$ GeV is about 1\%.
%Electrons are reconstructed from the association of a Gaussian Sum Filter track %\cite{Adams}
%with an energy deposit in the electromagnetic calorimeter.
%The di--electron mass resolution at the $Z$ mass is $1.56$ GeV in the barrel and $2.57$ GeV in the endcaps.
%Jets are reconstructed by clustering the particle--flow particles with an anti--$k_T$ algorithm %\cite{AntiKT}
%with radius $R=0.5$. The jet momentum is defined as the vector sum of the momenta of its constituents.
%A residual calibration of the jet momentum of about $5-10\%$ of the true jet momentum
%is applied to correct for detector inhomegeneties.
%The transverse momentum resolution for central jets
%is $\sigma(p_T)/p_T = 85\% / \sqrt{ p_T/(\mbox{GeV})} \oplus 4\%$.
%A $b$--tagging algorithm identifies jets from the fragmentation of $b$--quark with 50\% efficiency and
%about $0.5\%$ fake rate.
%The HPS algorithm \cite{TauComm} is used to reconstruct the semileptonic decays of $\tau$ leptons by
%a combinatorial association of charged particles and photons inside jets.
The missing transerse energy ($\vec{E}_T^{miss}$) is defined as the negative vector sum of all
particles transverse momenta. 
%The typical $E_T^{miss}$ resolution is $50\%/\sum E_T \: \mbox{GeV}$,
%where $\sum E_T$ is the scalar sum of all particle transverse momenta in GeV.

The analyses presented in this talk are based on up to 4.7 fb$^{-1}$ of LHC data collected throughout 2011 at a
center--of--mass energy of 7 TeV, with a peak instantaneous luminosity of $3.5\cdot 10^{33}$ cm$^{-2}$s$^{-1}$,
and an average of 9 pile--up interactions per bunch crossing.

\section{Higgs searches}

\subsection{$H\to b\bar{b}$}

A search for the SM Higgs boson decaying to a pair of $b$--quarks, and produced in association with a gauge boson $V=W,Z$,
is documented in Ref. \cite{HIG-11-031}.
Events are selected online requiring electron/muon triggers, or
large $E_T^{miss}$, depending on which of five exclusive final state of the vector $V$ is tagged.
A pair of $b$--tagged jets is required offline. The di--jet system is required to have transverse momentum in excess
of 150 GeV.
%The request for a transverse ``boost'' has a twofold effect: to suppress the irreducible $V+bb$ background,
%which features a softer di--jet $p_T$ spectrum, and to improve the di--jet mass resolution.
The main SM backgrounds consist of $V+bb$ (dominant), $V$+light quarks, di--boson, and 
$t\bar{t}$. They are normalized from background--enriched sidebands.
%The background rates are calibrated from control regions (sidebands), designed
%to enhance one background component at the time, using the Monte Carlo simulation to extrapolate to the signal region.
The interpretation of the results is performed
%using two statistical analyses: a cut--based and a multivariate. The cut--based analysis (``$M_{jj}$'' analysis)
%consists in counting events for which the di--jet mass is within sliding windows centered around the value of
%$M_H$ under test.
using a multivariate analysis (``BDT''), cross--checked with a cut--based one.
%Every event is assigned a score given by the output of a Boosted Decision Tree (BDT), trained on eight discriminating variables.
A counting experiment of events with a score of the BDT above a given threshold is used to set exclusion limits.
%The number of events with a score of the BDT above a given threshold is then used for the statistical interpretation.
%The BDT analysis provides
%the most stringent expected exclusion limits and is therefore adopted as the main way to report results.
No evidence of a signal over the SM background is found. The observed (expected) exclusion
limit at 95\% CL on the cross--section of a SM--like Higgs boson is $4.3$ ($5.7$) times the SM prediction
for $M_H=125$ GeV.

\subsection{$H\to \tau^+\tau^-$}

For $M_H\lesssim145$ GeV, the decay into a pair of tau leptons \cite{HIG-11-029} provides
an important discovery channel for the SM Higgs boson, allowing in principle for a direct
measurement of the Higgs coupling to leptons.
Three final states are considered: when both taus decay leptonically, one into a muon plus neutrinos and
the other into an electron plus neutrinos ($\tau_{e}\tau_{\mu}$),
or when one tau decays leptonically and the other semileptonically ($\tau_{e}\tau_h$, $\tau_{\mu}\tau_h$).
Depending on the jet content, events are classified into a ``VBF''--like, a ``Boosted'', and
a ``$0/1$--jet'' category.
%(two jets with $p_T$ in excess of 30 GeV each, di--jet mass above $400$ GeV, and separated by
%more than $4.0$ units in $\eta$), a ``Boosted'' category (one jet with $p_T>150$ GeV), and
%a ``$0/1$--jet'' category.
%Events with a pair of jets with $p_T$ in excess of 30 GeV each, di--jet mass above $400$ GeV, and separated by
%more than $4.0$ units of pseudorapidity, are classified as ``VBF''--like.
%Events with one jet with $p_T>150$ GeV are classified
%in the ``Boosted'' category.
%All other events, provided they don't contain two jets above 30 GeV, end up in the ``$0/1$--jet''
%category.
The dominant background ($Z\to\tau\tau$) is estimated from $Z\to\mu\mu$ data events,
where the muons are replaced with simulated tau leptons.
The second largest source of background comes from events where a jet is misidentified
as a tau ($W$+jets, QCD).
The di--tau mass is reconstructed from the visible tau momenta and $\vec{E}_T^{miss}$,
using a likelihood--based technique; the resulting di--tau mass resolution is at most 20\%.
A binned shape analysis of the di--tau mass spectrum is performed for the statistical interpretation of the results.
The observation is consistent with the background--only hypothesis. The observed (expected) exclusion
limit at 95\% CL on the cross--section of a SM--like Higgs boson is $3.6$ ($2.3$)
times the SM prediction for $M_H=125$ GeV.

%\section{Low--to--high mass searches}
\subsection{$H\to W^+W^- \to \ell^+\nu\ell^-\nu$}

A search for the SM Higgs boson decaying to $W$ bosons in the fully--leptonic final state is documented
in Ref. \cite{HIG-11-024}. Events with a pair of opposite--charge, isolated and high--$p_T$ leptons (electrons or muons)
are considered. The Drell--Yan and $t\bar{t}$ backgrounds are reduced 
by a cut on the ``projected'' $\vec{E}_T^{miss}$ and a $b$--tag veto, respectively.
The largest background comes from the $WW$ continuum, whose contribution is calibrated from sidebands or normalized to the theoretical
NLO cross--section, depending on the value of $M_H$ under test.
Subleading backgrounds come from $t\bar{t}$, $W$+jets and Drell--Yan,
and are estimated from sidebands.
%The total background normalization uncertainty is 15\%.
Events are further split into a 0--jet, 1--jet and 2--jets category,
the latter optimized for the VBF production mode. For the first two categories, a BDT
classifies events as signal or background like, depending on the event kinematics. The output of the BDTs is used in a
shape analysis.
The SM Higgs boson is ruled out in the range $[129,270]$ GeV,
compared with an expectation of $[127,270]$ GeV in the background--only hypothesis.
%The lower limit is weaker than expected due to a modest excess of events.

\subsection{$H\to ZZ \to \ell^+\ell^- q\bar{q}$}

The final state $H\to ZZ \to \ell^+\ell^- q\bar{q}$, with $q=u,d,c,s,b$, has the largest branching ratio among the $H\to ZZ$
decays \cite{HIG-11-027}. To enhance the statistical power,
events are categorized depending on the number of $b$--tagged jets.
To reduce the dominant $Z$+jets background, the analysis exploits an angular likelihood and a quark/gluon likelihood
discriminator.
A shape analysis of the four--body mass spectrum is performed, with a data--driven parametrization of the
background template. %The mass resolution for the signal is about 3\%.
Two separate analyses are optimized
for the $[130,164]$ GeV and for the $[200,600]$ GeV range. The observed limit
is consistent with the background--only expectation in the full search range.

%\begin{figure}[htb]
%\begin{center}
%\epsfig{file=magnet.eps,height=1.5in}
%\includegraphics[width=0.65\linewidth]{combinedWbt.pdf}
%\caption{Expected and observed exclusion limit on the SM Higgs boson signal strength modifier, obtained
%from the combination of the $H\to b\bar{b}$, $H\to\tau^+\tau^-$ and $H\to W^+W^- \to 2\ell2\nu$ anayses
%(from Ref. \cite{HIG-11-032}).}
%\label{fig:magnet}
%\end{center}
%\end{figure}
%\section{High mass searches}
%For $M_H\gtrsim 2M_Z$, the Higgs decay into a pair of $Z$ bosons, followed by at least one decay $Z\to\ell^+\ell^-$
%with $\ell=e,\mu$, provides a powerful search channel. The case where even the second $Z$ boson decays 
%into electrons or muons is hisorically referred to as the ``golden--plated'' channel, and it will not be discussed here.

\subsection{$H\to ZZ \to \ell^+\ell^- \nu\nu$}

A search for the Higgs boson in the $H\to ZZ \to \ell^+\ell^- \nu\nu$ final state is documented in Ref. \cite{HIG-11-026}.
In addition to a pair of isolated and opposite--sign electrons or muons, the $E_T^{miss}$ is required
to be in excess of 70 GeV. The largest background comes from events with genuine leptons and missing energy, namely
$t\bar{t}$ and $WW$, followed by $WZ$, $ZZ$ and Drell--Yan di--lepton production with instrumental $E_T^{miss}$.
The dominant backgrounds are estimated from data sidebands with opposite--flavor leptons.
A binned shape analysis of the transverse mass distribution of the di--lepton and $\vec{E}_T^{miss}$ allows to
exclude the SM Higgs boson at 95\% CL in the range $[270,440]$ GeV.

\subsection{$H\to ZZ \to \ell^+\ell^- \tau^+\tau^-$}

A search for the Higgs boson decaying to a pair of $Z$ bosons in the $2\ell2\tau$ final state is documented
in Ref. \cite{HIG-11-028}. A total of eight independent channels from combinatorial association
of the two $Z$ boson final states are simultaneously analyzed.
The dominant background is represented by the $ZZ$ continuum,
which is normalized to the measured inclusive $Z$ cross--section, scaled by the $\sigma(ZZ)/\sigma(Z)$ theoretical ratio.
The residual backgrounds come from misidentified leptons and are estimated from data using the fake rate method.
A binned shape analysis of the visible four--body mass is used to set limits.
The upper limit on the cross section is approximately between a factor four and seven larger than the SM cross section in the range
$[190,500]$ GeV, consistent with the background--only expectation.

\section{Conclusions}

A search for the SM Higgs boson in six different final states, using up to 4.7 fb$^{-1}$ of CMS data at $\sqrt{s}=7$ TeV,
has been presented. The analyses presented here target the ``low mass resolution'' channels.
The SM Higgs boson is excluded at 95\% CL over large intervals of $M_H$ in both the intermediate and high mass range.
A moderate excess in the low--mass range, with a maximal local significance of about $2\sigma$,
is observed from the combination of the $\ell^+\nu\ell^-\nu$, $b\bar{b}$, and $\tau^+\tau^-$ channels.


%\bigskip
%I am grateful to Don Alfonso d'Alba for certain services essential to 
%this investigation.

\begin{thebibliography}{99}

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%S.~L. Glashow,
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%\bibitem{StandardModel2}
%S. Weinberg,
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%\bibitem{StandardModel3}
%A.~Salam and N~(ed.) Svartholm,
%\newblock ``Elementary particle physics",
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%\bibitem{HiggsMechanism1}
%F.~Englert and R.~Brout,
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%\bibitem{HiggsMechanism2}
%P.~W. Higgs,
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%\bibitem{HiggsMechanism3}
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%\bibitem{HiggsMechanism4}
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%\bibitem{HiggsMechanism5}
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%\bibitem{HiggsMechanism6}
%T.W. B. Kibble,
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A.~Djouadi,
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\bibitem{LEPExc}
The~LEP Collaborations,
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%\bibitem{Barbieri2}
%G. Altarelli, R. Barbieri, F. Caravaglios,
%\newblock ``Electroweak Precision Test: a Concise Review",
%\newblock {\em International Journal of Modern Physics A}, 13, 1998.

%\bibitem{TevatronExc}
%The CDF, D0 Collaborations,
%\newblock ``Combined cdf and d0 upper limits on standard model higgs boson production with up to 8.6 fb-1 of data",
%\newblock {\em arXiv:1107.5518v2}, 2011.

\bibitem{CMS}
CMS Collaboration,
\newblock ``The CMS experiment at the CERN LHC",
\newblock {\em JINST 3}, S08004, 2008.

%\bibitem{PFT-09-001}
%CMS Collaboration,
%\newblock ``Particle--flow event reconstruction in cms and performance for jets, taus, and missing $E_{\rm t}$",
%\newblock {\em CMS PAS PFT-09-001}, 2009.

%\bibitem{Adams}
%W. Adam, R. Fruhwirth, A. Strandlie, T. Todorov,
%\newblock ``Reconstruction of electrons with the Gaussian--Sum Filter in the CMS tracker at LHC",.
%\newblock {\em J.Phys. G31}, 2005.

%\bibitem{AntiKT}
%G.~P.~Salam M.~Cacciari and G.~Soyez,
%\newblock ``The anti-kt jet clustering algorithm",
%\newblock {\em JHEP}, 04:063, 2008.

%\bibitem{TauComm}
%CMS Collaboration,
%\newblock ``Performances of $\tau$-lepton reconstruction and identification in CMS",
%\newblock {\em JINST 7}, P01001, 2012.

\bibitem{HIG-11-031}
CMS Collaboration,
\newblock ``Search for the Standard Model Higgs Boson decaying to Bottom Quarks",
\newblock {\em CMS PAS HIG-11-031}, 2011.

\bibitem{HIG-11-029}
CMS Collaboration,
\newblock ``Search for neutral higgs bosons decaying to tau pairs in pp collisions at $\sqrt{s}=7$ TeV",
\newblock {\em CMS PAS HIG-11-029}, 2011.

\bibitem{HIG-11-024}
CMS Collaboration,
\newblock ``Search for the Higgs Boson Decaying to WW in the Fully Leptonic Final State",
\newblock {\em CMS PAS HIG-11-024}, 2011.

%\bibitem{HIG-11-032}
%CMS Collaboration,
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%\newblock {\em CMS PAS HIG-11-032}, 2011.

\bibitem{HIG-11-026}
CMS Collaboration,
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CMS Collaboration,
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CMS Collaboration,
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detector at $ \sqrt{s}= 7$ TeV",
\newblock {\em CMS PAS HIG-11-028}, 2011.

\end{thebibliography}

\def\Discussion{
\setlength{\parskip}{0.3cm}\setlength{\parindent}{0.0cm}
     \bigskip\bigskip      {\Large {\bf Discussion}} \bigskip}
\def\speaker#1{{\bf #1:}\ }
\def\endDiscussion{}

%\Discussion

%\speaker{D. Giovanni (University of Seville)}  My analysis indicates that the
%recovery of the two gentlemen is due simply to their embrace of the masculine
%principle and has nothing to do with magnetism at all.  Could you comment on 
%this?

%\speaker{Reggiano} Professor Giovanni has discussed this hypothesis in several
%forums, but, I do not believe there is anything in print.  I understand that
%he is spending his time in other pursuits.

%\endDiscussion
 
\end{document}

