Search for a Standard Model Higgs boson in the decay channel H to ZZ to 2l2tau
Abstract
A search for the standard model Higgs boson in the
decay mode $ H \to ZZ \to 2l2\tau$, where $l = {\mu, e}$ is presented
based on CMS data corresponding to an integrated luminosity of 1.1 fb$^{-1}$
at $\sqrt{s}=7$
TeV.
No evidence is found for a significant deviation from standard model expectations anywhere in the ZZ mass range
considered in this analysis.
An upper limit at 95\% C.L. is placed on
the product of the cross-section and decay branching ratio for the
Higgs boson decaying with
standard model-like couplings, which excludes cross-sections of about ten times the expected
value for Higgs boson masses in the range $200 < m_{\rm H} < 400 \, \rm{GeV/c^2}$.
Main Results
In $1.1 \fbinv$ of data one event isobserved in the 8 search channels, in the $eee\tau$ state, as compared to 2.5
background events expected.
The reconstructed $2l2\tau$ invariant mass for all decay channels is presented i
n
Fig.~\ref{figure:invmass}. The stacked background shapes are simulated using MC and normalized to
the values obtained using the method outlined above. The expected mass distributions for the SM Higgs with masses
$m_{\rm H} = 200$ and $m_{\rm H} = 400 \, \rm{GeV/c^2}$ are also shown.
No evidence is found for a significant deviation from standard model expectations anywhere in the $ZZ$ mass range
considered in this analysis.
The total signal acceptance, which also includes the branching ratios of
individual tau channels, varies
between 0.01--0.02 for a Higgs mass of 200
GeV and various tau decay channels and increases by factor of three to four towards
450
GeV. This is expected since the final-state leptons produced in tau decays are softer than those from
direct $Z \to ll$ production and the selection requirements and lepton reconstruction become more efficient
at high Higgs masses.
Expected and observed 95\% C.L. (confidence level) upper limits are set on the cross-section ratio to the nominal SM
Higgs cross-section using the modified frequentist construction CL$_{\rm{s}}$~\cite{CLS1, CLS2}. They are presented
as a function of the Higgs mass
in Fig.~\ref{figure:limitPlot}.
The bands represent the $1 \sigma$ and $2 \sigma$ probability intervals around the expected limit.
The upper limit on the cross-section is approximately ten times the SM cross-section in the range of
$200 < m_{\rm H} < 400 \, \rm{GeV/c^2}$.
Figures from HIG-11-013
Figure |
Label |
Description |
|
pdf |
The expected and observed 95\% C.L. upper limits on the product of the production cross-section and decay branching ratio for a Higgs boson normalized to the SM expectation as a function of $m_{\rm H}$. At $m_{\rm H} = 180\, \rm{GeV/c^2} $ the less restrictive limit is due to the rapidly decreasing branching ratio of $H \to ZZ$ in the SM. The one- and two-standard-deviation ranges are also shown. |
|
pdf |
The four-lepton reconstructed mass summed for all $2l2\tau$ final states. The data corresponds to an integrated luminosity of 1.1 \fbinv. The stacked background shapes are the result of a MC simulation and normalized to the values obtained using the data--driven techniques explained in the text. The expected mass distributions for the SM Higgs boson with a mass 200 or 400 GeV are also shown. |
|
pdf |
Comparison between data and simulation for the background estimation in same-sign, anti-isolated control region for $\mu \mu \tau \tau$ (left plot) events. |
|
pdf |
Comparison between data and simulation for the background estimation in same-sign, anti-isolated control region for $ee \tau \tau$ (right plot) events. |
--
AlexanderSavin - 21-Aug-2011