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<font size="-1"><font face="Courier New, Courier, monospace">Dear
all, <br>
<br>
welcome to this week's JYFL Colloquium, Fri 29 April, at 10:15
in FYS1, and coffee at 10:00.<br>
<br>
Speaker: Lauri Wendland, Helsinki Institute of Physics<br>
<br>
Title: Status of Higgs Boson Searches in the CMS Experiment at
the CERN LHC<br>
<br>
Abstract:<br>
The breaking of the electroweak symmetry is the last unconfirmed
part of the standard model of particle physics, which describes
elementary particles and their interactions. The spontaneous
breaking of the electroweak symmetry is assumed to account for
the generation of masses of different particles through the
Higgs mechanism. The Higgs mechanism requires, however, the
existence of one or more Higgs bosons, which so far have not
been experimentally discovered. Since the mass of the Higgs
boson is limited by theoretical constraints below the TeV energy
scale, the LHC and its general-purpose detectors, including the
CMS experiment [1], are, for the first time, in a position to
either confirm or exclude the existence of the Higgs boson.<br>
The current status of efforts for finding the Higgs boson at the
CMS experiment is discussed for both the standard model (SM) and
the minimal supersymmetric standard model (MSSM), the currently
most prominent theory to extend the standard model to a more
general theory. Results of the following four different Higgs
boson searches are presented [2-5]:<br>
<br>
• SM Higgs boson search in<br>
H --> W^+ W^− --> (ℓ^+ nu_ℓ) (ℓ^− nu_ℓ),<br>
• MSSM heavy neutral Higgs boson search in<br>
H/A --> tau^+ tau^− --> (e^± nu_e nu_tau ) (μ^∓
nu_μ nu_τ ) or (tau^±_hadr nu_τ )(ℓ^∓ nu_ℓ nu_tau ),<br>
• MSSM light charged Higgs bosons search in<br>
t tbar --> (b H^±) (bbar W^∓) --> (b tau^± nu_tau
)(bbar ℓ^∓ nu_ℓ) --> (b tau^±_hadr nu_tau nu_tau )(bbar
ℓ^∓nu_ℓ), and<br>
• doubly charged Higgs boson search in Higgs triplet models via<br>
Z/gamma --> Φ^++ Φ^−− --> (ℓ^+ℓ^+) (ℓ^−ℓ^−) and W^±
--> Φ^++ Φ^− --> (ℓ^+ℓ^+)(ℓ^− nu_ℓ),<br>
<br>
where ℓ = e or μ and tau_hadr denotes hadronic tau decays. The
results are based on the 36 pb^−1 of data collected in 2010. No
excess of events has been observed over the SM backgrounds, but
sensitivity is found to be good enough to experimentally narrow
down the existing mass limits in some of the analyzed decay
channels. Therefore, the data to be collected during 2011 has
already the potential to show first hints of the elusive Higgs
boson or to exclude its existence over a large area of parameter
space.<br>
References<br>
[1] The CMS Collaboration, “The CMS Experiment at the CERN LHC”,
JINST 3:S08004 (2008)<br>
[2] The CMS Collaboration, “Measurement of W+W− Production and
Search for the Higgs Boson in pp Collisions at ps=7 TeV”, Phys.
Lett. B 699 (2011) 25-47, arXiv:1102.5429<br>
[3] The CMS Collaboration, “Search for Neutral MSSM Higgs Bosons
Decaying to Tau Pairs in pp Collisions at ps=7 TeV”, submitted
to Phys.Rev.Lett., arXiv:1104.1619<br>
[4] The CMS Collaboration, “Search for the charged Higgs boson
in the etau and mutau dilepton channels of top quark pair
decays”, CMS-PAS-HIG-11-002<br>
[5] The CMS Collaboration, “Search four doubly charged Higgs to
charged leptons”, CMS-PAS-HIG-11-001<br>
<br>
See you all there!<br>
Kari Eskola and Ilari Maasilta<br>
<br>
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