[f(k)] Colloquium by Wendland, Fri 29.4. at 10 in FYS1

[Kari J. Eskola]

Dear all,

welcome to this week's JYFL Colloquium, Fri 29 April, at 10:15 in FYS1, 
and coffee at 10:00.

Speaker: Lauri Wendland, Helsinki Institute of Physics

Title: Status of Higgs Boson Searches in the CMS Experiment at the CERN LHC

Abstract:
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.
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]:

. SM Higgs boson search in
     H  -->  W^+ W^-  -->  (l^+ nu_l) (l^- nu_l),
. MSSM heavy neutral Higgs boson search in
     H/A -->  tau^+ tau^-  -->  (e^± nu_e nu_tau ) (?^? nu_? nu_? ) or 
(tau^±_hadr nu_? )(l^? nu_l nu_tau ),
. MSSM light charged Higgs bosons search in
       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
. doubly charged Higgs boson search in Higgs triplet models via
     Z/gamma --> ?^++ ?^-- --> (l^+l^+) (l^-l^-)  and W^± --> ?^++ ?^- 
--> (l^+l^+)(l^- nu_l),

where l = e or ? 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.
References
[1] The CMS Collaboration, "The CMS Experiment at the CERN LHC", JINST 
3:S08004 (2008)
[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
[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
[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
[5] The CMS Collaboration, "Search four doubly charged Higgs to charged 
leptons", CMS-PAS-HIG-11-001

See you all there!
     Kari Eskola and Ilari Maasilta

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