Physics topics in the LIP/CMS group
- Title: Measurement of the top quark properties and tests of the Standard Model at the LHC with the CMS detector
Characterization of the top quark events are among the first studies to be performed with the Large Hadron Collider (LHC) data.
Top quarks are mostly produced in pairs with subsequent decay to W bosons and b-jets. The dilepton channel denotes the case where both W decay leptonically.
The LHC will deliver approximately 0.5-5 fb-1 of data in 2011/2012 and first tests of the Standard Model (SM) with Top candidates can already be performed.
The candidate will contribute in the context of the Portuguese participation at the CMS experiment at the LHC. The work will focus on top quark
production cross-section measurement in dilepton events and on the b-tagging efficiency estimation by determining the heavy-flavor content of
top quark pair events. These aspects have already been studied with simulated events and are within reach with early LHC data. Any deviation
from the SM expectations may provide hints of New Physics.
- Title: Search for the charged Higgs boson in proton-proton collisions at the Large Hadron Collider with the CMS detector
The study aims at the search for charged Higgs bosons from top quark decays. As the charged Higgs boson predominantly decays to tau leptons,
a larger-than-expected production rate of events with tau leptons in the final state may be indicative of the presence of the charged Higgs
boson in the data. The work is placed in the context of the Portuguese participation in the CMS experiment at the LHC. The feasibility of this
research has been studied using simulated data and will be carried out with beam data. Searches for new physics in this channel are possible
with an integrated luminosity of a few hundred inverse picobarn, expected to be collected in 2011-2012.
- Title: Search for low mass Higgs boson decaying in two photons in the CMS experiment at the Large Hadron Collider
The study aims at the search for low mass Higgs boson decaying in two photons in the CMS experiment at LHC. The current predictions of the
Standard Model favor an Higgs boson with low mass below the WW threshold. In this mass region the Higgs decay in two photons is the channels
with the most favorable prospects for discovery at LHC. The excellent photon energy resolution and large acceptance of the CMS crystal calorimeter
offer the best experimental conditions for this research available today. The work is placed in the context of the LIP Lisbon participation in the
CMS experiment at the LHC.
- Title: Search for supersymmetric top decaying into leptonic final states with the CMS detector at the Large Hadron Collider
The study aims at the search for the scalar partner of the top quark (stop: t1) across various stop and Lightest Supersymmetric Particle masses.
It will first focus on the stop pair production in final states with two leptons, two b-jets and missing transverse energy for which the LIP group
has a solid experience. A feasibility study has to be done where the top quark mass may be used to separate the signal from the
ttbar background. If this separation is satisfactory, then the full analysis of the stop signal in this production mode and final state will
start and continue with accumulating data through 2011-2012. If not, then the stop signal will be searched for in the p p -> t tbar t1 t1bar
production mode, among seven possible final states with two or three leptons; multilepton final states is also an area where the LIP group has experience.
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