Seminar zur Teilchenphysik, SS 2011
Donnerstag, 26.5.2011, 16:30Uhr, D10.08
Dr. Jeannine Wagner-Kuhr
Karlsruher Institut für Technologie (KIT)
Charge asymmetry in top pair production - a window for new physics
The top quark discovered 15 years ago at the ppbar accelerator Tevatron
at Fermilab close to Chicago is by far the heaviest fermion. Due to its
large coupling to the Higgs boson it plays an important role in the
Standard Model (SM) of particle physics but also in many models with new
phenomena. In the last years, both Tevatron experiments, CDF and D0,
performed a detailed survey of the top quark properties and the newly
observed quark was found to be well consistent with the predictions of a
SM top quark. However, a first hint for new physics in the top quark
sector might be the observed charge asymmetry which is about 2sigma
above the SM prediction. The recently published analysis from CDF in the
lepton+jets decay channel observes a deviation of 3.4sigma from the SM
prediction for invariant top pair masses above 450GeV. This new CDF
charge asymmetry measurement will be summarized in this talk and a
comparison with the most recent D0 measurement and with a first
measurement in the dileptonic decay channel performed by CDF will be
given. In case the large charge asymmetry observed at the Tevatron is
indeed due to new physics, like new heavy exchange particles, this
effect, although significantly reduced, should be observable at the
pp-collider LHC in Geneva and a first measurement of the charge
asymmetry at the CMS experiment using data recorded in 2010 is presented.
 Slides
gez. D. Wicke
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