Top Quark Mass: Latest CDF results, Tevatron Combinations, and Electroweak Implications
We present results on the precision measurement of the top quark mass and a combination of the best CDF top mass measurements as of March 2008. We present also a combination by the TevEWWG (Tevatron electroweak working group) of the best top mass results from CDF and D0 in Run 1 and Run 2 of the Tevatron. This result is the current world average, and offers an uncertainty less than 1%. The new mass value has been included in traditional LEP EWWG fits to precision electroweak data, and implications for the Standard Model Higgs have been derived.
|
Top Quark Properties and Searches for New Physics in Top Event Sample at CDF
More than a decade after its discovery we are still trying to find out more about the nature of the top quark. The current statistics of the Tevatron allow us to make stringent tests. In this talk we will present state of the art measurements of top quark properties. By studying rates and distributions sensitive to the production and decay mechanisms of top quarks, we can search for contamination from non-standard model particles, or subtle differences in the electroweak or strong interactions that govern top quark interactions. We will present state of the art measurements of such new physics prospects as supersymmetric top quarks, charged Higgs bosons, fourth generation quarks, heavy electroweak bosons, and flavor changing neutral currents.
|
Measurement of the Single Top Production Cross Section at CDF
We report a measurement of electroweak single top quark production in 2.2 fb-1 of ppbar collision data collected by the Collider Detector at Fermilab at 1.96 TeV. Candidate events are selected for further classification by three parallel analysis techniques; one using a likelihood discriminant, one using a
matrix-element discriminant, and one using a neural network. The results of these three analyses are combined in order to improve the expected sensitivity. We observe a signal consistent with the Standard Model expectation, but inconsistent with the background-only model by $3.7\sigma$, with a median expected sensitivity of 5.1 sigma. We measure a cross section of sigma_{st}=2.2 +- 0.7 pb and extract the value of the CKM matrix element |V_{tb}|=0.88 +- 0.14(stat+sys) +- 0.07(theory), with a 95% C.L. lower limit of |V_{tb}|>0.66.
|
Search for Heavy Top-like Quarks Using Lepton Plus Jets Events in 1.96-TeV ppbar Collisions
We present the results of a search for pair production of a new heavy top-like quark t' decaying to a W boson and another quark using the CDF II detector in Run II of the Tevatron ppbar collider. Using a data sample corresponding to 2.3 fb-1 of integrated luminosity we fit the observed spectrum of total transverse energy and reconstructed t' quark mass to a combination of standard model processes and t' pair production. We set limits
on the t't'bar production cross section assuming a 100% branching ratio of t'->Wq and standard strong couplings for the t'.
|
Search for Pair Production of Stop Quarks Mimicking Top Event Signatures in 1.96-TeV ppbar Collisions
We present the results of a search for pair-produced super-symmetric partner of the top quark (stop quark) in a data sample corresponding to 1.9 fb^{-1} of integrated luminosity collected with the CDF II detector of the Tevatron ppbar collider. We search for the scalar top quarks via their decay channel: stop -> b + chi^+ -> b + chi0 + W(*), where both the W+ and W- bosons decay leptonically, and give an event signature mimicking the one of a top dilepton event. We infer 95% CL limits on the stop quark, chargino and neutralino masses assuming that m_chi0+ <~ m_stop <~ m_top.
|
Measurement Of The Front Back Asymmetry In Top-Antitop Quark Pairs In 1.9 fb-1
A method of reconstructing t-tbar events in the lepton plus jets mode is applied to a measurement of the forward backward asymmetry in t-tbar pair production at CDF. The measurement is a test of discrete symmetries in t-tbar production and strong interactions at large Q2. In the present data set it is potentially sensitive to the the presence of parity-violating production channels such as a massive Z'-like boson or new physics within Strong Interactions. Larger data sets will have sensitivity for an interesting charge asymmetry arising from pure QCD calculated at next-to-leading order. We measure the top quark forward-backward asymmetry in 1.9 fb-1 of CDF collision data, using 484 candidate t-tbar lepton plus jets events in the high Pt lepton trigger streams. The measurement is performed in two complimentary rest frames: the proton anti-proton frame and the top anti-top frame. We measure Afb(lab) = 0.17 +/- 0.07 (stat) +/- 0.04 (sys) and Afb(t-tbar) = 0.24 +/- 0.13 (stat) +/- 0.04 (sys) which can be compared to the Standard Model prediction Afb (lab) = 0.04 +/- 0.01 and Afb (t-tbar) = 0.05 +/- 0.01, respectively.
|
|
