A Limit on the Branching Ratio of the Flavor-Changing Top Quark Decay T→Zc
- Univ. of Chicago, IL (United States)
We have used the Collider Detector at Fermilab (CDF-II) to set upper limits on the branching ratio of the flavor-changing neutral-current (FCNC) top quark decay t → Zc using a technique employing ratios of W and Z production, measured in 1.52 fb-1 of p$$\bar{p}$$ data. The analysis uses a comparison of two decay chains, p$$\bar{p}$$ → t$$\bar{t}$$ → WbWb → ℓvbjjb and p$$\bar{p}$$ → t$$\bar{t}$$ ZcWb → ℓ+ℓ- cjjb, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the MC modeling of acceptance and efficiency for lepton identification over the multi-year dataset also using a ratio of W and Z production, in this case the observed ratio of inclusive production of W to Z-bosons, a technique that will be essential for precision comparisons with the standard model at the LHC. We introduce several methods of determining backgrounds to the W and Z samples. To improve the discrimination against SM backgrounds to top quark decays, we calculate the top mass for each event with two leptons and four jets assuming it is a t$$\bar{t}$$ event with one of the top quarks decaying to Zc. The upper limit on the Br(t → Zc) is estimated from a likelihood constructed with the {ell}+ℓ- cjjb top mass distribution and the number of ℓvbjjb events. Limits are set as a function of the helicity of the Z-boson produced in the FCNC decay. For 100%-longitudinally-polarized Z-bosons we find a limit of 8.3% (95% C.L.).
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 952638
- Report Number(s):
- FERMILAB-THESIS-2009-12; TRN: US0902560
- Country of Publication:
- United States
- Language:
- English
Similar Records
Search for the neutral current top quark decay t{yields}Zc using the ratio of Z-boson+4 jets to W-boson+4 jets production
Search for Higgs Boson Production in Association with the W boson in 1.96-TeV Proton-Antiproton Collisions