# Search for the Neutral Current Top Quark Decay t-->Zc Using the Ratio of Z-Boson + 4 Jets to W-Boson + 4 Jets Production

Abstract : We have used the Collider Detector at Fermilab (CDF II) to search for the flavor-changing neutral-current (FCNC) top quark decay ${t\goes Zc}$ using a technique employing ratios of $W$ and $Z$ production, measured in \ppbar data corresponding to an integrated luminosity of 1.52 $fb^{-1}$. The analysis uses a comparison of two decay chains, ${p\bar{p}\goes t\bar{t}\goes WbWb\goes\ell\nu bjjb}$ and ${p\bar{p}\goes t\bar{t}\goes ZcWb\goes\ell\ell cjjb}$, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the modeling of acceptance and efficiency for lepton identification over the multi-year dataset using another ratio of $W$ and $Z$ production, in this case the observed ratio of inclusive production of $W$ to $Z$ bosons. To improve the discrimination against standard model backgrounds to top quark decays, we calculate the top quark 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 $Zc$. For additional background discrimination we require at least one jet to be identified as originating from a $b$-quark. No significant signal is found and we set an upper limit on the FCNC branching ratio $Br({t\goes Zc})$ using a likelihood constructed from the ${\ell\ell cjjb}$ top quark mass distribution and the number of ${\ell\nu bjjb}$ 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 limits of 8.3% and 9.3% (95% C.L.) depending on the assumptions regarding the theoretical top quark pair production cross-section.
Document type :
Preprints, Working Papers, ...

http://hal.in2p3.fr/in2p3-00416546
Contributor : Swarna Bassava Connect in order to contact the contributor
Submitted on : Monday, September 14, 2009 - 3:37:27 PM
Last modification on : Wednesday, September 15, 2021 - 2:56:02 PM

### Identifiers

• HAL Id : in2p3-00416546, version 1
• ARXIV : 0905.0277

### Citation

T. Aaltonen, J. Adelman, T. Akimoto, M.G. Albrow, B. Alvarez Gonzalez, et al.. Search for the Neutral Current Top Quark Decay t-->Zc Using the Ratio of Z-Boson + 4 Jets to W-Boson + 4 Jets Production. 2009. ⟨in2p3-00416546⟩

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