# A Direct Top-Quark Width Measurement from Lepton + Jets Events at CDF II

Abstract : We present a measurement of the top-quark width using $t\bar{t}$ events produced in $p\bar{p}$ collisions at Fermilab's Tevatron collider and collected by the CDF II detector. In the mode where the top quark decays to a $W$ boson and a bottom quark, we select events in which one $W$ decays leptonically and the other hadronically~(lepton + jets channel) . From a data sample corresponding to 4.3~fb$^{-1}$ of integrated luminosity, we identify 756 candidate events. The top-quark mass and the mass of $W$ boson that decays hadronically are reconstructed for each event and compared with templates of different top-quark widths~($\Gamma_t$) and deviations from nominal jet energy scale~($\Delta_{JES}$) to perform a simultaneous fit for both parameters, where $\Delta_{JES}$ is used for the {\it in situ} calibration of the jet energy scale. By applying a Feldman-Cousins approach, we establish an upper limit at 95$\%$ confidence level~(CL) of $\Gamma_t <$ 7.6 GeV and a two-sided 68$\%$ CL interval of 0.3 GeV $< \Gamma_t <$ 4.4 GeV for a top-quark mass of 172.5 GeV$/c^2$, which are consistant with the standard model prediction. This is the first direct measurement of $\Gamma_t$ to set a lower limit with 68$\%$ CL.
Document type :
Preprints, Working Papers, ...

http://hal.in2p3.fr/in2p3-00511289
Contributor : Swarna Bassava <>
Submitted on : Tuesday, August 24, 2010 - 2:51:22 PM
Last modification on : Saturday, December 12, 2020 - 3:16:00 AM

### Identifiers

• HAL Id : in2p3-00511289, version 1
• ARXIV : 1008.3891

### Citation

T. Aaltonen, B. Alvarez Gonzalez, S. Amerio, D. Amidei, A. Anastassov, et al.. A Direct Top-Quark Width Measurement from Lepton + Jets Events at CDF II. 2010. ⟨in2p3-00511289⟩

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