We present a measurement of the top-quark width using tt-bar events produced in p anti-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's) and deviations from nominal jet energy sale (Delta_JES) to perform a simultaneous fit for both parameters, where Delta_JES is used for the 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 &lt; 7.6 GeV and a two-sided 68% CL interval of 0.3 GeV < Gamma_t &lt; 4.4 GeV for a top-quark mass of 172.5 GeV/c2, which are consistent with the standard model prediction. This is the first direct measurement of Gamma_t to set a lower limit with 68% CL.

T. AALTONEN, B.ALVAREZ GONZALEZV, S. AMERIO, D. AMIDEI, A. ANASTASSOV, A. ANNOVI, et al. (2010). Direct Top Quark Width Measurement at CDF. PHYSICAL REVIEW LETTERS, 105, 232003-1-232003-7 [10.1103/PhysRevLett.105.232003].

Direct Top Quark Width Measurement at CDF

CASTRO, ANDREA;DENINNO, MARIA MADDALENA;MARGAROLI, FABRIZIO;MAZZANTI, PAOLO;MOGGI, NICCOLO';MUSSINI, MANUEL;RIMONDI, FRANCO;ZUCCHELLI, STEFANO
2010

Abstract

We present a measurement of the top-quark width using tt-bar events produced in p anti-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's) and deviations from nominal jet energy sale (Delta_JES) to perform a simultaneous fit for both parameters, where Delta_JES is used for the 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/c2, which are consistent with the standard model prediction. This is the first direct measurement of Gamma_t to set a lower limit with 68% CL.
2010
T. AALTONEN, B.ALVAREZ GONZALEZV, S. AMERIO, D. AMIDEI, A. ANASTASSOV, A. ANNOVI, et al. (2010). Direct Top Quark Width Measurement at CDF. PHYSICAL REVIEW LETTERS, 105, 232003-1-232003-7 [10.1103/PhysRevLett.105.232003].
T. AALTONEN; B.ALVAREZ GONZALEZV; S. AMERIO; D. AMIDEI; A. ANASTASSOV; A. ANNOVI; J. ANTOS; G. APOLLINARI; J.A. APPEL; A. APRESYAN; T. ARISAWA; A. AR...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/97994
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