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Measurement of the mass of the top quark in decays with a J/$\psi$ meson in pp collisions at 8 TeV

The CMS collaboration
No Journal Information, 2016

Abstract (data abstract)
CERN-LHC. A first measurement is presented of the top quark mass using the decay channel $\text{t}\to(\text{W}\to\ell\nu)\,(\text{b}\to\text{J}/\psi+\text{X}\to\mu^+\mu^-+\text{X})$, in events selected in proton-proton collisions and recorded with the CMS detector at the LHC at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 /fb, with 666 $\text{t}\bar{\text{t}}$ and single top quark candidate events containing a reconstructed J/$\psi$ candidate decaying into an oppositely-charged muon pair. The top quark mass is extracted from an unbinned maximum-likelihood fit to the invariant mass of the (J/$\psi$+$\ell$) system, where $\ell$ is an electron or a muon from W boson decay. The resulting top quark mass measurement is 173.5 $\pm$ 3.0(stat) $\pm$ 0.9(syst) GeV. Even though the results are statistically limited, the dominant systematic uncertainties are different from those of the most precise direct reconstruction methods. As the sensitivity to jet-related uncertainties is negligible, this allows the possibility to contribute significantly in combination with other top quark mass measurements. Furthermore, with the larger data set expected in the next runs of the LHC, the method described in this paper will provide a result which will be more competitive with those obtained from the conventional reconstruction techniques.

  • Table 1

    Data from Page 4 of preprint


    Number of selected events from simulations and observed in data. The uncertainties are statistical.

  • Table 2

    Data from Page 10 of preprint


    Summary of the impact of systematic uncertainties on the top quark mass according to the contributions from each source.

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