Abstract
The first observation of top quark production in proton-nucleus collisions is reported using proton-lead data collected by the CMS experiment at the CERN LHC at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=8.16 TeV. The measurement is performed using events with exactly one isolated electron or muon candidate and at least four jets. The data sample corresponds to an integrated luminosity of 174 nb^{-1}. The significance of the tt[over ¯] signal against the background-only hypothesis is above 5 standard deviations. The measured cross section is σ_{tt[over ¯]}=45±8 nb, consistent with predictions from perturbative quantum chromodynamics.
Highlights
The measured cross section is σtt 1⁄4 45 Æ 8 nb, consistent with predictions from perturbative quantum chromodynamics
The top quark, the heaviest elementary particle in the standard model, has been the subject of numerous detailed studies based on data samples with large integrated luminosities in ppand pp collisions [1] accumulated at the Fermilab Tevatron and the CERN LHC, respectively
Top quark studies remained inaccessible in nuclear collisions because of the small integrated luminosities of the first heavy ion runs at the LHC and thpeffiffilffiffioffiffiwffi nucleon-nucleon (NN) center-of-mass energies
Summary
The measured cross section is σtt 1⁄4 45 Æ 8 nb, consistent with predictions from perturbative quantum chromodynamics. The tt cross section is extracted from a combined maximum-likelihood fit of the invariant mass of the two light-quark jets from the W-boson decay, in different categories of events with zero, one, or at least two b-tagged jets.
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