Measurement of the top quark mass in the lepton+jets channel using the ideogram method

Abstract

A measurement of the top quark mass using events with one charged lepton, missing transverse energy, and jets in the final state, collected by the D0 detector from $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ at the Fermilab Tevatron collider, is presented. A constrained fit is used to fully reconstruct the kinematics of the events. For every event a top quark mass likelihood is calculated taking into account all possible jet assignments and the probability that an event is signal or background. Lifetime-based identification of $b$ jets is employed to enhance the separation between $t\overline{t}$ signal and background from other physics processes and to improve the assignment of the observed jets to the quarks in the $t\overline{t}$ hypothesis. We extract a multiplicative jet energy scale (JES) factor in situ, greatly reducing the systematic effect related to the jet energy measurement. In a data sample with an integrated luminosity of $425\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$, we observe 230 candidate events, with an estimated background of 123 events, and measure ${m}_{t}=173.7\ifmmode\pm\else\textpm\fi{}4.4(\mathrm{stat}+\mathrm{JES}{)}_{\ensuremath{-}2.0}^{+2.1}(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}$. This result represents the first application of the ideogram technique to the measurement of the top quark mass in lepton+jets events.