Direct Measurement of the Top Quark Mass at D0

TL;DR

This paper reports a measurement of the top quark mass using data from the D0 detector at Fermilab, employing various fitting techniques and analyzing different decay channels to obtain a precise estimate.

Contribution

The paper presents a new measurement of the top quark mass using likelihood and constraint fitting methods on Tevatron data, improving the precision of previous estimates.

Findings

Measured top quark mass as 172.1 GeV/c^2 with combined uncertainties.

Used multiple decay channels and fitting techniques for cross-validation.

Provided kinematic distribution studies of top quark candidates.

Abstract

We determine the top quark mass m_t using t-tbar pairs produced in the D0 detector by \sqrt{s} = 1.8 TeV p-pbar collisions in a 125 pb^-1 exposure at the Fermilab Tevatron. We make a two constraint fit to m_t in t-tbar -> b W^+bbar W^- final states with one W boson decaying to q-qbar and the other to e-nu or mu-nu. Likelihood fits to the data yield m_t(l+jets) = 173.3 +- 5.6 (stat) +- 5.5 (syst) GeV/c^2. When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain m_t = 172.1 +- 5.2 (stat) +- 4.9 (syst) GeV/c^2. An alternate analysis, using three constraint fits to fixed top quark masses, gives m_t(l+jets) = 176.0 +- 7.9 (stat) +- 4.8 (syst) GeV/C^2, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented.