Measurement of the Top Quark Mass with the Collider Detector at Fermilab

TL;DR

The paper presents a precision measurement of the top-quark mass using CDF Run 1 data at 1.8 TeV, focusing on the lepton+jets channel where a constrained kinematic fit and a template-based likelihood extract $M_{top}$. By subdividing the data into four mass-subsamples with varying signal-to-background, the analysis achieves a combined top mass of 176.1 GeV/$c^2$ with total uncertainty 6.6 GeV/$c^2$, and cross-validates with all-hadronic and dilepton channels. Systematic uncertainties are dominated by the jet energy scale, with substantial effort dedicated to jet corrections, ISR/FSR modeling, and background shape. The result provides a high-precision direct determination of the top-quark mass, reinforcing SM constraints and contributing to global electroweak fits.

Abstract

This report describes a measurement of the top quark mass in $\ppbar$ collisions at a center of mass energy of 1.8 TeV. The data sample was collected with the CDF detector during the 1992--95 collider run at the Fermilab Tevatron, and corresponds to an integrated luminosity of 106 \pb. Candidate $t\bar{t}$ events in the ``lepton+jets'' decay channel provide our most precise measurement of the top quark mass. For each event a top mass is determined by using energy and momentum constraints on the production of the $\ttbar$ pair and its subsequent decay. A likelihood fit to the distribution of reconstructed masses in the data sample gives a top mass in the lepton+jets channel of $176.1\pm 5.1 (stat.)\pm 5.3 (syst.) \gevcc$. Combining this result with measurements from the ``all-hadronic'' and ``dilepton'' decay topologies yields a top mass of $176.1\pm 6.6 \gevcc$.

Figures (41)

• Figure 1: Side view of one quadrant of the CDF detector for Run 1. The detector is symmetric about the interaction point.
• Figure 2: The negative log-likelihood function for obtaining a given number of background events in each mass subsample: (a) SVX Double tags, (b) SVX Single tags, (c) SLT (no SVX) tags, and (d) No Tag events.
• Figure 3: Uncertainty in jet ${\rm E}_{\rm T}$ scale as measured with a jet clustering cone of size 0.4. The vertical axis shows the extent to which the measured jet ${\rm E}_{\rm T}$ response varies due to different systematic effects.
• Figure 4: "Flavor-independent" jet corrections, for a jet clustering cone of R=0.4. (a) Absolute correction, $f_{abs}$, and out-of-cone correction factor, 1+ OC/${\rm P}_{\rm T}$, versus corrected jet ${\rm P}_{\rm T}$, ${\rm P}_{\rm T}^{cor}$ . (b) Total correction, ${\rm P}_{\rm T}^{cor}$/${\rm P}_{\rm T}^{raw}$, as a function of ${\rm P}_{\rm T}^{cor}$. (c) total correction, ${\rm P}_{\rm T}^{cor}/{\rm P}_{\rm T}^{raw}$, as a function of ${\rm P}_{\rm T}^{raw}$. (d) fraction of measured momentum, ${\rm P}_{\rm T}^{raw}/{\rm P}_{\rm T}^{cor}$ versus ${\rm P}_{\rm T}^{cor}$.
• Figure 5: Fractional difference in corrected jet ${\rm P}_{\rm T}$ obtained using cone radii of 0.4 and 1.0 as a function of the corrected jet ${\rm P}_{\rm T}$ from $W$+1 jet events. The circles are the results from the data sample and the triangles are from a sample of HERWIG Monte Carlo events which have been processed through the CDF detector simulation.