Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s}=1.96 TeV using Lepton + Jets Events with Secondary Vertex b-tagging

TL;DR

This work measures the ttbar production cross section in ppbar collisions at sqrt{s}=1.96 TeV using lepton+jets events with secondary-vertex b-tagging. It combines data-driven background estimation, robust heavy-flavor tagging calibration, and HT-based optimization to extract a cross section of 5.6 pb (statistical) and 0.9–0.6 pb (systematic) for mt=175 GeV/c^2, with a cross-check in a nearly background-free double-tag sample yielding 5.0 pb. The analysis leverages AlpGen/Hherwig simulations for W+heavy flavor, data-driven scale factors for tagging efficiency, and a comprehensive assessment of mistags and non-W QCD backgrounds. The results align with Standard Model predictions and demonstrate the viability of SecVtx-based b-tagging for precision top-quark measurements and future top-property studies.

Abstract

We present a measurement of the ttbar production cross section using events with one charged lepton and jets from ppbar collisions at a center-of-mass energy of 1.96 TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb-1 of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5 +- 1.8 events are expected from background contributions. We measure a ttbar production cross section of 5.6^{+1.2}_{-1.1} (stat.) ^{+0.9}_{0.6} (syst.) pb.

Figures (20)

• Figure 1: Transverse mass of the identified lepton and inferred neutrino, consistent with $W$ boson production (162 $\mathrm{pb}^{-1}$ data sample).
• Figure 2: Data/Monte Carlo comparison of some quantities of tagged electron jets ($L_{2D}>0$, identified conversions have been removed for plotting purposes). Histograms are normalized to unit area. From top-left, clockwise: electron $E_T$, electron-jet $E_T$, away-jet $E_T$, electron $p_T$. (The last bin includes all overflow entries.)
• Figure 3: Data/Monte Carlo comparison of some quantities of tagged electron jets (identified conversions have been removed for plotting purposes). Histograms are normalized to unit area. From top-left, clockwise: number of good tracks in the jet, number of tracks in the tagged vertex, vertex mass of positively tagged electron-jets; pseudo-$c\tau$ of (positively or negatively) tagged electron-jets.
• Figure 4: Fit (solid line) of the relative $b$ and $c$ contributions to the vertex tag mass distribution. Templates for the different flavors are derived from simulation (and the data in the case of light flavor). The error bars for the data are contained within the markers.
• Figure 5: Radius of identified conversions in data, with location of the silicon detector layers (L00, SVX and ISL), readout system, and ISL and COT main mechanical structures.