Dependence of the $t\bar{t}$ production cross section on the transverse momentum of the top quark

Abstract

We present a measurement of the differential cross section for $t\bar{t}$ events produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV as a function of the transverse momentum ($p_T$) of the top quark. The selected events contain a high-$p_T$ lepton ($\ell$), four or more jets, and a large imbalance in $p_T$, and correspond to 1 fb${}^{-1}$ of integrated luminosity recorded with the D0 detector. Each event must have at least one candidate for a $b$ jet. Objects in the event are associated through a constrained kinematic fit to the $t\bar{t}\to WbW\bar{b} \to \ellνb q\bar{q}'\bar{b}$ process. Results from next-to-leading-order perturbative QCD calculations agree with the measured differential cross section. Comparisons are also provided to predictions from Monte Carlo event generators using QCD calculations at different levels of precision.

Figures (6)

• Figure 1: The reconstructed top-quark mass compared with expectation. Hashed areas represent statistical and jet energy calibration uncertainties on the prediction.
• Figure 2: The $p_T$ spectrum of top quarks (two entries per event) compared with expectation. Hashed areas represent statistical and jet energy calibration uncertainties on the prediction.
• Figure 3: Comparison between the background-subtracted reconstructed top-quark $p_T$ spectrum and the one corrected for the effects of finite experimental resolution (two entries per event). Inner and outer error bars represent the statistical and total (statistical and systematic added in quadrature) uncertainties, respectively.
• Figure 4: Inclusive ${\rm d}\sigma/{\rm d}p_T$ for $t\bar{t}$ production (two entries per event) in data (points) compared with expectations from NLO pQCD (solid lines), from an approximate NNLO pQCD calculation, and for several event generators (dashed and dot-dashed lines). The gray band encompasses uncertainties on the pQCD scale and parton distribution functions. Inner and outer error bars represent the statistical and total (statistical and systematic added in quadrature) uncertainties, respectively.
• Figure 5: Ratio of ${\rm d}\sigma/{\rm d}p_T$ for top quarks in $t\bar{t}$ production (two entries per event) to the expectation from NLO pQCD. The gray band encompasses uncertainties on the scale of pQCD and parton distribution functions. Also shown are ratios relative to NLO pQCD for an approximate NNLO pQCD calculation and of predictions for several event generators. Inner and outer error bars represent statistical and total (statistical and systematic added in quadrature) uncertainties, respectively.