Measurement of the Differential Cross Section d{\sigma}/d(cos {\theta}t) for Top-Quark Pair Production in p-pbar Collisions at sqrt{s} = 1.96 TeV

TL;DR

This paper measures the angular distribution of top-quark pairs in proton-antiproton collisions at 1.96 TeV, using Legendre polynomials, and finds mostly good agreement with the Standard Model except for an excess in the linear term.

Contribution

It provides a detailed measurement of the differential cross section for top-quark pairs at Tevatron energies, highlighting a deviation in the linear Legendre coefficient from Standard Model predictions.

Findings

Legendre coefficients mostly agree with Standard Model

An excess linear-term coefficient (a1) observed

Results constrain models of top-quark production

Abstract

We report a measurement of the differential cross section, d{\sigma}/d(cos {\theta}t), for top-quark-pair production as a function of the top-quark production angle in proton-antiproton collisions at sqrt{s} = 1.96 TeV. This measurement is performed using data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.4/fb. We employ the Legendre polynomials to characterize the shape of the differential cross section at the parton level. The observed Legendre coefficients are in good agreement with the prediction of the next-to-leading-order standard-model calculation, with the exception of an excess linear-term coefficient, a1 = 0.40 +- 0.12, compared to the standard-model prediction of a1 = 0.15^{+0.07}_{-0.03}.