Percent level precision physics at the Tevatron: first genuine NNLO QCD corrections to q qbar -> t tbar + X

Abstract: We compute the Next-to-Next-to-Leading Order (NNLO) QCD corrections to the partonic reaction that dominates top-pair production at the Tevatron. This is the first ever NNLO calculation of an observable with more than two colored partons, and/or massive fermions, at hadron colliders. Augmenting our fixed order calculation with soft-gluon resummation through Next-to-Next-to-Leading Logarithmic (NNLL) accuracy, we observe that the predicted total inclusive cross-section exhibits a very small perturbative uncertainty, estimated at +-2.7%. We expect that once all sub-dominant partonic reactions are accounted for, and work in this direction is ongoing, the perturbative theoretical uncertainty for this observable could drop below +-2%. Our calculation demonstrates the power of our computational approach and proves it can be successfully applied to all processes at hadron colliders for which high-precision analyses are needed.

• The paper delivers the first complete NNLO QCD correction for q-qbar→t-tbar+X, achieving percent-level precision.
• It employs NNLL soft-gluon resummation and a novel two-loop constant extraction to refine theoretical predictions.
• Numerical results demonstrate a reduced perturbative uncertainty of ±2.7%, enhancing the accuracy of top-quark pair production estimates.

A Detailed Examination of NNLO QCD Corrections to Top Quark Pair Production at the Tevatron

The research paper under review delivers a comprehensive calculation of NNLO (Next-to-Next-to-Leading Order) QCD corrections to the partonic process $q\bar{q} \to t\bar{t} + X$, which principally governs top quark pair production at the Tevatron. This study marks a pivotal advancement as it presents the first NNLO calculation for a hadron collider with scenarios involving more than two colored partons and/or massive fermions. The practical application of this work is evidenced by the dramatically reduced perturbative uncertainty in predicting the total inclusive cross-section for this process, estimated at $\pm2.7\%$. It stands as a testament to the efficacy of the computational techniques employed, with further implications suggesting possible reductions in theoretical uncertainty to levels below $\pm2\%$.

Core Contributions and Methodology

The calculation of NNLO corrections presented in this paper is a significant technical achievement, allowing for improved precision in theoretical predictions of top-quark pair production cross-sections. The research introduces soft-gluon resummation to NNLL (Next-to-Next-to-Leading Logarithmic) accuracy, achieving small perturbative uncertainties. This methodological advancement demonstrates the utility and robustness of the computational approach, which is poised to be applicable across a spectrum of processes, particularly those requiring high-precision analysis at hadron colliders.

The study extensively details the complete derivation of the $\sigma^{(2)}_{q\bar q}$ function pertaining to this partonic reaction. This includes a novel extraction of the two-loop constant term, an integral for deriving the hard matching constant that forms a critical component of the soft-gluon resummation at NNLL accuracy. The paper further validates the exact evaluation by contrasting it with existing approximations, highlighting the lack of precision in the latter.

Numerical Results and Significance

The paper provides a numerical analysis of the cross-section predictions for the Tevatron using the updated NNLO calculations. By implementing these corrections, the paper reports precise cross-section values while performing a thorough error analysis incorporating both scale and PDF variations. The results indicate not only an improvement over prior calculations but also an advancement in theoretical prediction capabilities when compared to experimental uncertainties from Tevatron measurements.

Moreover, this study discusses the impacts of the higher-order corrections on the perturbative series convergence, reflecting improved theoretical predictions as confirmed by reduced scale dependence with subsequent approximation levels. This outcome not only affirms the consistency of the scale variation method per perturbative order but also lays groundwork for future studies exploring PDF comparisons and top-quark mass extractions with higher precision.

Theoretical and Practical Implications

This research holds substantial implications for theoretical and practical developments in particle physics. On a theoretical level, the precision achieved in calculating top-pair production cross-sections offers a more solid foundation for future explorations into the implications of QCD corrections, facilitating enhanced scrutiny of the Standard Model. Practically, the insights realized here can aid current and future collider experiments in enhancing their analytic capabilities, shedding light on fundamental properties and interactions involving the top quark.

Additionally, the findings have implications for other top-quark related observables, such as the top-quark forward-backward asymmetry, which is known for its deviation from the Standard Model predictions. These refined calculations equip experimentalists and theorists with the tools necessary for critical investigations into discrepancies and new physics at the Tevatron and other collider facilities.

In conclusion, this paper presents a methodological leap in the precision calculation of NNLO QCD corrections for top-quark pair production. It paves the way for refined experimental validation and offers computational techniques that are likely to enhance precision studies across various hadron collider experiments, maintaining a strong alignment with both theoretical and practical advancements in particle physics research. Future developments should focus on integrating residual contributions from other subdominant processes and extending these methodologies to explore differential cross-sections for comprehensive top sector analysis across current and forthcoming colliders like the LHC.