Single-top Wt-channel production matched with parton showers using the POWHEG method (1009.2450v1)

Abstract: We present results for the next-to-leading order calculation of single-top Wt-channel production interfaced to Shower Monte Carlo programs, implemented according to the POWHEG method. A comparison with MC@NLO is carried out. Results obtained using the PYTHIA shower are also shown and the effect of typical cuts is briefly discussed.

• The paper presents a next-to-leading order calculation merged with parton showers for precise single-top Wt-channel simulation.
• It compares Diagram Removal and Diagram Subtraction approaches to effectively manage interference with ttbar production.
• Results validated against MC@NLO benchmarks enhance the modeling of electroweak processes at LHC energies.

Overview of Next-to-Leading Order Calculation of Single-Top $Wt$-Channel Production

The paper under discussion presents a detailed examination of the calculation of single-top $Wt$-channel production at next-to-leading order (NLO) accuracy, interfaced with parton shower Monte Carlo simulations using the POWHEG method. This paper contributes to a broader effort to enhance the precision of theoretical predictions for processes significant in collider physics, specifically within the context of the Large Hadron Collider (LHC).

Single-top quark production is an electroweak process whose understanding is pivotal due to its sensitivity to the properties of the electroweak sector of the Standard Model (SM). It serves as a background in various channels, including those pertinent to Higgs boson searches. Thus, achieving high precision in theoretical predictions of single-top production rates and distributions is essential.

Methodology and Algorithms

The implementation involves merging NLO calculations with parton showers, aiming to amalgamate the fixed-order accuracy provided by NLO computations with the resummation of large logarithms afforded by parton shower algorithms. The paper applies the POWHEG method, which is known for generating positive-weight events, maintaining the physicality and interpretability of the results.

Two primary approaches for treating the interference between $Wt$-channel and $t\bar{t}$ production are implemented: Diagram Removal (DR) and Diagram Subtraction (DS). The DR method isolates the single-top signal by removing contributions from $t\bar{t}$ interference directly from the amplitude. In contrast, DS uses a subtraction term to suppress these contributions at the cross-section level. The distinction between these treatments offers insights into the scale of theoretical uncertainties introduced by interference.

Numerical Analysis and Results

The paper emphasizes the validation of the $Wt$-channel implementation through comparisons with the MC@NLO method, achieving consistent results across benchmark distributions and demonstrating strong agreement in both DR and DS approaches. Both methods present a congruent picture of the production dynamics, though their comparison aids in estimating the theoretical uncertainties stemming from interference effects. Moreover, differential analyses, particularly for observables sensitive to soft radiation, highlight the capability of POWHEG in modeling these effects, which are absent in fixed-order predictions.

Practical and Theoretical Implications

This work significantly impacts the precise modeling of single-top processes, supporting the interpretation of experimental results, especially within the LHC where single-top production occurs in conjunction with numerous other processes. The careful handling of top-quark polarization and spin correlation effects enhances the predictive power of the simulation, which is crucial for searches of new physics in top decay correlations.

Future Directions

The continued development of NLO+PS methods in simulating collider events promises further progress in precision collider phenomenology. Future developments could involve more refined treatments of interference effects and extensions into additional processes where interference plays a significant role. As experimental precision improves, theoretical models must continue to evolve, ensuring their compatibility and enhancing their predictive accuracy.

In conclusion, the paper underscores the essential role of sophisticated computational techniques such as the POWHEG method in enhancing the accuracy and reliability of predictions for SM processes and their implications for future discoveries in particle physics. This work advances the field of collider physics simulations, providing a robust framework for further investigations into the complex dynamics of hadronic interactions.