HW/HZ + 0 and 1 jet at NLO with the POWHEG BOX interfaced to GoSam and their merging within MiNLO

Abstract: We present a generator for the production of a Higgs boson H in association with a vector boson V=W or Z (including subsequent V decay) plus zero and one jet, that can be used in conjunction with general-purpose shower Monte Carlo generators, according to the POWHEG method, as implemented within the POWHEG BOX framework. We have computed the virtual corrections using GoSam, a program for the automatic construction of virtual amplitudes. In order to do so, we have built a general interface of the POWHEG BOX to the GoSam package. With this addition, the construction of a POWHEG generator within the POWHEG BOX is now fully automatized, except for the construction of the Born phase space. Our HV + 1 jet generators can be run with the recently proposed MiNLO method for the choice of scales and the inclusion of Sudakov form factors. Since the HV production is very similar to V production, we were able to apply an improved MiNLO procedure, that was recently used in H and V production, also in the present case. This procedure is such that the resulting generator achieves NLO accuracy not only for inclusive distributions in HV + 1 jet production but also in HV production, i.e. when the associated jet is not resolved, yielding a further example of matched calculation with no matching scale.

• The paper introduces an NLO computational method for HW/HZ production that integrates POWHEG BOX with GoSam for automated virtual corrections.
• It employs an improved MiNLO merging technique to achieve NLO precision for both inclusive HV and HV+1 jet production, streamlining phase space handling.
• Numerical results validate the method's robustness, enhancing simulation accuracy for Higgs signatures and reducing theoretical uncertainties at the LHC.

Overview of Higgs Boson Production in Association with Vector Bosons

This paper presents a detailed exploration of next-to-leading order (NLO) calculations involving the production of a Higgs boson in association with vector bosons (either W or Z) — collectively referred to as $HV$ production — with the inclusion of up to one jet. The authors leverage the POWHEG BOX framework to perform these calculations and subsequently merge the results using the MiNLO method. A significant aspect of this work is the integration of the POWHEG BOX with the GoSam package, automating the generation of virtual corrections for such processes.

Methodological Advancements

The study achieves noteworthy advancements in the computational approach to $HV$ production. The virtual corrections are obtained through GoSam, which automates the computation of one-loop amplitudes, thereby streamlining the generator construction within the POWHEG BOX framework. This integration is complemented by an interface between POWHEG and GoSam, facilitating seamless generation of virtual amplitudes, with considerations for the automatic handling of the Born phase space.

The application of an improved MiNLO procedure permits the matching of NLO accuracy for inclusive $HV + 1$ jet production and for $HV$ production when the extra jet is unresolved. This effectively results in a generator that possesses NLO precision across a broader set of production conditions, exemplifying a refined method for achieving matched calculations devoid of matching scale complications.

Numerical Insights

Numerical results, as indicated by the paper, highlight efficacy in the approach, evidenced by consistent cross-sections and distributions when compared to traditional POWHEG outputs over a variety of scale choices. Results demonstrate the robustness of the implemented method, showcased through comparisons of rapidity and transverse momentum distributions for the $HV$ system and leptonic decay products from the associated vector bosons.

Implications and Future Directions

The better handling of Higgs production processes at the LHC (Large Hadron Collider) is vital for probing Higgs properties, such as branching ratios, particularly into $b\bar{b}$ and potentially invisible particles. This paper's enhanced precision in the descriptions of $HV + 1$ jet final states enriches the experimental reach for both current analyses and future collider scenarios.

Practically, the research augments computational tools for high-energy physics communities, improving predictions for experimental endeavors investigating Higgs signatures amidst complex backgrounds. Theoretically, the incorporation of Sudakov form factors within the MiNLO framework opens pathways for heightened precision in future NLO and potentially NNLO (next-to-next-to-leading order) explorations of other final state processes.

The work provides a framework that could be extended to other electroweak processes, contributing to the larger objective of reducing theoretical uncertainties in simulations approximating experimental conditions. This exploration delineates a progressive stride towards fully automatic, accurate, perturbative QCD calculations and could serve as a foundation for future work that seeks to bridge the gap between fixed-order perturbations and parton shower methodologies in particle physics.