Abstract
We present the implementation of several color-singlet final-state processes at Next-to-Next-to Leading Order (NNLO) accuracy in QCD to the publicly available parton-level Monte Carlo program MCFM. Specifically we discuss the processes pprightarrow H, pprightarrow Z, pprightarrow W, pprightarrow HZ, pprightarrow HW and pprightarrow gamma gamma . Decays of the unstable bosons are fully included, resulting in a flexible fully differential Monte Carlo code. The NNLO corrections have been calculated using the non-local N-jettiness subtraction approach. Special attention is given to the numerical aspects of running MCFM for these processes at this order. We pay particular attention to the systematic uncertainties due to the power corrections induced by the N-jettiness regularization scheme and the evaluation time needed to run the hybrid openMP/MPI version of MCFM at NNLO on multi-processor systems.
Highlights
The second run of the LHC (Run II) which is currently under way, will result in the accumulation of an unprecedented amount of high-quality data in a new high energy regime.Version 8.0 of MCFM can be downloaded from the mcfm.fnal.gov website.In tandem with the well-understood and carefully calibrated detectors, this will lead to experimental uncertainties that are at the level of a few percent or smaller for many of the most important processes
This paper presents a first step in this journey by summarizing the implementation of the N -jettiness subtraction procedure in MCFM, and presenting a detailed breakdown of the method for the processes released in the initial version of the Next-to-Next-to Leading Order (NNLO) code
The agreement is excellent for all processes, so that we can be sure that MCFM should produce the same results as the other codes when computing the next-to-leading order (NLO) and NNLO predictions using the N -jettiness subtraction method
Summary
The second run of the LHC (Run II) which is currently under way, will result in the accumulation of an unprecedented amount of high-quality data in a new high energy regime. In tandem with the well-understood and carefully calibrated detectors, this will lead to experimental uncertainties that are at the level of a few percent or smaller for many of the most important processes These include various Higgs boson production channels, as well as standard candle processes such as vector boson production. While calculations at next-to-leading order (NLO) in the strong coupling constant are quite standard, only about 20 processes have been calculated through to next-tonext-to-leading order (NNLO) At NLO local subtraction schemes, such as FKS [41] or Catani–Seymour dipole subtraction [42], are typically preferred In these local subtraction formalisms, the singular unresolved infrared limits are cancelled point-wise by local counterterms. These local counterterms, after analytic integration over the unresolved partons, are added to the virtual corrections yielding a finite result
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