Precise predictions for $$V+$$ V + jets dark matter backgrounds

Abstract

High-energy jets recoiling against missing transverse energy (MET) are powerful probes of dark matter at the LHC. Searches based on large MET signatures require a precise control of the Z (νν)+ jet background in the signal region. This can be achieved by taking accurate data in control regions dominated by Z ( + − )+ jet, W ( ν)+ jet and γ + jet production, and extrapolating to the Z (νν)+ jet background by means of precise theoretical predictions. In this context, recent advances in perturbative calculations open the door to significant sensitivity improvements in dark matter searches. In this spirit, we present a combination of state-of-the-art calculations for all relevant V + jets processes, including throughout NNLO QCD corrections and NLO electroweak corrections supplemented by Sudakov logarithms at two loops. Predictions at parton level are provided together with detailed recommendations for their usage in experimental analyses based on the reweighting of Monte Carlo samples. Particular attention is devoted to the estimate of theoretical uncertainties in the framework of dark matter searches, where subtle aspects such as correlations across different V + jet processes play a key role. The anticipated theoretical uncertainty in the Z (νν)+ jet background is at the few percent level up to the TeV range.G. P. Salam: On leave from CNRS, UMR 7589, LPTHE, F-75005,

NNLO QCD + NLO EW with Matrix+OpenLoops: precise predictions for vector-boson pair production

“…A thorough estimate of O(α S α) uncertainties for the hard-V V regions requires more detailed studies along the lines of ref. [91] and is left to future work.…”

On-the-fly reduction of open loops

“…The availability of child diagrams of type (44) is an obvious prerequisite for the applicability of the parent-child approach, and in QCD most one-loop diagrams turn out to be the parent of a corresponding child. Moreover, the correspondence between the first k dressed segments in (43) and (44) requires an appropriate cutting rule, i.e. a prescription that determines the cut propagator and the dressing direction in a similar way as in (43)- (44).…”

“…This new method builds on OpenLoops [9,16], a fully automated framework for the automated generation of scattering amplitudes in the Standard Model. The original implementation of the open-loop approach [9,16] supports NLO QCD [31,[33][34][35][36][37][38][39] as well as NLO EW [40][41][42][43][44] calculations and is interfaced to various multi-purpose Monte Carlo tools. The OpenLoops program is also part of Matrix [45] and has already been applied to several NNLO calculations [46][47][48][49][50][51][52][53][54][55].…”

Phenomenology of single-inclusive jet production with jet radius and threshold resummation

“…The list of those processes includes the hadroproduction of gauge bosons V þ jet (V ¼ W AE ; Z; γ) as well as single-inclusive jets and dijets, but it is limited to 2 → 2 reactions at the Born level due to the enormous computational complexity at NNLO. In particular, the calculations for V þ jet production have already been shown to greatly improve the description of the available LHC data [10][11][12].…”