Abstract
We have developed a framework for automated transverse momentum resummation for arbitrary electroweak final states based on reweighting tree-level events. It is fully differential in the kinematics of the electroweak final states, which facilitates a straightforward analysis of arbitrary observables in the small transverse momentum region. We have implemented the resummation at next-to-next-to-leading logarithmic accuracy and match to next-to-leading fixed-order results using the event generator MadGraph5_aMC@NLO. Results for Z and W boson production with leptonic decay as well as WZ production are presented. We compare to experimental measurements for the transverse momentum and the angular observable phi ^*.
Highlights
Since the emission of particles with large transverse momentum qT is suppressed by the strong coupling αs(qT ), most of the cross section at hadron colliders arises from events with low-qT radiation
We have developed a framework for automated transverse momentum resummation for arbitrary electroweak final states based on reweighting tree-level events
The prime example in a collider context is provided by the parton distribution functions which capture the low-energy physics of arbitrary hard-scattering processes
Summary
Since the emission of particles with large transverse momentum qT is suppressed by the strong coupling αs(qT ), most of the cross section at hadron colliders arises from events with low-qT radiation. In order to achieve this flexibility, we make use of MadGraph5_aMC@NLO [25], to compute the process-specific parts of the resummed cross section and supply it with the universal ingredients needed to achieve the resummation. Our implementation of the reweighting follows [28], in which we used MadGraph5_aMC@NLO for automated jet-veto cross section resummation Compared to this earlier work, transverse-momentum resummation involves a number of complications, which include the Fourier inversion back to momentum space and the necessity to account for recoil effects. An important example of a kinematic quantity which correlates with the dilepton transverse momentum is the variable φ∗ introduced in [26,30,31] It is defined using the directions of the final-state leptons from the decay Z → + − as follows φ∗ := tan π − φ sin(θ ∗), with 2 cos(θ ∗) := tanh η.
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