Abstract
In view of precision studies of the Higgs sector at the Run II of the LHC, the improvement of the accuracy of the theoretical prediction is becoming a pressing issue. In this framework, we detail a calculation of the full Next-to-Leading Order (NLO) electroweak corrections to Higgs boson decay into four charged leptons, by considering the gold-plated channel H → Z (∗) Z (∗) → 2l2l ′ , l, l ′ = e, μ. We match the NLO corrections with a QED Parton Shower (PS), in order to simulate exclusive multiple photon emission and provide novel results at NLOPS electroweak accuracy. We compare our NLO predictions to those of the program Prophecy4f and present NLOPS phenomenological results relevant for Higgs physics studies, with particular attention to precision measurements of the Higgs boson mass, spin-parity assignment and tests of the Standard Model. Our calculation is implemented in a new code, Hto4l, which can be easily interfaced to any generator describing Higgs boson production. As an example, we provide illustrative results for Higgs production and decay in the process gg → H → 4l using POWHEG with NLOPS accuracy in the production mode.
Highlights
Various tests of the couplings of the new particle to bosons and fermions have been carried out both by ATLAS and CMS collaborations
We show a sample of illustrative results obtained by interfacing Hto4l with POWHEG [42] for the simulation of Higgs boson production in gluon-gluon fusion
In this work we have presented a precision calculation of the SM Higgs boson decay into four charged leptons, in view of improved measurements of the properties of the Higgs particle at the LHC Run II
Summary
The NLO electroweak corrections to the Higgs boson decay into four charged leptons consist of QED and purely weak contributions. In order to allow the cancellation of soft IR singularities, the tree-level kinematics is calculated with complete lepton mass effects taken into account This gives automatically the correct phase space integration boundaries for the diagrams of the virtual contribution where a virtual photon is connected to one external lepton pair. The kinematics is treated exactly, the non-IR O(α) virtual amplitudes are calculated in the approximation of neglecting finite fermion mass effects (with the exception of the quark Yukawa couplings, e.g. in the fermion-loop Higgs vertex corrections) These contributions are neglected in our calculation as they are irrelevant in view of a target theoretical accuracy of the order of 0.1% and their inclusion would make the numerical computation more time consuming. Our predictions for the Higgs boson decay into four leptons at NLO EW accuracy are given by the sum of eq (2.1), eq (2.2) and eq (2.3), supplemented with the necessary renormalization conditions
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