Abstract
A search for non-resonant Higgs boson pair production, as predicted by the Standard Model, is presented, where one of the Higgs bosons decays via the H→bb channel and the other via one of the H→WW⁎/ZZ⁎/ττ channels. The analysis selection requires events to have at least two b-tagged jets and exactly two leptons (electrons or muons) with opposite electric charge in the final state. Candidate events consistent with Higgs boson pair production are selected using a multi-class neural network discriminant. The analysis uses 139 fb−1 of pp collision data recorded at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. An observed (expected) upper limit of 1.2 (0.9−0.3+0.4) pb is set on the non-resonant Higgs boson pair production cross-section at 95% confidence level, which is equivalent to 40 (29−9+14) times the value predicted in the Standard Model.
Highlights
In 2012, the ATLAS and CMS Collaborations reported the observation of a new particle in the search for the Standard Model (SM) Higgs boson (H ) [1,2]
Two schemes are typically used to remove the overlap between these two processes: the so-called diagram removal (DR) and diagram subtraction (DS) schemes [51]; the former is used in the present analysis to remove the overlapping events and the latter is used to evaluate the systematic uncertainty in corresponding background event yields
In order to extract information about the H H → bb ν ν signal cross-section, a counting experiment is performed with a profilelikelihood fit [131] simultaneously across the CR-Top, CR-Z+HF, SR-SF, and SR-DF regions using the predicted and observed event counts in each region as inputs
Summary
In 2012, the ATLAS and CMS Collaborations reported the observation of a new particle in the search for the Standard Model (SM) Higgs boson (H ) [1,2]. The ggF process has two leading order contributions: the first corresponds to the so-called ‘triangle diagram’, which includes the Higgs boson selfcoupling, and the second is the so-called ‘box diagram’, which includes a heavy-quark loop with two fermion–fermion–Higgs ( f f H ) vertices These two amplitudes interfere destructively, resulting in a low cross-section of only 31.05 ± 1.90 fb for the ggF H H production mode, computed at next-to-next-to-leading order (NNLO) and including finite top-quark mass effects [13,14,15,16,17,18,19,20]. The ATLAS and CMS Collaborations have performed searches for non-resonant H H production in a variety of final states at 13 TeV [24,25,26,27,28,29,30,31,32,33]. The ATLAS Collaboration / Physics Letters B 801 (2020) 135145 by ATLAS in searches for H H → bbW W ∗ [28] and in the dilepton channel by CMS in searches for H H → bbW W ∗/bb Z Z ∗ [31]
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