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Search for a light pseudoscalar Higgs boson in the boosted μμττ final state in proton-proton collisions at √s = 13 TeV

par Sirunyan, A.M.;Beghin, Diego ;Bilin, Bugra ;Clerbaux, Barbara ;De Lentdecker, Gilles ;Delannoy, Hugo ;Dorney, Brian ;Favart, Laurent ;Grebenyuk, Anastasia ;Kalsi, Amandeep Kaur ;Makarenko, Inna ;Moureaux, Louis ;Pétré, Laurent ;Popov, Andrey ;Postiau, Nicolas ;Starling, Elizabeth Rose ;Thomas, Laurent ;Vander Velde, Catherine ;Vannerom, David ;Wezenbeek, Liam ;Malara, Andrea ; [et al.]
Référence The Journal of high energy physics, 2020, 8, 139
Publication Publié, 2020-08-01

Article révisé par les pairs

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Résumé :

A search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H → aa → μμττ, and considers pseudoscalar masses in the range 3.6 < ma< 21 GeV. Because of the large mass difference between the H and the a bosons and the small masses of the a boson decay products, both the μμ and the ττ pairs have high Lorentz boost and are collimated. The ττ reconstruction efficiency is increased by modifying the standard technique for hadronic τ lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of ma, on the branching fraction (ℬ) for H → aa → μμττ, down to 1.5 (2.0) × 10−4 for mH = 125 (300) GeV. Model-dependent limits on ℬ(H → aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV. [Figure not available: see fulltext.].