Search for associated production of a Higgs boson and a single top quark in proton-proton collisions at s=13  TeV

Abstract

A search is presented for the production of a Higgs boson in association with a single top quark, based on data collected in 2016 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of 35.9 fb −1 . The production cross section for this process is highly sensitive to the absolute values of the top quark Yukawa coupling, y t , the Higgs boson coupling to vector bosons, g HVV , and, uniquely, to their relative sign. Analyses using multilepton signatures, targeting H → WW, H → ττ, and H → ZZ decay modes, and signatures with a single lepton and a bb pair, targeting the H → bb decay, are combined with a reinterpretation of a measurement in the H → γγ channel to constrain y t . For a standard model-like value of g HVV , the data favor positive values of y t and exclude values of y t below about −0.9 y SM t .Published in Physical Review D as

Top-quark electroweak interactions at high energy

“…[12], the relatively small cross-section coupled with the challenging final state means that it is unlikely that this process will be accessed at differential level. Existing searches for this mode suffer from a significant overlap with the much larger tth process, meaning that current sensitivity is at the level of 25 times the SM prediction while the totally opposite sign Yukawa scenario has been excluded [41]. The inclusive measurement of this channel and the differential measurement of the tZj counterpart are therefore argued to be complementary ways to access the operators that we consider.…”

“…It could however, be searched for in combination with thj since they both have very similar sensitivity profiles. Indeed, the latest LHC search for single-top in association with a Higgs boson [41] considers both of these channels as part of their signal region. Figure 16.…”

NLO QCD+EW predictions for tHj and tZj production at the LHC

“…Finally the tHj rate is about 10% of the ttH one, and the process has been searched for at the LHC [5][6][7].…”

“…In both cases, the variation is performed in the range 1/2 < µ F /µ R < 2. 7 In each of the plots of figure 2 we also show the QCD K-factor, namely the ratio between the NLO QCD and LO predictions, in the lower inset, for both the 4FS and the 5FS.…”

Probing the top Yukawa coupling at the LHC via associated production of single top and Higgs

“…As is well known, the cross sections for the Higgs production with single t ort are sensitive to the relative sign of the htt and the hW W couplings, which becomes 13 times larger than the SM value at |ξ htt | = π where the sign of the htt coupling is reversed [3]. Because of this huge enhancement factor, LHC experiments [14][15][16][17][18] have ruled out the region around |ξ htt | ∼ π for κ htt = 1. It is worth noting, however, that we focus our attention in this paper on a relatively small magnitude of the CP phase |ξ htt | 0.1π, where the total cross sections do not deviate much from the SM values, σ(th +th) = 60.85 fb and σ(tth) = 406.26 fb in the LO, as shown in figure 1.…”