Measurements of tt¯H Production and the CP Structure of the Yukawa Interaction between the Higgs Boson and Top Quark i

Abstract

The first observation of the ttH process in a single Higgs boson decay channel with the full reconstruction of the final state (H → γγ) is presented, with a significance of 6.6 standard deviations (σ). The CP structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure CP-odd structure of the top Yukawa coupling at 3.2σ. The measurements are based on a sample of protonproton collisions at a center-of-mass energy ffiffi ffi s p ¼ 13 TeV collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb −1. The cross section times branching fraction of the ttH process is measured to be σ ttH B γγ ¼ 1.56 þ0.34 −0.32 fb, which is compatible with the standard model prediction of 1.13 þ0.08 −0.11 fb. The fractional contribution of the CP-odd component is measured to be f Htt CP ¼ 0.00 AE 0.33.

New features in the JHU generator framework: Constraining Higgs boson properties from on-shell and off-shell production

“…It can be freely downloaded at [87]. The package has been employed in the Run-I and Run-II analyses of LHC data for the H boson property measurements [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76].…”

“…Some new features in this framework have been reported earlier [41] and have been used for LHC experimental analyses. Most notably, this framework was employed in recent Run-II measurements of the HVV anomalous couplings from the first joint analysis of on-shell production and decay [71,72], from the first joint analysis of onshell and off-shell H boson production [73], for the first measurement of the CP structure of the Yukawa interaction between the H boson and top quark [74], in the search for a second resonance in interference with the continuum background [75,76], and in projections to future on-shell and off-shell H boson measurements at the high luminosity (HL) LHC [77]. In this paper, we document, review, and highlight the new features critical for exploring the full Run-II dataset at the LHC and preparing for Run-III and the HL-LHC.…”

Indirect $$ \mathcal{CP} $$ probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

“…Up to now, the most stringent experimental bounds on the CP nature of the top-Yukawa coupling have been obtained by dedicated CMS [25] and ATLAS [26] analyses using full Run 2 data. Both analyses combine the direct and the indirect approach by fitting the rate of the ttH, tH and tW H processes to data in the Higgs to di-photon decay channel in certain kinematic configurations.…”

“…Presenting the results of such a combined study in a fully model-independent format, however, is very challenging and would entail the public release of the likelihood as a function of all relevant parameters (including the relevant Higgs coupling scale factors). As this has not been done for the present analyses [25,26] we could not include these results as input for the CP study carried out in the present paper, which is performed for several "Higgs characterization models" of different complexities. We will discuss the results of refs.…”

“…At each parameter point we evaluate the predicted cross sections and decay rates, as detailed in section 4, and include them into the HiggsBounds/HiggsSignals framework [66,[73][74][75][76][77]. HiggsSignals (version 2.5.0) [75][76][77][78] incorporates the latest available Higgs rate measurements from ATLAS and CMS from Run 2 [25,69,[79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97], as well as the combined measurements from Run 1 [98]. In total, HiggsSignals includes 81 Run-2 measurements and 20 Run-1 measurements.…”