Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at s√= 13 TeV

Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam, Janik Walter Andrejkovic, Thomas Bergauer, Suman Chatterjee, Marko Dragicevic, Alberto Escalante Del Valle, Rudolf Fruehwirth, Manfred Jeitler, Natascha Krammer, Lukas Lechner (+2328 others)
2021
Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at √ s = 13 TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb −1 . Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated
more » ... with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12±0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations. Since the discovery of a Higgs boson (H) by the ATLAS and CMS collaborations in 2012 [1] [2] [3] , an extensive programme of measurements focused on characterising its properties and testing its compatibility with the standard model (SM) of particle physics has been performed. Analysis of data collected during the second run of the CERN LHC at √ s = 13 TeV has already resulted in the observation of Higgs boson production mechanisms and decay modes predicted by the SM [4] [5] [6] [7] . The most precise measurements are obtained by combining results from different Higgs boson decay channels. Such combinations have enabled the total Higgs boson production cross section to be measured with an uncertainty of less than 7% [8, 9] . All reported results have so far been consistent with the corresponding SM predictions. In the SM, the H → γγ decay has a small branching fraction of approximately 0.23% for a Higgs boson mass (m H ) around 125 GeV [10]. However, its clean final-state topology with two well-reconstructed photons provides a narrow invariant mass (m γγ ) peak that can be used to effectively distinguish it from background processes. As a result, H → γγ is one of the most important channels for precision measurements of Higgs boson properties. Furthermore, it is one of the few decay channels that is sensitive to all principal Higgs boson production modes. The results reported in this paper build upon previous analyses performed by the CMS collaboration [11, 12] . Here, the data collected by the CMS experiment between 2016 and 2018 are analysed together. The resulting statistical power of the combined data set improves the precision on existing measurements and allows new measurements to be made. The structure of this analysis is designed to enable measurements within the simplified template cross section (STXS) framework [10] . Using this structure, various measurements of Higgs boson properties can be performed. These include SM signal strength modifiers, production cross sections, and the Higgs boson's couplings to other particles. Measurements of all these quantities are reported in this paper. The STXS framework provides a coherent approach with which to perform precision Higgs boson measurements. Its goal is to minimise the theory dependence of Higgs boson measurements, lessening the direct impact of SM predictions on the results, and to provide access to kinematic regions likely to be affected by physics beyond the SM (BSM). At the same time, this approach permits the use of advanced analysis techniques to optimise sensitivity. Reducing theory-dependence is desirable because it makes the measurements both easier to reinterpret and means they are less affected by potential updates to theoretical predictions, making them useful over a longer period of time [13] . The results presented within the STXS framework nonetheless depend on the SM simulation used to model the experimental acceptance of the signal processes, which could be modified in BSM scenarios. The strategy employed in this analysis is to construct analysis categories enriched in events from as many different kinematic regions as possible, thereby providing sensitivity to the individual regions defined in the STXS framework. This permits measurements to be performed across all the major Higgs boson production modes, including gluon fusion (ggH), vector boson fusion (VBF), vector boson associated production (VH), production -2 - Data samples and simulated events The analysis exploits proton-proton collision data at √ s = 13 TeV, collected in 2016, 2017, and 2018 and corresponding to integrated luminosities of 35.9, 41.5, and 59.4 fb −1 , respectively. The integrated luminosities of the 2016-2018 data-taking periods are individually known with uncertainties in the 2.3-2.5% range [38] [39] [40] , while the total (2016-2018) integrated luminosity has an uncertainty of 1.8%, the improvement in precision reflecting the (uncorrelated) time evolution of some systematic effects. In this section, the data sets and simulated event samples for all three years are described. Any differences between the years are highlighted in the text. Events are selected using a diphoton high-level trigger with asymmetric photon p T thresholds of 30 (30) and 18 (22) GeV in 2016 (2017 and 2018) data. A calorimetric selection is applied at trigger level, based on the shape of the electromagnetic shower, the isolation of the photon candidate, and the ratio of the hadronic and electromagnetic energy -8 -
doi:10.18154/rwth-2021-07801 fatcat:5v4u5z7txfgafa5lrcg3ecs7jq