Study of the difference between substructure variables of large-R jets using AFII and FS simulations

With the discovery of a 125 GeV Higgs boson and the rapid progress made at the Large Hadron Collider (LHC), it is essential to precisely measure the properties of the Higgs boson as any potential disagreement could hint at fascinating new phenomena. The Yukawa coupling of the Higgs boson to the top quark is a key parameter of the Standard Model (SM). It can be determined from the ratio of the top quark mass and Higgs field vacuum expectation value, from the cross section of gg → H production through a top quark loop, or from the cross section of the process gg/qq → ttH [1, 2], which is a tree-level process at lowest order in perturbation theory. Comparison of these measurements has the potential to identify and disambiguate new physics effects that can modify the ttH production cross section relative to the SM expectation. Discrepancies in the high-momentum Higgs boson production in the presence of new physics are predicted to be as high as 50% [3] with respect to the SM expectations. As in any high-energy physics analysis, a precise simulation of the detector response, with an accurate description of the interactions between the particles with the detector components, is essential. However, due to the large number of events demanded and large LHC luminosity, a full detector simulation can be challenging and extremely time-consuming. In some cases, the use of a simplified and fast approach may be a satisfactory alternative. In this work, a study was performed to compare the fast detector simulation Atlfast-II (AFII) [4] with the ATLAS full simulation (FS), and verify the modelling of substructure variables of large-R jets using t ¯