Measurements of differential cross sections of top quark pair production as a function of kinematic event variables in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV

Abstract

Measurements of differential tt production cross sections are presented in the single-lepton decay channel, as a function of a number of kinematic event variables. The measurements are performed with proton-proton collision data at √ s = 13 TeV, collected by the CMS experiment at the LHC during 2016, with an integrated luminosity of 35.9 fb −1 . The data are compared to a variety of state-of-the-art leading-order and next-to-leadingorder tt simulations. A Tabulated normalized differential tt production cross sections 25 B Tabulated absolute differential tt production cross sections 29 C Tabulated minimum and maximum relative uncertainties for absolute cross sections 32The CMS collaboration 38 IntroductionIn 2016 the CERN LHC collided protons at √ s = 13 TeV, resulting in a data set recorded by the CMS experiment [1], with an integrated luminosity of 35.9 fb −1 . Approximately 30 million top quark-antiquark pairs (tt) are present in this data set, which allows detailed studies of the production properties of tt events to be performed.Measurements of kinematic distributions in tt events are important for verifying current theoretical models of tt production and decay. As tt production and top quark decay can be a significant source of background events in many searches for physics beyond the standard model, for example in searches for supersymmetric models with top-quark-like signatures, it is important that tt production be well understood and modeled. In addition to physics beyond the standard model, a good understanding of tt production is necessary -1 - JHEP06(2018)002for measurements of rare standard model processes, such as tt production in association with a W, Z, or Higgs boson.In this paper, we present measurements of differential tt production cross sections, as a function of kinematic event variables that do not require the reconstruction of the tt system. Events are considered when the final state includes exactly one isolated lepton ( = e or µ) with large transverse momentum p T and at least four jets, of which at least two are tagged as originating from a bottom (b) quark. The kinematic event variables are the jet multiplicity (N jets ), the scalar sum of the jet p T (H T ), the scalar sum of the p T of all particles (S T ), the transverse momentum imbalance (p miss T ), the magnitude of the p T of the leptonically decaying W boson (p W T ), and the magnitudes of the p T and pseudorapidity of the lepton (p T and |η |).The measurements of the differential tt production cross sections are presented at particle level, i.e. with respect to generated "stable" particles (with a mean lifetime longer than 30 ps), in a phase space that closely resembles that accessible by the CMS detector (the visible phase space). This avoids the influence of large theoretical uncertainties that would be introduced by extrapolating the measurements to a larger phase space, or by presenting the measurements at parton level.Several measurements of the differential tt production cross sections as a function of the pro...

Search for vector-like T and B quark pairs in final states with leptons at $$ \sqrt{s}=13 $$ TeV

“…The H tag algorithm is efficient for both H → bb and Z → bb decays. The systematic difference between data and background (bkg) is due to known issues with jet momentum distributions in the tt simulation that are only partially corrected by applying the top quark momentum weight [71]. The residual difference is described by the uncertainty in the renormalization and factorization energy scales, discussed further in Section 8.…”

Robust Independent Validation of Experiment and Theory: Rivet version 3

“…RIVET has also been used by the LHC experiments as a part of their analysis and interpretation toolkit (see, for example [23][24][25][26][27]), and in studies for future experiments [28][29][30][31]. It has been used for development of new analysis techniques including machine learning applications, jet substructure, boosted-particle tagging and pile-up suppression [32][33][34][35].…”

Recent results of inclusive and differential top quark pair production cross section measurements at CMS

“…The first cross section analysis presented here forms the first differential s pp!tt paper produced by CMS using the 2016 data set [4]. Normalised and absolute cross sections are measured with respect to kinematic event variables (do not require tt system to be reconstructed) in the single lepton decay channel and is presented to particle level in a visible phase space.…”

“…By applying the corrections the observed trend flattens, however it is not covered completely. Figure 2: A set of absolute differential cross section measurements with respect to the H T [4], additional jet multiplicity [5] and p t T [6] variables. The right plot corresponds to the dilepton final state and is presented at parton level, while the other two correspond to the single lepton final state at particle level.…”