Measurement of Jet Multiplicity Distributions in Top Quark Pair Events with Two Leptons in the Final State at a center of mass energy of 7 TeV.

C Diez Pardos

doi:10.1051/epjconf/20134918007

Abstract

The jet activity in top-antitop quark pair events is measured in pp collisions at p s =7 TeV with the CMS detector using a dataset recorded in 2011 corresponding to an integrated luminosity of 5.0 fb 1 . The measurement is performed in the dileptonic decay channels (where the two W bosons decay to leptons) of the top-antitop quark pairs, with at least two isolated leptons and at least one b-jet in the final state. The di erential top anti-top quark cross section is measured as a function of the jet multiplicity. Furthermore, the distribution of the fraction of events without additional jets above a momentum threshold is measured. Several QCD calculations are compared with the data.

Highlights

Measurements of top-antitop quark pair production cross sections and properties are being performed at unprecedented precision, providing crucial information for testing the expectations of the Standard Model
The jet activity in top-antitop quark pair events is measured in pp collisions at s =7 TeV with the CMS detector using a dataset recorded in 2011 corresponding to an integrated luminosity of 5.0 fb−1
The measurement is performed in the dileptonic decay channels of the top-antitop quark pairs, with at least two isolated leptons and at least one b-jet in the final state

Summary

Introduction

Measurements of top-antitop quark pair production cross sections and properties are being performed at unprecedented precision, providing crucial information for testing the expectations of the Standard Model. At LHC energies, the fraction of ttevents with additional hard jets in the final state is about half of the total number of events. The jet activity in top-antitop quark pair events is studied with the CMS detector [1] using the dataset recorded in 2011 in the dileptonic decay channels [2]. The understanding of these processes is crucial to constrain ISR/FSR and provides a test of QCD at the LHC energy regime. New physics can potentially manifest in top final states, so tt+jets is a background for many searches

Event Selection

Differential Cross Section as Function of Jet Multiplicity

Gap fraction

Findings

Dilepton Combined