Early Run 2 Hard QCD Results from the ATLAS Collaboration

Nicola Orlando

doi:10.1051/epjconf/201612009002

Abstract

We provide an overview of hard QCD results based on data collected with the ATLAS detector in proton-proton collision at √ s = 13 TeV at the Large Hadron Collider. The production of high transverse momentum jets, photons and photon-pairs were studied; the inclusive jet cross section is found to agree well with the prediction of perturbative QCD calculations performed at next-to-leading accuracy. The production cross sections for W and Z bosons in their e and μ decays was measured; in general, agreement is found with the expectation of next-to-next-to leading order QCD calculations and interesting sensitivities to the proton structure functions are already observed. The top production cross sections were measured in different top decay channels and found to agree with the state of the art QCD predictions.

Highlights

Since June 2015 the Large Hadron Collider (√LHC) has started to deliver proton-proton collisions at the unprecedented centre-of-mass energy s = 13 TeV
The 13 TeV ATLAS physics program benefits from the installment of the Insertable B-Layer (IBL) [2], a fourth layer added to the present Pixel detector between a new beam pipe and the current inner Pixel layer (B-layer) and many other improvements affecting the detector, data-taking as well as analysis software-framework
The measurement of cross-sections of jets produced at high transverse momentum provides a test of the validity of perturbative QCD at the TeV scale

Summary

Introduction

Since June 2015 the Large Hadron Collider (√LHC) has started to deliver proton-proton (pp) collisions at the unprecedented centre-of-mass energy s = 13 TeV. The ATLAS [1] collaboration has analysed this very early 13 TeV data taken in both special conditions with very low pileup and those dedicated to high pT physics. The 13 TeV ATLAS physics program benefits from the installment of the Insertable B-Layer (IBL) [2], a fourth layer added to the present Pixel detector between a new beam pipe and the current inner Pixel layer (B-layer) and many other improvements affecting the detector, data-taking as well as analysis software-framework. The measurements presented in this paper use between 6.4√pb−1 up to 85 pb−1 of integrated luminosity collected at LHC in proton-proton (pp) collisions at s = 13 TeV. The precision of many measurements is limited by the early luminosity calibration is based on pair of x-y beam-separation scans performed in June 2015, leading to about 9% uncertainty on the luminosity scale determination

Jets and photons measurements

Heavy flavour production

Top quark pair cross sections