Top pair production at 5.02 TeV

by Mr Georgios Krintiras (Doctoral Student)

Wednesday 21 Sept 2016, 13:00 → 14:00 Europe/Brussels

E/3rd floor-E.349 - Seminar room (E.349) (Marc de Hemptinne (chemin du Cyclotron, 2, Louvain-la-Neuve))

At hadron colliders, top quarks - the heaviest elementary particles known - are dominantly produced in pairs (ttbar), a production mechanism discovered more than twenty years ago at Tevatron, Fermilab. Although the ttbar process has already entered the domain of 'precision' Physics, especially with the advent of the multi-TeV energies at the CERN Large Hadron Collider, there still remains room (and interest) for dedicated experimental measurements of the top quark in the 'gap' of energies between Tevatron and LHC. Even with limited precision, ttbar cross-section measurements in this energy range can be valuable to set stronger constraints to the poorly known gluon distribution (PDF) inside the proton at large longitudinal parton momentum fraction. The study presented here measured the total inclusive cross-section for pair production at a center-of-mass energy of 5.02 TeV, with the CMS detector, taking advantage of a low-pileup proton-proton (pp) collision dataset whose integrated luminosity amounts to 26 pb-1. This first measurement made use of the final state with two opposite-sign high-energy leptons, a muon and an electron. The precision of this measurement being limited by the statistical and luminosity uncertainties, two directions for improvements have been already addressed since the release of the first public result: the inclusion of the same-flavour leptonic channels and a dedicated calibration of the luminosity scale. The last part of this talk will elaborate on how this measurement can pave the way for the very first observation of this elementary particle in nucleus-nucleus (AA) collisions, opening an entire new sub-area of Heavy Ion studies. --- This seminar is based on the following public results where the speaker has been leading author: CMS-TOP-16-015: Inclusive ttbar cross section in the dilepton channel at 5.02 TeV CMS-LUM-16-001: CMS Luminosity Calibration for the pp Reference Run at 5.02 TeV