QCD tests in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC

by Javier Merino

Tuesday 2 Feb 2016, 08:00 → 09:00 Asia/Shanghai

Several aspects of the strong interaction are tested in this work using the ATLAS detector at the LHC. The parton shower and hadronisation models are probed by means of a measurement of jet shapes in tbar events. The main observation is that the momentum density inside $b$-quark jets is higher at large values of the jet internal radius r, while light-quark jets present larger densities at low values of r. This effect is explained by the so-called angular screening effects, due to the heavier mass of the b-quark. This difference allows us to determine the mass of the bottom quark to be mb = 4.86^{+0.49}_{-0.42} GeV. The value of the strong coupling constant αs at the Z-pole scale has also been measured in this work. To do this, a sample of multijet events at high-momentum scales is selected by demanding the scalar sum of transverse momenta of the two leading jets to be greater than 500 GeV. A measurement of the transverse energy-energy correlation function and its asymmetry is performed and a comparison between the data and NLO pQCD calculations is presented. This allows us to determine $\alpha_s(m_\Zboson) = 0.1173 \pm 0.0010 \mbox{ (exp.)}^{+0.0065}_{-0.0026} \mbox{ (theo.)}$

Slides seminar_20160202_Javier.pdf