# Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at $\sqrt{s}=8$ TeV Using the ATLAS Detector

Philip James Clark (Member of Consortium), Christos Leonidopoulos (Member of Consortium), Victoria Jane Martin (Member of Consortium), Corrinne Mills (Member of Consortium), Atlas Collaboration, Liza Mijovic (Member of Consortium)

Research output: Contribution to journalArticlepeer-review

## Abstract

A measurement of spin correlation in $t\bar{t}$ production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The correlation between the top and antitop quark spins is extracted from dilepton $t\bar{t}$ events by using the difference in azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to $A_{helicity} = 0.38 \pm 0.04$, in agreement with the Standard Model prediction. A search is performed for pair production of top squarks with masses close to the top quark mass decaying to predominantly right-handed top quarks and a light neutralino, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 191 GeV are excluded at the 95% confidence level.
Original language English Aad:2014mfk 142001 Physical Review Letters 114 14 https://doi.org/10.1103/PhysRevLett.114.142001 Published - 8 Apr 2015

• hep-ex

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