Measurement of spin correlations in t t-bar production using the matrix element method in the muon + jets final state in pp collisions at sqrt(s) = 8 TeV

TL;DR

This paper measures the spin correlation in top quark pair production at 8 TeV using the CMS detector, comparing data with the Standard Model prediction and no-correlation hypothesis, achieving the most precise measurement in the lepton + jets channel.

Contribution

It introduces a measurement of the spin correlation fraction in top quark pairs using the matrix element method in the muon + jets final state at 8 TeV, providing the most precise result to date.

Findings

Measured spin correlation fraction: 0.72 +/- 0.08 (stat) +0.15 -0.13 (syst)

Results are consistent with the Standard Model prediction

First precise measurement in the muon + jets final state at this energy

Abstract

The consistency of the spin correlation strength in top quark pair production with the standard model (SM) prediction is tested in the muon + jets final state. The events are selected from pp collisions, collected by the CMS detector, at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The data are compared with the expectation for the spin correlation predicted by the SM and with the expectation of no correlation. Using a template fit method, the fraction of events that show SM spin correlations is measured to be 0.72 +/- 0.08 (stat) +0.15 -0.13 (syst), representing the most precise measurement of this quantity in the lepton + jets final state to date.