Observation of quantum entanglement in top quark pair production in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Abstract

Entanglement is an intrinsic property of quantum mechanics and is predicted to be exhibited in the particles produced at the Large Hadron Collider. A measurement of the extent of entanglement in top quark-antiquark ($\mathrm{t}\bar{\mathrm{t}}$) events produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed with the data recorded by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 36.3 fb${}^{-1}$. The events are selected based on the presence of two leptons with opposite charges and high transverse momentum. An entanglement-sensitive observable $D$ is derived from the top quark spin-dependent parts of the $\mathrm{t}\bar{\mathrm{t}}$ production density matrix and measured in the region of the $\mathrm{t}\bar{\mathrm{t}}$ production threshold. Values of $D$ $<$ $-$1/3 are evidence of entanglement and $D$ is observed (expected) to be $-$0.480 ${}_{-0.029}^{+0.026}$ $(-$0.467 ${}_{-0.029}^{+0.026})$ at the parton level. With an observed significance of 5.1 standard deviations with respect to the non-entangled hypothesis, this provides observation of quantum mechanical entanglement within $\mathrm{t}\bar{\mathrm{t}}$ pairs in this phase space. This measurement provides a new probe of quantum mechanics at the highest energies ever produced.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/TOP-23-001 (CMS Public Pages)

References in corpus (17)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Herwig++ Physics and Manual
• Particle-flow reconstruction and global event description with the CMS detector
• The CMS trigger system
• Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations
• Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV
• Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at sqrt(s) = 8 TeV
• Performance of missing transverse momentum reconstruction in proton-proton collisions at $\sqrt{s}=$ 13 TeV using the CMS detector
• Colour reconnections in Herwig++
• Demonstration of entanglement-by-measurement of solid state qubits
• Effects of color reconnection on $t\bar{t}$ final states at the LHC
• Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
• Spin Correlation Effects in Top Quark Pair Production at the LHC
• Top-quark pair production near threshold at LHC
• Measurement of ttbar Spin Correlation in ppbar Collisions Using the CDF II Detector at the Tevatron

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