CMS-PAS-TOP-25-001

CMS-PAS-TOP-25-001
Observation of magic states of top quark pairs produced in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
14 March 2025

Abstract: An observation of magic states of top quark-antiquark ( $\mathrm{t\bar{t}}$ ) systems produced in proton-proton collisions at the LHC at $\sqrt{s}=$ 13 TeV is presented. Magic, defined here using the second stabilizer Renyi entropy, is an important property used to characterize quantum states in quantum information science. Quantum states with high magic provide computational advantage over classical systems. This observation is based on measurements of the polarization and spin correlation coefficients in $\mathrm{t\bar{t}}$ systems using the final states with an electron or muon and jets. Magic is determined in various kinematic regions of the $\mathrm{t\bar{t}}$ system and is found to agree with the standard model predictions. This study represents the first experimental measurement of this quantity at the TeV energy scale.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Results of $\tilde{M}_\mathrm{2}$ measurements in bins of $m({\mathrm{t}\overline{\mathrm{t}}} )$ (upper left ), $m({\mathrm{t}\overline{\mathrm{t}}} )$ with $\|\cos(\theta)\| <$ 0.4 (upper right ), and $p_{\mathrm{T}}(\mathrm{t})$ (lower). The measurements (points) are shown with the statistical uncertainty (inner error bars) and total uncertainty (outer error bars) and compared to the predictions of POWHEG + PYTHIA, POWHEG + HERWIG, MADGRAPH5\_aMC@NLO+ PYTHIA, and MINNLO+ PYTHIA. The POWHEG + PYTHIA prediction is displayed with the matrix element scale and parton distribution function uncertainties, while for all other predictions only the central values are indicated.
png pdf	Figure 1-a: Results of $\tilde{M}_\mathrm{2}$ measurements in bins of $m({\mathrm{t}\overline{\mathrm{t}}} )$ (upper left ), $m({\mathrm{t}\overline{\mathrm{t}}} )$ with $\|\cos(\theta)\| <$ 0.4 (upper right ), and $p_{\mathrm{T}}(\mathrm{t})$ (lower). The measurements (points) are shown with the statistical uncertainty (inner error bars) and total uncertainty (outer error bars) and compared to the predictions of POWHEG + PYTHIA, POWHEG + HERWIG, MADGRAPH5\_aMC@NLO+ PYTHIA, and MINNLO+ PYTHIA. The POWHEG + PYTHIA prediction is displayed with the matrix element scale and parton distribution function uncertainties, while for all other predictions only the central values are indicated.
png pdf	Figure 1-b: Results of $\tilde{M}_\mathrm{2}$ measurements in bins of $m({\mathrm{t}\overline{\mathrm{t}}} )$ (upper left ), $m({\mathrm{t}\overline{\mathrm{t}}} )$ with $\|\cos(\theta)\| <$ 0.4 (upper right ), and $p_{\mathrm{T}}(\mathrm{t})$ (lower). The measurements (points) are shown with the statistical uncertainty (inner error bars) and total uncertainty (outer error bars) and compared to the predictions of POWHEG + PYTHIA, POWHEG + HERWIG, MADGRAPH5\_aMC@NLO+ PYTHIA, and MINNLO+ PYTHIA. The POWHEG + PYTHIA prediction is displayed with the matrix element scale and parton distribution function uncertainties, while for all other predictions only the central values are indicated.
png pdf	Figure 1-c: Results of $\tilde{M}_\mathrm{2}$ measurements in bins of $m({\mathrm{t}\overline{\mathrm{t}}} )$ (upper left ), $m({\mathrm{t}\overline{\mathrm{t}}} )$ with $\|\cos(\theta)\| <$ 0.4 (upper right ), and $p_{\mathrm{T}}(\mathrm{t})$ (lower). The measurements (points) are shown with the statistical uncertainty (inner error bars) and total uncertainty (outer error bars) and compared to the predictions of POWHEG + PYTHIA, POWHEG + HERWIG, MADGRAPH5\_aMC@NLO+ PYTHIA, and MINNLO+ PYTHIA. The POWHEG + PYTHIA prediction is displayed with the matrix element scale and parton distribution function uncertainties, while for all other predictions only the central values are indicated.

Summary

In conclusion, we performed the first evaluation of the generalized magic

$\tilde{M}_\mathrm{2}$ in top quark-antiquark (

$\mathrm{t} \overline{\mathrm{t}}$ ) pairs, a property from quantum information science. Magic reflects how far a quantum state is from being efficiently simulated by classical systems, making it an important measure of a state's potential for quantum computational advantages. The observed magic values are in agreement with the standard model expectations. The results underscore the potential of collider experiments as a platform for exploring fundamental aspects of quantum mechanics, including properties like magic, which play a crucial role in quantum computation. Future studies could refine these measurements further and explore their implications for both quantum information science and high-energy physics.

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