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Entanglement is a key property of quantum systems. In this study, the first measurements of quantum entanglement between spins in pairs of Z bosons are reported, using proton-proton collision data from the Large Hadron Collider (LHC) at center-of-mass energies of 13 TeV and 13.6 TeV, recorded with the ATLAS detector. Measurements of angular observables sensitive to ZZ spin-density-matrix elements in the H->ZZ->4l process yield coefficients C2,1,2,-1 = -0.71 ± 0.45 and C2,2,2,-2 = 0.08 ± 0.44, consistent with their Standard Model predictions. A complementary hypothesis test using the full angular distribution, and relying on several Standard Model assumptions in the decays, provides substantially higher sensitivity to quantum correlations and disfavors the separable-state hypothesis at a significance of 4.7 standard deviations (expected 4.9 sigma) relative to the entangled Standard Model hypothesis. These results provide strong evidence of quantum entanglement between massive bosons (spin qutrits) at the electroweak scale.
| 请选择分会 | TeV物理和超出标准模型新物理 |
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