arXiv subjects

Baptiste Ravina

Publications and source records attributed to Baptiste Ravina.

5 recordsLinked to original sources

arXiv2026

Experimental characterization of the hierarchy of quantum correlations in top quark pairs

Recent results from the Large Hadron Collider have demonstrated quantum entanglement of top quark-antiquark pairs using the spin degrees of freedom. Based on the doubly differential measurement of the spin density matrix of the top quark and antiquark performed by the CMS collaboration in the helicity and beam bases, we evaluate a set of quantum observables, including discord, steerability, Bell correlation, and magic. These observables allow for a quantitative characterization of the quantum correlations present in a top quark-antiquark system, thus enabling an interpretation of collider data in terms of quantum states and their properties. Discord is observed to be greater than zero with a significance of more than 5 standard deviations ($σ$) in several regions of phase space, some of which correspond to separable quantum states. Evidence for steerability is established for the first time in a high-energy system, with a significance of more than 3$σ$. No Bell correlation is observed within the currently probed phase space, in agreement with the theoretical prediction. These results experimentally corroborate the hierarchy of quantum correlations in top quarks with discord being the most basic form of quantum correlation, followed by entanglement, steerability, and Bell correlation. The significance of nonzero magic, which is a complementary observable to the quantum correlation hierarchy, is found to exceed 5$σ$ in several regions of phase space.

quant-ph↗

arXiv2026

ATLAS and CMS measurements of the $t\bar{t}$ cross section, including off-shell and near threshold

Recent measurements of the $t\bar{t}$ cross section, performed both inclusively and differentially by the ATLAS and CMS Collaborations, are reported. In particular, off-shell effects are probed in the $pp\to W^+bW^-\bar{b}$ and $pp\to e^\pmμ^\mp +b\bar{b}$ processes, and modelling aspects of the POWHEG bb4$\ell$ Monte Carlo generator are discussed. Cross section and properties measurements are also performed at the threshold: we review an indirect extraction of the top quark Yukawa coupling, as well as the recent observations by both experiments of an excess of events near the top pair production threshold that is consistent with the formation of quasi-bound states.

hep-ex↗

arXiv2025

Quantum Information meets High-Energy Physics: Input to the update of the European Strategy for Particle Physics

Some of the most astonishing and prominent properties of Quantum Mechanics, such as entanglement and Bell nonlocality, have only been studied extensively in dedicated low-energy laboratory setups. The feasibility of these studies in the high-energy regime explored by particle colliders was only recently shown and has gathered the attention of the scientific community. For the range of particles and fundamental interactions involved, particle colliders provide a novel environment where quantum information theory can be probed, with energies exceeding by about 12 orders of magnitude those employed in dedicated laboratory setups. Furthermore, collider detectors have inherent advantages in performing certain quantum information measurements, and allow for the reconstruction of the state of the system under consideration via quantum state tomography. Here, we elaborate on the potential, challenges, and goals of this innovative and rapidly evolving line of research and discuss its expected impact on both quantum information theory and high-energy physics.

hep-ph↗

arXiv2024

Observation of quantum entanglement in top quark pairs at the ATLAS experiment

The ATLAS Collaboration has recently reported the first observation of quantum entanglement in top quark pair production at the Large Hadron Collider (LHC). A brief review of the experimental status of top quark pair spin correlations is given, before highlighting the expected differences between classical and quantum correlations. A criterion for the detection of spin entanglement in top quark pairs has been proposed; the experimental strategy to implement it and observe the effect is discussed, and the positive results of the ATLAS measurement are presented.

hep-ex↗

arXiv2021

Observing $t\bar{t}Z$ spin correlations at the LHC

Spin correlations in the production of top-antitop quark ($t\bar{t}$) pairs at the Large Hadron Collider (LHC) are an experimentally verified prediction of the Standard Model. In this paper, we compute the full spin density matrix for $t\bar{t}Z$ production at next-to-leading order precision in QCD, for center-of-mass energies of 13 and 14 TeV. We find that the additional emission of a $Z$ boson leads to significantly different spin correlations with respect to the $t\bar{t}$ case, and induces small longitudinal polarisations of the top quarks. We further propose an analysis strategy that could lead to the observation of spin correlations in $t\bar{t}Z$ events at the end of Run 3 of the LHC, or possibly earlier by combining the ATLAS and CMS datasets. In addition, we show that the pure angular information contained in the spin density matrix provides novel constraints on the dimension-6 effective field theory (EFT) operators relevant to the $t$-$Z$ interaction, without any reference to the total production rates.

hep-ph↗