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

Journal Article · Wed Oct 23 00:00:00 EDT 2024 · Reports on Progress in Physics

DOI:https://doi.org/10.1088/1361-6633/ad7e4d· OSTI ID:2475241

CMS Collaboration, The

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 ( $\mathrm{t}\overline{\mathrm{t}}$ ) 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 $\mathrm{t}\overline{\mathrm{t}}$ production density matrix and measured in the region of the $\mathrm{t}\overline{\mathrm{t}}$ 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 $\mathrm{t}\overline{\mathrm{t}}$ pairs in this phase space. This measurement provides a new probe of quantum mechanics at the highest energies ever produced.

• Research Organization: AGH-UST, Cracow; AUM, Kuwait; Aachen, Tech. Hochsch.; Adiyaman U.; Ain Shams U., Cairo; Alabama U.; Andes U., Bogota; Annecy, LAPP; Antioquia U.; Antwerp U.; Athens U.; Bangalore, Indian Inst. Sci.; Bari U.; Baylor U.; Beihang U.; Beijing, Inst. High Energy Phys.; Belgrade U.; Bethel Coll.; Bhubaneswar, Inst. Phys.; Bhubaneswar, NISER; Bingöl U.; Bogazici U.; Boskovic Inst., Zagreb; Boston U.; Brandenburg Tech. U.; Bristol U.; British U. in Egypt; Brown U.; Brunel U.; Brussels U.; Bucharest, IFIN-HH; Budapest, RMKI; CC, Villeurbanne; CERN; CHEP, Taegu; CINVESTAV, IPN; Cairo, Acad. Sci. Res. Tech.; Caltech; Cantabria Inst. of Phys.; Canterbury U.; Carnegie Mellon U.; Catholic U. America; Charles U.; Chonnam Natl. U.; Chulalongkorn U.; Colombo U.; Colorado U.; Conacyt, Mexico; Cornell U.; Cukurova U.; Cyprus U.; DESY; Debrecen, Inst. Nucl. Res.; Delhi U.; Democritos Nucl. Res. Ctr.; EKU KRC, Gyongyos; Ecole Polytechnique; Eotvos U.; Erzincan U.; Fayoum U.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Florida Inst. Tech.; Florida State U.; Florida U.; Frascati; Fudan U.; GTU, Tbilisi; Gangneung-Wonju Natl. U.; Gent U.; Guglielmo Marconi U.; Hacettepe U.; Hamburg U.; Hanyang U.; Haute Alsace U.; Helsinki Inst. of Phys.; Helsinki U.; Helwan U.; IAS, Julich; IISER, Pune; INFN, Bari; INFN, Bologna; INFN, Catania; INFN, Florence; INFN, Genoa; INFN, Milan Bicocca; INFN, Naples; INFN, Padua; INFN, Pavia; INFN, Perugia; INFN, Pisa; INFN, Rome; INFN, Trieste; INFN, Turin; IP2I, Lyon; IPM, Tehran; IRFU, Saclay; Iberoamericana U.; Illinois U., Chicago; Imperial Coll., London; Indian Inst. Tech., Bhubaneswar; Indian Inst. Tech., Madras; Inst. Scintill. Mat., Kharkiv; Ioannina U.; Iowa U.; Isfahan Tech. U.; Istanbul Tech. U.; Istanbul U.; Istinye U., Istanbul; Johns Hopkins U.; KIT, Karlsruhe, EKP; Kafkas U.; Kansas State U.; Kansas U.; Karamanoglu Mehmetbey U., Karaman; Kharkov, KIPT; Korea U.; Kyung Hee U.; LIP, Lisbon; Lappeenranta U. Tech.; Louvain U.; MIT; Madrid, Autonoma U.; Madrid, CIEMAT; Malaya U.; Marmara U.; Maryland U.; Middle East Tech. U., Ankara; Minnesota U.; Monash U.; Montenegro U.; NCBJ, Swierk; NICPB, Tallinn; Nanjing Normal U.; Naples U.; Natl. Tech. U., Athens; Naval Academy, Annapolis; Nebraska U.; Northeastern U.; Northwestern U.; Notre Dame U.; Ohio State U.; Oviedo U.; PSI, Villigen; Panjab U.; Peking U.; Pisa U.; Pisa, Scuola Normale Superiore; Princeton U.; Puebla U., Inst. Fis.; Puerto Rico U., Mayaguez; Purdue U.; Purdue U., Calumet; Quaid-i-Azam U.; Rice U.; Riga Tech. U.; Rio Grande do Sul U.; Rio de Janeiro State U.; Rio de Janeiro, CBPF; Rochester U.; Ruhuna U.; Rutgers U., Piscataway; Rutherford; SUNY, Buffalo; SYSU, Guangzhou; Saha Inst.; San Francisco de Quito U.; Sejong U.; Seoul Natl. U.; Seoul U.; Sharif U. of Tech.; Sinop U.; Sofiya U.; Sofiya, Inst. Nucl. Res.; Sonora U.; South China Normal U.; Southampton U.; Split Tech. U.; Split U.; Stefan Meyer Inst. Subatomare Phys.; Strasbourg, IPHC; Suez Canal U.; Sungkyunkwan U.; TIFR, Mumbai, DHEP; TU Vienna; Taiwan, Natl. Central U.; Taiwan, Natl. Taiwan U.; Tarapaca U.; Tashkent, IYF; Tennessee U.; Texas A&M U. Qatar, Doha; Texas A-M; Texas Tech.; Tsinghua U., Beijing; Turin U.; U. Campinas; U. Debrecen, Inst. Phys.; UC, Davis; UC, Riverside; UC, San Diego; UC, Santa Barbara; UCAS, Beijing; UCLA; USTM, Behshahr; University Coll., Dublin; Unlisted; VINCA Inst. Nucl. Sci., Belgrade; Vanderbilt U.; Vienna, OAW; Vilnius U.; Virginia U.; Visva Bharati U.; Vrije U., Brussels; Warsaw U.; Warsaw U. of Tech.; Wayne State U.; Wisconsin U., Madison; Yerevan Phys. Inst.; Yildiz Tech. U.; Yonsei U.; Zhejiang U.; Zurich U.; Zurich, ETH
• Sponsoring Organization: US Department of Energy; USDOE
• Grant/Contract Number: 89243024CSC000002; AC02-07CH11359
• OSTI ID: 2475241
• Alternate ID(s): OSTI ID: 2467499
• Report Number(s): CERN-EP-2024-137; CMS-TOP-23-001; FERMILAB-PUB-24-0754-CMS
• Journal Information: Reports on Progress in Physics, Journal Name: Reports on Progress in Physics Journal Issue: 11 Vol. 87; ISSN 0034-4885
• Publisher: IOP Publishing
• Country of Publication: United Kingdom
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
CMS
entanglement
top quark