A1 Journal article (refereed)
First Observation of an Attractive Interaction between a Proton and a Cascade Baryon (2019)

ALICE Collaboration (2019). First Observation of an Attractive Interaction between a Proton and a Cascade Baryon. Physical Review Letters, 123 (11), 112002. DOI: 10.1103/PhysRevLett.123.112002

JYU authors or editors

Publication details

All authors or editors: ALICE Collaboration

Journal or series: Physical Review Letters

ISSN: 0031-9007

eISSN: 1079-7114

Publication year: 2019

Volume: 123

Issue number: 11

Article number: 112002

Publisher: American Physical Society

Publication country: United States

Publication language: English

DOI: http://doi.org/10.1103/PhysRevLett.123.112002

Open Access: Open access publication published in a hybrid channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/65825


This Letter presents the first experimental observation of the attractive strong interaction between a proton and a multistrange baryon (hyperon) Ξ−. The result is extracted from two-particle correlations of combined p−Ξ−⊕¯p−¯Ξ+ pairs measured in p−Pb collisions at √sNN=5.02  TeV at the LHC with ALICE. The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a standard deviation in the range [3.6, 5.3] is found. Since the measured p−Ξ−⊕¯p−¯Ξ+ correlation is significantly enhanced with respect to the Coulomb prediction, the presence of an additional, strong, attractive interaction is evident. The data are compatible with recent lattice calculations by the HAL-QCD Collaboration, with a standard deviation in the range [1.8, 3.7]. The lattice potential predicts a shallow repulsive Ξ− interaction within pure neutron matter and this implies stiffer equations of state for neutron-rich matter including hyperons. Implications of the strong interaction for the modeling of neutron stars are discussed.

Keywords: particle physics

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2019

JUFO rating: 3

Last updated on 2020-18-08 at 13:26