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Polarization and entanglement in baryon-antibaryon pair production in electron-positron annihilation
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.ORCID iD: 0000-0002-6945-716x
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.ORCID iD: 0000-0003-4937-2270
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Number of Authors: 4692019 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 15, no 7, p. 631-634Article in journal (Refereed) Published
Abstract [en]

Particles directly produced at electron-positron colliders, such as the J/psi meson, decay with relatively high probability into a baryon-antibaryon pair(1). For spin-1/2 baryons, the pair can have the same or opposite helicites. A non-vanishing phase Delta Phi between the transition amplitudes to these helicity states results in a transverse polarization of the baryons(2-4). From the joint angular distribution of the decay products of the bary-ons, this phase as well as the parameters characterizing the baryon and the antibaryon decays can be determined. Here, we report the measurement of Delta Phi = 42.4 +/- 0.6 +/- 0.5 degrees using Lambda -> p pi(-) and (Lambda) over bar -> (p) over bar pi(+), (n ) over bar pi(0) decays at BESIII. We find a value for the Lambda -> p pi(-) decay parameter of alpha(-) = 0.750 +/- 0.009 +/- 0.004, 17 +/- 3% higher than the current world average, which has been used as input for all Lambda polarization measurements since 1978(5,6). For (Lambda) over bar -> (p) over bar pi(+) we find alpha(+) = -0.758 +/- 0.010 +/- 0.007, giving A(CP) = (alpha(-) + alpha(+))/(alpha(-) - alpha(+)) = -0.006 +/- 0.012 +/- 0.007, a precise direct test of charge-parity symmetry (CP) violation in Lambda decays.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019. Vol. 15, no 7, p. 631-634
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:uu:diva-390921DOI: 10.1038/s41567-019-0494-8ISI: 000473331000013OAI: oai:DiVA.org:uu-390921DiVA, id: diva2:1343190
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

For complete list of authors see http://dx.doi.org/10.1038/s41567-019-0494-8

Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2019-08-15Bibliographically approved

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Ikegami Andersson, WalterJohansson, TordKupsc, AndrzejLi, CuiPapenbrock, MichaelPettersson, JoachimSchönning, KarinWolke, Magnus

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