Kaon photoproduction and the Lambda decay parameter alpha

Ireland, D.G. , Doring, M., Glazier, D.I., Haidenbauer, J., Mai, M., Murray-Smith, R. and Ronchen, D. (2019) Kaon photoproduction and the Lambda decay parameter alpha. Physical Review Letters, 123, 182301. (doi: 10.1103/PhysRevLett.123.182301)

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The weak decay parameter α − of the Λ is an important quantity for the extraction of polarization observables in various experiments. Moreover, in combination with α + from ¯ Λ decay it provides a measure for matter-antimatter asymmetry. The weak decay parameter also affects the decay parameters of the Ξ and Ω baryons and, in general, any quantity in which the polarization of the Λ is relevant. The recently reported value by the BESIII Collaboration of 0.750(9)(4) is significantly larger than the previous PDG value of 0.642(13) that had been accepted and used for over 40 years. In this work we make an independent estimate of α − , using an extensive set of polarization data measured in kaon photoproduction in the baryon resonance region and constraints set by spin algebra. The obtained value is 0.721(6)(5). The result is corroborated by multiple statistical tests as well as a modern phenomenological model, showing that our new value yields the best description of the data in question. Our analysis supports the new BESIII finding that α − is significantly larger than the previous PDG value. Any experimental quantity relying on the value of α − should therefore be reconsidered.

Item Type:Articles
Additional Information:This work was supported by the United Kingdom’s Science and Technology Facilities Council (STFC) from Grant No. ST/P004458/1; M. D. acknowledges support by the National Science Foundation (Grant No. PHY1452055) and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177 and Grant No. DESC0016582. This work is supported in part by DFG and NSFC through funds provided to the Sino-German CRC 110 “Symmetry and the Emergence of Structure in QCD” (NSFC Grant No. 11621131001, DFG Grant No. TRR110) and R. M-S. acknowledges EPSRC Grants No. EP/ M01326X/1 and No. EP/R018634/1.
Glasgow Author(s) Enlighten ID:Murray-Smith, Professor Roderick and Glazier, Dr Derek and Ireland, Professor David
Authors: Ireland, D.G., Doring, M., Glazier, D.I., Haidenbauer, J., Mai, M., Murray-Smith, R., and Ronchen, D.
College/School:College of Science and Engineering > School of Computing Science
College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review Letters
Publisher:American Physical Society
ISSN (Online):1079-7114
Published Online:28 October 2019
Copyright Holders:Copyright © 2019 American Physical Society
First Published:First published in Physical Review Letters 123:182301
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
301379Nuclear Physics Consolidated GrantDavid IrelandScience and Technology Facilities Council (STFC)ST/P004458/1P&S - Physics & Astronomy
300982Exploiting Closed-Loop Aspects in Computationally and Data Intensive AnalyticsRoderick Murray-SmithEngineering and Physical Sciences Research Council (EPSRC)EP/R018634/1Computing Science