Kaon Photoproduction and the Λ Decay Parameter α–

Ireland, David G.; Döring, M.; Glazier, Derek I.; Haidenbauer, J.; Mai, M.; Murray-Smith, Roderick; Rönchen, D.

doi:10.1103/PhysRevLett.123.182301

Title: Kaon Photoproduction and the $Λ$ Decay Parameter $α_{-}$

Journal Article · 28 October 2019 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.123.182301 · OSTI ID:1572152

^[1]; Döring, M. ^[2]; Glazier, Derek I. ^[1]; Haidenbauer, J. ^[3]; Mai, M. ^[4]; Murray-Smith, Roderick ^[1]; Rönchen, D. ^[5]

Univ. of Glasgow, Glasgow (United Kingdom)
The George Washington Univ., Washington, D.C. (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Forschungszentrum Jülich, Julich (Germany)
The George Washington Univ., Washington, D.C. (United States)
Univ. Bonn, Bonn (Germany)

The weak decay parameter $$\alpha_-$$ of the $$\Lambda$$ is an important quantity for the extraction of polarization observables in various experiments. Moreover, in combination with $$\alpha_+$$ from $$\bar\Lambda$$ decay it provides a measure for matter-antimatter asymmetry. The weak decay parameter also affects the decay parameters of the $$\Xi$$ and $$\Omega$$ baryons and, in general, any quantity in which the polarization of the $$\Lambda$$ 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 $$\alpha_-$$, 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. Furthermore, our analysis supports the new BESIII finding that $$\alpha_-$$ is significantly larger than the previous PDG value. Any experimental quantity relying on the value of $$\alpha_-$$ should therefore be re-considered.

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Research Organization:: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)

Grant/Contract Number:: AC05-06OR23177; SC0016582

OSTI ID:: 1572152

Report Number(s):: JLAB-THY--19-3019; DOE/OR/23177--4767; arXiv:1904.07616

Journal Information:: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 18 Vol. 123; ISSN 0031-9007; ISSN PRLTAO

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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