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Title: Kaon Photoproduction and the Λ Decay Parameter α

Abstract

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.

Authors:
ORCiD logo [1];  [2];  [1];  [3];  [4];  [1];  [5]
  1. Univ. of Glasgow, Glasgow (United Kingdom)
  2. The George Washington Univ., Washington, D.C. (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  3. Forschungszentrum Jülich, Julich (Germany)
  4. The George Washington Univ., Washington, D.C. (United States)
  5. Univ. Bonn, Bonn (Germany)
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1572152
Report Number(s):
JLAB-THY-19-3019; DOE/OR/23177-4767; arXiv:1904.07616
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:  
ST/P004458/1; PHY-1452055; AC05-06OR23177; SC0016582; TRR110; 11621131001; EP/M01326X/1; EP/R018634/1
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 123; Journal Issue: 18; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Ireland, David G., Döring, M., Glazier, Derek I., Haidenbauer, J., Mai, M., Murray-Smith, Roderick, and Rönchen, D. Kaon Photoproduction and the Λ Decay Parameter α–. United States: N. p., 2019. Web. doi:10.1103/PhysRevLett.123.182301.
Ireland, David G., Döring, M., Glazier, Derek I., Haidenbauer, J., Mai, M., Murray-Smith, Roderick, & Rönchen, D. Kaon Photoproduction and the Λ Decay Parameter α–. United States. doi:10.1103/PhysRevLett.123.182301.
Ireland, David G., Döring, M., Glazier, Derek I., Haidenbauer, J., Mai, M., Murray-Smith, Roderick, and Rönchen, D. Mon . "Kaon Photoproduction and the Λ Decay Parameter α–". United States. doi:10.1103/PhysRevLett.123.182301.
@article{osti_1572152,
title = {Kaon Photoproduction and the Λ Decay Parameter α–},
author = {Ireland, David G. and Döring, M. and Glazier, Derek I. and Haidenbauer, J. and Mai, M. and Murray-Smith, Roderick and Rönchen, D.},
abstractNote = {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.},
doi = {10.1103/PhysRevLett.123.182301},
journal = {Physical Review Letters},
number = 18,
volume = 123,
place = {United States},
year = {2019},
month = {10}
}

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