The {pi}{sup +}-emission puzzle in 4 over Lambda He decay

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The observed {pi}{sup +} emission from the weak decay of 4 over {Lambda} He has long been an intriguing puzzle. Experimentally, the {pi}{sup +} to {pi}{sup {minus}} ratio for 4 over {Lambda} He decay is about 5%. Because mesonic decay modes of the free {Lambda} ({yields} p + {pi}{sup {minus}}, n + {pi}{sup 0}) produce no {pi}{sup +}s, more complicated mechanisms must be responsible for the {pi}{sup +} decay of 4 over {Lambda} He. Dalitz and von Hippel explored two-body decay processes of the type: (1) {Lambda} {yields} {pi}{sup 0} + n decay followed by a {pi}{sup 0} + p ... continued below

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7 p.

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Gibson, B.F. & Timmermans, R. October 1, 1997.

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  • Gibson, B.F. Los Alamos National Lab., NM (United States). Theoretical Div.
  • Timmermans, R. Univ. of Groningen (Netherlands). Kernfysisch Versneller Inst.

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  • Los Alamos National Laboratory
    Publisher Info: Los Alamos National Lab., Applied Theoretical Physics Div., NM (United States)
    Place of Publication: New Mexico

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The observed {pi}{sup +} emission from the weak decay of 4 over {Lambda} He has long been an intriguing puzzle. Experimentally, the {pi}{sup +} to {pi}{sup {minus}} ratio for 4 over {Lambda} He decay is about 5%. Because mesonic decay modes of the free {Lambda} ({yields} p + {pi}{sup {minus}}, n + {pi}{sup 0}) produce no {pi}{sup +}s, more complicated mechanisms must be responsible for the {pi}{sup +} decay of 4 over {Lambda} He. Dalitz and von Hippel explored two-body decay processes of the type: (1) {Lambda} {yields} {pi}{sup 0} + n decay followed by a {pi}{sup 0} + p {yields} {pi}{sup +} + n charge-exchange reaction, and (2) {Sigma}{sup +} {yields} {pi}{sup +} + n decay following a {Lambda} + p {yields} {Sigma}{sup +} + n conversion. They concluded that neither process could account for even a 1% {pi}{sup +} + n decay as a p-wave process ruled out the promising explanation coming from von Hippel`s calculations, which had found that s-wave {Sigma}{sup +} decay might yield a sufficiently high rate. Cieply and Gal re-examined the charge-exchange contribution and concluded that, although up-to-date input parameters yield a 1.2% branching ratio, the charge-exchange mechanism cannot account for the experimental value of about 5%.

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7 p.

Notes

INIS; OSTI as DE98004378

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  • 6. international conference on hypernuclear and strange particle physics, Upton, NY (United States), 13-18 Oct 1997

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  • Other: DE98004378
  • Report No.: LA-UR--97-4990
  • Report No.: CONF-9710193--
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 651044
  • Archival Resource Key: ark:/67531/metadc702191

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • October 1, 1997

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • Nov. 3, 2016, 1:31 p.m.

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Gibson, B.F. & Timmermans, R. The {pi}{sup +}-emission puzzle in 4 over Lambda He decay, article, October 1, 1997; New Mexico. (digital.library.unt.edu/ark:/67531/metadc702191/: accessed December 12, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.