Branching Ratio for Pion-beta Decay
Author : Robert B. Bacastow
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Page : 50 pages
File Size : 38,58 MB
Release : 1963
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Author : Robert B. Bacastow
Publisher :
Page : 50 pages
File Size : 38,58 MB
Release : 1963
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Author : Kétévi Adiklè Assamagan
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Page : 500 pages
File Size : 28,60 MB
Release : 1995
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Author : Erin E. Abouzaid
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Page : 328 pages
File Size : 37,32 MB
Release : 2007
Category : Kaons
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Author : Rune Niclasen
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Page : 124 pages
File Size : 31,7 MB
Release : 2006
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A precise branching ratio measurement of the rare decay {pi}{sup 0} {yields} e{sup +}e{sup -} has been made. The measurement was made with the rare kaon decay experiment KTeV at Fermilab where the source of {pi}{sup 0}s was K{sub L} {yields} {pi}{sup 0}{pi}{sup 0}{pi}{sup 0} decaying in flight. A total of 794 fully reconstructed K{sub L} {yields} 3{pi}{sup 0} events consistent with two of the intermediate {pi}{sup 0}s decaying into {gamma}{gamma} and one into e{sup +}e{sup -} were collected. An estimated 53.2 {+-} 11.0 of these events were expected to be background. Normalizing to the {pi}{sup 0} Dalitz decay they found Br({pi}{sup 0} {yields} e{sup +}e{sup -}, (m{sub e{sup +}e{sup -}}/m{sub {pi}{sup 0}}){sup 2}> 0.95) = (6.44 {+-} 0.25(stat) {+-} 0.22(syst)) x 10{sup -8} where internal radiation, {pi}{sup 0} {yields} e{sup +}e{sup -}({gamma}), was limited by the requirement (m{sub e{sup +}e{sup -}}/m{sub {pi}{sup 0}}){sup 2}> 0.95 which separated it from the tree level Dalitz decay, {pi}{sup 0} {yields} e{sup +}e{sup -}P{gamma}.
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Page : 14 pages
File Size : 17,68 MB
Release : 1993
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Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay [pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon] is predicted by the Standard Model (SM) to be R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.3999[plus minus]0.0005 s[sup [minus]1]. The best experimental number, obtained using in-flight decays, is R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.394 [plus minus] 0.015 s[sup [minus]1]. A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required.
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Page : 183 pages
File Size : 29,40 MB
Release : 2007
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The authors present a measurement of B([pi]0 2!e+e-[gamma])/B([pi]0 2![gamma][gamma]) using data taken in 1999 by the E832 KTeV experiment at Fermilab. The [pi]0s were produced by KL decays in flight that are fully reconstructed. They find 63,693 KL 2!3[pi]0 2![gamma][gamma] [gamma][gamma] e+e-[gamma] decays in KTeV data (an increase of a factor of ~ 20 in event statistics over previous experiments), and normalize to KL 2!3[pi]0 2!6[gamma], to extract B([pi]0 2!e+e-[gamma], me+e-> 15 MeV/c2
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Page : pages
File Size : 10,38 MB
Release : 1976
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The branching ratio for the decay .pi. .-->. e.nu gamma. was measured in a counter experiment in which the e was detected in a magnetic spectrometer and the .gamma.-ray in a lead glass hodoscope. The number of observed events is 226.2 +- 22.4. The branching ratio into the phase space with electron momentum above 56 MeV/c and the electron/photon opening angle greater than 132° is found to be (5.6 +- 0.7) x 10−8. From the measured branching ratio one determines .gamma., the ratio of the axial vector to vector form factor. The vector form factor is computed using CVC and the .pi.° lifetime. For T/sub .pi./° = 0.828 x 10−16 sec, .gamma. = 0.44 +- 0.12 or .gamma. = --2.36 +- 0.12 is obtained. A comparison between the measured values of .gamma. and various theories is made.
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Page : pages
File Size : 36,74 MB
Release : 1991
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Page : 0 pages
File Size : 16,83 MB
Release : 1976
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Author : C. M. Turner
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Page : 40 pages
File Size : 12,5 MB
Release : 1949
Category : Beryllium
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