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Title: The positron peak puzzle - Recent results from APEX

Abstract

Results are presented from a new experiment, APEX, designed to study the previously reported sharp lines in sum-energy spectra of positrons and electrons produced in collisions of very heavy ions. Data have been collected for 238U + 181Ta and 238U + 232Th. No evidence is found for narrow structures similar to those previously reported. For the specific case of the isolated decay of a neutral particle of mass 1.4–2.1 MeV/c 2, the upper limits on cross sections obtained are significantly less than previously reported. Data are also presented for internal pair conversion in 206Pb. These results are used to set limits for the possible contribution to the pair yield of a 1780 keV transition in 238U observed in heavy-ion gamma-ray coincidence measurements.

Authors:
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Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Org.:
APEX Collaboration
OSTI Identifier:
1407011
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Acta Physica Polonica. Series B
Additional Journal Information:
Journal Volume: 27; Journal ID: ISSN 0587-4254
Publisher:
Jagiellonian University
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Ahmad, I, Austin, SM, Back, BB, Betts, RR, Calaprice, FP, Chan, KC, Chishti, A, Chowdhury, P, Conner, C, Dunford, RW, Fox, JD, Freedman, SJ, Freer, M, Gazes, S, Hallin, AL, Happ, T, Kaloskamis, N, Kashy, E, Kutschera, W, Last, J, Lister, CJ, Liu, M, Maier, MR, Mercer, DJ, Mikolas, D, Perera, A, Rhein, MD, Roa, E, Schiffer, JP, Trainor, T, Wilt, P, Winfield, JS, Wolanski, M, Wolfs, FLH, Wuosmaa, AH, Young, A, and Yurkon, JE. The positron peak puzzle - Recent results from APEX. United States: N. p., 1996. Web.
Ahmad, I, Austin, SM, Back, BB, Betts, RR, Calaprice, FP, Chan, KC, Chishti, A, Chowdhury, P, Conner, C, Dunford, RW, Fox, JD, Freedman, SJ, Freer, M, Gazes, S, Hallin, AL, Happ, T, Kaloskamis, N, Kashy, E, Kutschera, W, Last, J, Lister, CJ, Liu, M, Maier, MR, Mercer, DJ, Mikolas, D, Perera, A, Rhein, MD, Roa, E, Schiffer, JP, Trainor, T, Wilt, P, Winfield, JS, Wolanski, M, Wolfs, FLH, Wuosmaa, AH, Young, A, & Yurkon, JE. The positron peak puzzle - Recent results from APEX. United States.
Ahmad, I, Austin, SM, Back, BB, Betts, RR, Calaprice, FP, Chan, KC, Chishti, A, Chowdhury, P, Conner, C, Dunford, RW, Fox, JD, Freedman, SJ, Freer, M, Gazes, S, Hallin, AL, Happ, T, Kaloskamis, N, Kashy, E, Kutschera, W, Last, J, Lister, CJ, Liu, M, Maier, MR, Mercer, DJ, Mikolas, D, Perera, A, Rhein, MD, Roa, E, Schiffer, JP, Trainor, T, Wilt, P, Winfield, JS, Wolanski, M, Wolfs, FLH, Wuosmaa, AH, Young, A, and Yurkon, JE. Mon . "The positron peak puzzle - Recent results from APEX". United States. https://www.osti.gov/servlets/purl/1407011.
@article{osti_1407011,
title = {The positron peak puzzle - Recent results from APEX},
author = {Ahmad, I and Austin, SM and Back, BB and Betts, RR and Calaprice, FP and Chan, KC and Chishti, A and Chowdhury, P and Conner, C and Dunford, RW and Fox, JD and Freedman, SJ and Freer, M and Gazes, S and Hallin, AL and Happ, T and Kaloskamis, N and Kashy, E and Kutschera, W and Last, J and Lister, CJ and Liu, M and Maier, MR and Mercer, DJ and Mikolas, D and Perera, A and Rhein, MD and Roa, E and Schiffer, JP and Trainor, T and Wilt, P and Winfield, JS and Wolanski, M and Wolfs, FLH and Wuosmaa, AH and Young, A and Yurkon, JE},
abstractNote = {Results are presented from a new experiment, APEX, designed to study the previously reported sharp lines in sum-energy spectra of positrons and electrons produced in collisions of very heavy ions. Data have been collected for 238U + 181Ta and 238U + 232Th. No evidence is found for narrow structures similar to those previously reported. For the specific case of the isolated decay of a neutral particle of mass 1.4–2.1 MeV/c2, the upper limits on cross sections obtained are significantly less than previously reported. Data are also presented for internal pair conversion in 206Pb. These results are used to set limits for the possible contribution to the pair yield of a 1780 keV transition in 238U observed in heavy-ion gamma-ray coincidence measurements.},
doi = {},
journal = {Acta Physica Polonica. Series B},
number = ,
volume = 27,
place = {United States},
year = {1996},
month = {1}
}

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