The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem”
We report the first measurement of alpha-particles from the interaction of neutrons with 7Be at “temperatures” of Big Bang Nucleosynthesis (BBN). We measured the Maxwellian averaged cross sections (MACS), with neutron beams produced by the LiLiT at the SARAF in Israel (with kT = 49.5 keV hence 0.57...
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doaj-88d7f884d7754bdd941f863516bda2b22021-08-02T06:27:28ZengEDP SciencesEPJ Web of Conferences2100-014X2020-01-012270100710.1051/epjconf/202022701007epjconf_enas2020_01007The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem”Gai M.0Kading E.E.1Hass M.2Nollett K.M.3Stern S.R.4Stora Th.5Weiss A.‘LNS at Avery Point, University of Connecticut‘LNS at Avery Point, University of ConnecticutDepartment of Particle Physics, Weizmann Inst. of ScienceDepartment of Physics, San Diego State University‘LNS at Avery Point, University of ConnecticutISOLDE, CERN,We report the first measurement of alpha-particles from the interaction of neutrons with 7Be at “temperatures” of Big Bang Nucleosynthesis (BBN). We measured the Maxwellian averaged cross sections (MACS), with neutron beams produced by the LiLiT at the SARAF in Israel (with kT = 49.5 keV hence 0.57 GK). In addition, we measured the cross section of the 7Be(n,p) reaction, which is in excellent agreement with the recent measurement of the n_TOF collaboration, further substantiating our method as a demonstration of “proof of principle”. The cross section for the 7Be(n,ga) and the 7Be(n,a) reaction measured in the “BBN window” is considerably smaller than compiled by Wagoner in 1969 and used today in Big Bang Nucleosynthesis (BBN). We also rule out a hitherto unknown resonance in 8Be at the BBN window, that was conjectured as a possible standard nuclear physics solution to the “Primordial 7Li Problem”. Together with previous results, we deduce a new Wagoner-like Rate for the destruction of 7Be by neutrons which is based on all current measured data. We conclude the lack of a standard nuclear solution to the “Primordial 7Li Problem”. Our upper limit on the cross sections for the high energy alpha-particles is in agreement with recent measurement of the n_TOF collaboration, but it is considerably smaller than the p-wave extrapolation of the Kyoto collaboration. We measured the alpha-particles from the 7Be(n,gi)8Be*(3.03 MeV) reaction, which is considerably larger than a previous s-wave estimate. Hence, in contrast, we conclude s-wave dominance at BBN energies, as would be expected due to the broad (122 keV) low lying 2” state at En = 10 keV.https://www.epj-conferences.org/articles/epjconf/pdf/2020/03/epjconf_enas2020_01007.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Gai M. Kading E.E. Hass M. Nollett K.M. Stern S.R. Stora Th. Weiss A. |
spellingShingle |
Gai M. Kading E.E. Hass M. Nollett K.M. Stern S.R. Stora Th. Weiss A. The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem” EPJ Web of Conferences |
author_facet |
Gai M. Kading E.E. Hass M. Nollett K.M. Stern S.R. Stora Th. Weiss A. |
author_sort |
Gai M. |
title |
The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem” |
title_short |
The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem” |
title_full |
The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem” |
title_fullStr |
The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem” |
title_full_unstemmed |
The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem” |
title_sort |
interaction of neutrons with 7be at bbn temperatures: lack of standard nuclear solution to the “primordial 7li problem” |
publisher |
EDP Sciences |
series |
EPJ Web of Conferences |
issn |
2100-014X |
publishDate |
2020-01-01 |
description |
We report the first measurement of alpha-particles from the interaction of neutrons with 7Be at “temperatures” of Big Bang Nucleosynthesis (BBN). We measured the Maxwellian averaged cross sections (MACS), with neutron beams produced by the LiLiT at the SARAF in Israel (with kT = 49.5 keV hence 0.57 GK). In addition, we measured the cross section of the 7Be(n,p) reaction, which is in excellent agreement with the recent measurement of the n_TOF collaboration, further substantiating our method as a demonstration of “proof of principle”. The cross section for the 7Be(n,ga) and the 7Be(n,a) reaction measured in the “BBN window” is considerably smaller than compiled by Wagoner in 1969 and used today in Big Bang Nucleosynthesis (BBN). We also rule out a hitherto unknown resonance in 8Be at the BBN window, that was conjectured as a possible standard nuclear physics solution to the “Primordial 7Li Problem”. Together with previous results, we deduce a new Wagoner-like Rate for the destruction of 7Be by neutrons which is based on all current measured data. We conclude the lack of a standard nuclear solution to the “Primordial 7Li Problem”. Our upper limit on the cross sections for the high energy alpha-particles is in agreement with recent measurement of the n_TOF collaboration, but it is considerably smaller than the p-wave extrapolation of the Kyoto collaboration. We measured the alpha-particles from the 7Be(n,gi)8Be*(3.03 MeV) reaction, which is considerably larger than a previous s-wave estimate. Hence, in contrast, we conclude s-wave dominance at BBN energies, as would be expected due to the broad (122 keV) low lying 2” state at En = 10 keV. |
url |
https://www.epj-conferences.org/articles/epjconf/pdf/2020/03/epjconf_enas2020_01007.pdf |
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