7Be(n, α)4He Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN

Scientific paper - Original scientific paper

• Author: M. Barbagallo
• Author: ...
• Author: Damir Bosnar; MBZ: 134936
• Author: ...
• Author: Petar Žugec; MBZ: 326085
• Collaboration: n_TOF Collaboration
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

The energy-dependent cross section of the 7Be(n, α)4He reaction, of interest for the so-called cosmological lithium problem in big bang nucleosynthesis, has been measured for the first time from 10 meV to 10 keV neutron energy. The challenges posed by the short half-life of 7Be and by the low reaction cross section have been overcome at n_TOF thanks to an unprecedented combination of the extremely high luminosity and good resolution of the neutron beam in the new experimental area (EAR2) of the n_TOF facility at CERN, the availability of a sufficient amount of chemically pure 7Be, and a specifically designed experimental setup. Coincidences between the two alpha particles have been recorded in two Si-7Be-Si arrays placed directly in the neutron beam. The present results are consistent, at thermal neutron energy, with the only previous measurement performed in the 1960s at a nuclear reactor. The energy dependence reported here clearly indicates the inadequacy of the cross section estimates currently used in BBN calculations. Although new measurements at higher neutron energy may still be needed, the n_TOF results hint at a minor role of this reaction in BBN, leaving the long-standing cosmological lithium problem unsolved.

• Keywords (english): 7Be(n; α)4He reaction; neutron time of flight; n_TOF; Cosmological Lithium Problem
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review Letters
• Numbering: vol. 117, no. 15, 152701
• p-ISSN: 0031-9007
• DOI: https://doi.org/10.1103/PhysRevLett.117.152701
• URN:NBN: urn:nbn:hr:217:940116
• Publication: 2016
• Project: Number: IP-2013-11-1680; Title (croatian): Precizna mjerenja svojstava hadronskih sustava i niskoenergijska QCD; Acronym: PExpQCD; Leader: Damir Bosnar; Jurisdiction: Croatia; Funding stream: IP
• Document URL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.152701
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2016 American Physical Society. This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Received 22 June 2016; revised manuscript received 12 August 2016; published 3 October 2016.
• Created on: 2020-02-23 19:56:33