TY  - JOUR
AU  - n_TOF Collaboration (Barbagallo, M. et al
AU  - Domingo-Pardo, C.
AU  - Tain, J. L.
AU  - Tarifeño-Saldivia, A.
PY  - 2016
DA  - 2016//
TI  - Be-7(n,alpha)He-4 Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN
T2  - Phys. Rev. Lett.
JO  - Physical Review Letters
SP  - 152701
EP  - 7pp
VL  - 117
IS  - 15
PB  - Amer Physical Soc
AB  - The energy-dependent cross section of the (7)Bed(n,alpha)He-4 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 Be-7 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 Be-7, and a specifically designed experimental setup. Coincidences between the two alpha particles have been recorded in two Si-Be-7-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.
SN  - 0031-9007
UR  - http://arxiv.org/abs/1606.09420
UR  - https://doi.org/10.1103/PhysRevLett.117.152701
DO  - 10.1103/PhysRevLett.117.152701
LA  - English
N1  - WOS:000384479300003
ID  - n_TOFCollaborationBarbagallo_etal2016
ER  -