Is there a dark decay of neutrons in 6He ?

by Marius Le Joubioux

The neutron lifetime discrepancy between beam and bottle experiments of 4σ could be interpreted as a possible sign of the neutron into dark particles [1]. If such a decay exists, it could also occur in unstable nuclei with sufficiently low neutron binding energy, a quasi-free neutron decay into a dark matter particle χ; as is the case of ⁶He with S_2n = 975.45keV < m_n − m_χ [2]. This quasi-free neutron dark decay would be as followed ⁶He →⁴He + n + χ which is the only way to have the emission of a free neutron in the decay of ⁶He. The SPIRAL1 facility at GANIL was used in June 2021 in order to produce a pure ⁶He¹⁺ radioactive beam at 25keV to observe an excess of neutrons in the decay of ⁶He which would be a unique signature for dark matter creation. In this presentation, we report the (preliminary) results of this experiment to set an upper limit for this dark decay mode in ⁶He.

[1] Bartosz Fornal and Benjam ́ ın Grinstein. “Dark Matter Interpretation of the Neutron Decay Anomaly”.

In: Phys. Rev. Lett. 120 (19 May 2018), p. 191801. doi: 10.1103/PhysRevLett.120.191801.

url: https://link.aps.org/doi/10.1103/PhysRevLett.120.191801

[2] M. Pf ̈ utzner and K. Riisager. “Examining the possibility to observe neutron dark decay in nuclei”.

In: Phys. Rev. C 97 (4 Apr. 2018), p. 042501. doi: 10 . 1103 / PhysRevC . 97 . 042501.

url: https://link.aps.org/doi/10.1103/PhysRevC.97.042501