Underground experimental study finds no evidence of low-energy resonance in theLi6(p,γ)Be7reaction

Abstract

The astrophysical 6 Li(p,γ) 7 Be reaction occurs during Big Bang nucleosynthesis and the pre-main sequence and main sequence phases of stellar evolution. The low-energy trend of its cross section remains uncertain, since different measurements have provided conflicting results. A recent experiment reported a resonance-like structure at center-of-mass energy 195 keV, associated to a positive-parity state of 7 Be. The existence of such resonance is still a matter of debate. We report a new measurement of the 6 Li(p,γ) 7 Be cross section performed at the Laboratory for Underground Nuclear Astrophysics, covering the center-of-mass energy range E = 60-350 keV. Our results rule out the existence of low-energy resonances. The astrophysical S-factor varies smoothly with energy, in agreement with theoretical models.

The $^6$Li$(p, γ)^7$Be reaction rate in the light of the new LUNA data

“…MeV with J π = 5/2 in the nucleon channel, or, in other words, the impossibility of the M1 transition from this resonance to the GS. This has been confirmed by the new LUNA results [9] and, indirectly, by the data of [30]. The width of the resonance peak at 9.29 MeV is taken from Table 7.10 of [30], although another state, 2 P 1/2 , is indicated therein.…”

“…In light of the new experimental LUNA data [9], we reexamine the 6 Li(p, γ) 7 Be reaction S −factor and reaction rate within the framework of the MPCM.…”

“…Results of previous theoretical calculations and the present work are presented in Table VII. Our calculations are analyzed and interpreted based on the experimental data [9] as one of the newest and most accurate.…”

“…The radiative 6 Li(p,γ) 7 Be capture reaction is of great interest in nuclear astrophysics [1,2]. Since 1955 the 6 Li(p,γ) 7 Be reaction at low energies has been studied by several experimental groups [3][4][5][6][7][8][9][10][11]. Measurements of the astrophysical S −factor of this reaction were limited to the energy range of 35 keV to 1.2 MeV.…”

“…In 2020, new experimental data were obtained in the Laboratory for Underground Nuclear Astrophysics (LUNA) [9], and it excluded the possibility of resonance mentioned in [8]. It seems challenging to consider this reaction in the astrophysical energy range, for which experimental data are available.…”