### Abstract

We use an underground counting lab with an extremely low background to perform an activity measurement for the [Formula presented] system with energies down to [Formula presented] MeV, at which the ^{12}C(^{13}C,p)^{24}Na cross section is found to be 0.22(7) nb. The [Formula presented] fusion cross section is derived with a statistical model calibrated using experimental data. Our new result of the [Formula presented] fusion cross section is the first decisive evidence in the carbon isotope systems which rules out the existence of the astrophysical S-factor maximum predicted by the phenomenological hindrance model, while confirming the rising trend of the S-factor towards lower energies predicted by other models, such as CC-M3Y+Rep, DC-TDHF, KNS, SPP and ESW. After normalizing the model predictions with our data, a more reliable upper limit is established for the [Formula presented] fusion cross sections at stellar energies.

Original language | English |
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Article number | 135170 |

Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 801 |

DOIs | |

Publication status | Published - 2020 Feb 10 |

### Keywords

- Astrophysical S-factor
- Extrapolation models
- Fusion cross section
- Hindrance

### ASJC Scopus subject areas

- Nuclear and High Energy Physics

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## Cite this

^{12}C+

^{12}C astrophysical S-factors with the

^{12}C+

^{13}C measurements at very low energies.

*Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics*,

*801*, [135170]. https://doi.org/10.1016/j.physletb.2019.135170