We report the first evidence of breakup dominance at deep sub-barrier energies for the proton halo nucleus ${}^8\mathrm{B}$ on a heavy target. Angular distribution measurements of the ${}^8\mathrm{B}$ breakup fragment, ${}^7\mathrm{Be}$, on lead were performed at the TwinSol facility of the University of Notre Dame at a beam energy of 30 MeV, 58% of the Coulomb barrier and corresponding to a distance of closest approach of 20.5 fm. The ${}^7\mathrm{Be}$ yield was observed in two double sided silicon strip detector telescopes symmetrical to the radioactive beam and normalized using the ${}^8\mathrm{B}$ Rutherford scattering. The results are in excellent agreement with continuum discretized coupled channel calculations with a total breakup cross section $(326\pm 84)\mathrm{mb}$. This is found to exhaust all of the total reaction cross section for the system ${}^8\mathrm{B}+{}^{208}\mathrm{Pb}$, possibly prohibiting a fusion enhancement. This finding is expected to give more insight to the puzzle of fusion suppression at deep sub-barrier energies with possible major consequences on nuclear astrophysics.

中文翻译：

---

在重目标上弱束缚核的深亚势垒能的直接反应通道占优势：案例B8 + Pb208

我们报告了质子晕核深子势垒能在分解支配地位的第一个证据。 ${}^8\mathrm{乙}$在一个沉重的目标。角分布测量${}^8\mathrm{乙}$ 分手碎片 ${}^7是$在铅上，是在圣母大学的TwinSol设施中以30 MeV的束能量，58％的库仑势垒进行的，对应的最接近距离为20.5 fm。的${}^7是$ 在两个与放射线对称的双面硅条探测器望远镜中观察到了屈服，并使用 ${}^8\mathrm{乙}$卢瑟福散射。结果与总离散截面的连续离散离散耦合通道计算非常吻合$（326\pm 84）\mathrm{兆字节}$。发现这耗尽了系统的所有总反应截面${}^8\mathrm{乙}+{}^{208}\mathrm{铅含量}$，可能会禁止融合增强功能。预期该发现将为深亚势垒能量的聚变抑制之谜提供更多见解，并可能对核天体物理学产生重大影响。