宇宙核时钟不确定度的研究

Uncertainties of nucleo-chronometers from nuclear physics inputs

基于经典快过程理论模型,研究了原子核物理输入量的不确定性对Th/U,Th/Hf,Th/Eu,Th/Os,Th/Ir等核时钟估算宇宙年龄的影响.其中利用蒙特卡罗模拟方法,计算了不同质量模型下由单中子分离能引起的不确定性.结果表明,Th/U核时钟由原子核质量不确定性引起的误差大约为1.66 Ga,比其他核时钟小2 Ga以上.对Th/Eu,Th/Os和Th/Ir核时钟,该误差分别为5.15,3.93和3.95 Ga.由于Th/Hf核时钟受质量模型影响太大,而Th/Os和Th/Ir的计算结果又明显偏大,因此在年龄计算中都需谨慎使用.综合考虑原子核物理输入量和天文观测带来的误差,利用Th/U核时钟估算的宇宙年龄为14.1±3.8 Ga.

The influences of uncertainties in nuclear physics inputs on the Th/U,Th/Hf,Th/Eu,Th/Os,Th/Ir nucleo-chronometers are investigated in the framework of the classical r-process approach.A Monte-Carlo method is used to evaluate the age uncertainty originating from neutron separation energies for each nuclear mass model.It is found that the deduced age uncertainty for Th /U can be up to 1.66 Ga,and for the three chronometers,Th/Eu,Th/Os,Th/Ir,the uncertainties are 5.15 Ga,3.93 Ga and 3.95 Ga,respectively. The recently proposed chronometer,Th/Hf,shows a clear model dependence,while Th/Os and Th/Ir chronometers tend to overestimate the age of Universe.Taking into account the uncertainties in nuclear physics inputs and observations,an up-to-date age estimation for the universe with the Th/U chronometer is 14.1±3.8 Ga.