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تسجيل مستخدم جديدSpace-Based Measurement of the Neutron Lifetime using Data from the Neutron Spectrometer on NASAs MESSENGER Mission
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We establish the feasibility of measuring the neutron lifetime via an alternative, space-based class of methods, which use neutrons generated by galactic cosmic ray spallation of planets surfaces and atmospheres. Free neutrons decay via the weak interaction with a mean lifetime of around 880 s. This lifetime constrains the unitarity of the CKM matrix and is a key parameter for studies of Big-Bang nucleosynthesis. However, current laboratory measurements, using two independent approaches, differ by over 4$sigma$. Using data acquired in 2007 and 2008 during flybys of Venus and Mercury by NASAs MESSENGER spacecraft, which was not designed to make this measurement, we estimate the neutron lifetime to be $780pm60_textrm{stat}pm70_textrm{syst}$ s, thereby demonstrating the viability of this new approach.
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We use data from the Lunar Prospector Neutron Spectrometer to make the second space-based measurement of the free neutron lifetime finding $tau_n=887 pm 14_text{stat}{:^{+7}_{-3:text{syst}}}$ s, which is within 1$sigma$ of the accepted value. This me
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