We derive new constraints on the neutron lifetime based on the recent Planck 2015 observations of temperature and polarization anisotropies of the CMB. Under the assumption of standard Big Bang Nucleosynthesis, we show that Planck data constrains the
neutron lifetime to $tau_n=(907 pm 69) , [text{s}]$ at $68 %$ c.l.. Moreover, by including the direct measurements of primordial Helium abundance of Aver et al. (2015) and Izotov et al. (2014), we show that cosmological data provide the stringent constraints $tau_n=(875 pm 19) , [text{s}]$ and $tau_n=(921 pm 11) , [text{s}]$ respectively. The latter appears to be in tension with neutron lifetime value quoted by the Particle Data Group ($tau_n=(880.3 pm 1.1) , [text{s}]$). Future CMB surveys as COrE+, in combination with a weak lensing survey as EUCLID, could constrain the neutron lifetime up to a $sim 6 , [text{s}]$ precision.
The recent measurements of the Cosmic Microwave Background Anisotropies provided by the Planck satellite experiment have significantly improved the constraints on several cosmological parameters. In this brief paper we point out a small but interesti
ng tension present between recent values of the primordial deuterium measured from quasar absorption line systems and the same value inferred, albeit indirectly, from the Planck measurements assuming {Lambda}CDM and Big Bang Nucleosynthesis. Here we discuss this tension in detail investigating the possible new physics that could be responsible for the tension. We found that, among 8 extra parameters, only an anomalous lensing component and a closed universe could change the Planck constraint towards a better consistency with direct deuterium measurements.
