Cosmology and the neutrino mass ordering

Abstract

We propose a simple method to quantify a possible exclusion of the inverted neutrino mass ordering from cosmological bounds on the sum of the neutrino masses. The method is based on Bayesian inference and allows for a calculation of the posterior odds of normal versus inverted ordering. We apply the method for a specific set of current data from Planck CMB data and large-scale structure surveys, providing an upper bound on the sum of neutrino masses of 0.14 eV at 95% CL. With this analysis we obtain posterior odds for normal versus inverted ordering of about 2:1. If cosmological data is combined with data from oscillation experiments the odds reduce to about 3:2. For an exclusion of the inverted ordering from cosmology at more than 95% CL, an accuracy of better than 0.02 eV is needed for the sum. We demonstrate that such a value could be reached with planned observations of large scale structure by analysing artificial mock data for a EUCLID-like survey.

Extracting Majorana properties from strong bounds on neutrinoless double beta decay

“…distribution of m ee from both neutrino oscillation measurements [44] and cosmological constraint [40]. The cosmological data predicts the probability for NH versus IH to be around 2:1.…”

“…Since the two mass squares ∆m 2 a and ∆m 2 s have been measured, the cosmological data can also constrain the lightest mass m 1 [40]. In Fig.…”

“…In Fig. 2, we show the sampled Oscillation + CMB + EUCLID NH+IH NH IH Figure 2: The probability distribution function (PDF) of the 0ν2β decay effective mass m ee , sampled from the global fit [44] of the neutrino oscillation parameters (oscillation), and the constraint on m 1 from the Planck data (CMB) plus the prospective data from EUCLID-like survey (EUCLID) [40]. Both NH (long-dashed red line) and IH (short-dashed blue line) have been sampled.…”

Status of Neutrino Properties and Future Prospects—Cosmological and Astrophysical Constraints

“…Very recently, several authors investigated the possibility that such an approximation could fail reproducing the physical behavior of massive neutrinos when observed with the high sensitivity of future cosmological surveys [132,145,157,158]. In addition, the issue of whether future surveys could unravel the unknown hierarchy has been addressed by several groups [98,[158][159][160][161][162]. We refer the reader to the relevant papers for a thorough discussion of these issues.…”

Half-life expectations for neutrinoless double beta decay in standard and nonstandard scenarios

“…Figure 1 of Ref. [7] shows the probability distributions of the smallest neutrino mass for both mass orderings, when current cosmology data are fitted (CMB, BAO and local measurements of the Hubble parameter). Integrating over those curves and taking the ratio of the integrals weighted by the prior probabilities for the orderings (assumed to be equal), gives the posterior probabilities for the orderings, namely NH : IH = 2 : 1.…”