Neutrino Anti-Particle and Flavor Mass Hierarchy

[aztronut]

"Other experiments to test whether the neutrino is, weirdly, its own antiparticle may be feasible only if the hierarchy is inverted."

Why?

http://news.sciencemag.org/physics/2015/08/u-s-neutrino-experiments-first-result-tantalizes?utm_campaign=email-news-latest&utm_src=email

 

[mfb]

As far as I know, the minimal effective mass in neutrinoless double beta decays would be higher, see e.g. this article and the plots shown there.
@Orodruin will know that in more detail.

 

[Orodruin]

As far as I know, the minimal effective mass in neutrinoless double beta decays would be higher,

The point is that, given the current knowledge on the neutrino mass squared differences and mixing angles, there is a minimal possible value for the effective neutrino mass to which neutrinoless double beta decay experiments are sensitive if the neutrino mass ordering is inverted. If the mass ordering is normal, then there is always a possibility of having a cancellation (for a range of absolute neutrino masses) and thus no lower bound on the neutrinoless double beta decay rate.

The plots shown in the paper linked by mfb summarises this - with the lowest neutrino mass on the x-axis and the effective neutrino mass to which neutrinoless double beta decay experiments are sensitive on the y-axis:

(The IS is the inverted and the NS the normal ordering and the bands show the possible values based on current knowledge (or rather, what was current in 2012 - bounds have improved but the basic idea is the same))
The cosmological limit on $m_{min}$ comes from cosmology placing a bound on the sum of the neutrino masses, while the current bound is the (2012) bound on the effective neutrino mass relevant for neutrinoless double beta decay experiments at the time.