Wednesday, March 16, 2011

MINOS at Neutel 11

According to the blog coverage, MINOS reported the new neutrino parameters, and confirmed the tension between the neutrino and antineutrino results, but we will have to wait for an update on the antineutrino parameters.

If we assume two Koide triplets at the same scale, around $0.1$ $\textrm{eV}$, then the new accurate $\nu$ parameter $\Delta m^2 =$ $2.32$ $\textrm{eV}^{2}$ does appear to reduce the first antineutrino mass (which was estimated at $0.00117$ $\textrm{eV}$) to slightly less than the CMB temperature. On the other hand, the experimental results at this point rely on a two generation analysis. We will have to take another look at all the parameters.

Other updates from the Neutel 11 blog include a link to all presentations, and stronger evidence for a positive $\theta_{13}$, now estimated at $\textrm{sin}^2 \theta_{13}$ $= -0.021 \pm 0.009$. Recall that this parameter complicates the simple tribimaximal mixing picture, where we had $\theta_{13} = 0$. With triality, the introduction of a small third mixing parameter would make neutrino mixing look a lot more like the three parameter quark mixing matrix.

This new $\theta_{13}$ value corresponds to an angle (in radians) of roughly $- \pi /24$. Stay tuned, because the $\theta_{13}$ results will probably be updated later today.

Update: In this 2010 review the authors point out that the low value for the neutrino $\Delta m^2$ is just for the so called inverted hierarchy, whereas the neutrino masses fit a normal hierarchy. In this case, the value of $2.46 \times 10^{-3}$ $\textrm{eV}^2$ is more accurate. This maintains the CMB fit to the mirror neutrino masses. Oh dear, I keep interchanging the terms antineutrino and mirror neutrino, but what can I do? The first term is ingrained in our vocabulary, and yet it is clearly the wrong term.

1 comment:

  1. Of course there are already overly complicated theoretical analyses of mixing with a non zero $\theta_{13}$. This link offers the interesting suggestion that $\textrm{sin} \theta_{13}$ should be given by $\lambda / \sqrt{2}$, where $\lambda$ is the Cabibbo parameter from the CKM matrix.

    So, at least we are not the only crazy people to take quark lepton complementarity seriously. Recall that $\sqrt{2}$ is one of the simple tribimaximal parameters.


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