Neutrino08 Day 3c

Kayser then moved on to nuclear matrix elements for $0\nu \beta \beta$, for example 76Ge, whose element lies somewhere between 2 and 6, a rather large uncertainty. He then discussed dipole moments and the present Borexino bound of $5.4\times 10^{11}{\mu }_B$.

G. Drexlin spoke about direct mass measurements at KATRIN and MARE. In cosmology, KATRIN could shift the allowed region for the equation of state $w$ away from $w=-1$ for Dark Energy to quintessence. His 2d plot of $w$ vs $\sum m_i$ is of course restricted to a line by Carl's normal hierarchy mass values, so a determination of $w$ is definitely on the cards. KATRIN hopes to begin long term data taking in 2011. Sensitivity is at $m\left(\nu \right)$ below 200meV at 90% confidence. Drexlin spent the second half of the talk focusing on the big spectrometer and the structure of the windowless gaseous source. To obtain an injection rate down to $\pm 0.1\%$, the flow out must be reduced by an amazing $10^{14}$ and the column density needs to get to $\pm 0.1\%$.

MARE starts phase I soon, in which they hope to improve sensitivity by a factor of 10 for their 187Re $\beta$ emitter and AgReO4 crystal pixel array detector. If this phase is successful, phase II would again improve sensitivity by a factor of 10, requiring much R&D.