occasional meanderings in physics' brave new world

Name:
Location: New Zealand

Marni D. Sheppeard

## Friday, May 30, 2008

### Neutrino08 Day 5a

Sadoulet started Friday morning with Dark Matter detection via cosmology, noble liquids, phonon mediated detectors and possibly DAMA. He started with the statement that WIMPs are a generic consequence of new physics at the TeV scale. This was followed by a clear, brief overview of a BBN/WMAP figure for baryonic fraction of $\Omega_{b} = 0.047 \pm 0.006$. His focus was on direct detection of DM via elastic scattering, occurring via a nuclear recoil signal at an expected rate of one event per kg target every two months. Signatures include uniformity throughout the detector and galaxy correlation. The big challenge is freedom from backgrounds.

A noble liquid detector using Xenon or Argon (see XENON, ZEPLIN-II, DEAP, MiniCLEAN, WARP and ArDM) takes advantage of recent breakthroughs in electron extraction and in separation of electron and nuclear recoils. Plots for cross section (vs WIMP mass) exclusion were shown for these experiments and also for phonon mediated experiments such as CDMS. A new CDMS result which improves the previous best XENON bound has been submitted. CDMS should run until December this year. We should reach $10^{-44} \textrm{cm}^{2}$ per nucleon by 2009 and he thinks $10^{-47}$ presents a considerable challenge, but by this level one would have to question the WIMP hypothesis.

Regarding the DAMA claim, Sadoulet says he is convinced there is a modulation, but it cannot be a WIMP. Could it be an axion like particle? Or perhaps it is an effect related to the well known modulation of muon flux (due to seasonal atmospheric differences), which has the same phase.