Thursday, 29 August 2013

SUSY 2013 Live Blog: Day Four

We return to a full day of talks at SUSY.  The morning's plenary sessions open with a talk on dark matter and another on cosmology.

9:00am: Laura Baudis, "Direct WIMP searches: an update"

Always worth remembering that current experiments are probing WIMP-nuclei cross sections of strength expected if they are mediated by the Higgs.  This is the last obvious avenue for WIMP-visible scattering, with Z couplings were ruled out many years ago.

Cryonic experiments: SuperCDMS currently running, detector mass 9kg; proposals for next-gen detector at 200kg!  Other similar machines: CRESST @ 5kg, EDELWEISS currently at 12kg, upgrading to 30kg this autumn.

3 events at CDMS-Si currently being checked by CDMS-lite, analysis ongoing; results ...?

Note Texono, small experiment but very low threshold of 500 eV; obviously very sensitive in low mass region.

Noble liquid detectors divided into two groups; single phase (e.g. XMASS, CLEAN, DEAP) and double phase (e.g. XENON100, LUX, PandaX, ArDM, DarkSide).  Former use liquid only, latter liquid and gas phase.  The latter would seem, too naive little me, to offer better background rejection thanks to the double nature of the signal; but the former class of experiments seem to be much bigger and currently under production.  Future detectors include DARWIN, planned to have 20 tonnes of LXe/LAr.

Room temperature scintillators include the infamous DAMA, also KIMS and ANAIS.  ANAIS is in construction; KIMS does not confirm DAMA.

Bubble chambers include SIMPLE, COUPP and PICASSO.  Plans for a 500 ton COUPP upgrade.

Finally, active R&D on directional detectors that would offer another important tool for background rejection.  This is hard, hence why it hasn't been done yet.

Best part of this talk is this image:
This shows the evolution of limits with time.  It's an exponential plot, so the limits get better by about a factor of ten every two years.

Q&A: skepticism on the non-CDMS signals due to thresholds, not much to say here.

9:35am: Benjamin Wandelt, "Fundamental Physics from Cosmology inthe (Post-)Planck Era"

Power of CMB is that the transfer function from the initial curvature perturbations is very very nearly linear.  This in turn is because the perturbation amplitude at that early time are very small.

Planck results in many ways similar to LHC results.  Everything is very good, very precise and very much in line with the simplest models.  No good evidence for new physics.  All the reasons we think the simple models are flawed fail in the face of this data.

Apparently the next space CMB observatory, emphasising polarisation data, is called PRISM.  Would detect all galactic clusters in the Hubble volume, and could even resolve the neutrino hierarchy.  This is actually promising; I thought that there was little more to be gained from the CMB after Planck, but it looks like the possible information in the polarisation data would actually be another significant step.

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