Thursday, August 17, 2017

Combined Direct Dark Matter Detection Experiment Exclusions

A new pre-print combines the exclusion areas of the leading direct dark matter detection experiments which leads to a stronger combined exclusion (it does not integrate particle collider exclusions, however).

The bottom line is that the combined exclusion clearly rules out any weakly interacting massive particle (WIMP) with a weak interaction coupling even close to that of a neutrino, in the WIMP mass range from about 10 GeV to 1000 GeV. The exclusion is strongest in the WIMP mass vicinity of 20 GeV to 30 GeV, where it is at least twenty times as weak as at the edge of this exclusion range.

The relative strength of the exclusions doesn't really have much of anything to do with the data actually gathered which has come up with no reliably observed events ever (a handful of false positives have been ruled out by non-replication of those findings by other experiments sensitive to the purported mass and cross-section of interaction of the false positive results). They are simply a product of the sensitivity of the experimental setup to various kinds of hypothetical WIMPS.

The sensitivity of these experiments deteriorates greatly for WIMP masses below 10 GeV. And, a major theoretical bound on the methodology used by these experiments, the lower "neutrino bound" when background static from interactions cased by neutrinos makes it difficult or impossible to distinguish dark matter interactions from neutrino interactions is only about two orders of magnitude away.

At the higher mass scale, there aren't any real theoretical barriers to detecting heavier WIMPS, the the sensitivity of the experiments declines much more gradually in ruling out heavier WIMP candidates, but the experiments are simply not tuned to look for heavier candidates.

This result directly challenges a huge part of the supersymmetry parameter space, because SUSY theories, generically, give rise to dark matter candidates in the 10 GeV to 1000 GeV mass range that should have cross-sections of interaction as a result of the weak force strong enough to be detected by these experiments.

Of course, this limits of the WIMP mass range that is excluded doesn't necessarily mean that spending a lot to probe potential WIMP masses of more than 1000 GeV or a bit less than 10 GeV make much sense. 

If dark matter is truly collisionless (i.e. lacks any electromagnetic, strong force or weak force interactions), no direct dark matter detection experiment will ever find it. 

And, multiple lines of independent astronomy based data strongly disfavors Cold Dark Matter theories generally, which certainly includes all WIMP candidates in the 1 MeV to 10 GeV and in the greater than 1000 GeV range.

In other dark matters news, observations of dwarf galaxies that appear to have a dark matter to ordinary matter mass ratio on the order of 1000-1 by the HESS telescopes have not detected any signatures of dark matter particle annihilation, which imposes significant constraints on the dark matter particle parameter space. The exclusion is particularly strong in the 400 GeV to 1000 GeV WIMP mass range.

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