Three strikes for dark matter theory this week, and it's only Tuesday.

[Michael]

Dark matter theory steps in deap-3600 Canadian do-do

Search for dark matter with a 231-day exposure of liquid argon...

DEAP-3600 is a single-phase liquid argon (LAr) direct-detection dark matter experiment, operating 2 km underground at SNOLAB (Sudbury, Canada). The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel. This paper reports on the analysis of a 758 tonne\cdot day exposure taken over a period of 231 live-days during the first year of operation. No candidate signal events are observed in the WIMP-search region of interest,....

Translation:

There'SNO dark matter to be seen at SNOLAB. Who would have guessed? Oh ya, me.

Strike one.

Bubble, bubble, more toil and trouble for dark matter theory in Canada:

Dark Matter Search Results from the Complete Exposure of the...

Final results are reported from operation of the PICO-60 C3F8 dark matter detector, a bubble chamber filled with 52 kg of C3F8 located in the SNOLAB underground laboratory. The chamber was operated at thermodynamic thresholds as low as 1.2 keV without loss of stability. A new blind 1404-kg-day exposure at 2.45 keV threshold was acquired with approximately the same expected total background rate as the previous 1167-kg-day exposure at 3.3 keV. This increased exposure is enabled in part by a new optical tracking analysis to better identify events near detector walls, permitting a larger fiducial volume. These results set the most stringent direct-detection constraint to date on the WIMP-proton spin-dependent cross section at 2.5 × 10−41 cm2 for a 25 GeV WIMP, and improve on previous PICO results for 3-5 GeV WIMPs by an order of magnitude.

Translation (to Spanish): "PiCO de nada" yet again. I love how the null results of dark matter experiments are never presented as a direct or actual "failure" to detect dark matter. The results are always a presented as a successful "constraint" of dark matter. Spin, spin, spin,....lather, rinse, repeat. "Ya we didn't find it this time but give us more money to spend on our next experiment so we can try, try again. We'll constrain the heck out of it next time."

Strike two.

But wait, there's more:

Apparently dark matter isn't just shy around Canadians. XENON1T was a strikeout in Italy too. DM is evidently 0 for 3 this week and it's only Tuesday.

Another tough week for dark matter proponents.

Constraining the spin-dependent WIMP-nucleon cross sections with XENON1T

We report the first experimental results on spin-dependent elastic WIMP-nucleon scattering from the XENON1T dark matter search experiment. The analysis uses the full tonne-year exposure of XENON1T to constrain the spin-dependent proton-only and neutron-only cases. No significant signal excess is observed, and a profile likelihood ratio analysis is used to set exclusion limits on the WIMP-nucleon interactions. This includes the most stringent constraint to date on the WIMP-neutron cross section, with a minimum of 6.3×10−42 cm2 at 30 GeV/c2 and 90% confidence level. The results are compared with those from collider searches and used to exclude new parameter space in an isoscalar theory with an axial-vector mediator.

Another major failure this week to find even a hint of DM, but hey, look on the bright side. It's the best 'constraint" of DM ever!

Spin, spin, spin....lather, rinse, repeat.

Between the recent quasar studies that show major problems with "dark energy" predictions at larger redshifts and three major null results on dark matter in the past two days, it's safe to say that it's been a pretty horrific month so far for the LCDM model of cosmology. If the inflation theory takes a hit over the next few weeks, it could be a perfect trifecta storm for the LCMD model.