Wednesday, 18 December 2013

Searching in the dust bin.

I often get annoyed about the amount of perfectly good data which is thrown away. It is like a lot of things in life you only realize the value when you can no longer get to it. I remembered reading a story a few years ago about how some  evidence of very strange matter was found in the most unusual place. I've dug up a reference and found a link to other data. Is this what Dark Matter is?

from Strange Quark Matter and Compact Stars

3.5 Unusual Seismographic Events
As already described in section 3.4, De R´ujula and Glashow speculated about the presence of lumps of stable strange matter, also referred to as strange nuggets or nuclearites, in the cosmic radiation [131].
The seismic signals caused by these nuclearites passing through the Earth would be very different from the seismic signals caused by an earthquake or a nuclear explosion [89, 131]. This follows from the rate of seismic energy produced by strange nuggets given by dE/dt = fσρv3, where σ is the nugget cross section, ρ the nominal Earth density, v the nugget speed, and f the fraction of nugget energy loss that results in seismic waves rather than other dissipation such as heat or breaking rock [90]. Underground nuclear explosions have f ≃ 0.01, chemical explosions f ≃ 0.02. In contrast to this, strange nuggets with a mass of several tons (size of 10−3 cm) passing through the Earth would imply that f ≃ 0.05.
Anderson et al. [90] looked at more than a million records collected by the US Geological Survey between 1990 and 1993 that were not associated with traditional seismic disturbances such as earthquakes. The seismic signature would be caused by the large ratio of the nuclearites speed, estimated to be around 400 km/s. Strange nuggets might thus pass through the Earth at 40 times the speed of seismic waves.
Most interestingly, Anderson et al. were able to single out two seismic events exhibiting this behavior.
One event occurred on 22 October 1993, the other event occurred on 24 November 1993. In the first case, an unknown object seems to have entered the Earth off Antarctica and left it south of India. It was recorded at seven monitoring stations in India, Australia, Bolivia and Turkey. In the second case, an object seems to have entered in the South Pacific, south of Australia, and left the Earth 16.8 seconds later in the Ross Ice Shelf near the South Pole. This event was recorded at nine monitoring stations in Australia and Bolivia. The chord length between the entry and exit points of the 24 November 1993 event is 4204 km so that the duration measured for this event, if caused by the passage of an object through the Earth, would imply a velocity for the hypothetical object of 250 km/s. The interpretation of the data as being caused by strange nuggets penetrating the Earth is backed by a Monte Carlo study that was used to identify the extent to which nuclearites could be detected by seismographic stations[90, 164]. The study showed that one would expect to detect as many as 25 4-ton nuclearite events per year if 4 ton strange nugget were to saturate the halo dark matter density. If 10% of the dark matter density were distributed in strange nuggets over the mass range from 0.25 to 100 tons one would expect about an event per year. Detection of a nuclearite would require at least six station sites to fix its impact time, location and velocity, and seismic detection of signals by at least seven stations is required in order to separate strange nuggets events from random spurious coincidences.


No comments:

Post a Comment