Dark Matter, WIMPS, and NASA's Alpha Magnetic Spectrometer Data

cylonlover writes "Recently the media has been saturated with overly-hyped reports that NASA's Alpha Magnetic Spectrometer may have detected dark matter. These claims may have some justification if the word 'may' is shouted, but they rest on a number of really major assumptions and guesses, some of which are on weak and shifting soil. So just what was seen in the experiment, and what are the possible explanations?"

Comments

Never trust...

[Anonymous Coward]

Never trust an Alpha Magnetic Spectrometer with important discoveries. I wouldn't even start considering it useful until it hit Beta.

Re:Blog Spam

[Black Parrot]

Usually we don't discuss these things until they appear on the Bad Astronomy blog.

more antimatter near Earth than expected

[peter303]

The PAMELA probe sees antiprotons in the Van Alen belts. The ISS-AMS sees more positrons than expected. Whatever the ultimate expanation, its interesting to see these surpluses.

The amounts are so small, dozens of protons for PAMELA and hundreds of thousands of positrons for AMS, that they would not be noticeable in human life.

Of Particular Significance

[mbone]

People who are interested in these matters should follow Matt Strassler's science blog, Of Particular Significance, which covered these same points back at the beginning of April, and then again two weeks later.

Re:why no dark matter black holes?

[habig]

If dark matter only reacts to gravity, why doesnt collapse into hgh density clumps over the eons? Ordinary matter is stopped from doing this by the electronmagnetic repulsion of atoms for masses less than a few hundred Jupiters and by hadronic stong force for less than couple Suns.

It does, we call those clumps "galaxies".

Note that the virtue of interacting only a little bit with normal stuff (via only the weak and gravitational forces, not gravity alone) actually makes it harder for dark matter to pack in tightly. Why? it's hard for a distribution of dark matter particles to shed kinetic energy and settle down more deeply into the gravitational potential well. Ordinary matter has all sorts of electromagnetic ways to shed energy and cool down.

If this thermal argument is opaque, imagine one WIMP, with some kinetic energy. It falls down towards the center of a galaxy. But, it seldom interacts to lose any energy, so zooms right back out the other side. Sort of a tiny, frictionless pendulum with a galaxy sized amplitude.

Improperly worded summary

[AchilleTalon]

From the summary: "... reports that NASA's Alpha Magnetic Spectrometer ..."

AMS isn't a NASA experiment, it is an international collaboration and NASA is only one among many other collaborators. Source: http://www.ams02.org/partners/participating-institutions/

I believe this summary is badly worded letting people think the AMS experiment is even a NASA initiative while it isn't neither. It is a CERN experiment that is taking advantage of the ISS and hence the NASA collaboration. Even other space agencies have contributed in this experiment.