Dark matter candidates, what chances would you give them?

SpaceTiger

An excellent link, thank you turbo-1. Unfortunately, you seem to have seriously misinterpreted the paper. Skip ahead to section 3.4, titled "Current status of direct searches":

In other words, the majority of WIMP candidates from theories of supersymmetry are undetectable by these experiments.

turbo

Maybe I wasn't clear. Direct detection of LSP may be some time away, but given the flux density of this proposed DM candidate, should we not have seen (serendipitously) the spontaneous production of the decay products of the LSP in at least some accelerator detectors by now? If the decay products and the energy released falls in the mass range of the LSP, that would be a very good indirect detection, and help nail down the sensitivities needed for direct detection. If the LSP is indeed weakly interactive, there is no way to exclude those particles from the detector chambers. Certainly the people monitoring that equipment have an idea what such a serendipitous observation should look like, including a range of energies that might be released.

We shouldn't have to concentrate on trying to make these WIMPS if they are as plentiful as expected. We should simply start watching for pair-decay. If the Standard Model is correct, the Universe has already produced all the LSPs we need and we can use existing detectors to watch for the decay of the LSPs, which will appear to us as if the decay products simply popped into existence with an accompanying realease of energy.

EL

Well, the LSP cannot decay, but I suppose what you mean is annihilation products produced by collisions between LSP's.
Think of this: Interactions between WIMPs and ordinary matter in the direct detection experiments are not frequent enough to be detected. The density of ordinary matter in a detector is way higher than the expected local WIMP density. Which event should occur more often: WIMPs interacting with the detector, or WIMPs interacting with WIMPs? What conclusion can be drawn?

turbo

From what I have read (and I will qualify this by saying that I have a physical revulsion to tacking over a hundred new dimensionless parameters on the standard model to extend it with MSSM, so I have not been a real fan of any brand of SUSY) LSPs (in pairs) can decay in pairs into lighter baryonic particles plus gamma rays. Given the predicted flux of LSPs, shouldn't we have observed at least one such decay by now? If not, why not? Indirect detections of LSP seem a whole lot more likely than direct detections.

EL

When two particles interact and annihilate into something new, we usually don't call it a "decay". "Decay" is something a single particle does. That's why I objected to your use of the word. But anyway...
I'll repeat:

turbo

Thanks for the clarification on the use of decay products vs aniihilation products. Do you know of a paper that lays out an estimate for the WIMP annihilation rate (perhaps as a percentage of total flux)? I have not been able to find one.

SpaceTiger

Here's an estimate based on an excess of microwave emission near the center of the galaxy:

Finkbeiner 2004

turbo

Thank you for the link, ST. I have done a little searching to determine detector volumes and found the dimensions of a "drift chamber" that is 26cm radius with a 16cm radis core through which the beam runs, and a chamber length of 2m. The detector has a radial cross section of about 1318cm² and a total volume of 263,600 cm³.

Assuming a flux of 6x10⁴ WIMPs /s/cm2 (from the paper I linked previously) and a longitudinal detector cross/section of 5200cm², there should be 3.12x10⁸ WIMPS traversing the detector every second. Shouldn't we have seen at least one WIMP annihilation event in all the years particle accelerators/colliders have been in operation?

Chronos

I assume you have some statistics in mind.