Re: Clue to Dark Matter Mystery

In article <[EMAIL PROTECTED]>,
stmx3  <[EMAIL PROTECTED]> wrote:

>Starblade Darksquall wrote:
 
>>>Their abstract:
>>>
>>>"We discuss the possibility that the recent detection of 511 keV 
>>>gamma-rays from the galactic bulge, as observed by INTEGRAL, is a 
>>>consequence of low mass (~MeV) particle dark matter annihilations. We 
>>>discuss the type of halo profile favored by the observations as well as 
>>>the size of the annihilation cross section needed to account for the 
>>>signal. We find that such a scenario is consistent with the observed 
>>>dark matter relic density and other constraints from astrophysics and 
>>>particle physics."

>> What these physicists seem to be implying is that dark matter is
>> simply a field of electrons and/or positrons.
 
They'd better not be implying that - just think about it!

You can't have vast quantities of electrons and/or positrons playing
the role of dark matter.  If you had *just* electrons or just positrons, 
their electric charge would have hurled them out of the galaxy a long
time ago.  And if you had *both*, they'd annihilate each other like
hell, since there'd be need to be so many - remember, dark matter 
accounts for more mass than visible matter, and electrons are 1800 
times lighter than protons.  So, we wouldn't just see some feeble 
511 keV glow: we'd see the whole galaxy exploding dramatically!

>They propose ~1 - 100 MeV darkmatter annihilation as the candidate to 
>produce 511 KeV photons.

That makes more sense.  But it sounds a little tough to exclude
alternate explanations, doesn't it?