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Are there positrons in a cosmic wave that are not produced as secondaries?


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#1 alexander

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Posted 14 May 2004 - 08:39 PM

Positrons are positively charged electrons that are unique among cosmic rays because they are the lightest charged leptons. Because of their low massiveness, high-energy positrons undergo interactions with the ISM which result in severe energy losses at high energies. The origin of positrons can not yet to be established. Positrons are a lot harder to observe than antiprotons because of the high flux of protons (about 1000 times higher than that of a antiproton). Consequently, all observations to date have suffered from the risk of subtracting significant background.
The positron spectral index below 15 GeV is found to be about -3.1: this value is what you would expect for secondary production without invoking rigidity dependent storage times or radiative energy losses expected at these energies. The spectrum should be steepening in this region but scientists found out that they are actually flattening.
Are there positrons in a cosmic wave that are not produced as secondaries, and if they are indeed all secondary particles, at what point do the radiative losses become important?

#2 alexander

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Posted 14 May 2004 - 08:40 PM

Oh another thing that i was thinking about...
What will happen if you aim a positron beam at a beam of electrons?
If positrons are positive and electrons are negative would you get a huge heating effect due to a very high friction between the 2colliding particles that travel at a spped of light(or close there anyways), and as a byproduct get a set of "molecules" consisteing of one electron and one positrone?
If friction is a force that wil create heat in this case, and force has to have mass and acceleration
F = m a
...

#3 sundog

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Posted 15 May 2004 - 09:56 AM

Alex, you ask - "What will happen if you aim a positron beam at a beam of electrons?"


Well, I don't know much on this subject, but I found this page -

http://www.crump.ucl...imagerecon.html

They are taking about "Positron emission and image reconstruction" for PET (Positron Emission Tomography) scanning. (used in cardiology, neurology and oncology)

Here it says-
"When a positron comes in contact with an electron, the two particles annihilate turning the mass of the two particles into two 511-keV gamma-rays that are emitted at 180-degree to each other."

I hope this helps.


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#4 alexander

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Posted 17 May 2004 - 07:00 AM

Sorry, i was out of town for the weekend so i wasn't able to reply, but thanx for the link, it kind of makes sense, but is kind of strange at the same time...
Thanks.

#5 sundog

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Posted 17 May 2004 - 08:47 AM

Alex,

I'm glad I could help.

quote - "it kind of makes sense, but is kind of strange at the same time..."

I know what you mean. For me, getting the concept of some things in physics, is like building sandcastles in the rain. Posted Image



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#6 alexander

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Posted 17 May 2004 - 06:19 PM

I know, especially the theoretical ones or things conserning that have extreme factors (ex: something to do with speed of light, very cold temperatures, or very hot temperatures, things that are too small to see, things that are so big that or ones that you can only imagine or things that don't exist but are still talked about in books...)