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Parity of a system composed by 2 particles 
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#1
Jun2714, 04:38 PM

P: 70

I have read that for a system of 2 particles, the total parity is given by:
[itex]P=P_1 P_2 (1)^L[/itex] where  [itex] P_1, P_2[/itex]= insisec parity of particle 1, 2  L= relative angular moment what's the meaning of "relative angular moment"? Do I have to add the [itex]l[/itex] numbers of the two particles? And what if I have 3 particles? Many thanks 


#2
Jun2814, 08:24 AM

P: 324

L is the "relative" angular momentum, which means that is the momentum of the system of the two particles "orbiting around each other" if considered as a whole.
If you have three particles you need to first study two of them and obtain the corresponding system and then compose this last system with the third particle. 


#3
Jun2814, 08:51 AM

P: 70




#4
Jun2814, 09:12 AM

P: 324

Parity of a system composed by 2 particles
The nomenclature is Swave (L=0), Pwave (L=1), Dwave (L=2), etc.



#5
Jun2814, 09:23 AM

P: 70

I imagined it... but I haven't understood what is a "Swave". The fist  and last  time that I have heard it, the prof said "The deuterium captures the pion in Swave". Could you explain me briefly in which way "Swave" and L (relative angular moment) are related? Does "Swave" imply that the relative angular moment is 0?



#6
Jun2814, 09:26 AM

P: 324

Yes, it's just a way of saying it. If you say that a system is in S/D/Pwave you are simply saying that the relative angular momentum of this system is L=0/1/2, nothing more. It's a nomenclature borrowed from atomic physics.



#7
Jun2814, 09:37 AM

P: 70

Oh, so many thanks!! :)
And so, if the prof hadn't said that the pion is captured in Swave, I wouldn't be able to say that L=0, isn't it? 


#8
Jun2814, 09:42 AM

P: 324

Generally speaking yes. In some cases the relative angular momentum is constrained by total angular momentum and parity conservation.
However, most of the times, a certain process can happen with different L. The distinction between the different cases must be made experimentally. 


#9
Jun2814, 09:50 AM

P: 70

Thanks again!



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