Re: [Phys-l] Help with particle physics preparations...

[Jack Uretsky <jlu@hep.anl.gov>]

On Thu, 12 Apr 2007, Jeff Loats wrote (in part):

> In my modern physics class this term we have rearranged (and eliminated)
> topics a bit, so I find myself with a few extra days to play with. With
> it we are delving into particle physics and the standard model. This is
> not a topic I ever studied in depth as a student, so I am learning a LOT!
>
> In preparation for our discussion of quarks I am reminded of a question
> that has haunted me since I first learned about quarks. I figured the
> good folks at Phys-l would be willing to help out. Here it is
>
> The strange, charm, top and bottom quarks all have their own quantum
> numbers, while the up and down quark do not.

Why do you say that "up" and "down" do not?  Down-ness, and up-ness 
(and strangeness) are perfectly good quantum numbers that are conserved in 
the strong interactions.  This conservation is reflected in "isotopic-spin"
(and strangeness) conservation in the strong interactions.

Weak interactions, of course, break this conservation rule, as, I take it, 
you understand.

				Regards,
					Jack

>

--
"Trust me.  I have a lot of experience at this."
		General Custer's unremembered message to his men,
		just before leading them into the Little Big Horn Valley