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

[Calvin Kalman <Calvin.Kalman@concordia.ca>]

> 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. It is quite possible that
> there is no "why" here, since all of these conservation laws are
> empirically derived from what we observe in particle reactions and
> decays. Is there any other way to describe why this is?
>
> Thanks in advance for your help!
>
> Jeff

The strange, charm, top and bottom quarks do not have their own quantum
numbers.

There are three generations of quarks and leptons. The first 
corresponding to our everyday world comprises the u,d quarks and the 
electron and its neutrino. When the first element of the second 
generation- the muon was discovered I. I. Rabi asked "Who ordered 
that. The second generation comprises the c, s quarks and the muon 
and its neutrino. The third generation comprises the b, t quarks the 
tauon and its neutrino. Each generation is identical in quantum 
numbers to the proceeding one. Only the masses of the particles are 
different. Both Cosmology and the decay of the Z boson indicate that 
there are no more than three generations. Sacharov was the first to 
realize the reason why three generations are required. In the 
Standard model, you can only get violation of the combined Charge 
reflection C and Parity reflection - combined -> CP violation with at 
least three generations. This violation means that in the VERY early 
universe VERY occasionally one extra particle is created. during 
normal interactions of radiation and matter. Normally at that stage 
there are equal numbers of particles and antiparticles so that you 
would end up with a universe comprising only of radiation. Sacharov 
pointed out that only because of  CP violation do we have a universe 
containing matter.
--

Best wishes

                     Calvin


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_/   Calvin S. Kalman, P. Phys.     Phone: (514) 848-2424 xt 3284
_/  Professor,Department of Physics   Fax: (514) 848-2828
_/  Fellow, Science College
_/  Member, Centre for the Study of Learning and Performance
_/  Concordia University
_/  Montreal, QC  H4B 1R6          Calvin.Kalman@Concordia.ca
_/
_/ Also Adjunct Professor Department of Educational
_/ and Counseling Psychology, McGill University, Montreal, Quebec
_/                                
_/ homepage- http://physics.concordia.ca/faculty/kalman.html
_/
_/ Information on my book, "Successful Science and Engineering
_/ Teaching in Colleges and Universities"  Go to:
_/ 
http://www.josseybass.com/WileyCDA/WileyTitle/productCd-1933371161,descCd-description.html
_/
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