
#1
Jan1014, 06:39 AM

P: 24

I'm doing a little research on quarks on stumbled upon the baryon number. Wikipedia says that the notion predates the quark model. I have no clue why particle physicists were motivated to introduce it before flavour quantum numbers came to the scene.
So... What's the (historical) origin of baryon number? 



#2
Jan1014, 07:04 AM

Mentor
P: 15,625

Baryon number as a conserved quantity was to explain why you didn't see decays like p > e+ pi0.




#3
Jan1014, 07:05 AM

Sci Advisor
HW Helper
P: 1,937

In all known experiments so far, the number of baryons is conserved, and the notion goes back to the early beta decay experiments. This has nothing to do with quarks, but most quark models incorporate baryon number conservation. Some extended symmetry theories predict proton decay into leptons and mesons which would violate baryon number conservation.




#4
Jan1014, 07:09 AM

Homework
Sci Advisor
HW Helper
Thanks ∞
PF Gold
P: 11,095

The origin of baryon number
Well baryons were observed before the quark model and their behaviors documented.
One of the things researchers try is to sort things into groups and see what makes sense. Doesn't it seem reasonable to count matter as +1 and antimatter as 1? Once you've done that for nucleons, and looked at what happens to the numbers in various nuclear reactions, what would be a sensible number to give mesons? 



#5
Jan1014, 09:05 AM

Sci Advisor
PF Gold
P: 4,863

Where the quark model helps explain baryon number is motivating why baryon number of mesons is zero (quark/antiquark pair). Baryon number could be replaced with quark number, but everyone was used to baryon number.




#6
Jan1014, 10:27 AM

P: 24

Thanks everyone for your input! Got the type of answers I wanted.



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