I believe the difference is in the overall angular momentum. (You can think that the quarks are somehow arranged differently inside the particle.) You can loo

I believe the difference is in the overall angular momentum. (You can think that the quarks are somehow arranged differently inside the particle.) You can look at the particle data group's entries[1,2] for \Xi_b^0, which has J=1/2 and for \Xi_b^*, which has J=3/2. [1]http://pdglive.lbl.gov/Rsummary.brl?nodein=S060&exp=Y&sub=Yr&return=BXXX045 http://pdglive.lbl.gov/Rsummary.brl?nodein=S060&exp=Y&#3... [2]http://pdglive.lbl.gov/Rsummary.brl?nodein=S062&sub=&return=SumB http://pdglive.lbl.gov/Rsummary.brl?nodein=S062&sub=&#38... -edit- Also, found a line on wikipedia discussing the notation of baryons that confirms this: >Baryons in total angular momentum J = 3⁄2 configuration that have the same symbols as their J = 1⁄2 counterparts are denoted by an asterisk.