Subject: what is the experiment that leads to the discovery of quark?

(Hi! I sent you some questions before, but your reply Email said there were 
some simlilar questions. However, after I looked through those 
informations, I still have some specific question. That will be great 
if anyone can answer the following questions)
How does the experiment of the isolation of electron from an atom leads to 
the discovery of quarks?
What does the mass unit "eV" stands for?
Thank you to take your time!!

Re: what is the experiment that leads to the discovery of quark?