It doesn't really work like that - you're still thinking billiard balls.
When two particles come close to each other there is a probability of their interaction depending on how close they come.
These are fundamental particles. a neutrino is a point - no size that we can determine. sampe goes for the quarks that make up nucleons
Neutinos have a very very small probability of interaction (this is what is meant by weakly interacting in Wimps).
Your typical neutrino "telescope" is a swimming pool in a mine deep underground totally lined with detectors.
http://en.wikipedia.org/wiki/Super-Kamiokande
Though some now use Ice at the South pole or are using the Sea off of France
With all the neutrinos flooding out of the sun you may get only a few hundred detections a day.