Question: what are b-jets

Andy Buckley answered on 8 Mar 2019:

Jets are collections of particles (and hence energy) all going in the same sort of direction in a particle detector. Oddly, when we hit protons together, what comes out isn’t just a random splash of stuff, but these really structured energy flows — what’s cool is that that’s a *prediction* of quantum mechanics.

b-jets are jets which contain b-hadrons: particles that contain bottom quarks. Bottom quarks are from the third and heaviest “generation” of quarks, which we suspect could be connected to new physics that we’ve not yet seen evidence for. They are also experimentally quite handy, because the b-quark decays slowly and maybe we can see evidence that it “flew” for a little distance (a millimeter or so) in our detector and hence work out that the jet is “b-flavoured”… and maybe use that hint to discover that new physics!