Sentence:  There were also particles no one had predicted that just appeared. Five of them [..., i]n order of increasing modernity, ... are the neutrino, the pi meson, the antiproton, the <WSD>quark</WSD> and the Higgs boson. 
Meaning of the word marked with <WSD> tags:  In the Standard Model, an elementary subatomic particle that forms matter. They combine to form hadrons, such as protons and neutrons.