Top Production .
Quarks are one type of matter particle.
Most of the matter we see around us is made from protons and neutrons, which are composed of quarks. Quarks also carry another type of charge called color charge , which we will discuss later. The most elusive quark, the top quark , was discovered in 1995 after its existence had been theorized for 20 years. Such charges had never been observed before. Quarks are never observed by themselves, and so initially these quarks were regarded as mathematical fiction.