Inside the proton - HERA

HERA is another circular accelerator, like LEP butsmaller. Instead of colliding electrons and positrons, HERA uses the electronas a probe to look inside the much larger proton. The two detectors used atHERA are similar to those at LEP, and RAL scientists are involved with both.

It has been known since the late 1960s that protons and neutrons are notfundamental particles but are made from smaller entities: 'the quarks'. At thesimplest level a proton or a neutron is made up of three quarks but experiments reveal a much more complicated picture. The strong nuclear force which gluesthe three quarks together also gives rise to a swarming sea of other quarksflickering in and out of existence. This is what HERA's electrons study.