![]() In addition, the HERA data beautifully proves the unification of the electromagnetic and weak forces at large energies that is predicted by the Standard Model of particle physics. The HERA results confirmed perfectly the QCD theory, showing that the apparent structure of the proton becomes more dynamic with increasing energy at which the proton is probed. The reactions were measured by the two multi-purpose detectors H1 and ZEUS, each of them as big as a house.Īs one of the results, the two experiments measured the probability for several behaviours of these lepton-proton scattering processes and confronted the results with the best understanding of the proton substructure, a theory called quantum chromodynamics (QCD). The leptons penetrated deeply into the proton and were scattered off one of the proton's constituents via exchange of the weak or the electromagnetic force. Electrons and positrons are members of a particle species called leptons. For that purpose, a 6.3-kilometre long superconducting proton ring accelerated these particles close to the speed of light before smashing them together with electrons or positrons which were accelerated the other way around. The particle accelerator HERA (Hadron Electron Ring Accelerator) was designed to look deep inside the proton using electrons as probes in order to study proton structure in detail. However, the real picture of the proton is much more complicated: the proton is a sizzling soup where gluons can produce more gluons and can also split into pairs of quarks and antiquarks – the so-called sea quarks – all of them interacting again very quickly. Their composition of three quarks – two up and one down quark – which are held together by so-called gluons, carrier particles of the strong force, is well known since decades and taught in schools. Protons are in the core of each single atomic nucleus in the universe. "This legacy is not only important for the understanding of the very basic properties of matter but also an essential basis for experiments at proton colliders like the LHC at CERN in Geneva." "This publication is the culmination of HERA´s scientific programme and will be the most precise picture of the proton for a long time," says DESY research director Joachim Mnich.
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