By hard processes one usually means clearly perturbative processes with momentum or mass scales of the order of several tens of GeV.
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Semi-hard processes refers to QCD-processes where partons with transverse momenta of a few GeV are produced.
Hard scattering in particle physics refers to high-energy collisions between fundamental particles, such as protons or electrons. These collisions occur at high speeds and result in the production of new particles, providing insight into the fundamental building blocks of matter and the forces that govern their interactions.
Hard scattering is characterized by a large energy transfer between the colliding particles, resulting in the production of high-mass particles. Semi-hard scattering, on the other hand, involves a smaller energy transfer and typically produces lower-mass particles. The distinction between hard and semi-hard scattering is based on the magnitude of the energy transfer and the resulting particle production.
The main techniques used to study hard and semi-hard scattering include particle accelerators, such as the Large Hadron Collider (LHC), and detectors that can measure the properties of the produced particles. These techniques allow scientists to recreate high-energy collisions and observe the resulting particles, providing valuable information about the nature of matter and the fundamental forces that govern it.
Hard and semi-hard scattering play a crucial role in our understanding of the universe. By studying the properties of the particles produced in these collisions, scientists can test theories about the fundamental laws of nature and the structure of matter. This research helps us to better understand the origins of the universe, the evolution of matter, and the forces that govern the interactions of particles at the smallest scales.
While the study of hard and semi-hard scattering is primarily focused on fundamental research, it has also led to numerous practical applications. For example, the development of particle accelerators and detectors for studying these collisions has led to advancements in medical imaging technology and other industrial applications. Additionally, the knowledge gained from these studies can potentially lead to new technologies and innovations in fields such as energy and materials science.