Scattering theory is a branch of physics and especially of quantum mechanics whose aim is the study of scattering events. A scattering event happens when two free particles collide with each other. This collision can be either elastic (the internal quantum states of the particles are not changed) or inelastic (the internal quantum states of the particles are changed). Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. ... Fig. ... In particle physics, scattering is a class of phenomena by which particles are deflected by collisions with other particles. ... Particles erupt from the collision point of two relativistic (100 GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Physical collision Dynamics Deflection happens when an object hits a plane surface In physics, collision means the action of bodies striking or coming together (touching). ... There are separate articles about elasticity in economics, and about British rubber bands. ... Inelastic collision is a collision in which some of the kinetic energy of the colliding bodies is converted into internal energy in one body so that kinetic energy is not conserved. ...

From the experimental viewpoint the observable quantity is the cross section. From the theoretical viewpoint the key quantity is the S matrix. In scattering, a differential cross section is defined by the probability to observe a scattered particle in a given quantum state per solid angle unit (i. ... The S-matrix is the matrix in quantum mechanics or quantum field theory that relates the final state in the infinite future and the initial state in the infinite past. ...

There is also an abstract, mathematical theory going under the same name, in Hilbert space theory. In mathematics, a Hilbert space is an inner product space that is complete with respect to the norm defined by the inner product. ...

Though scattering theory is taught in quantum mechanics, the same methods are applicable to such fields as acoustics and classical electromagnetism, with appropriate changes in notation. For example, engineers tend to use a "reaction integral" in place of an inner product. Acoustics is a branch of physics and is the study of sound, mechanical waves in gases, liquids, and solids. ... Quadrupole (four-pole) magnet, focus particle beams in a particle accelerator. ... In mathematics, an inner product space is a vector space with additional structure, an inner product, scalar product or dot product, which allows us to introduce geometrical notions such as angles and lengths of vectors. ...

External links

Lectures of the European school on theoretical methods for electron and positron induced chemistry, Prague, Feb. 2005