particle physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
, an oblique correction refers to a particular type of radiative correction to the
electroweak
In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very differe ...
sector of the Standard Model. Oblique corrections are defined in four- fermion scattering processes, ( + → + ) at the CERN
Large Electron–Positron Collider
The Large Electron–Positron Collider (LEP) was one of the largest particle accelerators ever constructed. It was built at CERN, a multi-national centre for research in nuclear and particle physics near Geneva, Switzerland.
LEP collided elect ...
. There are three classes of radiative corrections to these processes:
vacuum polarization
In quantum field theory, and specifically quantum electrodynamics, vacuum polarization describes a process in which a background electromagnetic field produces virtual electron–positron pairs that change the distribution of charges and curr ...
corrections, vertex corrections, and box corrections. The vacuum polarization corrections are referred to as oblique corrections, since they only affect the mixing and propagation of the gauge bosons and they do not depend on which type of fermions appear in the initial or final states. (The vertex and box corrections, which depend on the identity of the initial and final state fermions, are called nonoblique corrections.)
Any new particles charged under the electroweak
gauge group
In physics, a gauge theory is a type of field theory in which the Lagrangian (and hence the dynamics of the system itself) does not change (is invariant) under local transformations according to certain smooth families of operations (Lie group ...
s can contribute to oblique corrections. Therefore, the oblique corrections can be used to constrain possible new physics beyond the Standard Model. To affect the nonoblique corrections, on the other hand, the new particles must couple directly to the external fermions.
The oblique corrections are usually parameterized in terms of the Peskin–Takeuchi parameters S, T, and U.