View source for Nonoblique correction

In [[Four-fermion interactions|four-fermion scattering process]]es of [[particle physics]], a '''nonoblique correction''', also called a '''direct correction''', refers to a [[radiative correction]] of type

{{Subatomic particle|Antielectron}}&nbsp;+&nbsp;{{Subatomic particle|Electron}}&nbsp;→&nbsp;{{Subatomic particle|quark}}&nbsp;+&nbsp;{{Subatomic particle|Antiquark}}

in the [[electroweak]] sector of the Standard Model.  These corrections are being studied at the [[CERN]] [[LEP]] collider. Together with the [[oblique correction]]s, ''nonoblique corrections'' can be used to constrain models of physics [[beyond the Standard Model]].

==Classes==
There are three classes of radiative corrections to these processes:{{why|date=April 2017}}
* [[vacuum polarization]] corrections,
* [[Vertex correction|vertex corrections]], and
* box corrections.
The vertex and box corrections, which depend on the identity of the initial and final state fermions, are referred to as the non-oblique corrections.{{why|date=April 2017}} The vacuum polarization corrections are referred to as [[oblique correction]]s, 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.{{clarify|wouldn't this sentence be more useful in the article on oblique corrections? Is it actually useful here?|date=April 2017}}

==Examples==
An example of a vertex correction is the nonuniversality (flavor dependence) of the couplings of the quarks and leptons to the charged and neutral weak currents. Another example is the [[anomalous magnetic dipole moment]].

In order to affect the nonoblique corrections, particles must couple directly to the external fermions{{why|date=April 2017}}. Such couplings are expected to be suppressed{{how|date=April 2017}} in most cases, with one exception being the <math>Z b \bar{b}</math> vertex.

== See also ==

* [[Initial and final state radiation]]
* {{slink|Lepton#Universality}}

==References==
* {{cite arXiv |first=J.L. |last=Hewett |title=The Standard Model and why we believe it |eprint=hep-ph/9810316 <!-- |series=Lectures given at TASI '97 |department=[[Theoretical Advanced Study Institute]] |publisher=[[University of Colorado at Boulder|University of Colorado]] |place=Boulder, Colorado --> |year=1997}}

[[Category:Standard Model]]
[[Category:Physics beyond the Standard Model]]

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