Direct photon
![]() | This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)
|
Produced in hadronic collisions, a direct photon is any real photon which originates directly from an electromagnetic vertex in a quark-quark, quark-gluon or gluon-gluon scattering subprocess (as opposed to "indirect" photons which arise from the decays of fragmentation products).
Because the QCD calculations for direct photon production are considerably easier to perform than for other processes studies of direct photons have been used to test predictions made by perturbative QCD.
Direct photons were predicted to exist by C.O. Escobar in 1975[1] and were first observed by the R412 group at the Intersecting Storage Rings at CERN in 1976, and were subsequently studied by various experiments, including E705 and E706 at Fermilab, NA3, NA24, WA70 and UA6 at the CERN SPS as well as UA1 and UA2 at the CERN SPPS collider.
References
- ^ Escobar, C.O. (1975). "Photoproduction of Large Transverse Momentum Mesons and Production of Large pT Photons and Leptons in Proton Proton Collisions". Nuclear Physics B. 98: 173–188. doi:10.1016/0550-3213(75)90208-4.
- Articles needing additional references from January 2017
- All articles needing additional references
- Justapedia articles that are too technical from August 2016
- Articles with invalid date parameter in template
- All articles that are too technical
- Articles with multiple maintenance issues
- Photons
- All stub articles
- Particle physics stubs