Electroweak Processes

This page contains processes involving Prompt-photon, gamma^*/Z^0 and W^+- production, plus a few with t-channel boson exchange.

Prompt photon processes

This group collects the processes where one or two photons are produced by the hard process. Additional sources of photons include parton showers and hadron decays. A pT cut is required to stay away from the unphysical low-pT region. An eikonalized description, intended to be valid at all pT, is included as part of the multiple-interactions framework.

flag  PromptPhoton:all   (default = off)
Common switch for the group of all prompt photon processes, as listed separately in the following.

flag  PromptPhoton:qg2qgamma   (default = off)
Scattering q g -> q gamma. Code 201.

flag  PromptPhoton:qqbar2ggamma   (default = off)
Scattering q qbar -> g gamma. Code 202.

flag  PromptPhoton:gg2ggamma   (default = off)
Scattering g g -> g gamma.
Note: This is a box graph. The full quark-mass dependence in the loop leads to very complicated expressions. The current implementation is based on assuming five massless quarks, and thus is questionable at small (pT < m_b) or large (pT > m_t) transverse momenta. Code 203.

flag  PromptPhoton:qqbar2gammagamma   (default = off)
Scattering q qbar -> gamma gamma. Code 204.

flag  PromptPhoton:gg2gammagamma   (default = off)
Scattering g g -> gamma gamma.
Note: This is a box graph. The full quark-mass dependence in the loop leads to very complicated expressions. The current implementation is based on assuming five massless quarks, and thus is questionable at small (pT < m_b) or large (pT > m_t) transverse momenta. Code 205.

Weak boson processes

Under this heading we group processes involving the production of a single electroweak gauge boson, i.e. a gamma^*/Z^0 or a W^+-, or a pair of them, or one of them in combination with a parton. Since the three sets are partly conflicting, each is associated with its own group flag. In addition, t-channel exchange of such a boson between two fermions form a separate group.

Boson exchange

The two processes in this subgroup is included as part of the multiple-interactions framework.

flag  WeakBosonExchange:all   (default = off)
Common switch for the group of gamma^*/Z^0 or W^+- exchange between two fermions.

flag  WeakBosonExchange:ff2ff(t:gmZ)   (default = off)
Scattering f f' -> f f' via gamma^*/Z^0 t-channel exchange, with full interference between the gamma^* and Z^0. Code 211.

flag  WeakBosonExchange:ff2ff(t:W)   (default = off)
Scattering f_1 f_2 -> f_3 f_4 via W^+- t-channel exchange. Code 212.

Single boson

flag  WeakSingleBoson:all   (default = off)
Common switch for the group of a single gamma^*/Z^0 or W^+- production.

flag  WeakSingleBoson:ffbar2gmZ   (default = off)
Scattering f fbar -> gamma^*/Z^0, with full interference between the gamma^* and Z^0. Code 221.

flag  WeakSingleBoson:ffbar2W   (default = off)
Scattering f fbar' -> W^+-. Code 222.

flag  WeakSingleBoson:ffbar2ffbar(s:gm)   (default = off)
Scattering f fbar -> gamma^* -> f' fbar'. Subset of process 221, but written as a 2 -> 2 process, so that pT can be used as ordering variable, e.g. in multiple interactions. As a consequence the scale for pdf's is pT rather than m, so results will not be identical even for the same phase space cuts. Hardcoded for the final state being either of the five quark flavours or three lepton ones. Not included in the WeakSingleBoson:all set, but included in the multiple-interactions framework. Code 223.

Boson pair

flag  WeakDoubleBoson:all   (default = off)
Common switch for the group of pair production of gamma^*/Z^0 and W^+-.

flag  WeakDoubleBoson:ffbar2gmZgmZ   (default = off)
Scattering f fbar' -> gamma^*/Z^0 gamma^*/Z^0. Code 231.

flag  WeakDoubleBoson:ffbar2ZW   (default = off)
Scattering f fbar' -> Z^0 W^+-. Note that here the gamma^* contribution is not (currently) included. Code 232.

flag  WeakDoubleBoson:ffbar2WW   (default = off)
Scattering f fbar -> W^+ W^-. Code 233.

Boson and parton

flag  WeakBosonAndParton:all   (default = off)
Common switch for the group of production of a single electroweak gauge boson, i.e. a gamma^*/Z^0 or a W^+-, in association with a parton, i.e. a quark, gluon, photon or lepton. These processes give first-order corrections to the ones in the WeakSingleBoson class, and both sets cannot be used simultaneously without unphysical doublecounting. The current class should only be used to study the high-pT tail of the gauge-boson production processes (for LHC applicatiosn at least pT > 20 GeV), while the ones in WeakSingleBoson should be used for inclusive production.

flag  WeakBosonAndParton:qqbar2gmZg   (default = off)
Scattering q qbar -> gamma^*/Z^0 g. Code 241.

flag  WeakBosonAndParton:qg2gmZq   (default = off)
Scattering q g -> gamma^*/Z^0 q . Code 242.

flag  WeakBosonAndParton:ffbar2gmZgm   (default = off)
Scattering f fbar -> gamma^*/Z^0 gamma. Code 243.

flag  WeakBosonAndParton:fgm2gmZf   (default = off)
Scattering f gamma -> gamma^*/Z^0 f. Code 244.

flag  WeakBosonAndParton:qqbar2Wg   (default = off)
Scattering q qbar -> W^+- g. Code 251.

flag  WeakBosonAndParton:qg2Wq   (default = off)
Scattering q g -> W^+- q. Code 252.

flag  WeakBosonAndParton:ffbar2Wgm   (default = off)
Scattering f fbar -> W^+- gamma. Code 253.

flag  WeakBosonAndParton:fgm2Wf   (default = off)
Scattering f gamma -> W^+- f. Code 254.