Electroweak Processes

This page contains processes involving Prompt-photon, gamma^*/Z^0 and W^+- production, plus a few with t-channel boson exchange. Many of the processes are not yet completed, e.g. there are not yet the correct angular decay distributions in many cases.

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.

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

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

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

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

flag name="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

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

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

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

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

flag name="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. Code 223.

Boson pair

The processes in this subset are not yet fully handled.

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

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

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

Boson and parton

The processes in this subset are not yet fully handled.

flag name="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 boths 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, while the ones in WeakSingleBoson should be used for inclusive production.

flag name="WeakBosonAndParton:qqbar2Wg" default="off"
Scattering f fbar -> W^+- g. Code 246.

flag name="WeakBosonAndParton:qg2Wq" default="off"
Scattering f g -> f W^+-. Code 247.

flag name="WeakBosonAndParton:ffbar2Wgm" default="off"
Scattering f fbar -> W^+- gamma. Code 248.