Dark Matter Processes

This page contains the production of Dirac fermion Dark Matter via new s-channel mediators. An example how these processes can be run is found in main75.cc.

Scalar Mediator

flag  DM:gg2S2XX   (default = off)
Scattering g g → S → X Xbar. Code 6001. S is assumed to be on-shell.

flag  DM:gg2S2XXj   (default = off)
Scattering g g →S → X Xbar j. Code 6002. S is assumed to be on-shell. (Not validated)

Fermion couplings to scalar S are assumed to be proportional to mass of the fermion and couplings are the factor multiplying SM Higgs coupling (i.e. sin(mixing) in case of portal models).

parm  Sdm:vf   (default = 0.1)
Scalar coupling of SM fermions.

parm  Sdm:af   (default = 0)
Pseudo-scalar coupling of SM fermions.

parm  Sdm:vX   (default = 1.0)
Scalar coupling of DM fermion.

parm  Sdm:aX   (default = 0)
Pseudo-scalar coupling of DM fermion.

Vector Mediator Z'

The Vector mediator model assumes a simplified U(1) model with couplings to fermionic Dark Matter. Both vector and axial couplings are possible.

flag  DM:ffbar2Zp2XX   (default = off)
Scattering f fbar →Z'^0 → X Xbar. Code 6001. Z' is assumed to be on-shell.

flag  DM:ffbar2ZpH   (default = off)
Scattering f fbar →Z'^0 H . Code 6004. Z' is assumed to be on-shell. The coupling of the Z' to the SM Higgs is given by the parameter Zp:coupH. Interference with gamma/Z currently not implemented, therefore this is only suitable when Z' → X Xbar. This can be ensured using
55:onMode = off
55:onIfAny = 52

flag  DM:ffbar2Zp2XXj   (default = off)
Scattering f fbar →Z'^0 → X Xbar. Code 6002. Z' is assumed to be on-shell. (Not validated)

flag  DM:qg2Zp2XXj   (default = off)
Scattering f fbar →Z'^0 → X Xbar. Code 6003. Z' is assumed to be on-shell. (Not validated)

The couplings of the Z'^0 to quarks and leptons are be assumed universal, i.e. generation-independent. The choice of fixed axial and vector couplings implies a resonance width that increases linearly with the Z' mass.

Here are the couplings:

parm  Zp:gZp   (default = 0.1)
Gauge coupling of new U(1).

parm  Zp:coupH   (default = 0.1)
Coupling to SM higgs.

parm  Zp:vu   (default = 1)
Vector coupling of up-type quarks.

parm  Zp:au   (default = 0)
Axial coupling of up-type quarks.

parm  Zp:vd   (default = 1)
Vector coupling of down-type quarks.

parm  Zp:ad   (default = 0)
Axial coupling of down-type quarks.

parm  Zp:vl   (default = 1)
Vector coupling of charged leptons.

parm  Zp:al   (default = 0)
Axial coupling of charged leptons.

parm  Zp:vv   (default = 1)
Vector coupling of neutrinos.

parm  Zp:av   (default = 0)
Axial coupling of neutrinos.

parm  Zp:vX   (default = 1)
Vector coupling of DM fermion.

parm  Zp:aX   (default = 0)
Axial coupling of DM fermion.