wiki:DMsimpt

Version 12 (modified by LucaMantani, 6 months ago) (diff)

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DMSimpt: A general framework for t-channel dark matter models at NLO in QCD

Contact Information

Benjamin Fuks

  • LPTHE / Sorbonne U.
  • fuks @ lpthe.jussieu.fr

Chiara Arina

  • UC Louvain
  • chiara.arina @ uclouvain.be

Luca Mantani

  • UC Louvain
  • luca.mantani @ uclouvain.be

See arXiv:2001.05024 [hep-ph].

Model Description and FeynRules Implementation

We extend the Standard Model by a dark matter candidate X and a coloured mediator Y. The model includes several spin possibilities for X and Y, the dark matter being either of a Majorana nature or not and of spin equal to 0, 1/2 or 1. The mediator is accordingly of spin 1/2 (scalar or bosonic dark matter) or 0 (fermionic dark matter). The model Lagrangian is given by

\begin{equation*}
  \mathcal{L} = \mathcal{L}_{\rm SM} + \mathcal{L}_{\rm kin} + \mathcal{L}_F(\chi) + \mathcal{L}_F(\tilde\chi) + \mathcal{L}_S(S) + \mathcal{L}_S(\tilde S)
       + \mathcal{L}_V(V)    + \mathcal{L}_V(\tilde V) \ .
\end{equation*}

The first term consists in the Standard Model Lagrangian, the second one includes gauge-invariant kinetic and mass terms for all new fields and the last ones describe the interactions of the dark matter state with the mediator and the Standard Model. The latter focus respectively on Dirac fermion, Majorana fermion, complex scalar, real scalar, complex vector and real vector dark matter, and are given by

\begin{eqnarray*}
   \mathcal{L}_F(X)& = & \Big[
           {\bf \lambda_{Q}} \bar X Q_L \varphi^\dag_{Q}
     \!+\! {\bf \lambda_{u}} \bar X u_R \varphi^\dag_{u}
     \!+\! {\bf \lambda_{d}} \bar X d_R \varphi^\dag_{d}
     \!+\! {\rm h.c.} \Big] \ ,\\
   \mathcal{L}_S(X)& = & \Big[
          {\bf \hat\lambda_{Q}} \bar\psi_{Q} Q_L X
    \!+\! {\bf \hat\lambda_{u}} \bar\psi_{u} u_R X
    \!+\! {\bf \hat\lambda_{d}} \bar\psi_{d} d_R X
    \!+\! {\rm h.c.} \Big] \ , \\
   \mathcal{L}_V(X)& = & \Big[
          {\bf \hat\lambda_{Q}} \bar\psi_{Q} \gamma^\mu X_\mu Q_L
    \!+\! {\bf \hat\lambda_{u}} \bar\psi_{u} \gamma^\mu X_\mu u_R
    \!+\! {\bf \hat\lambda_{d}} \bar\psi_{d} \gamma^\mu X_\mu d_R
    \!+\! {\rm h.c.} \Big] \ ,
\end{eqnarray*}

where φ and ψ consists in coloured scalar and fermionic mediators.

The above Lagrangian was implemented in the Feynman gauge into FeynRules 2.3.35. QCD renormalisation and R2 rational counterterms were determined using NLOCT v1.02 and FeynArts 3.9. Feynman rules were collected into a single UFO, in which 5 flavours of massless quarks are considered, which enables tree-level calculations at LO and NLO QCD and loop-induced calculations at LO QCD using MadGraph_aMC@NLO.

The above new physics couplings can be controlled on run-time through the Les Houches blocks DMS3Q, DMS3U, DMS3D (scalar mediator interactions with the QL, uR and dR quarks), as well as DMF3Q, DMF3U, DMF3D (scalar mediator interactions with the QL, uR and dR quarks). The mass of the new particles can be modified through the usual mass blocks. The PDG codes of the new particles are:

  • Dark matter: 51 (real scalar), 52 (Majorana fermion), 53 (real vector), 56 (complex scalar), 57 (Dirac fermion) and 58 (complex vector).
  • Scalar mediators: 1000001 (φdL), 1000002 (φuL), 1000003 (φsL), 1000004 (φcL), 1000005 (φbL), 1000006 (φtL), 2000001 (φdR), 2000002 (φuR), 2000003 (φsR), 2000004 (φcR), 2000005 (φbR) and 2000006 (φtR).
  • Fermionic mediators: 5910001 (ψdL), 5910002 (ψuL), 5910003 (ψsL), 5910004 (ψcL), 5910005 (ψbL), 5910006 (ψtL), 5920001 (ψdR), 5920002 (ψuR), 5920003 (ψsR), 5920004 (ψcR), 5920005 (ψbR) and 5920006 (ψtR).

More information can be found in arXiv:2001.05024 [hep-ph].

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