Changes between Version 11 and Version 12 of VLQ
 Timestamp:
 05/15/13 11:29:24 (7 years ago)
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VLQ
v11 v12 42 42 All the above parameter classes are combined internally in the FeynRules model file [attachment:VLQ.fr] to match the modelindependent prescription presented above [1]. The default parameter cards use the standard MadGraph values for the SM input parameters, as given in [attachment:Parameters.pdf]. For consistency, all light quarks included in the proton definition are restricted to be massless (5F scheme) using the restriction file [attachment:Massless.rst] when loading the FeynRules model, except for the top, bottom and tau lepton masses. The default model loads the real 3X3 CKM matrix given in [attachment:Parameters.pdf] [2] as an external parameter. In general, the presence of new top partners induce modeldependent corrections to the mixings between the novel heavy fermions and the lighter quark families, and the SM electroweak couplings must be modified accordingly. 43 43 44 In addition to the above parameterisation, an extension including chromomagnetic couplings between VL and Standard Model quarks is provided in the file VLQ_Chromomagnetic.fr. The new couplings (typically generated at loop level in minimal SM extensions) are implemented in terms of the dimension 6 operator:44 '''Extension''': In addition to the above parameterisation, an extension including chromomagnetic couplings between VL and Standard Model quarks is provided in the file VLQ_Chromomagnetic.fr. The new couplings (typically generated at loop level in minimal SM extensions) are implemented in terms of the dimension 6 operator: 45 45 [[Image(LagrangianChromo.png)]] 46 46 where G denotes the field strength tensor of the gluon, v is the Higgs field vacuum expectation value and gs is the QCD coupling. The KAPPA block is complemented with the additional parameter kappa_g (set to 1 by default), specifying the strength of the new corresponding strong coupling. The new GLUON block includes the new Tqg(g) and Bqg(g) couplings to the three SM quark families, together with the energy scale Lambda (set to 10 TeV by default). These parameters can be adjusted independently from the others described above.