.. _setting_parameters: Setting parameters ------------------ Couplings and masses ==================== .. currentmodule:: pyrecola Setting parameters can be done by invoking :py:meth:`set_parameter_rcl`. For SM-like theories |recola2| comes with dedicated functions to set certain parameters which are all listed below. .. autosummary:: :toctree: _autosummary :template: functiontemplate.rst set_parameter_rcl set_pole_mass_w_rcl set_pole_mass_z_rcl set_pole_mass_h_rcl set_pole_mass_top_rcl set_pole_mass_bottom_rcl set_pole_mass_charm_rcl set_pole_mass_strange_rcl set_pole_mass_up_rcl set_pole_mass_down_rcl set_pole_mass_tau_rcl set_pole_mass_muon_rcl set_pole_mass_electron_rcl .. _cms: Complex-Mass scheme =================== By default, |recola| uses the Complex-Mass scheme for any process. When unstable final state particles are present one should switch to the on-shell scheme by invoking: .. autosummary:: :toctree: _autosummary :template: functiontemplate.rst set_complex_mass_scheme_rcl set_on_shell_scheme_rcl Renormalization of alphas ========================= A running :m:`\alpha_\mathrm{s}` is implemented for various different scenarios. 1. The running is given externally (obtained from pdfs or other sources). In this case it is enough to update the value :m:`\alpha_\mathrm{s}(Q)` at the scale :m:`Q` before computing the next phase-space-point using :py:meth:`set_alphas_rcl`. 2. The running can be computed by Recola to 1 and 2-loop order via :py:meth:`compute_running_alphas_rcl`. Computations are typically performed for different scale choices at the same time in order to give an estimate of missing higher orders. The additional scale variation can be obtained at zero cost by using the following sequence of calls: First the a default scale is computed via the squence: * :py:meth:`set_alphas_rcl` * :py:meth:`compute_process_rcl` and then other scales are obtained by rescaling: * :py:meth:`set_alphas_rcl` * :py:meth:`rescale_process_rcl` .. currentmodule:: pyrecola .. autosummary:: :toctree: _autosummary :template: functiontemplate.rst set_alphas_rcl get_alphas_rcl compute_running_alphas_rcl set_alphas_masses_rcl Renormalization of alpha ************************ .. currentmodule:: pyrecola .. autosummary:: :toctree: _autosummary :template: functiontemplate.rst use_gfermi_scheme_rcl use_alpha0_scheme_rcl use_alphaZ_scheme_rcl get_alpha_rcl Scales ====== .. currentmodule:: pyrecola .. autosummary:: :toctree: _autosummary :template: functiontemplate.rst set_delta_uv_rcl get_delta_uv_rcl set_delta_ir_rcl get_delta_ir_rcl set_mu_uv_rcl get_mu_uv_rcl set_mu_ms_rcl get_mu_ms_rcl set_dynamic_settings_rcl set_compute_ir_poles_rcl Dimensionional and mass regularisation ====================================== |recola| + |collier| supports amplitudes in dimensional and mass regularisation for collinear singularties. In order to perform the computation in mass regularisation one has to assign mass values to the corresponding charged particles and declare them as ``light`` particles. E.g. for the muon call :py:meth:`set_pole_mass_muon_rcl` (with zero width) and then :py:meth:`set_light_muon_rcl`. In the output the muon is then declared as ``light`` next to the mass (regulator) value. Alternatively, all particles with a mass lower than some cut (:py:meth:`set_light_fermions_rcl`) can be tagged as ``light``. Note that the regulator mass does not need to be ``light`` in the strict sense, and can take any positive value. Finally, it is important that the phasespace points passed to |recola| are onshell with ``light`` particles being treated massless. .. autosummary:: :toctree: _autosummary :template: functiontemplate.rst set_light_fermions_rcl set_light_electron_rcl unset_light_electron_rcl set_light_muon_rcl unset_light_muon_rcl set_light_tau_rcl unset_light_tau_rcl set_light_down_rcl unset_light_down_rcl set_light_up_rcl unset_light_up_rcl set_light_strange_rcl unset_light_strange_rcl set_light_charm_rcl unset_light_charm_rcl set_light_bottom_rcl unset_light_bottom_rcl set_light_top_rcl unset_light_top_rcl