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Commit 78ef147

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Uwe Hernandez Acosta
committed
add implementation of the cross section interface
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6 files changed

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‎src/QEDprocesses.jl

+31-1
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@@ -1,5 +1,14 @@
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module QEDprocesses
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# constants
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export
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ALPHA,
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ALPHA_SQUARE,
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ELEMENTARY_CHARGE,
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ELEMENTARY_CHARGE_SQUARE,
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ELECTRONMASS,
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ONE_OVER_FOURPI
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# Abstract model interface
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export AbstractModelDefinition, fundamental_interaction_type
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@@ -28,16 +37,37 @@ export AbstractCoordinateSystem, SphericalCoordinateSystem
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export AbstractFrameOfReference, CenterOfMomentumFrame, ElectronRestFrame
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export AbstractPhasespaceDefinition, PhasespaceDefinition
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# specific compute models
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export PerturbativeQED
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# specific scattering processes
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export Compton, omega_prime
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using DocStringExtensions
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using StaticArrays
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using QEDbase
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include("utils.jl")
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###
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# Generic implementations
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###
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include("constants.jl")
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include("phase_spaces.jl")
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include("interfaces/model_interface.jl")
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include("interfaces/process_interface.jl")
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include("interfaces/setup_interface.jl")
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include("models/models.jl")
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include("momentum_generation.jl")
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include("propagators.jl")
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include("probabilities.jl")
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include("cross_sections.jl")
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include("processes/one_photon_compton/one_photon_compton.jl")
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include("utils.jl")
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include("patch_QEDbase.jl")
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end

‎src/processes/one_photon_compton/one_photon_compton.jl

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#################
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# The one-photon Compton process
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#
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# This file contains the implementation of the abstract process setup for
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# Compton
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##################
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export Compton
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export omega_prime
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include("process.jl")
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include("perturbative/kinematics.jl")
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include("perturbative/cross_section.jl")

‎src/processes/one_photon_compton/perturbative/cross_section.jl

+178
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#####
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# Perturbative one-photon Compton scattering
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# Implementation of the cross section interface
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#####
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function _incident_flux(
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proc::Compton, model::PerturbativeQED, in_ps::AbstractVector{T}
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) where {T<:QEDbase.AbstractFourMomentum}
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return prod(in_ps)
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end
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function _matrix_element(
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proc::Compton,
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model::PerturbativeQED,
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in_ps::AbstractVector{T},
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out_ps::AbstractVector{T},
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) where {T<:QEDbase.AbstractFourMomentum}
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return _pert_compton_matrix_element(proc, in_ps, out_ps)
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end
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"""
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!!! note "Convention"
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We average over the initial spins and pols, and sum over final.
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"""
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function _averaging_norm(proc::Compton)
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normalizations = number_of_spin_pol.(_in_spin_and_pol(proc))
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return inv(prod(normalizations))
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end
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function _all_onshell(
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proc::Compton, in_ps::AbstractVector{T}, out_ps::AbstractVector{T}
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) where {T<:QEDbase.AbstractFourMomentum}
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sq_in_moms = getMass2.(in_ps)
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sq_out_moms = getMass2.(out_ps)
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sq_in_masses = mass.(incoming_particles(proc)) .^ 2
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sq_out_masses = mass.(outgoing_particles(proc)) .^ 2
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return isapprox(sq_in_moms, SVector(sq_in_masses)) &&
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isapprox(sq_out_moms, SVector(sq_out_masses))
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end
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function _is_in_phasespace(
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proc::Compton,
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model::PerturbativeQED,
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in_ps_def::AbstractPhasespaceDefinition,
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in_ps::AbstractVector{T},
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out_ps_def::AbstractPhasespaceDefinition,
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out_ps::AbstractVector{T},
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) where {T<:QEDbase.AbstractFourMomentum}
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return (!isapprox(sum(in_ps), sum(out_ps))) ? false : _all_onshell(proc, in_ps, out_ps)
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end
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@inline function _phase_space_factor(
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proc::Compton,
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model::PerturbativeQED,
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in_ps_def::AbstractPhasespaceDefinition,
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in_ps::AbstractVector{T},
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out_ps_def::AbstractPhasespaceDefinition,
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out_ps::AbstractVector{T},
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) where {T<:QEDbase.AbstractFourMomentum}
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return _pert_compton_ps_fac(in_ps_def, in_ps[2], out_ps_def, out_ps[2])
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end
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#######
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# Matrix elements
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#######
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@inline function _pert_compton_matrix_element(
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proc::Compton, in_ps::AbstractVector{T}, out_ps::AbstractVector{T}
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) where {T<:QEDbase.AbstractFourMomentum}
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in_electron_mom = in_ps[1]
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in_photon_mom = in_ps[2]
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out_electron_mom = out_ps[1]
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out_photon_mom = out_ps[2]
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in_electron_state = base_state(Electron(), Incoming(), in_electron_mom, proc.in_spin)
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in_photon_state = base_state(Photon(), Incoming(), in_photon_mom, proc.in_pol)
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out_electron_state = base_state(Electron(), Outgoing(), out_electron_mom, proc.out_spin)
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out_photon_state = base_state(Photon(), Outgoing(), out_photon_mom, proc.out_pol)
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return _pert_compton_matrix_element(
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in_electron_mom,
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in_electron_state,
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in_photon_mom,
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in_photon_state,
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out_electron_mom,
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out_electron_state,
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out_photon_mom,
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out_photon_state,
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)
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end
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function _pert_compton_matrix_element(
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in_electron_mom::T,
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in_electron_state,
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in_photon_mom::T,
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in_photon_state,
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out_electron_mom::T,
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out_electron_state,
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out_photon_mom::T,
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out_photon_state,
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) where {T<:QEDbase.AbstractFourMomentum}
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base_states_comb = Iterators.product(
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QEDbase._as_svec(in_electron_state),
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QEDbase._as_svec(in_photon_state),
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QEDbase._as_svec(out_electron_state),
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QEDbase._as_svec(out_photon_state),
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)
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matrix_elements = Vector{ComplexF64}()
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sizehint!(matrix_elements, length(base_states_comb))
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for (in_el, in_ph, out_el, out_ph) in base_states_comb
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push!(
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matrix_elements,
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_pert_compton_matrix_element_single(
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in_electron_mom,
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in_el,
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in_photon_mom,
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in_ph,
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out_electron_mom,
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out_el,
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out_photon_mom,
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out_ph,
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),
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)
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end
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return matrix_elements
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end
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function _pert_compton_matrix_element_single(
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in_electron_mom::T,
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in_electron_state::BiSpinor,
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in_photon_mom::T,
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in_photon_state::SLorentzVector,
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out_electron_mom::T,
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out_electron_state::AdjointBiSpinor,
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out_photon_mom::T,
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out_photon_state::SLorentzVector,
142+
) where {T<:QEDbase.AbstractFourMomentum}
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in_ph_slashed = slashed(in_photon_state)
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out_ph_slashed = slashed(out_photon_state)
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prop1 = _fermion_propagator(in_photon_mom + in_electron_mom, mass(Electron()))
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prop2 = _fermion_propagator(in_electron_mom - out_photon_mom, mass(Electron()))
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# TODO: fermion propagator is not yet in QEDbase
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diagram_1 =
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out_electron_state *
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(out_ph_slashed * (prop1 * (in_ph_slashed * in_electron_state)))
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diagram_2 =
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out_electron_state *
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(in_ph_slashed * (prop2 * (out_ph_slashed * in_electron_state)))
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result = diagram_1 + diagram_2
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# TODO: find (preferably unitful) global provider for physical constants
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# elementary charge
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return ELEMENTARY_CHARGE_SQUARE * result
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end
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#######
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# Phase space factors
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#######
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function _pert_compton_ps_fac(
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in_ps_def::PhasespaceDefinition{inCS,ElectronRestFrame},
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in_photon_mom,
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out_ps_def::PhasespaceDefinition{SphericalCoordinateSystem},
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out_photon_mom,
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) where {inCS}
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# TODO
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omega = getE(in_photon_mom)
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omega_prime = getE(out_photon_mom)
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return omega_prime^2 / (16 * pi^2 * omega * mass(Electron()))
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end

‎src/processes/one_photon_compton/perturbative/kinematics.jl

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@@ -0,0 +1,44 @@
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omega_prime(::PerturbativeQED, om, cth; mass=1.0) = _pert_omega_prime(om, cth; mass=mass)
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3+
@inline function _pert_omega_prime(omega, cth; mass=1.0)
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return omega / (1 + omega / mass * (1 - cth))
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end
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function generate_momenta(
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proc::Compton,
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model::PerturbativeQED,
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in_ps_def::PhasespaceDefinition{SphericalCoordinateSystem,ElectronRestFrame},
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in_ps::AbstractVector{T},
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out_ps_def::PhasespaceDefinition{SphericalCoordinateSystem,ElectronRestFrame},
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out_ps::AbstractVector{T},
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) where {T<:Real}
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return _generate_momenta(proc, model, in_ps_def, in_ps, out_ps_def, out_ps)
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end
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function _generate_momenta(
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proc::Compton,
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model::PerturbativeQED,
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in_ps_def::PhasespaceDefinition{SphericalCoordinateSystem,ElectronRestFrame},
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in_ps::AbstractVector{T},
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out_ps_def::PhasespaceDefinition{SphericalCoordinateSystem,ElectronRestFrame},
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out_ps::AbstractVector{T},
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) where {T<:Real}
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omega = in_ps[1]
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cth = out_ps[1]
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phi = out_ps[2]
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P, K, Pp, Kp = _generate_momenta_elab_sph(omega, cth, phi) # TODO: do this coord and frame dependent
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in_moms = SVector(P, K)
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out_moms = SVector(Pp, Kp)
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return in_moms, out_moms
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end
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function _generate_momenta_elab_sph(om, cth, phi, m=1.0)
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P = SFourMomentum(m, zero(m), zero(m), zero(m))
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K = SFourMomentum(om, zero(om), zero(om), om)
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omp = _pert_omega_prime(om, cth)
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sth = sqrt(1 - cth^2)
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sphi, cphi = sincos(phi)
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Kp = SFourMomentum(omp, omp * sth * cphi, omp * sth * sphi, omp * cth)
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Pp = P + K - Kp
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return P, K, Pp, Kp
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end

‎src/processes/one_photon_compton/process.jl

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1+
"""
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Compton(
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in_spin [= AllSpin()]
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in_pol [= AllPol()]
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out_spin [= AllSpin()]
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out_pol [= AllPol()]
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)
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"""
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struct Compton{InElectronSpin,InPhotonPol,OutElectronSpin,OutPhotonPol} <:
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AbstractProcessDefinition where {
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InElectronSpin<:AbstractSpin,
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InPhotonPol<:AbstractPolarization,
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OutElectronSpin<:AbstractSpin,
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OutPhotonPol<:AbstractPolarization,
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}
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in_spin::InElectronSpin
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in_pol::InPhotonPol
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out_spin::OutElectronSpin
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out_pol::OutPhotonPol
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end
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function Compton()
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return Compton(AllSpin(), AllPol(), AllSpin(), AllPol())
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end
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Compton(in_pol::AbstractPolarization) = Compton(AllSpin(), in_pol, AllSpin(), AllPol())
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function Compton(in_pol::AbstractPolarization, out_pol::AbstractPolarization)
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return Compton(AllSpin(), in_pol, AllSpin(), out_pol)
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end
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_polarizations(proc::Compton) = (proc.in_pol, proc.out_pol)
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_spins(proc::Compton) = (proc.in_spin, proc.out_spin)
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_in_spin_and_pol(proc::Compton) = (proc.in_spin, proc.in_pol)
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_out_spin_and_pol(proc::Compton) = (proc.out_spin, proc.out_pol)
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function QEDprocesses.incoming_particles(::Compton)
40+
return (Electron(), Photon())
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end
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function QEDprocesses.outgoing_particles(::Compton)
44+
return (Electron(), Photon())
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end
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function _spin_or_pol(process::Compton, ::Electron, ::Incoming)
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return process.in_spin
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end
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function _spin_or_pol(process::Compton, ::Electron, ::Outgoing)
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return process.out_spin
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end
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function _spin_or_pol(process::Compton, ::Photon, ::Incoming)
56+
return process.in_pol
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end
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function _spin_or_pol(process::Compton, ::Photon, ::Outgoing)
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return process.out_pol
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end

‎src/propagators.jl

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77

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"""
99
10-
```julia
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propagator(particle::AbstractParticleType, mom::QEDbase.AbstractFourMomentum, [mass::Real])
12-
```
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propagator(particle::AbstractParticleType, mom::QEDbase.AbstractFourMomentum, [mass::Real])
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1412
Return the propagator of a particle for a given four-momentum. If `mass` is passed, the respective propagator for massive particles is used, if not, it is assumed the particle passed in is massless.
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