Package madgraph :: Package loop :: Module loop_helas_objects :: Class LoopHelasAmplitude
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Class LoopHelasAmplitude

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                 object --+            
                          |            
                       dict --+        
                              |        
core.base_objects.PhysicsObject --+    
                                  |    
  core.helas_objects.HelasAmplitude --+
                                      |
                                     LoopHelasAmplitude

LoopHelasAmplitude object, behaving exactly as an amplitude except that it also contains loop wave-functions closed on themselves, building an amplitude corresponding to the closed loop.

Nested Classes [hide private]

Inherited from core.base_objects.PhysicsObject: PhysicsObjectError

Instance Methods [hide private]
new empty dictionary

__init__(self, *arguments)
Constructor for the LoopHelasAmplitude.
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is_equivalent(self, other)
Comparison between different LoopHelasAmplitude in order to recognize which ones are equivalent at the level of the file output.
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default_setup(self)
Default values for all properties
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D[k] if k in D, else d
get(self, name)
Get the value of the property name.
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filter(self, name, value)
Filter for valid LoopHelasAmplitude property values.
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get_sorted_keys(self)
Return LoopHelasAmplitude property names as a nicely sorted list.
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get_lcut_size(self)
Return the wavefunction size (i.e.
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get_starting_loop_wavefunction(self)
Return the starting external loop mother of this loop helas amplitude.
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get_final_loop_wavefunction(self)
Return the non-external loop mother of the helas amplitude building this loop amplitude
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get_base_diagram(self, wf_dict, vx_list=[], optimization=1)
Return the loop_base_objects.LoopDiagram which corresponds to this amplitude, using a recursive method for the wavefunctions.
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set_mothers_and_pairing(self)
Sets the mothers of this amplitude in the same order as they will be used in the arguments of the helas calls building this loop
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get_vertex_leg_numbers(self, veto_inter_id=[0, -1, -2], max_n_loop=0)
Get a list of the number of legs in vertices in this diagram
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get_denominators(self)
Returns the denominator structure as a tuple (tupleA, tupleB) whose...
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get_masses(self)
Returns the list of the masses of the loop particles as they should appear for cuttools (L-cut particles specified last)
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get_couplings(self)
Returns the list of the couplings of the different helas objects building this HelasLoopAmplitude.
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get_helas_call_dict(self, OptimizedOutput=False, specifyHel=True, **opt)
return a dictionary to be used for formatting HELAS call.
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get_call_key(self)
The helas call to a loop is simple and only depends on the number of loop lines and mothers.
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get_orders(self)
Compute the orders building this loop amplitude only (not from the struct wavefunctions.
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get_analytic_info(self, info, alohaModel=None)
Returns an analytic information of the loop numerator, for example the 'wavefunction_rank' i.e.
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compute_analytic_information(self, alohaModel)
Make sure that all analytic pieces of information about this wavefunction are computed so that they can be recycled later, typically without the need of specifying an alohaModel.
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calculate_fermionfactor(self)
The fermion factor is not implemented for this object but in the subamplitude
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calculate_loopsymmetryfactor(self)
Calculate the loop symmetry factor.
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Inherited from core.helas_objects.HelasAmplitude: __eq__, __ne__, __str__, check_and_fix_fermion_flow, find_outgoing_number, get_aloha_info, get_base_vertex, get_color_indices, get_conjugate_index, get_epsilon_order, get_s_and_t_channels, has_multifermion, needs_hermitian_conjugate, nice_string, set, set_coupling_color_factor

Inherited from core.base_objects.PhysicsObject: __getitem__, __repr__, is_valid_prop

Inherited from dict: __cmp__, __contains__, __delitem__, __ge__, __getattribute__, __gt__, __iter__, __le__, __len__, __lt__, __new__, __setitem__, __sizeof__, clear, copy, fromkeys, has_key, items, iteritems, iterkeys, itervalues, keys, pop, popitem, setdefault, update, values, viewitems, viewkeys, viewvalues

Inherited from object: __delattr__, __format__, __reduce__, __reduce_ex__, __setattr__, __subclasshook__

Static Methods [hide private]

Inherited from core.helas_objects.HelasAmplitude: sign_flips_to_order

Class Variables [hide private]

Inherited from dict: __hash__

Properties [hide private]

Inherited from object: __class__

Method Details [hide private]

__init__(self, *arguments)
(Constructor)

source code 

Constructor for the LoopHelasAmplitude. For now, it works exactly as for the HelasMatrixElement one.

Returns:
new empty dictionary

Overrides: object.__init__

is_equivalent(self, other)

source code 

Comparison between different LoopHelasAmplitude in order to recognize which ones are equivalent at the level of the file output. I decided not to overload the operator __eq__ to be sure not to interfere with other functionalities of the code.

default_setup(self)

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Default values for all properties

Overrides: core.base_objects.PhysicsObject.default_setup

get(self, name)

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Get the value of the property name.

Returns: D[k] if k in D, else d
Overrides: dict.get

filter(self, name, value)

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Filter for valid LoopHelasAmplitude property values.

Overrides: core.base_objects.PhysicsObject.filter

get_sorted_keys(self)

source code 

Return LoopHelasAmplitude property names as a nicely sorted list.

Overrides: core.base_objects.PhysicsObject.get_sorted_keys

get_lcut_size(self)

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Return the wavefunction size (i.e. number of elements) based on the spin of the l-cut particle

get_starting_loop_wavefunction(self)

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Return the starting external loop mother of this loop helas amplitude. It is the loop wavefunction of the l-cut leg one.

get_base_diagram(self, wf_dict, vx_list=[], optimization=1)

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Return the loop_base_objects.LoopDiagram which corresponds to this amplitude, using a recursive method for the wavefunctions. Remember that this diagram is not tagged and structures are not recognized.

Overrides: core.helas_objects.HelasAmplitude.get_base_diagram

get_vertex_leg_numbers(self, veto_inter_id=[0, -1, -2], max_n_loop=0)

source code 

Get a list of the number of legs in vertices in this diagram

Overrides: core.helas_objects.HelasAmplitude.get_vertex_leg_numbers

get_denominators(self)

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Returns the denominator structure as a tuple (tupleA, tupleB) whose
elements are of this form ((external_part_ids),mass) where
external_part_ids are all the leg id building the momentum flowing in 
the loop, i.e:
       D_i=(q+Sum(p_j,j))^2 - m^2

get_couplings(self)

source code 

Returns the list of the couplings of the different helas objects building this HelasLoopAmplitude. They are ordered as they will appear in the helas calls.

get_helas_call_dict(self, OptimizedOutput=False, specifyHel=True, **opt)

source code 

return a dictionary to be used for formatting HELAS call.

Overrides: core.helas_objects.HelasAmplitude.get_helas_call_dict

get_call_key(self)

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The helas call to a loop is simple and only depends on the number of loop lines and mothers. This how it is reflected in the call key.

Overrides: core.helas_objects.HelasAmplitude.get_call_key

get_orders(self)

source code 

Compute the orders building this loop amplitude only (not from the struct wavefunctions. Uses the cached result if available.

get_analytic_info(self, info, alohaModel=None)

source code 

Returns an analytic information of the loop numerator, for example the 'wavefunction_rank' i.e. the maximum power to which the loop momentum is elevated in the loop numerator. All analytic pieces of information are for now identical to the one retrieved from the final_loop_wavefunction.

compute_analytic_information(self, alohaModel)

source code 

Make sure that all analytic pieces of information about this wavefunction are computed so that they can be recycled later, typically without the need of specifying an alohaModel. For now, all analytic information about the loop helas amplitude are identical to those of the final loop wavefunction.

calculate_fermionfactor(self)

source code 

The fermion factor is not implemented for this object but in the subamplitude

Overrides: core.helas_objects.HelasAmplitude.calculate_fermionfactor

calculate_loopsymmetryfactor(self)

source code 

Calculate the loop symmetry factor. For one-loop matrix elements, it is always 2 for bubble with identical particles and tadpoles with self-conjugated particles and 1 otherwise.