Import Geant4 11.0.0 source tree

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+               Examples for event biasing: B01, B02 and B03
+               --------------------------------------------
+
+B01, B02 and B03 applications demonstrate the usage of different variance
+reduction techniques supported in Geant4, or possible from the user
+applications.
+
+General remark to variance reduction
+------------------------------------
+The tools provided for importance sampling (or geometrical splitting and
+Russian roulette) and for the weight window technique require the user to 
+have a good understanding of the physics in the problem. This is because 
+the user has to decide which particle types have to be biased, define the 
+cells (physical volumes, replicas) and assign importances or weight 
+windows to that cells. If this is not done properly it can not be 
+expected that the results describe a real experiment. The examples given 
+here only demonstrate how to use the tools technically. They don't intend 
+to produce physical correct results.
+
+General remark to scoring
+-------------------------
+Scoring is carried out using the built-in Multifunctional detectors. For
+parallel geometries this requires a special scoring physics process.
+See examples/extended/runAndEvent (especailly RE05) for clarification.
+
+Known problems - should not happen
+----------------------------------
+In the following scenario it can happen that a particle is not
+biased and it's weight is therefore not changed even if it crosses
+a boundary where biasing should happen.
+Importance and weight window sampling create particles on boundaries 
+between volumes. If the GPIL method of a physical process returns 
+0 as step length for a particle on a boundary and if the PostStepDoIt of
+that process changes the direction of the particle to go back in the 
+former volume the biasing won't be invoked. 
+This will produce particles with weights that do not correspondent to the
+importance of the current volumes.
+
+Further information:
+--------------------
+Short description of importance sampling and scoring:
+http://cern.ch/geant4/working_groups/geometry/biasing/Sampling.html
+
+Example B01
+===========
+
+The example uses importance sampling or the weight window technique 
+according to an input parameter. It uses scoring in both cases. 
+Importance values or weight windows are defined according to the mass 
+geometry. In this example the weight window technique is configured such 
+that it behaves equivalent to importance sampling: The window is actually 
+not a window but simply the inverse of the importance value and only
+one energy region is used that covers all energies in the problem.
+The user may change the weight window configuration by changing the
+initialization of the weight window algorithm in example,cc. 
+Different energy bounds for the weight window technique may be specified 
+in B01DetectorConstruction.
+
+The executable takes one optional argument: 0 or 1. Without argument or
+with argument: 0, the importance sampling is applied with argument: 1,
+the weight window technique is applied.
+
+A modular approach is applied to the physicslist and the extension for biasing.
+
+Example B02
+===========
+
+This example uses a parallel geometry to define G4GeometryCell objects
+for scoring and importance sampling. The output should be equivalent to B01.
+
+A modular approach is applied to the physicslist and the extension for biasing.
+The parallel geometry is included in this extension.
+
+Example B03
+===========
+
+This example uses a parallel geometry to define G4GeometryCell objects
+for scoring and importance sampling. The output should be statistically 
+equivalent to B02 (and B01).
+
+This demonstrates a customised "flat" physics implementation with the addition
+of biasing. Complementary approach to the modular physics lists of B01 and B02
+
+
+ ___________________________________________________________________________
+
+
+                  Generic biasing examples GB01 - GB06
+                  ------------------------------------
+
+These examples illustrate the usage of a biasing scheme implemented since
+version Geant4 10.0.
+The scheme is meant to be extensible, not limited to these six examples.
+
+Example GB01:
+=============
+
+This example illustrates how to bias process cross-sections in this scheme.
+
+
+Example GB02:
+=============
+
+Illustrates a force collision scheme similar to the MCNP one.
+
+
+Example GB03:
+=============
+
+Illustrates geometry based biasing.
+
+
+Example GB04:
+=============
+
+Illustrates a bremsstrahlung splitting.
+
+
+Example GB05:
+=============
+
+Illustrates a "splitting by cross-section" technique: a splitting-based
+technique using absorption cross-section to control the neutron population.
+
+
+Example GB06:
+=============
+
+Illustrates the usage of parallel geometries with generic biasing.
+
+Example GB07:
+=============
+
+Illustrates the usage of leading particle biasing with generic biasing.
+
+
+ ___________________________________________________________________________
+
+
+             Reverse MonteCarlo Technique example: ReverseMC01
+             -------------------------------------------------
+
+Example ReverseMC01
+===================
+
+Example illustrating the use of the Reverse Monte Carlo (RMC) mode in a Geant4
+application. See details in ReverseMC01/README.
+