UPDATE Matt King 07/07/2015 Region Finding 2 Have been working - PowerPoint PPT Presentation

1 MOEDAL SIMULATION UPDATE Matt King 07/07/2015

Region Finding 2  Have been working on an automated fiducial region finding algorithm for the MMTs  With assistance from Katarina Bendtz, who designed the algorithm for ATLAS.  Our situation is a little different from ATLAS  Two distinct regions (main MMT box, box top)  No full coverage in eta  Don’t need the other analysis code in which the region finder is embedded  => Have been working on a new algorithm “inspired” by the ATLAS one 07/07/2015 Matthew King, IFIC

The algorithm 3  The basic idea of the algorithm is to find the largest possible region, inside a mother-region, that meets some criteria.  Algorithm *always* finds the largest possible region, not an approximation.  Current criteria is:  Average efficiency in region > effmin  More advanced selection, optimization of a function is also possible  Requires more study. A simple selection seems sufficient for now. 07/07/2015 Matthew King, IFIC

Initial results 4  Several obvious tuning parameters:  Region size limit  Region efficiency limit  Region efficiency standard deviation limit (ignoring for now) Region size: theta * KEz( MeV) Efficiency*3 (because of phi coverage) 07/07/2015 Matthew King, IFIC

“Best” regions 5 effmin = 0.4 effmin = 0.5 effmin = 0.6 effmin = 0.7 07/07/2015 Matthew King, IFIC

Geant4 steps 6  Have looked further into the problem of large numbers of Geant4 steps.  “Remove air” solution:  Works, but number of steps in other materials is still large for other materials. Solves the immediate problem, but may run into problems later.  Increase “ thePILfactor ”:  Experimental (undocumented) Geant4 feature that manually multiplies the step length by some factor.  Works, does not affect continuous energy loss but effectively reduces effect of secondaries by the factor (in all materials).  Observed to be a lesser effect than the continuous energy loss, but not a rigorous solution. 07/07/2015 Matthew King, IFIC

Geant4 steps 7  “Correct” solution.  There are two possible approaches to an energy loss algorithm:  PostStepDoIt (current): computes a step based on the mean free path, does secondaries at the end of every step.  AlongStepDoIt (target): much larger step length, secondaries generated along the length of the step.  Some success in getting this to work. Still needs much more work though.  Not trivial to make this change. 07/07/2015 Matthew King, IFIC