## Meeting 2015 10 30 » History » Version 5

*Nicolas Ponieman, 10/26/2015 04:07 PM *

1 | 1 | Nicolas Ponieman | {{toc}} |
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3 | 1 | Nicolas Ponieman | h1. Meeting 2015 10 30 |

4 | 1 | Nicolas Ponieman | |

5 | 1 | Nicolas Ponieman | h2. Objectives Proposed during last meeting |

6 | 1 | Nicolas Ponieman | |

7 | 4 | Nicolas Ponieman | # (P0) (DONE) Check the values and precision of the parameters involved in Geant4, QSS and analytical solution are exactly the same. |

8 | 4 | Nicolas Ponieman | # (P0) (DONE) Plot the difference between the simulated velocity and the expected value (which is a parameter in the model). |

9 | 2 | Nicolas Ponieman | # (P1) For each simulation with a certain number of planes, calculate the error of the simulation. |

10 | 2 | Nicolas Ponieman | # (P3) Improve last meeting plots which compare Geant4, QSS3 and DOPRI5 performance. |

11 | 1 | Nicolas Ponieman | |

12 | 1 | Nicolas Ponieman | * Format issues (scales, line colors, etc.) |

13 | 1 | Nicolas Ponieman | * Make statistic on many (10?) simulations for the points and add {simulationTime, simulationTimeError} for each number of planes. |

14 | 1 | Nicolas Ponieman | * How does DOPRI5 find the intersection with the planes? |

15 | 2 | Nicolas Ponieman | # (P1) New Experiment: varying stepMax (from 0.1mm to 100mm) calculate the error in the first steps (in the position and in the velocity, also the error which is compared to epsilon in Geant4) |

16 | 2 | Nicolas Ponieman | # (P1) Repeat Experiment 1: debug what is the error in Geant4 stepper, which is to be compared with epsilon. |

17 | 2 | Nicolas Ponieman | # (P2) New Experiment: study impact of deltaInt parameter in Geant4 when changing the number of planes. |

18 | 2 | Nicolas Ponieman | # (P3) Make some experiments with a different magnetic field: |

19 | 1 | Nicolas Ponieman | B(x,y) = (B/R) sqrt( x*x + (y+R)*(y+R)) zhat (where B= constant, zhat is the directional vector along the z axis, R is the radius of the circle) |

20 | 1 | Nicolas Ponieman | This field will keep the problem same as it is, but will give a deviation if the particle is off the circle |

21 | 1 | Nicolas Ponieman | (due to the error of the stepper). |

22 | 2 | Nicolas Ponieman | # (P3) Introduce discrete stochastic events simulating an artificial decay. |

23 | 1 | Nicolas Ponieman | # Introduce a different graphical representation (such as changing the color of the scatter points) for each different type of errors. |

24 | 1 | Nicolas Ponieman | |

25 | 1 | Nicolas Ponieman | * What are the different possible kind of errors? |

26 | 1 | Nicolas Ponieman | # (P1) Summarize all the information Nico learnt with Soon about the transportation chain in a slide, or a handwritten sketch. |

27 | 1 | Nicolas Ponieman | # (P1) Group presentation on Thursday by Nico. |

28 | 4 | Nicolas Ponieman | |

29 | 4 | Nicolas Ponieman | h2. Constant Values |

30 | 4 | Nicolas Ponieman | |

31 | 4 | Nicolas Ponieman | After last meeting, we found a few inconsistencies in the constants we were using as parameters in our external scripts and the ones used internally by Geant4. |

32 | 4 | Nicolas Ponieman | |

33 | 4 | Nicolas Ponieman | * c is consistent |

34 | 4 | Nicolas Ponieman | |

35 | 4 | Nicolas Ponieman | ** In Line 54: /opt/geant4/geant4.10.01.p01/source/externals/clhep/include/CLHEP/Units/PhysicalConstants. |

36 | 4 | Nicolas Ponieman | static const double c_light = 2.99792458e+8 * m/s; |

37 | 4 | Nicolas Ponieman | |

38 | 4 | Nicolas Ponieman | ** We used: |

39 | 4 | Nicolas Ponieman | c = 299.792458 |

40 | 4 | Nicolas Ponieman | |

41 | 4 | Nicolas Ponieman | * gamma is inconsistent |

42 | 4 | Nicolas Ponieman | |

43 | 4 | Nicolas Ponieman | ** We used: |

44 | 4 | Nicolas Ponieman | gamma = 22.366272 |

45 | 4 | Nicolas Ponieman | |

46 | 4 | Nicolas Ponieman | ** which is inconsistent with the value |

47 | 4 | Nicolas Ponieman | gamma = np.sqrt(1/(1 - (v0/c)**2)) = 22.3662720421 |

48 | 4 | Nicolas Ponieman | |

49 | 4 | Nicolas Ponieman | * Electron mass (M) is inconsistent |

50 | 4 | Nicolas Ponieman | |

51 | 4 | Nicolas Ponieman | ** In Line 85 /opt/geant4/geant4.10.01.p01/source/externals/clhep/include/CLHEP/Units/PhysicalConstants.h |

52 | 4 | Nicolas Ponieman | static const double electron_mass_c2 = 0.510998910 * MeV; |

53 | 4 | Nicolas Ponieman | |

54 | 4 | Nicolas Ponieman | ** We used: |

55 | 4 | Nicolas Ponieman | old_M = 0.5109989 |

56 | 4 | Nicolas Ponieman | |

57 | 4 | Nicolas Ponieman | * Kinetic Energy is inconsistent: |

58 | 4 | Nicolas Ponieman | ** In Geant4, we were using a value for Kinetic Energt which was different to the one that can be calculated either with the old or new values of the constants: |

59 | 4 | Nicolas Ponieman | /gun/energy 10.9181415106 MeV (this 'wrong' value was taken from the original wiki entry). |

60 | 4 | Nicolas Ponieman | |

61 | 4 | Nicolas Ponieman | ** The new and correct value for Kinetic Energy should be: |

62 | 4 | Nicolas Ponieman | /gun/energy 10.9181417243 MeV |

63 | 4 | Nicolas Ponieman | |

64 | 4 | Nicolas Ponieman | * A few experiments were reran and no difference in the plots nor in the errors was noticed. |

65 | 4 | Nicolas Ponieman | This seems reasonable considering this corrections are of very low order, and our errors are larger. |

66 | 4 | Nicolas Ponieman | |

67 | 4 | Nicolas Ponieman | * As a conclusion, this is an error we have to correct but which doesn't modify our previous results and leaves open the same questions as before regarding the invariance of error when changing epsilon. |

68 | 4 | Nicolas Ponieman | |

69 | 4 | Nicolas Ponieman | h2. Velocity Error Plots |

70 | 5 | Nicolas Ponieman | |

71 | 5 | Nicolas Ponieman | !https://cdcvs.fnal.gov/redmine/attachments/download/29964/VError_vs_dist.png! |

72 | 5 | Nicolas Ponieman | Figure 1: VError (difference between simulated and expected value) vs distance |

73 | 5 | Nicolas Ponieman | |

74 | 5 | Nicolas Ponieman | !https://cdcvs.fnal.gov/redmine/attachments/download/29963/VError_hist.png! |

75 | 5 | Nicolas Ponieman | Figure 2: VError (difference between simulated and expected value) histogram |

76 | 5 | Nicolas Ponieman | |

77 | 5 | Nicolas Ponieman | * We notice the simulated velocity is *always* smaller than the expected velocity. |

78 | 5 | Nicolas Ponieman | * Why is this happening? |