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Question Tracking of low energy muons stops without apparent reason 

Forum: Event and Track Management
Date: 02 Feb, 2012
From: Kamil Sedlak <Kamil Sedlak>

Dear All, I am simulating transport of low energy muons in a He gas in the presence of a constant electric field (500V over a few cm) and in a 5T magnetic field (parallel to the electric field). Muons loose their initial energy (e.g. via ionisation), but should not stop completly, because the electric field should re-accelerate them. This indeed happens for some muons, however some muons suddenly stop (for a reason which I do not understand). Here is an example of the last steps of one such muon:

  980   -540 um   -663 um    -12 cm   2.02 keV 0.827 eV      1 mm   97.5 cm   phys_target  Transportation
  981   -915 um   -837 um  -11.9 cm   1.96 keV  73.3 eV      1 mm   97.6 cm   phys_target  Transportation
  982   -779 um   -471 um  -11.9 cm   1.42 keV   545 eV      1 mm   97.7 cm   phys_target  Transportation
  983   -835 um   -737 um  -11.8 cm   1.29 keV   134 eV      1 mm   97.8 cm   phys_target  Transportation
  984   -718 um   -442 um  -11.7 cm   1.06 keV   230 eV      1 mm   97.9 cm   phys_target  Transportation
  985   -718 um   -640 um  -11.6 cm   1.07 keV  4.52 eV      1 mm     98 cm   phys_target  Transportation
  986   -752 um   -390 um  -11.5 cm   1.06 keV  11.6 eV      1 mm   98.1 cm   phys_target  Transportation
  987   -787 um   -755 um  -11.4 cm    500 eV    565 eV      1 mm   98.2 cm   phys_target  Transportation
  988   -605 um   -560 um  -11.3 cm    504 eV  0.101 eV   1.01 mm   98.3 cm   phys_target  Transportation
  989   -853 um   -594 um  -11.3 cm    508 eV 2.1e-06 eV   1.01 mm   98.4 cm   phys_target  Transportation
  990   -896 um   -981 um  -11.2 cm    496 eV   13.9 eV   1.01 mm   98.5 cm   phys_target  Transportation
  991   -571 um   -933 um  -11.2 cm    497 eV   1.01 eV   1.01 mm   98.6 cm   phys_target  Transportation
  992   -451 um   -653 um  -11.2 cm    497 eV   2.66 eV   1.01 mm   98.7 cm   phys_target  Transportation
  993   -775 um   -534 um  -11.2 cm    499 eV 0.000187 eV   1.01 mm   98.8 cm   phys_target  Transportation
  994   -659 um   -798 um  -11.1 cm    502 eV 0.0826 eV   1.01 mm   98.9 cm   phys_target  Transportation
  995   -349 um   -740 um  -11.1 cm    503 eV 0.000518 eV   1.01 mm     99 cm   phys_target  Transportation
  996   -372 um   -370 um  -11.1 cm    505 eV  0.362 eV   1.01 mm   99.1 cm   phys_target  Transportation
  997   -650 um   -615 um    -11 cm    508 eV  0.026 eV   1.01 mm   99.2 cm   phys_target  Transportation
  998   -315 um   -695 um    -11 cm    509 eV 0.0106 eV   1.01 mm   99.3 cm   phys_target  Transportation
  999   -139 um   -501 um    -11 cm    508 eV   3.06 eV   1.01 mm   99.4 cm   phys_target  Transportation
 1000   -377 um   -304 um  -10.9 cm    509 eV  0.658 eV   1.01 mm   99.5 cm   phys_target  Transportation
 1001   -592 um   -551 um  -10.9 cm    325 eV    186 eV   1.01 mm   99.6 cm   phys_target  Transportation
 1002   -537 um   -631 um  -10.9 cm    325 eV   0.06 eV   1.02 mm   99.7 cm   phys_target  Transportation
 1003   -466 um   -693 um  -10.9 cm    327 eV 2.32e-05 eV   1.02 mm   99.8 cm   phys_target  Transportation
 1004   -375 um   -732 um  -10.8 cm    329 eV 0.00844 eV   1.02 mm   99.9 cm   phys_target  Transportation
 1005   -304 um   -638 um  -10.9 cm   52.9 eV    275 eV   1.02 mm    100 cm   phys_target  Transportation
 1006   -366 um   -524 um  -10.8 cm   51.6 eV 9.39e-76 eV   1.12 mm      1 m    phys_target  Transportation
 1007   -347 um   -245 um  -10.8 cm   54.2 eV 1.08e-202 eV   1.12 mm      1 m    phys_target  Transportation
 1008   -448 um   -437 um  -10.8 cm   55.9 eV 1.4e-92 eV   1.12 mm      1 m    phys_target  Transportation
 1009   -126 um   -293 um  -10.7 cm   3.64 eV   55.9 eV   1.12 mm      1 m    phys_target  Transportation
 1010   -162 um   9.41 um  -10.7 cm    7.5 eV      0 eV   1.03 mm   1.01 m    phys_target       muMsc
 1011   -170 um  -22.8 um  -10.6 cm      9 eV      0 eV   1.13 mm   1.01 m    phys_target  Transportation
 1012    128 um   -113 um  -10.6 cm   13.8 eV 4.44e-192 eV   1.03 mm   1.01 m    phys_target       muMsc
 1013   44.9 um   -467 um  -10.5 cm   19.5 eV 1.13e-55 eV   1.12 mm   1.01 m    phys_target  Transportation
 1014   -165 um   -607 um  -10.4 cm   21.4 eV      0 eV   1.12 mm   1.01 m    phys_target  Transportation
 1015   -158 um   -532 um  -10.5 cm   19.4 eV 1.59e-192 eV   1.12 mm   1.01 m    phys_target  Transportation
 1016  -86.9 um   -482 um  -10.5 cm   18.7 eV 5.8e-78 eV   1.12 mm   1.01 m    phys_target  Transportation
 1017  -39.5 um   -475 um  -10.5 cm   18.6 eV 4.1e-195 eV   1.12 mm   1.01 m    phys_target  Transportation
 1018  -42.4 um   -481 um  -10.5 cm   14.7 eV 1.25e-281 eV   1.12 mm   1.01 m    phys_target  Transportation
 1019   -266 um   -417 um  -10.5 cm   11.6 eV      0 eV   1.03 mm   1.02 m    phys_target       muMsc
 1020   19.3 um   -665 um  -10.5 cm   14.1 eV 2.8e-15 eV   1.12 mm   1.02 m    phys_target  Transportation
 1021   27.9 um   -928 um  -10.5 cm   18.1 eV 2.87e-110 eV   1.03 mm   1.02 m    phys_target       muMsc
 1022  -16.5 um   -931 um  -10.5 cm   18.9 eV 7.22e-22 eV   1.12 mm   1.02 m    phys_target  Transportation
 1023  -7.15 um   -999 um  -10.4 cm   20.7 eV 1.3e-199 eV   1.12 mm   1.02 m    phys_target  Transportation
 1024     30 um   -922 um  -10.4 cm   22.7 eV      0 eV   1.12 mm   1.02 m    phys_target  Transportation
 1025   -247 um   -765 um  -10.3 cm   26.5 eV 2.56e-247 eV   1.12 mm   1.02 m    phys_target  Transportation
 1026   -191 um   -409 um  -10.3 cm   31.8 eV 0.00206 eV   1.12 mm   1.02 m    phys_target  Transportation
 1027   -315 um   -147 um  -10.2 cm   34.3 eV 2.35e-99 eV   1.12 mm   1.02 m    phys_target  Transportation
 1028   -549 um   32.5 um  -10.3 cm   32.8 eV 1.88e-151 eV   1.12 mm   1.03 m    phys_target  Transportation
 1029   -206 um   15.3 um  -10.3 cm     30 eV 3.63e-279 eV   1.12 mm   1.03 m    phys_target  Transportation
 1030   -348 um   -203 um  -10.3 cm   31.4 eV 4.41e-152 eV   1.12 mm   1.03 m    phys_target  Transportation
 1031   -362 um   -410 um  -10.4 cm   32.4 eV      0 eV   1.12 mm   1.03 m    phys_target  Transportation
 1032   -239 um   -329 um  -10.3 cm   35.3 eV 1.88e-177 eV   1.12 mm   1.03 m    phys_target  Transportation
 1033   -549 um   -562 um  -10.3 cm   36.2 eV 1.36e-53 eV   1.12 mm   1.03 m    phys_target  Transportation
 1034   -706 um   -490 um  -10.4 cm   33.2 eV 4.78e-42 eV   1.12 mm   1.03 m    phys_target  Transportation
 1035   -493 um   -398 um  -10.5 cm   29.5 eV 1.86e-12 eV   1.12 mm   1.03 m    phys_target  Transportation
 1036   -366 um   -684 um  -10.5 cm   25.8 eV 5.12e-145 eV   1.12 mm   1.03 m    phys_target  Transportation
 1037   -754 um   -542 um  -10.6 cm     23 eV 1.79e-150 eV   1.12 mm   1.04 m    phys_target  Transportation
 1038   -675 um   -571 um  -10.6 cm   20.8 eV      0 eV   1.12 mm   1.04 m    phys_target  Transportation
 1039   -745 um   -523 um  -10.6 cm   21.4 eV      0 eV   1.12 mm   1.04 m    phys_target  Transportation
 1040  -1.11 mm   -635 um  -10.7 cm   15.9 eV 5.46e-238 eV   1.12 mm   1.04 m    phys_target  Transportation
 1041  -1.36 mm   -408 um  -10.8 cm   10.8 eV      0 eV   1.04 mm   1.04 m    phys_target       muMsc
 1042  -1.06 mm   -141 um  -10.9 cm   6.28 eV 2.03e-94 eV   1.12 mm   1.04 m    phys_target  Transportation
 1043  -1.07 mm   -153 um  -10.9 cm   2.13 eV      0 eV   1.03 mm   1.04 m    phys_target       muMsc
 1044  -1.36 mm  -2.34 um  -10.9 cm   1.51 eV   2.13 eV   1.15 mm   1.04 m    phys_target  Transportation
 1045  -1.14 mm    301 um  -10.8 cm   5.27 eV   1.51 eV   1.03 mm   1.04 m    phys_target       muMsc
 1046   -984 um    605 um  -10.8 cm   9.19 eV      0 eV   1.13 mm   1.05 m    phys_target  Transportation
 1047  -1.15 mm    786 um  -10.7 cm   13.1 eV      0 eV   1.03 mm   1.05 m    phys_target       muMsc
 1048  -1.16 mm    790 um  -10.6 cm   18.6 eV 2.99e-112 eV   1.12 mm   1.05 m    phys_target  Transportation
 1049  -1.02 mm    579 um  -10.6 cm   22.6 eV 0.000157 eV   1.12 mm   1.05 m    phys_target  Transportation
 1050  -1.26 mm    693 um  -10.6 cm   26.4 eV      0 eV   1.12 mm   1.05 m    phys_target  Transportation
 1051  -1.22 mm    816 um  -10.6 cm   27.1 eV 1.35e-27 eV   1.12 mm   1.05 m    phys_target  Transportation
 1052  -1.21 mm    982 um  -10.6 cm   25.8 eV 6.57e-164 eV   1.12 mm   1.05 m    phys_target  Transportation
 1053  -1.28 mm    673 um  -10.6 cm   25.2 eV      0 eV   1.12 mm   1.05 m    phys_target  Transportation
 1054  -1.51 mm    839 um  -10.6 cm     28 eV 5.33e-05 eV   1.12 mm   1.05 m    phys_target  Transportation
 1055  -1.84 mm   1.01 mm  -10.5 cm   32.2 eV 6.58e-05 eV   1.12 mm   1.06 m    phys_target  Transportation
 1056  -1.51 mm   1.01 mm  -10.5 cm   36.2 eV 3.39e-116 eV   1.12 mm   1.06 m    phys_target  Transportation
 1057  -1.59 mm    967 um  -10.4 cm   39.4 eV 4.49e-24 eV   1.12 mm   1.06 m    phys_target  Transportation
 1058   -1.8 mm    891 um  -10.4 cm   43.5 eV 3.27e-10 eV   1.12 mm   1.06 m    phys_target  Transportation
 1059  -1.89 mm    960 um  -10.3 cm   46.8 eV 8.27e-167 eV   1.12 mm   1.06 m    phys_target  Transportation
 1060   -1.7 mm    687 um  -10.2 cm   52.2 eV 2.2e-104 eV   1.12 mm   1.06 m    phys_target  Transportation
 1061  -1.48 mm    527 um  -10.2 cm   53.8 eV   2.42 eV   1.12 mm   1.06 m    phys_target  Transportation
 1062  -1.81 mm    667 um  -10.1 cm   59.3 eV 2.05e-78 eV   1.12 mm   1.06 m    phys_target  Transportation
 1063  -1.76 mm    311 um  -9.99 cm   65.3 eV 6.14e-83 eV   1.12 mm   1.06 m    phys_target  Transportation
 1064   -1.7 mm    429 um  -9.92 cm   67.3 eV 7.2e-66 eV   1.12 mm   1.07 m    phys_target  Transportation
 1065   -1.7 mm    433 um   -9.9 cm   68.5 eV 1.78e-06 eV   1.12 mm   1.07 m    phys_target  Transportation
 1066  -1.69 mm    444 um  -9.89 cm   69.5 eV 0.000723 eV   1.12 mm   1.07 m    phys_target  Transportation
 1067  -1.68 mm    458 um  -9.87 cm   70.3 eV 1.67e-21 eV   1.12 mm   1.07 m    phys_target  Transportation
 1068  -1.43 mm    717 um  -9.79 cm   75.7 eV 3.82e-18 eV   1.12 mm   1.07 m    phys_target  Transportation
 1069  -1.39 mm    666 um  -9.78 cm   76.8 eV 0.000491 eV   1.12 mm   1.07 m    phys_target  Transportation
 1070  -1.33 mm    651 um  -9.76 cm   77.8 eV 2.99e-167 eV   1.12 mm   1.07 m    phys_target  Transportation
 1071  -1.06 mm    407 um  -9.87 cm   70.6 eV    1.1 eV   1.12 mm   1.07 m    phys_target  Transportation
 1072  -1.32 mm    171 um  -9.95 cm   65.1 eV 8.09e-38 eV   1.12 mm   1.07 m    phys_target  Transportation
 1073  -1.12 mm    463 um    -10 cm   60.4 eV  0.106 eV   1.12 mm   1.08 m    phys_target  Transportation
 1074  -1.13 mm    517 um    -10 cm   59.9 eV 0.000267 eV   1.12 mm   1.08 m    phys_target  Transportation
 1075   -1.1 mm    566 um    -10 cm   59.4 eV 4.52e-50 eV   1.12 mm   1.08 m    phys_target  Transportation
 1076  -1.04 mm    549 um    -10 cm     60 eV 2.9e-31 eV   1.12 mm   1.08 m    phys_target  Transportation
 1077  -1.01 mm    512 um    -10 cm   60.3 eV 1.5e-120 eV   1.12 mm   1.08 m    phys_target  Transportation
 1078  -1.02 mm    462 um    -10 cm   60.4 eV 9.64e-74 eV   1.12 mm   1.08 m    phys_target  Transportation
 1079   -716 um    253 um  -9.96 cm   64.2 eV 2.63e-63 eV   1.12 mm   1.08 m    phys_target  Transportation
 1080  -1.02 mm    294 um  -9.91 cm   64.3 eV   4.54 eV   1.12 mm   1.08 m    phys_target  Transportation
 1081  -1.03 mm    270 um  -9.97 cm   60.3 eV 2.58e-211 eV   1.12 mm   1.08 m    phys_target  Transportation
 1082   -944 um   56.7 um    -10 cm     57 eV 3.86e-134 eV   1.12 mm   1.09 m    phys_target  Transportation
 1083   -874 um   84.9 um  -10.1 cm      0 eV     54 eV   1.12 mm   1.09 m    phys_target  Transportation
 1084   -874 um   84.9 um  -10.1 cm      0 eV      0 eV      0 fm   1.09 m    phys_target  DecayWithSpin

______________ D E T A I L ___ O F ___ S T E P ___ 1082(3) _______________________________

#Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng    Volume     Process
 1082   -944 um   56.7 um    -10 cm     57 eV 3.86e-134 eV   1.12 mm   1.09 m    phys_target  Transportation

 >>AlongStepDoIt (after all invocations):
    ++List of invoked processes 
      1) Transportation
      2) muMsc
      3) muIoni
      4) muBrems
      5) muPairProd

    ++G4Step Information 
      Address of G4Track    : 0x2e407c0
      Step Length (mm)      : 1.11690335420266
      Energy Deposit (MeV)  : 5.398394121200206e-05
      -----------------------------------------------------------------------
        StepPoint Information               PreStep            PostStep
      -----------------------------------------------------------------------
         Position - x (mm)   :  -0.9443480572571483  -0.874467690445256
         Position - y (mm)   :  0.05668384456395437 0.08489558055106174
         Position - z (mm)   :   -100.4920640130659  -100.9730955109959
         Global Time (ns)    :    507.7144828910103   510.9704817859767
         Local Time (ns)     :    507.7144828910103   510.9704817859767
         Proper Time (ns)    :     507.620097473749   510.8760946129879
         Momentum Direct - x :   0.4519680780716918  0.8600388587929407
         Momentum Direct - y :   0.7371468222148083 -0.2229456766809377
         Momentum Direct - z :  -0.5023339714799219 -0.4589426833662513
         Momentum - x (MeV/c):  0.04959218557139464                   0
         Momentum - y (MeV/c):   0.0808834158301816                  -0
         Momentum - z (MeV/c): -0.05511858191121276                  -0
         Total Energy (MeV)  :    105.6584239740334          105.658367
         Kinetic Energy (MeV): 5.697403335775722e-05                   0
         Velocity (mm/ns)    :   0.3113307807661723                   0
         Volume Name         :          phys_target         phys_target
         Safety (mm)         :   0.1193128057227171  0.4605856082359621
         Polarization - x    :    -0.33912216259746-0.07602045689061387
         Polarization - y    :  0.08602730155603611  0.3415763707343362
         Polarization - Z    :  -0.9368006523386974 -0.9367745049473226
         Weight              :                    1                   1
         Step Status         :           Geom Limit          Geom Limit
         Process defined Step:       Transportation      Transportation
      -----------------------------------------------------------------------

    ++List of secondaries generated (x,y,z,kE,t,PID):  No. of secodaries = 0

 **PostStepDoIt (after all invocations):
    ++List of invoked processes 
      1) Transportation
      2) muMsc
      3) DecayWithSpin (Forced)

    ++G4Step Information 
      Address of G4Track    : 0x2e407c0
      Step Length (mm)      : 1.11690335420266
      Energy Deposit (MeV)  : 5.398394121200206e-05
      -----------------------------------------------------------------------
        StepPoint Information               PreStep            PostStep
      -----------------------------------------------------------------------
         Position - x (mm)   :  -0.9443480572571483  -0.874467690445256
         Position - y (mm)   :  0.05668384456395437 0.08489558055106174
         Position - z (mm)   :   -100.4920640130659  -100.9730955109959
         Global Time (ns)    :    507.7144828910103   510.9704817859767
         Local Time (ns)     :    507.7144828910103   510.9704817859767
         Proper Time (ns)    :     507.620097473749   510.8760946129879
         Momentum Direct - x :   0.4519680780716918  0.8600388587929407
         Momentum Direct - y :   0.7371468222148083 -0.2229456766809377
         Momentum Direct - z :  -0.5023339714799219 -0.4589426833662513
         Momentum - x (MeV/c):  0.04959218557139464                   0
         Momentum - y (MeV/c):   0.0808834158301816                  -0
         Momentum - z (MeV/c): -0.05511858191121276                  -0
         Total Energy (MeV)  :    105.6584239740334          105.658367
         Kinetic Energy (MeV): 5.697403335775722e-05                   0
         Velocity (mm/ns)    :   0.3113307807661723                   0
         Volume Name         :          phys_target         phys_target
         Safety (mm)         :   0.1193128057227171  0.4605856082359621
         Polarization - x    :    -0.33912216259746-0.07602045689061387
         Polarization - y    :  0.08602730155603611  0.3415763707343362
         Polarization - Z    :  -0.9368006523386974 -0.9367745049473226
         Weight              :                    1                   1
         Step Status         :           Geom Limit          Geom Limit
         Process defined Step:       Transportation      Transportation
      -----------------------------------------------------------------------

    ++List of secondaries generated (x,y,z,kE,t,PID):  No. of secodaries = 0
      [Note]Secondaries from AlongStepDoIt included.

#Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng    Volume     Process
 1083   -874 um   84.9 um  -10.1 cm      0 eV     54 eV   1.12 mm   1.09 m    phys_target  Transportation

There should be nothing special at the position around z=-10cm, where the muon suddenly stopped in step 1083.

Could you advice me where the problem may come from or what can I check to understand it?

I use Geant4.9.5 on a SL6.

Thanks, Kamil

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1 Feedback: Re: Tracking of low energy muons stops without apparent reason   (Gumplinger Peter - 02 Feb, 2012)
(_ None: Re: Tracking of low energy muons stops without apparent reason   (Kamil Sedlak - 03 Feb, 2012)
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