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Question Wrong of the reaction B10(n,alpha)Li7 !! 

Forum: Hadronic Processes
Date: 03 Dec, 2008
From: <csi505>

Hello:
   I am a student from USTC in China。 Recently I have made a simulation
on the reaction  B10(n,alpha)Li7 with Geant4.9.2。The energy of neutron 
is 0.0253ev。Now I accounted a problem。As I know, at the creation of alpha 
the distribution is isotropic(the total momentum of the system is  very 
low)。But in my simulation I got a distribution of alpha which is not 
isotropic, but has a peak in the angle of 47 degree。I have run 5000000,
my run words are 

  /testhadr/TargetLength     2.4 um(This is the thickness of B10)
  /testhadr/CutsAll          1 mm
  /testhadr/Physics          LHEP_PRECO_HP
  /run/initialize
  /gun/particle neutron
  /gun/energy 0.0253 eV
  /run/beamOn 100

My

The result as follows:

Angle Counts 0 63 1 232 2 312 3 491 4 629 5 769 6 924 7 1030 8 1192 9 1315 10 1449 11 1540 12 1693 13 1748 14 1970 15 2068 16 2249 17 2384 18 2421 19 2516 20 2698 21 2714 22 2932 23 2957 24 3060 25 3185 26 3343 27 3470 28 3471 29 3551 30 3713 31 3685 32 3898 33 3895 34 3943 35 4088 36 4115 37 4105 38 4331 39 4245 40 4215 41 4199 42 4300 43 4407 44 4368 45 4365 46 4346 47 4409 48 4329 49 4404 50 4379 51 4332 52 4378 53 4323 54 4317 55 4118 56 4113 57 4071 58 4102 59 4100 60 3994 61 3902 62 3769 63 3650 64 3638 65 3542 66 3414 67 3212 68 3152 69 3030 70 2907 71 2713 72 2670 73 2471 74 2451 75 2248 76 2088 77 1871 78 1802 79 1643 80 1458 81 1324 82 1121 83 967 84 893 85 659 86 553 87 355 88 212 89 63

So as you see, the distribution of alpha is anisotropy。I have thought 
it several days, but I can not come to a Conclusion。So I want to get 
help of you。In my opion, it is Geant4's problem。I'm looking forword to
your reply。
   Many Thanks.           

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