Message: elastic scattering does not respect energy conservation? Not Logged In (login)
 Next-in-Thread Next-in-Thread
 Next-in-Forum Next-in-Forum

Question elastic scattering does not respect energy conservation? 

Forum: Hadronic Processes
Date: 21 May, 2010
From: Simone <Simone>

Hi,

I'm using the space science physics list provided by the slac site (http://www.slac.stanford.edu/comp/physics/geant4/slac_physics_lists/space/physlistdoc.html) and I'm trying to simulate passage of protons in my detector using geant4.9.3, and in my output it seems that the process HadronElastic does not conserve energy.

I'm sorry for the lenght of the explaination but I thought more time would be wasted in following explaination if I did not start from the beginning

The first time I run the simulation with solid objects (the detector and the shielding around that) the energy dE lost by the protons was really higher than the kinetic energy of the produced nucleus (tipically 1 order of magnitude).

I guessed that part of the energy went into excitation of the nucleus (i read on some tutorials that there are some anelastic corrections in the model), lowered the cut and searched for particle emission by the excited nucleus, and ruled out this hypotesis...

then I thought that part of the energy could have been transfered to nearby atoms and decided to change the geometry, filling world volume only with a gas (air), and try to analyze the output and sistematically obtained this results in wich the energy gained by the N atom is around 300 TIMES the energy lost by the proton:

*********************************************************************************************************
* G4Track Information:   Particle = proton,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm)    KinE(MeV)  dE(MeV) StepLeng   TrackLeng  NextVolume  ProcName
    9 3.21e+05 3.99e+05 9.64e+04       721 0.000803 8.02e+03  5.21e+05     expHall HadronElastic

*********************************************************************************************************
* G4Track Information:   Particle = N14[0.0],   Track ID = 10,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0 3.21e+05 3.99e+05 9.64e+04     0.264        0        0         0     expHall initStep
    1 3.21e+05 3.99e+05 9.64e+04     0.226    0.038      121       121     expHall ionIoni
    2 3.21e+05 3.99e+05 9.65e+04     0.191   0.0345      114       235     expHall ionIoni
    3 3.21e+05 3.99e+05 9.66e+04     0.164   0.0271      106       341     expHall ionIoni
    4 3.21e+05 3.99e+05 9.67e+04     0.139   0.0246     96.3       437     expHall ionIoni
    5 3.21e+05 3.99e+05 9.67e+04     0.116   0.0228     86.4       524     expHall ionIoni
    6 3.21e+05 3.99e+05 9.68e+04    0.0961   0.0203     76.7       601     expHall ionIoni
    7 3.21e+05 3.99e+05 9.68e+04    0.0767   0.0194     67.6       668     expHall ionIoni
    8 3.21e+05 3.99e+05 9.69e+04    0.0636    0.013     58.2       726     expHall ionIoni
    9 3.21e+05 3.99e+05 9.69e+04    0.0547  0.00897     51.5       778     expHall ionIoni
   10 3.21e+05 3.99e+05 9.69e+04    0.0459  0.00874     46.6       825     expHall ionIoni
   11 3.21e+05 3.99e+05  9.7e+04    0.0361  0.00987     41.7       866     expHall ionIoni
   12 3.21e+05 3.99e+05  9.7e+04    0.0295  0.00657     35.9       902     expHall ionIoni
   13 3.21e+05 3.99e+05  9.7e+04    0.0274   0.0021     31.8       934     expHall ionIoni
   14 3.21e+05 3.99e+05 9.71e+04    0.0204    0.007     30.5       964     expHall ionIoni
   15 3.21e+05 3.99e+05 9.71e+04    0.0183  0.00211     25.8       990     expHall ionIoni
   16 3.21e+05 3.99e+05 9.71e+04    0.0141  0.00414     24.3  1.01e+03     expHall ionIoni
   17 3.21e+05 3.99e+05 9.71e+04   0.00986  0.00428     21.4  1.04e+03     expHall ionIoni
   18 3.21e+05 3.99e+05 9.71e+04   0.00714  0.00272       18  1.05e+03     expHall ionIoni
   19 3.21e+05 3.99e+05 9.71e+04   0.00474   0.0024     15.4  1.07e+03     expHall ionIoni
   20 3.21e+05 3.99e+05 9.71e+04   0.00295  0.00179     12.6  1.08e+03     expHall ionIoni
   21 3.21e+05 3.99e+05 9.71e+04   0.00243 0.000522     9.99  1.09e+03     expHall ionIoni
   22 3.21e+05 3.99e+05 9.71e+04   0.00225 0.000177     9.07   1.1e+03     expHall ionIoni
   23 3.21e+05 3.99e+05 9.71e+04   0.00185 0.000405     8.74  1.11e+03     expHall ionIoni
   24 3.21e+05 3.99e+05 9.71e+04   0.00145 0.000396     7.93  1.12e+03     expHall ionIoni
   25 3.21e+05 3.99e+05 9.71e+04  0.000926 0.000528     7.05  1.12e+03     expHall ionIoni
   26 3.21e+05 3.99e+05 9.71e+04  0.000673 0.000254     5.67  1.13e+03     expHall ionIoni
   27 3.21e+05 3.99e+05 9.71e+04  0.000466 0.000207     4.86  1.14e+03     expHall ionIoni
   28 3.21e+05 3.99e+05 9.71e+04  0.000465 1.38e-06     4.07  1.14e+03     expHall ionIoni
   29 3.21e+05 3.99e+05 9.71e+04  0.000435 2.98e-05     4.07  1.14e+03     expHall ionIoni
   30 3.21e+05 3.99e+05 9.71e+04  0.000304 0.000131     3.94  1.15e+03     expHall ionIoni
   31 3.21e+05 3.99e+05 9.71e+04  0.000258  4.6e-05     3.33  1.15e+03     expHall ionIoni
   32 3.21e+05 3.99e+05 9.71e+04  0.000235 2.32e-05     3.08  1.15e+03     expHall ionIoni
   33 3.21e+05 3.99e+05 9.71e+04  0.000213 2.24e-05     2.94  1.16e+03     expHall ionIoni
   34 3.21e+05 3.99e+05 9.71e+04  0.000146  6.7e-05     2.81  1.16e+03     expHall ionIoni
   35 3.21e+05 3.99e+05 9.71e+04  0.000129  1.7e-05     2.36  1.16e+03     expHall ionIoni
   36 3.21e+05 3.99e+05 9.71e+04  0.000122  6.8e-06     2.23  1.16e+03     expHall ionIoni
   37 3.21e+05 3.99e+05 9.71e+04  7.69e-05 4.49e-05     2.17  1.17e+03     expHall ionIoni
   38 3.21e+05 3.99e+05 9.71e+04  5.12e-05 2.57e-05     1.76  1.17e+03     expHall ionIoni
   39 3.21e+05 3.99e+05 9.71e+04  3.26e-05 1.86e-05     1.47  1.17e+03     expHall ionIoni
   40 3.21e+05 3.99e+05 9.71e+04  2.69e-05 5.73e-06     1.21  1.17e+03     expHall ionIoni
   41 3.21e+05 3.99e+05 9.71e+04  2.06e-05  6.3e-06     1.11  1.17e+03     expHall ionIoni
   42 3.21e+05 3.99e+05 9.71e+04  1.87e-05 1.85e-06    0.997  1.17e+03     expHall ionIoni
   43 3.21e+05 3.99e+05 9.71e+04  1.54e-05 3.36e-06     0.96  1.17e+03     expHall ionIoni
   44 3.21e+05 3.99e+05 9.71e+04  1.04e-05 4.98e-06    0.886  1.17e+03     expHall ionIoni
   45 3.21e+05 3.99e+05 9.71e+04  5.63e-06 4.78e-06     0.76  1.18e+03     expHall ionIoni
   46 3.21e+05 3.99e+05 9.71e+04   4.2e-06 1.43e-06    0.606  1.18e+03     expHall ionIoni
   47 3.21e+05 3.99e+05 9.71e+04  4.15e-06 4.72e-08    0.547  1.18e+03     expHall ionIoni
   48 3.21e+05 3.99e+05 9.71e+04  4.06e-06 9.36e-08    0.545  1.18e+03     expHall ionIoni
   49 3.21e+05 3.99e+05 9.71e+04  3.47e-06 5.95e-07    0.541  1.18e+03     expHall ionIoni
   50 3.21e+05 3.99e+05 9.71e+04  3.15e-06 3.11e-07    0.513  1.18e+03     expHall ionIoni
   51 3.21e+05 3.99e+05 9.71e+04  3.03e-06 1.26e-07    0.498  1.18e+03     expHall ionIoni
   52 3.21e+05 3.99e+05 9.71e+04  2.48e-06 5.49e-07    0.491  1.18e+03     expHall ionIoni
   53 3.21e+05 3.99e+05 9.71e+04  1.89e-06 5.91e-07    0.461  1.18e+03     expHall ionIoni
   54 3.21e+05 3.99e+05 9.71e+04         0 1.89e-06    0.424  1.18e+03     expHall ionIoni

- this surely is not due to thermal iniection of kinetic Energy (air at 300 K --> Ekin=0.027 eV...)

- since the energy gained is HIGHER then the energy lost I can guess that the problem is not the energy going lost in some channel I did not consider as I tought before

maybe I misunderstood something important? does anyone have any explaination/suggestion on other tests to do?

thanks

simone

Inline Depth:
 1 1
 All All
Outline Depth:
 1 1
 2 2
 All All
Add message: (add)

1 Idea: Re: elastic scattering does not respect energy conservation?   (Vladimir Ivanchenko - 12 Jun, 2010)
 Add Message Add Message
to: "elastic scattering does not respect energy conservation?"

 Subscribe Subscribe

This site runs SLAC HyperNews version 1.11-slac-98, derived from the original HyperNews


[ Geant 4 Home | Geant 4 HyperNews | Search | Request New Forum | Feedback ]