Changes between Version 1 and Version 2 of Reweight


Ignore:
Timestamp:
07/01/13 06:24:30 (7 years ago)
Author:
omatt
Comment:

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  • Reweight

    v1 v2  
    44 This methods works only if the original hypothesis and the new one are both significant in the same part of the phase-space.
    55 the new weight is given by
    6 $$W_{new} = |M_{new}|^2 /|M_{old}|^2 * W_{old} $$
     6 $$W_{new} = |M_{new}|^2 /|M_{old}|^2 * W_{old} $$
    77
    8 = Technical details.
    9  
     8= Technical details
     9 == Limitation
    1010  1. The two theoretical hypothesis should differ ONLY by difference in the model parameters. So this should be the same process, the same model and the same pdf.
    1111  2. The scale choice for the reweighting is done events by events and is given by the value in the LHE file. The same scale is used for both Hypothesis
    1212  3. In presence of decay chain the order of the particle in the events file is important. This is important if you want to use this tools with LHE events not produced by MadGraph/MadEvent.
     13
     14 == How to get the code
     15 The code is currently (30/06/13) in beta, and is still expect to be modify before the official release (especially on the interface).
     16 In order to download the code, you need to have bazaar install on your computer. Then you can download the code via the command
     17{{{bzr branch lp:~maddevelopers/madgraph5/reweight_module}}} 
     18After that in order to update your version. You only need to do:
     19{{{bzr pull}}}
     20 
     21 == How to use the code.
     22 1. go to the process directory.
     23 2. launch the '''./bin/madevent''' script
     24 3. type '''reweight RUN_NAME'''
     25 4. then you will see the following question:
     26    {{{Do you want to edit one cards (press enter to bypass editing)?
     27  1 / reweight  : reweight_card.dat
     28 you can also
     29   - enter the path to a valid card.
     30 [0, done, 1, reweight, enter path][60s to answer]}}}
     31If you didn't define the content of this file already. You need to do it.
     32The syntax is explained inside the file, and you can see example below (validation section).
     33The '''important''' point, is that the first line should be launch, and then you specify which parameter, you want to modify. 
     34This is the exact same syntax has for scripting a scan over parameter.
     35 5. exit the file and you are done.
     36
     37 = Input/Output format
     38
     39 1. the output format follows the Leshouches agreement (not yet published): http://phystev.in2p3.fr/wiki/2013:groups:tools_lheextension#the_proposal
     40
     41as an example the header looks like:
     42 {{{
     43<initrwgt>
     44<weightgroup type='mg_reweighting'>
     45<weight id='mg_reweight_1'>set param_card dim6 1 100.0
     46</weight>
     47<weight id='mg_reweight_2'>set param_card dim6 2 100.0
     48</weight>
     49<weight id='mg_reweight_3'>set param_card dim6 3 100.0
     50</weight>
     51</weightgroup>
     52</initrwgt>
     53}}}
     54and one associated events:
     55{{{
     56<event>
     57 8      0 +7.9887000e-06 1.24664300e+02 7.95774700e-02 1.23856500e-01
     58        1 -1    0    0  501    0 +0.0000000e+00 +0.0000000e+00 +1.3023196e+03 1.30231957e+03 0.00000000e+00 0.0000e+00 -1.0000e+00
     59       -2 -1    0    0    0  501 +0.0000000e+00 +0.0000000e+00 -1.4499581e+02 1.44995814e+02 0.00000000e+00 0.0000e+00 1.0000e+00
     60      -24  2    1    2    0    0 -1.2793809e+01 -8.3954553e+01 -1.1792566e+02 1.65987064e+02 8.02071978e+01 0.0000e+00 0.0000e+00
     61       23  2    1    2    0    0 +1.2793809e+01 +8.3954553e+01 +1.2752494e+03 1.28132832e+03 9.12640692e+01 0.0000e+00 0.0000e+00
     62       11  1    3    3    0    0 -1.2462673e+01 +1.3647422e+01 -2.6083861e+01 3.19677669e+01 0.00000000e+00 0.0000e+00 -1.0000e+00
     63      -12  1    3    3    0    0 -3.3113586e-01 -9.7601975e+01 -9.1841804e+01 1.34019297e+02 0.00000000e+00 0.0000e+00 1.0000e+00
     64        4  1    4    4  502    0 -1.8321803e+01 +9.0929609e+01 +9.3905973e+02 9.43629724e+02 0.00000000e+00 0.0000e+00 -1.0000e+00
     65       -4  1    4    4    0  502 +3.1115612e+01 -6.9750557e+00 +3.3618969e+02 3.37698598e+02 0.00000000e+00 0.0000e+00 1.0000e+00
     66<rwgt>
     67<wgt id='mg_reweight_1'> 4.55278761371e-06 </wgt>
     68<wgt id='mg_reweight_2'> 2.65941887458e-06 </wgt>
     69<wgt id='mg_reweight_3'> 8.68203803896e-06 </wgt>
     70</rwgt>
     71</event>
     72}}}
     73The reweight_card in that case was:
     74{{{
     75launch
     76   set Dim6 1 100
     77   set Dim6 2 0
     78   set Dim6 3 0
     79   set Dim6 4 0
     80   set Dim6 5 0
     81launch
     82   set Dim6 1 0
     83   set Dim6 2 100
     84   set Dim6 3 0
     85   set Dim6 4 0
     86   set Dim6 5 0
     87launch
     88   set Dim6 1 0
     89   set Dim6 2 0
     90   set Dim6 3 100
     91   set Dim6 4 0
     92   set Dim6 5 0
     93}}}
     94Note:
     95    a. The production events were in this case made via the SM where all those coefficient were in fact set to zero. Therefore all the line setting the line to zero were superfluous, and this is the reason why they didn't appear in the banner.
     96    b. You can also specify a path to a param_card in the reweight_card. The content of the header being computed automatically with the difference of the two param_card.
     97 
     98 = Validation
     99
     100 The validation of this tools is not yet finish. Use this tools with care. In particular in presence of decay chain, if you have identical particles in the final states coming from different decay. (For example p p > w+ z, w+ > e+ ve, z > e+ e-)
     101
     102 == p p > e+ e- cross-section
     103
     104 
     105
     106
     107
     108
     109