User Tools

Site Tools


2013:groups:tools_lheextension

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
Last revision Both sides next revision
2013:groups:tools_lheextension [2013/02/05 10:19]
benjamin.fuks [The proposal]
2013:groups:tools_lheextension [2013/09/20 10:07]
benjamin.fuks
Line 1: Line 1:
 ===== Extending the Les Houches Event file format ===== ===== Extending the Les Houches Event file format =====
 +=== => in order to handle reweighting information === 
  
  
-==== Participants ==== 
  
  
Line 8: Line 8:
 After discussions with both ATLAS, CMS, aMC@NLO and POWHEG people, it has been found out that it is valuable to include in the LHE format some extra information about event reweighting. And thus comes the problematics of standardizing the way to pass this information. This would allow to have, in one single LHE file, unweighted events corresponding to a given MC setup (for instance, central scales, central PDF, etc…), together with weights related to the variation of one or several of the MC parameters. ​ After discussions with both ATLAS, CMS, aMC@NLO and POWHEG people, it has been found out that it is valuable to include in the LHE format some extra information about event reweighting. And thus comes the problematics of standardizing the way to pass this information. This would allow to have, in one single LHE file, unweighted events corresponding to a given MC setup (for instance, central scales, central PDF, etc…), together with weights related to the variation of one or several of the MC parameters. ​
  
-The proposal below starts from the first try in this direction in the LH proceedings of 2009 ([[http://http://​arxiv.org/​abs/​1003.1643|arXiv:​1003.1643]]),​ and include+The proposal below starts from the first try in this direction in the LH proceedings of 2009 ([[http://​arxiv.org/​abs/​1003.1643|arXiv:​1003.1643]]),​ and include
   * more information in the header,   * more information in the header,
   * a reorganization of the weights, collecting them into categories.   * a reorganization of the weights, collecting them into categories.
  
-**Any comment, suggestion or criticism is welcome. Please update [[#​the_proposal|the text]]. Points to be discussed can be found [[#​To_be_discussed|below]] the proposal.**+The current version of the proposal is currently being implemented in the NLO tools, MadGraph 5 as well as in MadAnalysis 5. Changes are of course still possible. ​**Any comment, suggestion or criticism is welcome. Please update [[#​the_proposal|the text]]. Points to be discussed can be found [[#​To_be_discussed|below]] the proposal.**
  
  
Line 71: Line 71:
 </​event></​code>​ </​event></​code>​
  
-The numbers should be normalized in the same way as the original weight of the event, //i.e.// if the weights sum-up to the total cross section, also the new ''<​nw>''​ weights should sum up to the total cross section (which is in general slightly different because different parameters were used). On the other hand, if the original weights are normalized to 1 (like in the event above), //i.e.// the number of events generated correspond directly to a given luminosity, the same normalization should be used for the ''<​nw>''​ weights. In other words, if you want to know the fractional variation of the <nw> weight corresponding to the original weight (after unweighting),​ it's always enough to divide the new weight by the original weight. The ordering here is irrelevant.+The numbers should be normalized in the same way as the original weight of the event, //i.e.// if the weights sum-up to the total cross section, also the new ''<​nw>''​ weights should sum up to the total cross section (which is in general slightly different because different parameters were used). ​
  
-The event ''​id''​ is important as soon as we have to deal event file after showering/​hadronization (stdHEP or HEPMC event files). This would allow to pass the reweighing information under the price of having multiple file to read. This also avoids to have to extend the standard stdHEP and HEPMC formats.+The event ''​id''​ is important as soon as we have to deal with event files after showering/​hadronization (stdHEP or HEPMC event files). This would allow to pass the reweighing information under the price of having multiple file to read. This also avoids to have to extend the standard stdHEP and HEPMC formats. When used jointly with a stdHEP or HEPMC file, the LHE file only contains the reweighting information.
 ==== To be discussed ==== ==== To be discussed ====
   * The ''<​clustering>''​ tag of 1003.1643   * The ''<​clustering>''​ tag of 1003.1643
2013/groups/tools_lheextension.txt · Last modified: 2013/10/31 15:09 by benjamin.fuks