Hi Costas,

Thanks for your reply. I understand better now.

Suppose, I did the following:
1) dump the ghep ROOT file to a text file using modified "gntpc" utility
2) feed the text file from step 1) to do detector simulation,
reconstruction
How to propagate this weight to the reconstructed quantities and then
compare the weighted one with the default one?

Thanks,
Xinchun

On 11/29/13 4:35 PM, "[log in to unmask]"
<[log in to unmask]> wrote:

>Hi Xinchun.
>
>No, don't multiply event variables with the weight. It doesn't make any
>sense. The event weight tells you how the probability of any given event
>is modified as a result of tweaking any set of input physics parameters.
>Assume you have an event sample and you fill a histogram with a
>kinematical variable, say Q2. Every Q2 value enters the histogram with a
>default weight of 1. If you change physics configuration, the events you
>already generated may become less or more probable. To get the Q2
>distribution that corresponds to the new physics configuration, each Q2
>value should enter the histogram with the weight computed for you by the
>ReWeight package. Hope this makes sense. Please see the manual.
>Cheers
>Costas 
>
>> On 29 Nov 2013, at 20:08, "Xinchun Tian" <[log in to unmask]> wrote:
>> 
>> Dear Expert,
>> 
>> I have a question on how to apply the reweight to an event. Suppose I
>>increase the CCRes Ma by 20%, and then I get the reweight for each
>>event, and then I want to apply this reweight to the event. Suppose I
>>have the following variables for further analysis.
>> 
>> vertexx, vertexy, vertexz, xbj, ybj, w2, q2
>>                   # primary vertex, Bjroken x, inelastic y, W2, Q2
>> nuid, numotherid, pxnu, pynu, pznu, enu
>>                # incoming neutrino id, mother id, momentum
>> tgtid, tgtmotherid, pxtgt, pytgt, pztgt, etgt
>>                # Target id, target mother id, momentum
>> lepid, lepmotherid, pxlep, pylep, pzlep, elep
>>                # outgoing lepton id, mother id, momentum
>> hadid[0], hadmotherid[0], pxhad[0], pyhad[0], pzhad[0], ehad[0]     #
>>hadrons id, mother id, momentum
>> Š..
>> 
>> Is it simply multiply this "reweight" to each variable except nuid,
>>motherid? How about w2 and Q2, it is reweight or reweight square?
>> 
>> Thanks,
>> Xinchun
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