[Brahms-dev-l] Momentum Resolution Unfolding

Hi,

I've looked a bit more at the momentum resolution unfolding business
today. I've made a small macro that can estimate the effect of the
smearing assuming some sigma_p/p**2, the fraction of the full field in the
magnet and some input distribution. A few comments:

- The numbers I have for sigma_p/p**2 are

  D2 : 0.0018
  D4 : 0.0011
  D3 : ???
  D5 : 0.0077

- The input distribution should be the raw momentum distributions for each
field/angle setting and for each collision system and centrality. The
invariant yields we normally plot are not good since they are in pt and
also they have a 1/pt normalization.

- The method is using the ROOT integration and it gets unstable if I try
to integrate over a wide x range. Therefore I've put in a limit so it only
integrates from -nSigma to +nSigma (nSigma=6). I hope it doesn't ruin the
result too much.

- I'm not sure if what I'm doing is 100% correct. You're welcome to use
it, but don't blame me if it turns out to be rubbish. Actually it would be
great if someone could look at it and see if it looks reasonable.

- I've checked it into CVS. You can pick it up in cej_app/unfolding/. The
test.C macro gives an example.

Cheers,

Claus

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