[Rivet] CMS analysis of dijet ratios at large rapdities

[Albert Knutsson]

Hi Hendrik,

thanks for checking the code. I have contacted the authors and analyzers.

Cheers,
Albert


On 10/1/12 4:51 PM, Hendrik Hoeth wrote:
> Hi Albert,
>
> thanks for the analysis. I've had a look at the code, and I have to
> admit that I don't understand the error calculation in your
> divide_set_by_subset_with_binomial_errors() function at all. There
> is a reference to some ROOT code, but it points to an empty line
> (http://root.cern.ch/root/html/src/TH1.cxx.html#2592) -- I can only
> suspect that it's meant to point at the TH1::Divide(const TH1 *h1, const
> TH1 *h2, Double_t c1, Double_t c2, Option_t *option) in line 2651 in the
> current version of TH1.cxx.
>
> Anyway, here is what I find suspicious:
>
> - In the main error formula "sqrt( ((1.-2.*w)*e1*e1 + w*w*e2*e2 )/(b2*b2))"
>    the errors appear in fourth power, while in the ROOT version they
>    don't.
>
> - Numerator and denominator seem to be swapped compared to the ROOT
>    version (b1 = h2.binHeight(i) and b2 = h1.binHeight(i)).
>
> - At the end you divide the error by a factor of 2.
>
> Can you please confirm that this code is actually what you want to do?
>
> Cheers,
>
>      Hendrik
>