[Rivet] Rivet analysis OPAL_2004_S613224

[Andy Buckley]

On 15/11/13 15:11, Christoph Pahl wrote:
> Hello Andy, Peter and all rivet developpers,
> 
> we would be happy if the OPAL 2004 Rivet analysis could in fact be used.
> We are still using the analysis code (working with Nadine Fischer led me
> back to this problem) and we have all data and MC samples.
> 
> The exclusion resulted from Peter Skands stating
> http://www.hepforge.org/lists-archive/rivet/2011-May/002220.html
> large deviations ~ factor 3 between data and rivet PYTHIA results in
> (for example) the lowest 1-thrust bin for OPAL at 91 GeV, but not for
> ALEPH.
> 
> The linked plots are hard to read as they are very dense, and the ratios
> go only up to 1.5 . From the numbers on the cited web page I calculate
> the deviation more precisely as 2.5; and from the ALEPH plot I see a
> HERWIG deviation in this bin of ~ 2, shouldn't you then exclude
> ALEPH as well?
> The lowest bin has experimental and theoretical difficulties and we
> never include it in any fitrange. So excluding an analysis because of a
> problem
> there is pretty sad. But as soon as I understand the problem better I
> can of course compare our code with the rivet analysis.

Hi again Christoph,

Apologies for the long delay -- we've again been working on Rivet 2
developments whenever there has been free time, but with the Rivet 2.1.0
release approaching I wanted to return to this issue.

I don't think we declare any particular analysis validity strictly based
on problems with MC. In these specific cases any information that you
have which could help us make the implementation better would be
*really* valued (and credited, of course).

Going back to your original email, I'm usually in the 3-D corridor
section of B40 at CERN if you want to talk in person about this and any
improvements that we could put into Rivet's implementations to help you
(and others).

> On Mon, 21 Oct 2013, Andy Buckley wrote
>> In particular, as part of the histogramming migration to Rivet 2.0, we
>> did discover some issues with the definition of _integrated_ jet rates
>> in the JADE_OPAL analysis. Depending on whether the integral is taken up
>> to the midpoint of the bin, the low edge, or the upper edge you can get
>> quite different answers. I am not sure which is correct for that
>> analysis -- are you? -- but the differential rates should be correct.
>> Please let us know if you've got any ideas or questions about this.
> 
> Stefan Kluth told me that OPAL always employed the bin midpoint to
> represent the point where the jet rate had been evaluated.

That's great to know: I have updated the analysis for version 2.1.0 and
credited you and Stefan for that information in the .info file and
ChangeLog. Thanks!

Best wishes,
Andy

-- 
Dr Andy Buckley, Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow / PH Dept, CERN