[Rivet] Rivet analysis OPAL_2004_S613224 (fwd)

[Andy Buckley]

Hi Christoph,

Apologies -- I don't think that I ever saw that email! Sorry, that
happens unintentionally for various reasons such as spam filters, too
much email, etc., but if you don't get a response then just ping again.
No need for an 18 month delay between pings ;-)  Also, please email the
Rivet developer list, not just me: you are far more likely to get a
useful response.

For these analyses, I am not sure to what extent the validation
reproduced the MC curves. The "rule" about doing that definitely applies
to new analyses for which the paper's MC samples are available and can
be checked inside the collaborations. For old ones we do our best but it
is much harder to perform an exact consistency check.

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.

Andy


On 21/10/13 11:39, Christoph Pahl wrote:
> Hello Andy,
> 
> may I send a short reminder about my email of last year. I'd like to
> work with this analysis again but aim to understand some details/problems.
> 
> Meanwhile I read that you excluded it from general use because you're
> not sure what the authors of the paper did with the MC exactly (or
> similar) - I'd be of course happy to tell you.
> 
> Could we meet at B40 cafeteria to discuss this a bit? I passed at your
> table some times, I've been informed in detail what you're doing when
> not there but have never seen you.
> 
> Thanks,
> Christoph
> 
> 
> ---------- Forwarded message ----------
> Date: Mon, 20 Feb 2012 16:21:09 +0100
> From: Christoph Pahl <pahl at mail.cern.ch>
> To: andy.buckley at cern.ch
> Subject: Rivet analysis OPAL_2004_S613224
> 
> Dear Mr. Buckley,
> 
> our group compares the old JADE and OPAL data with new calculations. I'd
> like to employ now the Sherpa MC and I'm checking how well it describes
> the data.
> 
> For this I'm using amongst others the Rivet analysis OPAL_2004_S613224.
> I give links to the results and details of the Sherpa run below, I'm
> discussing this also with Jan Winter. However, I'm very interested in
> some statement in the Rivet manual,
> 
>> The Rivet “validation procedure” is not (as of February 2011) formally
>> defined, but generally implies that an analysis has been checked to
>> ensure
>> reproduction of MC points shown in the paper where possible
> 
> Have the MC points been reproduced in this example? In this case, how
> have the MC generators PYTHIA 6.158, HERWIG 6.2 and ARIADNE 4.11 - all
> with OPAL tune - been coupled to Rivet? I'd be very happy if I could
> reproduce this without much effort - this would let me trust much more
> in my Sherpa results.
> 
> Thanks a lot,
> Christoph Pahl
> 
> 
>  I ran Sherpa example LEP91 (see Sherpa dokumentation
>  http://projects.hepforge.org/sherpa/doc/SHERPA-MC-1.3.1.html )
>  and will explain varied parameters. I generated 10^6 MC events.
> 
>  91 GeV point
>    plots:
>  
> http://www.mppmu.mpg.de/~pahl/90.2/PR404/MEvs/plots/OPAL_2004_S6132243/index.html
> 
> 
>    ISR_SMIN=0.987;
> 
>    cuts on (energy^2 after ISR)/ cms-energy^2 :
>    Energy after ISR at least cms energy - 1 GeV, this is exactly what we
>    did for the hadron level predictions in the paper (at > 91 GeV this
>    cut is essential).
> 
>  133 GeV point
>    plots:
>  
> http://www.mppmu.mpg.de/~pahl/132/PR404/MEvs/plots/OPAL_2004_S6132243/index.html
> 
> 
>    BEAM_ENERGY_1 = 66.5;
>    BEAM_ENERGY_2 = 66.5;
>    (there was no LEP beam energy like this. But from averaging various
>    energies we get equivalent results)
>    ISR_SMIN=0.985;
> 
>  177 GeV point:
>    plots:
> 
> http://www.mppmu.mpg.de/~pahl/176/PR404/MEvs/plots/OPAL_2004_S6132243/index.html
> 
> 
>    BEAM_ENERGY_1 = 88.5;
>    BEAM_ENERGY_2 = 88.5;
>    ISR_SMIN=0.989;
> 
>  197 GeV point:
>    plots:
> 
> http://www.mppmu.mpg.de/~pahl/196/PR404/MEvs/plots/OPAL_2004_S6132243/index.html
> 
>    BEAM_ENERGY_1 = 98.5;
>    BEAM_ENERGY_2 = 98.5;
>    ISR_SMIN=0.990;
> 
> The lower plots, MC-data in standard deviations (stat.+sys.) in the
> cases 91
> and 197 GeV can be compared well with the paper.
> In some portions of phase space, event shape distributions are not
> described as well as by the MCs which have been tuned to OPAL data. For
> the moments this is less obvious, except for T_min.


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