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ZEUS_2021_I1869927: azimuthal correlations at HERA

Ilkka Heleniusrequested to merge
ih-zeus-2021-correlations into release-4-1-x

A ZEUS analysis for single-particle properties and two- and four-particle correlations in DIS and photoproduction. Analysis works and reproduces Pythia results shown in the paper (https://inspirehep.net/literature/1869927). There are, however, a few issues with the plotting:

  • The data is provided as discrete histograms with just the center point given as a string. A mapping from a continuous bins has been added to the analyses with binning deduced from the experimental plots. In principle this should be fine but
    • In one of the histograms in the YODA file (d09-x01-y01), the x values are not given as strings but as integers. This has been changed in the included yoda file but means that automatic HepData download might not work as expected.
    • The x labels are not pretty because of discrete values
    • There is a hole in the Q2 bins between 1 and 5 GeV^2. This has been accounted for in the analysis but not in the plotting. Similarly there are a few histograms with variable bind widths that are not accounted correctly in the plotting.

Earlier issue with numerical instabilities was not because of subtractions but I was using int as a type for the nEntries variable within a bin that should have been double. With large enough statistics int run out of range and conversion returned non-sense.

Assigning @20DM for this as we have already discussed a few things related to the analyses but tagging also @jonbutterworth1 for suggestions how to improve plotting. A yoda file from Pythia run with 100M events is attached and results shown at https://users.jyu.fi/~ilmahele/html-zeus-data/.
test-zeus-corr-4-100M.yoda

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