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Minutes of H1/ZEUS meeting held on Feb 20, 2019
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The formal procedures to possibly have a preliminary combined H1+ZEUS
result on NNLO fits with HERA jets were discussed.
The following decisions were taken
- to have the preliminary "request" meeting on March 20, 2019 at
14:00. Iris volunteered to take care of the short writeup
- to have the preliminary "approval" meeting in the week of April 1.
After the meeting the date was discussed in the H1/ZEUS
management and is now fixed to April 4 at 10:00
- to create a web page to collect internal material (presentations etc).
Stefan volunteered to set up the web-page, with help from the
main analyzer team.
The fit results were presented and discussed.
The possible content of the preliminary results were discussed.
We agreed on looking at various extra studies to be presented next
time. Where possible, the corresponding plots should be shown in
"conference style", such that changes between the "request" and
"approval" meetings are expected to be small.
Decisions:
- the fit will be named
HERAPDF2.0Jets NNLO (prel)
- for the preliminary we include the fit chi**2 and NDF, but nothing
on the intermediate (NLO) fits with datasets different from
HERAPDF2.0Jets NLO
- we would like to release an alpha_s value with error breakdown
- the writeup will be minimal: abstract, table with datasets,
brief description or table with selection cuts and minimal fit
details, figures with self-explaining captions.
Requests of studies/plots to be shown next time:
- chi**2 as a function of alpha_s with "many" points, to read off the
experimental error, compare to the Minuit error.
- hadronisation uncertainty derived from offset method. The
correlated H1 hadronisation uncertainty will be counted twice for
practical reasons. This is accepted for the preliminary but will
have to be corrected for the publication
- parameterisation uncertainty
- scale uncertainty to be determined as for HERAPDF2.0Jets NLO
- comparisons of PDFS. There are three fits to be compared:
HERAPDF2.0 NNLO
HERAPDF2.0Jets NNLO (fixed alpha_s)
HERAPDF2.0Jets NNLO (free alpha_s)
we would like to see all sensible comparisons (of the "standard"
PDF flavors) and then select the most instructive figures for the
preliminary.
Where available, we would like to include error bands on the new fits.
- if possible, also show results with a cut cut on
Q^2>10,20 on inclusive data (as done for HERADPF2.0) but not on
jet data. jet data are already restricted to high scales
sqrt(Q^2+pt^2)>10, there is no need to cut on Q^2 alone.
the main comparison here would be
(a) alpha_s scans [as figure 65 in HERAPDF2.0 but now in NNLO]
(b) the PDFs, in particular the gluon density with the Q^2>10,20 cuts
these studies may be beyond the preliminary, but we still would
like to see as much as possible of this next time.
Stefan Schmitt, 22.2.2019