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News:
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- Conferences ongoing: LHCp, HP, stay tuned
- Preference for ZOOM vs. Vidyo ? Let us know !
- Roadmap of activities of the group ready
- Any suggestion on the common activities/need for
summary plots
- Today's subject: nPDF
Ingo Schienbein : CTEQ and HonexComb (HC)
====================================
- Possible ways HC can help CTEQ ?
=> More precise data for combination analyses,
cannot be done by the theorists (!)
o this would allow to reduce the uncertainties
of the PDFs
- Interesting subjects for CTEQ at the LHC (pPb)
o W/Z, heavy quarks, prompt photon, inclusive jets
= some data exist, not complete
= +ve y : small x, -ve y : large x
= global fits exist also, using Atlas+CMS for W/Z in pPb
to extract the pdfs of light quarks
= comparison with W CMS data Run I and Run II shows still
some discrepancies
= also compared with Lambda_c and D0, and their ratio
for ALICE and CMS (same y, good place for combination)
= also compared with heavy quark(onium) => better description
= Reweighted gluon results in good agreement with LHCb data
for beauty production
- Outlook:
- prompt photon studies could help in small-x region
- combination could help for reducing the precisions
Questions:
- Marco van Leeuwen: the statistical uncertainties are taken properly into account in the combination ?combination only relevant if stat very very low
- RGdC: Need cleaner probes
- MWinn: LHCb results are published
- A.Andronic: are different datasets treated independently ? not exactly correct.
Petja Paakkinen : EPPS and HonexComb
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o Introduction to EPPS
o Uses RFB measurements
o compared with LHCb and CMS measurements
- dijet and D0 data support antishadowing/shadowing in
specific regions of x
- also CMS W boson to be included soon
o would like to know the correlations between
the measurements to constrain the fits and
reduce the uncertainties
Questions:
- RGdC: would a measurement of DY at low mass (<10GeV) help
for the nPDF ? - yes, would put contrains the small-x gluons
- Ingo: also the photon distributions would be useful
- MWinn: is UPC with high statistics (in pp, Durham group)
important for PDFs measurements ?
=> PP: it depends on observables, e.g. JPsis affected by theory uncertainties
not under control (it is probing not the inclusive PDF but the
generalised PDF, at a certain limit these two can be the same,
but not clear if that limit is accessible experimentally or not
just); dijet in UPC is a cleaner probe (Atlas)
=> IS: idem.
o CMS measurement of DY:
https://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/HIN-18-003/index.html
o Work of the Durham group
C.Flett, S.Jones, A.Martin, M.Ryskin and T.Teubner,
``How to include exclusive $J/\psi$ production data in global PDF analyses,''
Phys. Rev. D \textbf{101} (2020) no.9, 094011 doi:10.1103/PhysRevD.101.094011
[arXiv:1908.08398 [hep-ph]].