HonexComb meeting #5

53/R-044 (CERN)



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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



- 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


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


- 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:


 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]].


There are minutes attached to this event. Show them.
    • 3:00 PM 3:10 PM
      Welcome 10m
      Speakers: Alexander Philipp Kalweit (CERN), Giulia Manca (Universita` degli studi di Cagliari and INFN, Cagliari, IT), Iwona Grabowska-Bold (AGH University of Science and Technology (PL)), Raphael Granier De Cassagnac (Centre National de la Recherche Scientifique (FR))
    • 3:10 PM 3:40 PM
      How nCTEQ could benefit from Honexcomb ? 30m
      Speaker: Ingo Schienbein (Universite Grenoble Alpes)
    • 3:40 PM 4:10 PM
      How EPPS could benefit from Honexcomb? 30m
      Speaker: Petja Kalle Matias Paakkinen (Helsinki Institute of Physics (FI))