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Probing proton PDFs at high x with LHCb
by Thomas Boettcher on behalf of the LHCb Collaboration
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Submission summary
| Authors (as registered SciPost users): | Thomas Boettcher |
| Submission information | |
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| Preprint Link: | scipost_202107_00091v1 (pdf) |
| Date submitted: | 2021-07-30 15:13 |
| Submitted by: | Boettcher, Thomas |
| Submitted to: | SciPost Physics Proceedings |
| Proceedings issue: | 28th Annual Workshop on Deep-Inelastic Scattering (DIS) and Related Subjects (DIS2021) |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
LHCb is a forward spectrometer at the LHC covering the pseudorapidity region $2<\eta<5$. Because of this forward coverage, LHCb can probe the proton parton distribution functions (PDFs) in previously unexplored kinematic regimes, in particular at very high and low Bjorken-$x$. This contribution presents LHCb measurements that can be used to constrain the proton PDFs, with a focus on the high-$x$ and high-$Q^2$ regime.
Current status:
Reports on this Submission
Anonymous Report 1 on 2021-8-9 (Invited Report)
- Cite as: Anonymous, Report on arXiv:scipost_202107_00091v1, delivered 2021-08-09, doi: 10.21468/SciPost.Report.3364
Strengths
Presents recent LHCb data which can constrain PDFs
Weaknesses
Does not really demonstrate these constraints
Report
This is a short conference report on the impact of LHCb data on high-x PDFs. Whereas it is undoubtedly true that these data can have impact this is only explicitly demonstrated in Fig 1. The rest of the time it is asserted with reference to figures which do not actually show this. In the case of top data there is not even a figure.
I have suggested that information could be added to Figs 2 and 3 below. I have also pointed out that PDFs for intrinsic charm have appeared long before the recent NNPF3.1. If these matter are addressed it can be pulished.
Requested changes
Both Fig 2 and Fig 3 present cross section data compared to theory with minimal information as to what the theory is (particularly for Fig 3). As a minimum the PDF used should be specified and its uncertainties quantified, better still predictions using different PDFs should e compared. Otherwise on cannot claim that these data have impact on PDFs.
it is also stated that NNPDF3.1 is the first general purpose PDFset to allow for intrinsic charm. This is not strictly true the older CTEQ66c set (~2006) did this.
Author: Thomas Boettcher on 2021-09-14 [id 1759]
(in reply to Report 1 on 2021-08-09)Thank you for the helpful comments. Additional information about the theory calculations has been added in the captions of Figures 2 and 3.
I disagree characterizing CTEQ66c as a "general purpose" PDF set. The CTEQ authors do not characterize it as a general purpose PDF set (see for example https://ct.hepforge.org/PDFs/cteq6.html where CTEQ6, 6.1, 6.5, and 6.6 are all explicitly labeled as "general purpose" while 6.5cn and 6.6C are not). In addition, CTEQ6.5cn and CTEQ6.6C were not published with eigenvector PDF sets to allow for uncertainty calculations.