# Probing proton PDFs at high x with LHCb

### Submission summary

 As Contributors: Thomas Boettcher Preprint link: scipost_202107_00091v1 Date submitted: 2021-07-30 15:13 Submitted by: Boettcher, Thomas Submitted to: SciPost Physics Proceedings Proceedings issue: DIS2021 Academic field: Physics Specialties: High-Energy Physics - Experiment Nuclear Physics - Experiment 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:
Has been resubmitted

### Submission & Refereeing History

Resubmission scipost_202107_00091v2 on 14 September 2021

Submission scipost_202107_00091v1 on 30 July 2021

## Reports on this Submission

### 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.

• validity: ok
• significance: good
• originality: high
• clarity: good
• formatting: good
• grammar: good

### Author:  Thomas Boettcher  on 2021-09-14

(in reply to Report 1 on 2021-08-09)