SciPost Submission Page

Identifying hadronic charmonium decays in hadron colliders

by Nicolo de Groot, Sergi Castells

This is not the current version.

Submission summary

As Contributors: Nicolo De Groot
Arxiv Link: https://arxiv.org/abs/1910.05334v3 (pdf)
Date submitted: 2020-03-17 01:00
Submitted by: De Groot, Nicolo
Submitted to: SciPost Physics
Discipline: Physics
Subject area: High-Energy Physics - Experiment
Approach: Experimental

Abstract

Identification of charmonium states at hadron colliders has mostly been limited to leptonic decays of the J/{\Psi}. In this paper we present and algorithm to identify hadronic decays of charmonium states (J/{\Psi}, {\Psi}(2S), \chi_{c0,1,2}) which make up the large majority of all decays.

Current status:
Has been resubmitted


Author comments upon resubmission

New version with comments of the referees addressed

List of changes

1. Cross-check with pile-up implemented
2. Higher statistics used in training
3. Cross-check for pt dependence inplemented
4. Improved binning in plots
5. References on rare Higgs decay added
6. Textual improvements, typos


Reports on this Submission

Anonymous Report 3 on 2020-4-24 Invited Report

  • Cite as: Anonymous, Report on arXiv:1910.05334v3, delivered 2020-04-24, doi: 10.21468/SciPost.Report.1641

Report

Thanks a lot for addressing my comments and questions on the earlier version of your draft. I'm satisfied with the answers, as well as your changes. I only have a few very minor additional suggestions:

o General comments:
-The PDG and most papers seem to use lowercase \psi when referring to the J/\psi particle. I'm not sure why you've decided to use \Psi. Similar comment for \psi(2s).

-You're using both p_T and p_t in the text, tables and figures. I would suggest using p_T consistently throughout the document.

o Section 5:
-Write out "Figure 2" when you start the paragraph.

-On Page 5, where you list the ranges of the three pT bins, I'd recommend adding a space between the numbers and "GeV" units.

o References Section:
-Ref. 2: The actual paper title uses a capital 'H'.

-Ref. 4: Something is really wrong with the paper title for this reference. Looks duplicated and one symbol is not recognized as a '?' appears instead.

-Ref. 10: I don't think that the capitalization used here matches that in the actual paper title.

o Figure 1: Please add a full stop at the end of the caption.

  • validity: -
  • significance: -
  • originality: -
  • clarity: -
  • formatting: -
  • grammar: -

Anonymous Report 2 on 2020-3-30 Invited Report

  • Cite as: Anonymous, Report on arXiv:1910.05334v3, delivered 2020-03-30, doi: 10.21468/SciPost.Report.1597

Strengths

1- The paper demonstrates that J/Psi and other hadronic charmonia decays can be distinguished from quark and gluon jets under a number of assumptions, and quantifies the performance of an algorithm that does this. This can be useful input for phenomenological studies of potential analyses that consider these decays or serve as a template for such an algorithm to be implemented in an experiment.

Weaknesses

1- Vague motivation. While the general motivation is intriguing, it is not clear which performance of the identification algorithm is required for it to be useful in an actual analysis of the suggested H-> J/Psi gamma search. Without at least a rough study and given the large photon + jet production cross section compared to the Higgs production cross section and, in addition, a branching fraction of 3 x 10e-6, it remains unclear if the results of the presented study will be of any practical use.

Report

The updated version addresses a few minor doubts on the performance, in particular in the presence of pileup, the size of the training samples, and the impact of the used pT distributions on the performance. I have no reason to doubt that the obtained results are solid.

With that said, a much stronger paper could have been obtained by demonstrating that the performance of the algorithm is good enough for a concrete analysis to become competitive. Without this demonstration, it remains to be seen if the performance of the presented algorithm is sufficient to be practically useful.

The presented study will however allow for such studies to be performed, and hence be potentially useful for experimentalists or phenomenologists who try to explore hadronic charmonium decays. To indeed be useful, the obtained ROCs should be made available in machine-readable format, and it would be good to also give the signal efficiencies for a lower background efficiency, as suggested below.

Requested changes

1- It would be instructive to not only give signal efficiencies for jet misidentification efficiencies of 1 per cent, but also for a much smaller one, e.g. 1 per mille. These cannot be inferred from the ROCs since they are not shown with logarithmic misidentification efficiency axis, but will likely be important in practical applications, similar to tau identification. In addition, the AUCs are not very instructive measures of the performance.

2- Abstract & Conclusion: Both the abstract and the conclusion should mention the performance of the algorithm.

3- There are still a few minor language and style issues:
- Caption figure 1, "used to" -> "used for"; Distribution -> Distributions
- Add reference for dropout

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

Report 1 by Yuta Takahashi on 2020-3-19 Invited Report

  • Cite as: Yuta Takahashi, Report on arXiv:1910.05334v3, delivered 2020-03-19, doi: 10.21468/SciPost.Report.1587

Strengths

Same as previous comment.

Weaknesses

Same as previous comment.

Report

The updated version has significant improvement compared to the previous version. At this point, I have just a few more comments.

1) Table1:
"abs(qj): pT weighted charge sum, kappa = 0.5" -> Kappa seems not defined in the text (it is different kappa as Eq.1 right?). Can you add description what it means or rephrase?

2) Figure1:
Can you add y-axis scales (e.g. 0, 0.5, 1 or something like that)? It is possible to roughly draw this information by eye but it is difficult for the variables with large number of binning.

3) Figure2, left plot:
I guess the plot is "stacked" (not overlaid). Can you be explicit about it?

Left over from last comment
- Why qg2ccbar(3S1)q, qq2ccbar(3S1)g were not considered, like you did for $\chi_c$?

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

Author Nicolo De Groot on 2020-03-31
(in reply to Report 1 by Yuta Takahashi on 2020-03-19)
Category:
answer to question

Dear Dr. Takahashi,

thank you for your comments. They seem quite minor and we hope to address them in the final version.

1) Table1: "abs(qj): pT weighted charge sum, kappa = 0.5" -> Kappa seems not defined in the text (it is different kappa as Eq.1 right?). Can you add description what it means or rephrase?

Will be fixed in the final version

2) Figure1: Can you add y-axis scales (e.g. 0, 0.5, 1 or something like that)? It is possible to roughly draw this information by eye but it is difficult for the variables with large number of binning.

We will try to see if this is an improvement. The plot is already very crowded with 20 subplots.

3) Figure2, left plot: I guess the plot is "stacked" (not overlaid). Can you be explicit about it?

Will be fixed in the final version

Left over from last comment - Why qg2ccbar(3S1)q, qq2ccbar(3S1)g were not considered, like you did for χ_c?

The reason for it is quite trivial. There is no qg2ccbar(3S1)q switch in Pythia8 for color singlet production. See http://home.thep.lu.se/~torbjorn/pythia82html/OniaProcesses.html

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