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Measurement of exclusive $J/ψ$ and $ψ(2S)$ production at $\sqrt{s}=13$ TeV
by LHCb collaboration, Roel Aaij, Patrick Koppenburg, et al.
This Submission thread is now published as
Submission summary
| Authors (as registered SciPost users): | Patrick Koppenburg |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2409.03496v3 (pdf) |
| Date accepted: | 2025-01-21 |
| Date submitted: | 2025-01-09 09:44 |
| Submitted by: | Koppenburg, Patrick |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
Measurements are presented of the cross-section for the central exclusive production of $J/\psi\to\mu^+\mu^-$ and $\psi(2S)\to\mu^+\mu^-$ processes in proton-proton collisions at $\sqrt{s} = 13 $ TeV with 2016-2018 data. They are performed by requiring both muons to be in the LHCb acceptance (with pseudorapidity $2<\eta_{\mu^\pm} < 4.5$) and mesons in the rapidity range $2.0 < y < 4.5$. The integrated cross-section results are \begin{equation*} \sigma_{J/\psi\to\mu^+\mu^-}(2.0<y_{J/\psi}<4.5,2.0<\eta_{\mu^\pm} < 4.5) = 400 \pm 2 \pm 5 \pm 12 \,{\rm pb}\,, \end{equation*} \begin{equation*} \sigma_{\psi(2S)\to\mu^+\mu^-}(2.0<y_{\psi(2S)}<4.5,2.0<\eta_{\mu^\pm} < 4.5) = 9.40 \pm 0.15 \pm 0.13 \pm 0.27 \,{\rm pb}\,, \end{equation*} where the uncertainties are statistical, systematic and due to the luminosity determination. In addition, a measurement of the ratio of $\psi(2S)$ and $J/\psi$ cross-sections, at an average photon-proton centre-of-mass energy of 1 TeV, is performed, giving \begin{equation*} \frac{\sigma_{\psi(2S)}}{\sigma_{J/\psi}} = 0.1763 \pm 0.0029 \pm 0.0008 \pm 0.0039 \,, \end{equation*} where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the involved branching fractions. For the first time, the dependence of the $J/\psi$ and $\psi(2S)$ cross-sections on the total transverse momentum transfer is determined in $pp$ collisions and is found consistent with the behaviour observed in electron-proton collisions.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
List of changes
Introduction:
- Clarified the rationale of the selection of references for PDFs.
- Explained how the larger samples improves the background control with respect to the measurement with 2015 data
Detector, etc:
- Added references for track fit and muon ID.
Two-dimensional signal fit:
- Clarified the definition of fit variables
- Specified the mass uncertainties in J/psi gamma fit
Efficiencies:
- Refer to Sec.5 for the SPD mismodelling
- Changed Fig.6(right) to show the most relevant pt^2 region
Systematics:
- Specified how the psi(2S) is constrained. Following a suggestion from a reviewer a systematic uncertainty is added, which has a negligible effect.
- Explained the choice of the pt^2 shape for the PD background
Results:
- Specified what 1.5sigma applied to
- Expanded the comment on the psi(2S) prediction differing from the data.
Conclusion:
- Slight rewording as suggested by reviewers
Published as SciPost Phys. 18, 071 (2025)