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Production of Upsilon States in p+p collisions at \sqrt{s}=500 GeV with STAR: Cross Sections, Ratios, and Multiplicity Dependenc

Updated on Thu, 2024-11-07 16:42. Originally created by lkosarz on 2020-02-28 16:03.

This is the webpage for collecting documents for the paper review process of:

"Production of Upsilon States in p+p collisions at \sqrt{s} = 500 GeV with STAR: Cross Sections, Ratios, and Multiplicity Dependence"

PAs: Leszek Kosarzewski*, Jaroslav Bielcik, Daniel Kikoła, Manuel Calderon

*leszek.kosarzewski@gmail.com

Target journal: Physical Review D
Alternative journal: European Physical Journal C

Overleaf paper draft (GPC only): https://www.overleaf.com/project/65e67f4b53da778a1ad4a344

Paper draft: drupal.star.bnl.gov/STAR/system/files/Upsilon500_Paper_LK_v17.pdf
Technical notes: https://drupal.star.bnl.gov/STAR/system/files/Upsilon500_TechNotes_LK_v4.pdf
Proposal presentation: drupal.star.bnl.gov/STAR/system/files/Upsilon_PWGC_LK_2021_5_14.pdf

Responses to GPC: drupal.star.bnl.gov/STAR/system/files/GPC_comments_2024.7.9.pdf
drupal.star.bnl.gov/STAR/system/files/GPC365_3rd_comment_Kong_response.docx
drupal.star.bnl.gov/STAR/system/files/Wangmei_Upsilon500_Paper_LK_v13.pdf
drupal.star.bnl.gov/STAR/system/files/Yi_comments_v14.docx
drupal.star.bnl.gov/STAR/system/files/Comments_Wangmei_v15.pdf

Responses to PWG comments to paper: https://drupal.star.bnl.gov/STAR/system/files/PWG_paper_responses_v6.pdf
Yi's comments to the paper: https://drupal.star.bnl.gov/STAR/system/files/PWG_paper_responses_v8_Yi.pdf
Isaac's comments to the paper: https://drupal.star.bnl.gov/STAR/system/files/PWG_paper_responses_v10_Isaac.pdf

Paper draft diff: https://drupal.star.bnl.gov/STAR/system/files/diff_Upsilon500_Paper_LK_v17-16.pdf
Paper draft (previous version): drupal.star.bnl.gov/STAR/system/files/Upsilon500_Paper_LK_v16.pdf

Responses to PWG comments to Technical notes: https://drupal.star.bnl.gov/STAR/system/files/PWG_notes_responses_v1.pdf
https://drupal.star.bnl.gov/STAR/system/files/PWG_notes_responses_v2.pdf

Technical notes diff: https://drupal.star.bnl.gov/STAR/system/files/diff_Upsilon500_TechNotes_LK_v2-4.pdf
Technical notes (previous version): drupal.star.bnl.gov/STAR/system/files/Upsilon500_TechNotes_LK.pdf

Analysis code: $CVSROOT/offline/paper/psn0826

Abstract:
We report measurements of $\varUpsilon(1S)$, $\varUpsilon(2S)$, $\varUpsilon(3S)$ production in \textit{$p+p$} collisions at $\sqrt{s}=500\:\mathrm{GeV}$ by the STAR experiment.
The results provide precise cross sections, transverse momentum ($p_{T}$) and rapidity ($y$) spectra, as well as cross section ratios within $p_{\mathrm{T}}<10\:\gevc$ and $|y|<1$.
The dependence of the normalized $\varUpsilon$ yield on normalized charged particle multiplicity is also measured, offering new insights into the mechanisms of quarkonium production.
The data are compared to various theoretical models: the CEM model accurately describes the $\varUpsilon(1S)$ production, while the CGC+NRQCD model overestimates the data, particularly at low $p_{T}$.
Conversely, the CSM model underestimates the rapidity dependence.
These discrepancies highlight the need for further development in understanding the production dynamics of heavy quarkonia in high-energy hadronic collisions.
The trend in the multiplicity dependence suggests CGC saturation-like effects in high-multiplicity collisions or $\varUpsilon$ production in multiple parton interactions.

Table 1:
Summary of systematic uncertainties on the $\varUpsilon(1S+2S+3S)$ cross section vs. $p_{T}$ and $y$.

pT [GeV/c]
Uncertainty 0-10 0-2 2-4 4-6 6-8 8-10
Raw yield extraction ±1.2% ±4.1% ±2.0% ±1.0% ±0.1% ±5.9%
Fixed Υ(2S)/Υ(3S) ±0.3% ±0.3% ±0.9% ±0.3% ±2.8% ±0.9%
pT smearing ±1.2% ±1.2% ±0.8% ±0.5% ±0.7% ±0.5%
Tracking ±1.3% ±1.4% ±1.3% ±1.3% ±1.4% ±1.3%
Polarization ±0.3% ±1.5% ±0.2% ±0.4% ±0.5% ±0.5%
Trigger ±7.6% ±17.0% ±8.0% ±2.9% ±1.4% ±0.9%
Total ±7.9% ±17.6% ±8.4% ±3.4% ±3.5% ±6.2%
|y|<0.5 0.5<|y|<1.0
±0.3% ±2.8%
±0.7% ±1.3%
±0.7% ±0.9%
±1.3% ±1.3%
±0.1% ±1.2%
±9.4% ±5.5%
±9.6% ±6.0%


Table 2:
Summary of global (correlated) systematic uncertainties on the $\varUpsilon(1S+2S+3S)$ cross section.

Uncertainty Effect
Luminosity ±8%
Vertex ±1%
Tracking efficiency const. ±10%
Acceptance ±3%
nσe cut ±3.6%



Table 3:
Summary of systematic uncertainties on the $\normupsAll$.

Uncertainty 0 − ⟨Nch⟩ ⟨Nch⟩ − 2 ⟨Nch⟩ 2 ⟨Nch⟩ − 3 ⟨Nch⟩ 3 ⟨Nch⟩ − 8 ⟨Nch⟩
Number of iterations ±1.3% ±1.3% ±0.5% ±0.5%
Reconstruction
efficiency		 ±0.2% ±0.6% ±0.4% ±3.8%
Tracking const. ±9.2% ±4.9% ±2.8% ±0.4%
Tracking vs. pT ±1% ±1% ±1% ±14%
Nch from NBD ±0.3% ±1.8% ±10% ±6.6%
Raw yield extraction ±1.1% ±2.5% ±0.2% ±15.7%
pT smearing ±0.3% ±0.3% ±0.2% ±1.8%
Fixed Υ(2S)/Υ(3S) ±0.4% ±0.4% ±2.7% ±10.8%
4Cx tune ±4% ±0.2% ±3.5% ±13.1%
Total ±10.3% ±6.1% ±11.4% ±28.1%



Table 4:
Summary of systematic uncertainties on the normalized multiplicity.

Uncertainty 0 − ⟨Nch⟩ ⟨Nch⟩ − 2 ⟨Nch⟩ 2 ⟨Nch⟩ − 3 ⟨Nch⟩ 3 ⟨Nch⟩ − 8 ⟨Nch⟩
Iterations ±0.1% ±0.4% ±0.3% ±0.2%
Tracking ±3.5% ±3.7% ±4.0% ±3.6%
Nch from NBD ±0.1% ±2.7% ±2.1% ±2.6%
4Cx tune ±1.9% ±0.0% ±0.6% ±0.3%
Total ±4.0% ±4.6% ±4.6% ±4.5%



Figure 1:
Invariant mass $\mee$ distribution for unlike-sign (red circles) and like-sign (blue diamonds) electron pairs.
The curves correspond to combinatorial background (blue dashed-dotted line), correlated background (black dotted line),
$\varUpsilon(1S)$ (green), $\varUpsilon(2S)$ (orange), and $\varUpsilon(3S)$ (purple).
The total (red) is a sum of the above components.




Figure 2:
(a) Electron efficiencies vs. $p_{\mathrm{T}}^{e_{MC}}$. Illustrated is the combined effect of successive application of the acceptance and tracking efficiency (black diamonds), $E_{tow}/E_{clu}$ cut (blue rectangles), $E_{clu}/p$ cut (green circles), $R_{SMD}$ cut (brown stars) and $n\sigma_{e}$ cut along with L0 High Tower match (red crosses).
(b) Reconstruction efficiencies of $\varUpsilon(1S)$ (closed diamonds), $\varUpsilon(2S)$ (open diamonds), and $\varUpsilon(3S)$ (open circles) vs. $p_{\mathrm{T}}^{\varUpsilon_{MC}}$.


Figure 3:
Integrated cross section of $\varUpsilon(1S+2S+3S)$ measured by STAR at $\sqrt{s}=200\:\mathrm{GeV}$~\cite{bib:Ups:STAR:dAu} and $\sqrt{s}=500\:\mathrm{GeV}$ compared to other experimental results~\cite{bib:Ups:AtlasRatio, bib:Ups:CMS:Xsec, bib:UpsCDF, bib:Ups:CFSpFe, bib:Ups:CFSppt, bib:Ups:CFSpp, bib:Ups:CFSpPtCu, bib:Ups:E605_pCu, bib:Ups:E605_pBe, bib:Ups:CCOR2, bib:Ups:CCOR2, bib:Ups:E866}, CEM model calculation (blue line)~\cite{bib:Frawley2008} and CSM calculation at LO (red dotted line and band) and NLO (red lines: solid, dashed, dotted)~\cite{bib:lansberg:energy} plotted vs. center of mass energy.


Figure 4:
(a) The $p_{\mathrm{T}}$ differential cross sections of $\varUpsilon(1S+2S+3S)$ (red circles), $\varUpsilon(2S+3S)$ (blue squares), $\varUpsilon(1S)$ (green diamonds), $\varUpsilon(2S)$ (black stars) and $\varUpsilon(3S)$ (brown crosses).
(b) Rapidity spectra for combined $\varUpsilon(1S+2S+3S)$ and each state separately (same as above).

Figure 5:
(a) The $\varUpsilon(1S)$ data are compared to the CEM model calculation for inclusive $\varUpsilon(1S)$ (gray band)~\cite{bib:CEM_shadow,bib:vogt:private}. The results are also compared to a CGC+NRQCD calculation for direct $\varUpsilon(1S)$ (purple shaded band) ~\cite{bib:upsCGC,bib:jpsi_cgc,bib:YQMa}.
(b) Comparison of a CGC+NRQCD calculation for $\varUpsilon(2S)$ (light blue shaded band) to STAR data.
(c) STAR data comparison with a CGC+NRQCD calculation for $\varUpsilon(3S)$ (brown shaded band).

Figure 6:
(a) The $\varUpsilon(1S)$ data are compared to CEM model calculation for inclusive $\varUpsilon(1S)$ (gray band)~\cite{bib:CEM_shadow,bib:vogt:private} and CGC+NRQCD predictions for direct $\varUpsilon(1S)$ (purple shaded band) ~\cite{bib:upsCGC,bib:jpsi_cgc,bib:YQMa} and Color Singlet model calculations at LO (teal band) and NLO (gray checked band)~\cite{bib:ups_csm}.
(b) Comparison of CGC+NRQCD calculation for $\varUpsilon(2S)$ (light blue shaded band) to STAR data.
(c) STAR data comparison to CGC+NRQCD calculation for $\varUpsilon(3S)$ (brown shaded band).

Figure 7:
$\varUpsilon$ invariant cross sections scaled with $\sqrt{s}^{n}$, where $n=5.6$ vs. $x_{\mathrm{T}}$ for $\varUpsilon(1S+2S+3S)$ (red closed circles), $\varUpsilon(1S)$ (green closed diamonds), $\varUpsilon(2S)$ (black open diamonds), $\varUpsilon(3S)$ (brown open circles) and $\varUpsilon(2S+3S)$ (blue closed squares) measured by STAR. The data are compared with $\varUpsilon(1S)$ results from Intersecting Storage Rings (ISR) (red open diamonds)~\cite{bib:UpsISR} and $\varUpsilon(1S)$, $\varUpsilon(2S)$, $\varUpsilon(3S)$ results measured by CDF (green open diamonds, blue open squares, black open crosses)~\cite{bib:UpsCDF} and ATLAS (green closed upward triangles, blue closed downward triangles, black open circles)~\cite{bib:Ups:AtlasRatio}.

Figure 8:
(a) Cross section ratios of $\frac{\varUpsilon(nS)}{\varUpsilon(1S)}$ as a function of energy, where
the STAR measured ratios are $\frac{\varUpsilon(2S)}{\varUpsilon(1S)}$ (red cross), $\frac{\varUpsilon(3S)}{\varUpsilon(1S)}$ (green cross) and $\frac{\varUpsilon(2S+3S)}{\varUpsilon(1S)}$ (blue cross) compared to fits to the world data from~\cite{bib:Ups:Ratios} (red, green and blue lines respectively) with STAR data included.
The uncertainties on the fits are shown as bands at the end of each line to the right.
Measurements by other experiments in $p+\bar{p}$~\cite{bib:Ups:CDFratio}, \textit{$p+p$}~\cite{bib:Ups:CFSpp, bib:Ups:E866, bib:UpsCMS_2010, bib:Ups:AtlasRatio, bib:Ups:LHCbRatio, bib:Ups:LHCb8Tev} are also shown along with $p+A$~\cite{bib:Ups:E605_pBe, bib:Ups:E605_pCu, bib:Ups:E866, bib:Ups:CFSppt}.
(b) Dependence of $\frac{\varUpsilon(nS)}{\varUpsilon(1S)}$ cross section ratios on charged particle multiplicity. The STAR data for $\frac{\varUpsilon(2S+3S)}{\varUpsilon(1S)}$ (blue crosses), $\frac{\varUpsilon(2S)}{\varUpsilon(1S)}$ (red crosses) and $\frac{\varUpsilon(3S)}{\varUpsilon(1S)}$ (green crosses) are fitted with a linear function (blue, red and green lines).
The $\frac{\varUpsilon(2S)}{\varUpsilon(1S)}$ and $\frac{\varUpsilon(3S)}{\varUpsilon(1S)}$ data are shifted along $N_{ch}$ by -1 and +1 for clarity.

Figure 9:
(a) Normalized yield as a function of normalized $N_{ch}$ measured in \textit{$p+p$} collisions. STAR $\varUpsilon$ results at $\sqrt{s}=500\:\mathrm{GeV}$ are compared to $J/\psi$ at $\sqrt{s}=200\:\mathrm{GeV}$~\cite{bib:Jpsi:pp:STAR:mult} as well as ALICE~\cite{bib:Jpsi:pp:STAR:mult} and CMS~\cite{bib:Ups:CMSactivity}.
(b) STAR $\varUpsilon$ results are compared to model calculations: PYTHIA with STAR Heavy Flavor Tune~\cite{bib:STAR_HFtune}, CGC-based Saturation model~\cite{bib:EventAct:Jpsi:3pom,bib:EventAct:QQ:CGC} and Percolation model for $J/\psi$~\cite{bib:PercolationJpsi}.

Conclusions:

  • Spectra:
    • First $p_{T}$ spectrum measurement of $\varUpsilon$ states at RHIC energy
    • Both $p_{T}$ and rapidity spectra are reasonably well described by CEM calculation for inclusive $\varUpsilon(1S)$
    • CGC+NRQCD calculation for direct $\varUpsilon(nS)$ overestimates the data
    • CSM LO and NLO below the data
    • No $x_{T}$ scaling observed in the measured $x_{T}$ range
  • Ratios:
    • No significant dependence of $\varUpsilon(nS)/\varUpsilon(1S)$ cross section ratios on multiplicity observed
  • Normalized $\varUpsilon$ yield vs. normalized multiplicity:
    • Shows similar trend to $J/\psi$ and LHC data and models
    • Data for $p_{T}>0\:\mathrm{GeV/c}$ closer to linear dependence
    • $\varUpsilon(1S)$ data for $p_{T}>4\:\mathrm{GeV/c}$ indication of faster than linear rise       
    • Data qualitatively described by the models
Groups: