Measurement of the exclusive Υ production cross-section in pp collisions at √s = 7 TeV and 8 TeV

The paper is available here.

arXiv: 1505.08139, LHCB-PAPER-2015-011

More detailed information: ANA note 2014-097


A study is presented of central exclusive production of Υ(nS) states, where the Υ(nS) resonances decay to the μ+ μ final state, using pp collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range 2 < y(Υ) < 4.5 where the muons are reconstructed in the pseudorapidity range 2 < η(μ ) < 4.5. The data sample corresponds to an integrated luminosity of 2.9 fb−1 and was collected at centre-of-mass energies of 7 TeV and 8 TeV. The measured Υ(1S) and Υ(2S) production cross-sections are

σ(pp → pΥ(1S)p) = 9.0 2.1 1.7 pb and

σ(pp → pΥ(2S)p) = 1.3 0.8 0.3 pb,

where the first uncertainties are statistical and the second are systematic. The Υ(1S) cross-section is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3S) production cross-section, including possible contamination from χb (3P ) → Υ(3S)γ decays.


(Note, eps versions are available under attachments).

Caption Figure
Figure 1: Leading Feynman diagram for photoproduction of Υ(nS) states, where the photon-pomeron interaction is indicated by the shaded grey circle. Fig1.png
Figure 2: Invariant dimuon mass spectrum for 7 TeV and 8 TeV data in the rapidity range 2 < y(Υ) < 4.5 (black points). The fit PDF is superimposed (solid blue line). The Υ(1S, 2S, 3S) signal components, used to derive weights, are indicated with a long-dashed (red) line, and the non-resonant background is marked with a short-dashed (grey) line. Fig2.png
Figure 3: Fit to the p2T distribution of the Υ candidates in the full rapidity range. Fig3.png
Figure 4: Measurements of exclusive Υ(1S) photoproduction compared to theoretical predictions. In (a), the Υ(1S) cross-section in bins of rapidity is shown, compared to LO and NLO predictions. The LHCb measurements are indicated by black points with error bars for uncorrelated errors, and solid rectangles indicating the total uncertainty. In (b), the photon-proton cross-sections extracted from the LHCb results are indicated by black points, where the statistical and systematic uncertainties are combined in quadrature. The entire W -region in which these LHCb measurements are sensitive is indicated. Measurements made by H1 and ZEUS in the low-W region are indicated by red and blue markers, respectively [4, 5, 7]. Predictions from Ref. [1] are included, resulting from LO and NLO fits to exclusive J/ψ production data. The filled bands indicate the theoretical uncertainties on the 7 TeV prediction and the solid lines indicate the central values of the predictions for 8 TeV. In (b) predictions from Ref. [2] using different models for the Υ(1S) wave function are included, indicated by bCGC. Fig4a.pngFig4b.png


[1] S. P. Jones, A. D. Martin, M. G. Ryskin, and T. Teubner, Probes of the small x gluon via exclusive J/ψ and Υ production at HERA and the LHC, JHEP 1311 (2013) 085, arXiv:1307.7099.

[2] V. P. Gon ̧calves, B. D. Moreira, and F. S. Navarra, Exclusive Υ photoproduction in hadronic collisions at CERN LHC energies, Phys. Lett. B742 (2015) 172, arXiv:1408.1344.

[4] ZEUS collaboration, J. Breitweg et al., Measurement of elastic Υ photoproduction at HERA, Phys. Lett. B437 (1998) 432, arXiv:hep-ex/9807020.

[5] H1 collaboration, C. Adloff et al., Elastic photoproduction of J/ψ and Υ mesons at HERA, Phys. Lett. B483 (2000) 23, arXiv:hep-ex/0003020.

[7] ZEUS collaboration, S. Chekanov et al., Exclusive photoproduction of Υ mesons at HERA, Phys. Lett. B680 (2009) 4, arXiv:0903.4205.

-- KatharinaMueller - 2015-06-05

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Unknown file formateps Fig1.eps r1 manage 356.0 K 2015-06-05 - 10:16 KatharinaMueller  
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PNGpng Fig1.png r1 manage 2.4 K 2015-06-05 - 10:16 KatharinaMueller  
Unknown file formateps Fig2.eps r1 manage 29.2 K 2015-06-05 - 10:16 KatharinaMueller  
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PNGpng Fig2.png r1 manage 21.9 K 2015-06-05 - 10:16 KatharinaMueller  
Unknown file formateps Fig3.eps r1 manage 17.4 K 2015-06-05 - 10:16 KatharinaMueller  
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PNGpng Fig3.png r1 manage 18.7 K 2015-06-05 - 10:16 KatharinaMueller  
Unknown file formateps Fig4a.eps r1 manage 55.1 K 2015-06-05 - 10:18 KatharinaMueller  
PDFpdf Fig4a.pdf r1 manage 32.2 K 2015-06-05 - 10:18 KatharinaMueller  
PNGpng Fig4a.png r1 manage 59.5 K 2015-06-05 - 10:18 KatharinaMueller  
Unknown file formateps Fig4b.eps r1 manage 2882.1 K 2015-06-05 - 10:18 KatharinaMueller  
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PNGpng Fig4b.png r1 manage 44.0 K 2015-06-05 - 10:18 KatharinaMueller  
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