CMS-PAS-BPH-14-008 | ||
Observation of Υ(1S) pair production at CMS | ||
CMS Collaboration | ||
May 2016 | ||
Abstract: The simultaneous production of two Υ(1S) mesons in proton-proton collisions is observed by CMS at √s= 8 TeV at LHC in a data sample corresponding to an integrated luminosity of 20.7 fb−1. The statistical significance is well in excess of 5 standard deviations. Both Υ candidates are fully reconstructed via their decays into μ+μ−. The acceptance region is defined by the individual Υ rapidity, y(Υ), and transverse momentum, pT(Υ): |y(Υ)|< 2.0 and pT(Υ)< 50 GeV. The total cross section for the production of Υ(1S) pairs assuming that both Υ(1S) mesons decay isotropically, is measured to be 68.8 ± 12.7 (stat) ± 7.4 (syst) ± 2.8 (BR) pb, where the third uncertainty results from the uncertainty in the Υ(1S)→μ+μ− branching fraction. Different assumptions about the Υ(1S) polarization imply modifications to the cross section ranging from -38% to 36%. | ||
Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 05 (2017) 013. The superseded preliminary plots can be found here. |
Figures | |
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Figure 1:
Lego plot of M(1)μμ vs M(2)μμ. |
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Figure 2-a:
Projections of the 2D fit. (a) invariant mass of higher mass muon pairs, M(1)μμ. (b) invariant mass of lower mass muon pairs, M(2)μμ. The lower pads show the difference between the total fit curve and data, with red lines corresponding to a difference of ±2 standard deviations. |
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Figure 2-b:
Projections of the 2D fit. (a) invariant mass of higher mass muon pairs, M(1)μμ. (b) invariant mass of lower mass muon pairs, M(2)μμ. The lower pads show the difference between the total fit curve and data, with red lines corresponding to a difference of ±2 standard deviations. |
Tables | |
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Table 1:
Summary of relative systematic uncertainties in the Υ pair production cross section. |
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Table 2:
Relative change of acceptance corrected yield for different polarization assumptions. |
Summary |
The Υ(1S) meson pair production where both Υ(1S) mesons originate from the common vertex is observed with the CMS detector in proton-proton collisions at √s= 8 TeV at the LHC from a sample corresponding to an integrated luminosity of 20.7 fb−1. A signal yield of 38 ± 7 Υ(1S)Υ(1S) events is measured with the local significance, including systematics, that exceeds five standard deviations. Using the measured muon kinematics in the data, an event-based acceptance and efficiency correction method is applied, minimizing the model dependence of the cross section measurement. The total cross section of Υ(1S) pair production measured within the single Υ acceptance, |y(Υ)|< 2.0 and pT(Υ)< 50 GeV, is found to be σT= 68.8 ± 12.7 (stat) ± 7.4 (syst) ± 2.8 (BR) pb, where the Υ(1S) decay into muons is assumed to be isotropic. Different assumptions about the Υ(1S) polarization imply modifications to the cross section ranging from -38% to 36%. |
References | ||||
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Compact Muon Solenoid LHC, CERN |
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