CMS-PAS-HIN-18-012 | ||
Production of prompt and nonprompt J/ψ mesons in jets in pp collisions at √s= 5.02 TeV | ||
CMS Collaboration | ||
May 2018 | ||
Abstract: The fragmentation of jets containing a J/ψ meson is studied in low pile-up pp data recorded in 2015, at a center-of-mass energy of √s= 5.02 TeV. The fraction of the jet transverse momentum pT,jet taken by the J/ψ is measured for both prompt and nonprompt J/ψ mesons. The value of pT,jet is restricted to the range of 25-35 GeV. The J/ψ mesons are measured above 3 and 6.5 GeV, in the endcap and barrel regions of the CMS detector, respectively. Whereas the results for nonprompt J/ψ are well-modeled by simulations using a Monte Carlo generator, the prompt J/ψ are found to be accompanied by a larger level of jet activity. The fraction of J/ψ mesons that are found to be inside a jet within the pT,jet selection is also reported, and found to be larger than simulation, for both prompt and nonprompt J/ψ. | ||
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; |
Figures | Summary | Additional Figures | References | CMS Publications |
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Figures | |
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Figure 1:
Invariant mass spectrum of μ+μ− pairs (left) and pseudo-proper decay length distribution (right) in pp collisions for 0 <|y|< 1.6, 6.5 <pT< 35.0 GeV. The result of the fit described in the text is also shown. |
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Figure 1-a:
Invariant mass spectrum of μ+μ− pairs in pp collisions for 0 <|y|< 1.6, 6.5 <pT< 35.0 GeV. The result of the fit described in the text is also shown. |
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Figure 1-b:
Pseudo-proper decay length distribution in pp collisions for 0 <|y|< 1.6, 6.5 <pT< 35.0 GeV. The result of the fit described in the text is also shown. |
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Figure 2:
The four-dimensional detector-response matrices for prompt (left) and nonprompt J/ψ (right), as a function of jet pT and z. The colors represent the bin-to-bin migration probabilities ranging from 0 (light yellow) to 1 (dark brown). |
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Figure 2-a:
The four-dimensional detector-response matrices for prompt J/ψ, as a function of jet pT and z. The colors represent the bin-to-bin migration probabilities ranging from 0 (light yellow) to 1 (dark brown). |
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Figure 2-b:
The four-dimensional detector-response matrices for nonprompt J/ψ, as a function of jet pT and z. The colors represent the bin-to-bin migration probabilities ranging from 0 (light yellow) to 1 (dark brown). |
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Figure 3:
Self-normalized prompt (left) and nonprompt z distributions in the rapidity range |y|< 1.6, for pp data and PYTHIA 8. For the nonprompt case, the z distribution of the parent b hadron is also shown. |
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Figure 3-a:
Self-normalized prompt z distributions in the rapidity range |y|< 1.6, for pp data and PYTHIA 8. |
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Figure 3-b:
Self-normalized nonprompt z distributions in the rapidity range |y|< 1.6, for pp data and PYTHIA 8. The z distribution of the parent b hadron is also shown. |
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Figure 4:
Self-normalized prompt (left) and nonprompt (right) z distributions in the rapidity range 1.6 <|y|<2.4, for pp data and PYTHIA 8. For the nonprompt case, the z distribution of the parent b hadron is also shown. |
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Figure 4-a:
Self-normalized prompt z distributions in the rapidity range 1.6 <|y|<2.4, for pp data and PYTHIA 8. |
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Figure 4-b:
Self-normalized nonprompt z distributions in the rapidity range 1.6 <|y|<2.4, for pp data and PYTHIA 8. The z distribution of the parent b hadron is also shown. |
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Figure 5:
Left: The fraction of prompt and nonprompt J/ψ in jets of 25 <pT< 35 GeV in pp data and in PYTHIA 8, compared to the total number of J/ψ in the relevant the pT interval, as indicated on the Figure. Right: The ratio of these J/ψ -in-jet fractions in data compared to simulation for prompt and nonprompt J/ψ. |
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Figure 5-a:
The fraction of prompt and nonprompt J/ψ in jets of 25 <pT< 35 GeV in pp data and in PYTHIA 8, compared to the total number of J/ψ in the relevant the pT interval, as indicated on the Figure. |
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Figure 5-b:
The ratio of these J/ψ -in-jet fractions in data compared to simulation for prompt and nonprompt J/ψ. |
Summary |
In this analysis, the self-normalized z distributions for J/ψ mesons in jets of 25 <pT< 35 GeV, for both prompt and nonprompt J/ψ production, were reported. The distributions are presented above a lower threshold of 3 and 6.5 GeV, in the endcap (1.6 <|y|< 2.4) and barrel (|y|< 1.6) regions of the CMS detector, respectively. These results confirm the findings of LHCb [8], albeit in a different rapidity range and √s, namely that the nonprompt J/ψ production is reasonably well modeled by simulation, in this case PYTHIA 8, but that the prompt J/ψ production is qualiltatively different than predicted. Prompt J/ψ in jets tend to carry a smaller fraction of the jet momentum, indicating that they are less isolated than suggested by production models. In addition, we also report the fraction of the J/ψ mesons in jets, for jets in the same window of pT (25-35 GeV), and for J/ψ meson above aforementioned lower pT thresholds. This additional information should provide further constraints on models of J/ψ production. |
Additional Figures | |
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Additional Figure 1:
The fraction of prompt J/ψ in jets of 25 <pT< 35 GeV in pp data and in PYTHIA 8, compared to the total number of J/ψ in the relevant the pT interval, as indicated on the Figure. |
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Additional Figure 2:
Data/MC ratio of the J/ψ -in-jet fraction for prompt J/ψ. |
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Additional Figure 3:
The fraction of prompt J/ψ in jets of 25 <pT< 35 GeV in pp data and in PYTHIA 8, compared to the total number of J/ψ in the relevant the pT interval, as indicated on the Figure. |
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Additional Figure 4:
Data/MC ratio of the J/ψ -in-jet fraction for nonprompt J/ψ. |
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Compact Muon Solenoid LHC, CERN |
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