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| CMS-PAS-SMP-16-011 | ||
| Measurement of triple-differential dijet cross sections at $\sqrt{s}=$ 8 TeV with the CMS detector and constraints on parton distribution functions | ||
| CMS Collaboration | ||
| November 2016 | ||
| Abstract: A measurement of triple-differential dijet cross sections at a centre-of-mass energy of $\sqrt{s} =$ 8 TeV is presented using 19.7 fb$^{-1}$ of data collected with the CMS detector in proton-proton collisions at the LHC. The cross sections are measured as a function of the average transverse momentum, half the rapidity separation, and the boost of the two leading jets. The cross sections are unfolded for detector effects and compared to calculations in perturbative quantum chromodynamics at next-to-leading order accuracy complemented with electroweak and nonperturbative corrections. Constraints on the parton distribution functions are derived and the strong coupling constant is determined to be $\alpha_s(M_Z) =$ 0.1199 $\pm$ 0.0015 (exp) $_{-0.0020}^{+0.0031}$(theo). | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, EPJC 77 (2017) 746. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Dijet event topologies. |
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Figure 2:
Subprocess decomposition. |
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Figure 2-a:
Subprocess decomposition. |
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Figure 2-b:
Subprocess decomposition. |
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Figure 2-c:
Subprocess decomposition. |
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Figure 2-d:
Subprocess decomposition. |
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Figure 2-e:
Subprocess decomposition. |
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Figure 2-f:
Subprocess decomposition. |
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Figure 3:
Overview of experimental uncertainties. |
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Figure 3-a:
Overview of experimental uncertainties. |
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Figure 3-b:
Overview of experimental uncertainties. |
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Figure 3-c:
Overview of experimental uncertainties. |
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Figure 3-d:
Overview of experimental uncertainties. |
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Figure 3-e:
Overview of experimental uncertainties. |
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Figure 3-f:
Overview of experimental uncertainties. |
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Figure 4:
Overview of theory uncertainties. |
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Figure 4-a:
Overview of theory uncertainties. |
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Figure 4-b:
Overview of theory uncertainties. |
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Figure 4-c:
Overview of theory uncertainties. |
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Figure 4-d:
Overview of theory uncertainties. |
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Figure 4-e:
Overview of theory uncertainties. |
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Figure 4-f:
Overview of theory uncertainties. |
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Figure 5:
Spectrum of the triple-differential dijet cross section. |
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Figure 6:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 6-a:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 6-b:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 6-c:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 6-d:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 6-e:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 6-f:
Ratio of the triple-differential dijet cross section to the {NLOJet++} prediction using the NNPDF3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added, the solid and dashed lines give the predictions calculated with different PDF sets. |
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Figure 7:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 7-a:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 7-b:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 7-c:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 7-d:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 7-e:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 7-f:
Ratio of the triple-differential dijet cross sections to the {NLOJet++} prediction using the NNPDF 3.0 set. The data points including statistical uncertainties are indicated by markers, the total experimental uncertainty is represented by the hatched band. The solid band shows the PDF, scale, and NP uncertainties quadratically added. The predictions of the NLO MC event generators POWHEG + PYTHIA and HERWIG are depicted by solid and dashed lines, respectively. |
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Figure 8:
Direct comparison of gluon and quark PDFs. |
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Figure 8-a:
Direct comparison of gluon and quark PDFs. |
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Figure 8-b:
Direct comparison of gluon and quark PDFs. |
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Figure 8-c:
Direct comparison of gluon and quark PDFs. |
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Figure 8-d:
Direct comparison of gluon and quark PDFs. |
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Figure 9:
Direct comparison of gluon and quark PDFs. |
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Figure 9-a:
Direct comparison of gluon and quark PDFs. |
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Figure 9-b:
Direct comparison of gluon and quark PDFs. |
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Figure 9-c:
Direct comparison of gluon and quark PDFs. |
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Figure 9-d:
Direct comparison of gluon and quark PDFs. |
| Tables | |
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Table 2:
Fit quality in the HERA DIS and combined fit. |
| Summary |
| A measurement of triple-differential dijet cross sections has been presented. The data were found to be well described by NLO predictions corrected for NP and EW effects except for a boosted event topology, which suffers from large PDF uncertainties. The precise data constrain the PDFs, especially in the boosted regime, where the highest momentum fractions $x$ of the PDFs are probed. The impact of the data on the PDFs was demonstrated by performing a simultaneous fit to DIS cross sections obtained from the HERA experiments and the dijet cross sections measured in this paper. If the dijet data are considered, a slightly harder gluon PDF is obtained and the overall uncertainties of the PDFs, especially those of the gluon PDF, are significantly reduced. The strong coupling constant has been determined together with the PDFs in a simultaneous fit. |
| References | ||||
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Compact Muon Solenoid LHC, CERN |
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