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| CMS-PAS-HIN-16-003 | ||
| Dijet pseudorapidity in pp and pPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV with the CMS detector | ||
| CMS Collaboration | ||
| July 2016 | ||
| Abstract: We report on measurements of the dijet pseudorapidity distributions in pp and pPb collisions at $\sqrt{s_{\mathrm{NN}}}= $ 5.02 TeV with the CMS detector. These measurements are sensitive to nuclear modifications of parton distribution functions (PDF). Recent theoretical studies based on NLO calculations show that the constraining power of pPb data on nuclear PDF fits can be improved by the knowledge of the corresponding measurement in pp collisions. Moreover, measurements of dijet average transverse momentum provide a good handle on $Q^2$. In this physics analysis summary, the dijet pseudorapidity spectra are studied in different dijet average transverse momentum intervals. These measurements can provide constraints on the nuclear PDF over a wide phase space of $x$ and $Q^2$. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRL 121 (2018) 062002. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1-a:
(a) Correlation between the ratio of $x_{\rm Pb}$ and $x_{\rm p}$ and $\eta _{\rm dijet}$. (b) Mean $x$ values obtained from particle-level PYTHIA are shown as a function of $\eta ^{\rm dijet}$ in bins of dijet $ p_{{\mathrm {T}}}^{\rm ave}$. |
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Figure 1-b:
(a) Correlation between the ratio of $x_{\rm Pb}$ and $x_{\rm p}$ and $\eta _{\rm dijet}$. (b) Mean $x$ values obtained from particle-level PYTHIA are shown as a function of $\eta ^{\rm dijet}$ in bins of dijet $ p_{{\mathrm {T}}}^{\rm ave}$. |
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Figure 2:
The measured pp dijet pseudorapidity spectra in bins of dijet average transverse momentum overlaid with NLO calculations with nPDF sets of CT14 and MMHT14. |
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Figure 3:
The measured pPb dijet pseudorapidity spectra in bins of dijet average transverse momentum overlaid with NLO calculations with nPDF sets of DSSZ, EPS09 and CTEQ15 for proton PDF baseline of CT14. |
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Figure 4:
The measured pPb dijet pseudorapidity spectra in bins of dijet average transverse momentum overlaid with NLO calculations with nPDF sets of DSSZ, EPS09 and CTEQ15 for proton PDF baseline of MMHT14. |
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Figure 5:
The ratio between pPb and pp dijet pseudorapidity is compared to NLO calculations. Calculations are with nPDF sets DSSZ, EPS09 and nCTEQ15 and proton PDF MMHT14. |
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Figure 6:
The ratio between pPb and pp dijet pseudorapidity is compared to NLO calculations. Calculations are with nPDF sets DSSZ, EPS09 and nCTEQ15 and proton PDF CT14. |
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Figure 7:
The difference between pPb and pp dijet pseudorapidity is compared to NLO calculations. Calculations are with nPDF sets DSSZ, EPS09 and nCTEQ15 and proton PDF MMHT14. |
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Figure 8:
The difference between pPb and pp dijet pseudorapidity is compared to NLO calculations. Calculations are with nPDF sets DSSZ, EPS09 and nCTEQ15 and proton PDF CT14. |
| Summary |
| Measurements of the dijet pseudorapidity in different dijet average $p_\mathrm{T}$ intervals in pp and pPb collisions at nucleon-nucleon centre-of-mass energy of 5.02 TeV are reported. The measured dijet pseudorapidity distributions are compared to NLO calculations using nuclear and proton parton distribution functions. Significant modifications of the dijet pseudorapidity are observed in pPb data compared to pp references. Those measurements are compared with NLO calculation with EPS09, DSSZ and nCTEQ15 which provide strong constrain to the nPDF. |
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