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CMS-SMP-16-016 ; CERN-EP-2019-127
Measurements of triple-differential cross sections for inclusive isolated-photon+jet events in pp collisions at $\sqrt{s} = $ 8 TeV
Eur. Phys. J. C 79 (2019) 969
Abstract: Measurements are presented of the triple-differential cross section for inclusive isolated-photon+jet events in pp collisions at $\sqrt{s} = $ 8 TeV as a function of photon transverse momentum (${p_{\mathrm{T}}^{\gamma}}$), photon pseudorapidity (${\eta^{\gamma}}$), and jet pseudorapidity (${\eta^{\text{jet}}}$). The data correspond to an integrated luminosity of 19.7 fb$^{-1}$ that probe a broad range of the available phase space, for $ | {\eta^{\gamma}} | < $ 1.44 and 1.57 $ < | {\eta^{\gamma}} | < $ 2.50, $ | {\eta^{\text{jet}}} | < $ 2.5, 40 $ < {p_{\mathrm{T}}^{\gamma}} < $ 1000 GeV, and jet transverse momentum, $p_{\mathrm{T}}^{\text{jet}}$, $ > $ 25 GeV. The measurements are compared to next-to-leading order perturbative quantum chromodynamics calculations, which reproduce the data within uncertainties.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
An example fit of candidate boosted-decision-tree distribution with a composite template (blue histogram). The signal (background) template is shown by the green (red) solid (hatched) region. The bottom panel shows the mean of the fit values for 500 templates varied within the signal and background shape uncertainties (F) subtracted from data (D) divided by the data.

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Figure 2:
Purity estimates as a function of $ {p_{\mathrm {T}}} ^\gamma $ for different photon and jet pseudorapidity regions. The values are offset by 0.3, 0.6 and 0.9 for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The total uncertainties are shown as error bars.

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Figure 2-a:
Purity estimates as a function of $ {p_{\mathrm {T}}} ^\gamma $ for $ < | {\eta^{\gamma}} | < $ 0.8 and different jet pseudorapidity regions. The values are offset by 0.3, 0.6 and 0.9 for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The total uncertainties are shown as error bars.

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Figure 2-b:
Purity estimates as a function of $ {p_{\mathrm {T}}} ^\gamma $ for 0.8 $ < | {\eta^{\gamma}} | < $ 1.44 and different jet pseudorapidity regions. The values are offset by 0.3, 0.6 and 0.9 for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The total uncertainties are shown as error bars.

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Figure 2-c:
Purity estimates as a function of $ {p_{\mathrm {T}}} ^\gamma $ for 1.56 $ < | {\eta^{\gamma}} | < $ 2.1 and different jet pseudorapidity regions. The values are offset by 0.3, 0.6 and 0.9 for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The total uncertainties are shown as error bars.

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Figure 2-d:
Purity estimates as a function of $ {p_{\mathrm {T}}} ^\gamma $ for 2.1 $ < | {\eta^{\gamma}} | < $ 2.5 and different jet pseudorapidity regions. The values are offset by 0.3, 0.6 and 0.9 for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The total uncertainties are shown as error bars.

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Figure 3:
Measured triple-differential cross section distributions as a function of $ {p_{\mathrm {T}}} ^\gamma $ in different bins of $ {{| \eta ^{\text {jet}} |}}$ for photons in the barrel region. Note that the distributions are multiplied by a factor of $10^2$, $10^4$ and $10^6$ for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The statistical (systematic) uncertainties are shown as error bars (color bands).

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Figure 3-a:
Measured triple-differential cross section distributions as a function of $ {p_{\mathrm {T}}} ^\gamma $ for $ < | {\eta^{\gamma}} | < $ 0.8. Note that the distributions are multiplied by a factor of $10^2$, $10^4$ and $10^6$ for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The statistical (systematic) uncertainties are shown as error bars (color bands).

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Figure 3-b:
Measured triple-differential cross section distributions as a function of $ {p_{\mathrm {T}}} ^\gamma $ for 0.8 $ < | {\eta^{\gamma}} | < $ 1.44. Note that the distributions are multiplied by a factor of $10^2$, $10^4$ and $10^6$ for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The statistical (systematic) uncertainties are shown as error bars (color bands).

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Figure 4:
Measured triple-differential cross section distributions as a function of $ {p_{\mathrm {T}}} ^\gamma $ in different bins of $ {{| \eta ^{\text {jet}} |}}$ for photons in the endcap region. Note that the distributions are multiplied by a factor of $10^2$, $10^4$ and $10^6$ for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The statistical (systematic) uncertainties are shown as error bars (color bands).

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Figure 4-a:
Measured triple-differential cross section distributions as a function of $ {p_{\mathrm {T}}} ^\gamma $ in different bins of $ {{| \eta ^{\text {jet}} |}}$ for 1.56 $ < | {\eta^{\gamma}} | < $ 2.1. Note that the distributions are multiplied by a factor of $10^2$, $10^4$ and $10^6$ for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The statistical (systematic) uncertainties are shown as error bars (color bands).

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Figure 4-b:
Measured triple-differential cross section distributions as a function of $ {p_{\mathrm {T}}} ^\gamma $ in different bins of $ {{| \eta ^{\text {jet}} |}}$ for 2.1 $ < | {\eta^{\gamma}} | < $ 2.5. Note that the distributions are multiplied by a factor of $10^2$, $10^4$ and $10^6$ for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5, 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1, and 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 respectively. The statistical (systematic) uncertainties are shown as error bars (color bands).

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Figure 5:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) in different bins of $ {{| \eta ^{\text {jet}} |}}$ for $ {| \eta ^\gamma |} < $ 0.8. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 5-a:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for $ {{| \eta ^{\text {jet}} |}} < $ 0.8 and $ {| \eta ^\gamma |} < $ 0.8. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 5-b:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5 and $ {| \eta ^\gamma |} < $ 0.8. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 5-c:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1 and $ {| \eta ^\gamma |} < $ 0.8. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 5-d:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 and $ {| \eta ^\gamma |} < $ 0.8. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 6:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) in different bins of $ {{| \eta ^{\text {jet}} |}}$ for 0.80 $ < {| \eta ^\gamma |} < $ 1.44. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 6-a:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for $ {{| \eta ^{\text {jet}} |}} < $ 0.8 and 0.80 $ < {| \eta ^\gamma |} < $ 1.44. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 6-b:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5 and 0.80 $ < {| \eta ^\gamma |} < $ 1.44. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 6-c:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1 and 0.80 $ < {| \eta ^\gamma |} < $ 1.44. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 6-d:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 and 0.80 $ < {| \eta ^\gamma |} < $ 1.44. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 7:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) in different bins of $ {{| \eta ^{\text {jet}} |}}$ for 1.56 $ < {| \eta ^\gamma |} < $ 2.10. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 7-a:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for $ {{| \eta ^{\text {jet}} |}} < $ 0.8 and1.56 $ < {| \eta ^\gamma |} < $ 2.10. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 7-b:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5 and1.56 $ < {| \eta ^\gamma |} < $ 2.10. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 7-c:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1 and1.56 $ < {| \eta ^\gamma |} < $ 2.10. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 7-d:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 and1.56 $ < {| \eta ^\gamma |} < $ 2.10. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 8:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) in different bins of $ {{| \eta ^{\text {jet}} |}}$ for 2.1 $ < {| \eta ^\gamma |} < $ 2.5. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 8-a:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for $ {{| \eta ^{\text {jet}} |}} < $ 0.8 and 2.1 $ < {| \eta ^\gamma |} < $ 2.5. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 8-b:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 0.8 $ < {{| \eta ^{\text {jet}} |}} < $ 1.5 and 2.1 $ < {| \eta ^\gamma |} < $ 2.5. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 8-c:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 1.5 $ < {{| \eta ^{\text {jet}} |}} < $ 2.1 and 2.1 $ < {| \eta ^\gamma |} < $ 2.5. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.

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Figure 8-d:
Ratio of triple-differential cross sections as a function of $ {p_{\mathrm {T}}} ^\gamma $ measured in data over the corresponding GamJet NLO theoretical prediction (obtained with the CJ15 PDFs) for 2.1 $ < {{| \eta ^{\text {jet}} |}} < $ 2.5 and 2.1 $ < {| \eta ^\gamma |} < $ 2.5. Error bars on the data are statistical uncertainties, and blue bands represent the systematic uncertainties.
Tables

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Table 1:
Summary of uncertainties in the estimated purity for photons in the barrel (endcap) region.

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Table 2:
Summary of the uncertainties in the measured cross section values for photons in the barrel (endcap) region.
Summary
Measurements of the triple-differential inclusive isolated-photon+jet cross section were performed as a function of photon transverse momentum (${p_{\mathrm{T}}^{\gamma}}$), photon pseudorapidity (${\eta^{\gamma}}$), and jet pseudorapidity (${\eta^{\text{jet}}}$). The measurements were carried out in pp collisions at $\sqrt{s} = $ 8 TeV using 19.7 fb$^{-1}$ of data collected by the CMS detector covering a kinematic range of $| {\eta^{\gamma}} | < $ 1.44 and 1.57 $ < | {\eta^{\gamma}} | < $ 2.50, $| {\eta^{\text{jet}}} | < $ 2.5, 40 $ < {p_{\mathrm{T}}^{\gamma}} < $ 1000 GeV, and jet transverse momentum, $p_{\mathrm{T}}^{\text{jet}}$, $ > $25 GeV. The photon purity was estimated using a combination of templates from data and simulation, based on a multivariate technique. The measured cross sections are in good agreement with the next-to-leading order perturbative quantum chromodynamics (pQCD) prediction, and the experimental uncertainties are comparable or smaller than the theoretical ones. These measured cross sections, in different combinations of photon and jet pseudorapidities, probe pQCD over a wide range of parton momentum fractions. Inclusion of such gluon-sensitive data into the global parton distribution function (PDF) fit analyses has the potential to constrain the gluon PDFs, particularly in the regions where the measured uncertainties are smaller than the uncertainty bands of theoretical predictions.
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