Measurement of the inclusive and differential $\mathrm{t\bar{t}}\gamma$ cross sections in the dilepton channel and effective field theory interpretation in proton-proton collisions at $\sqrt{s}$ =13 TeV

The collaboration
JHEP 05 (2022) 091, 2022.

Abstract
The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions in the decay channel with two oppositely charged leptons (e$^\pm\mu^\mp$, e$^+$e$^-$, or $\mu^+\mu^-$). The measurement is performed using 138 fb$^{-1}$ of proton-proton collision data recorded by the CMS experiment at $\sqrt{s} =$ 13 TeV during the 2016-2018 data-taking period of the CERN LHC. A fiducial phase space is defined such that photons radiated by initial-state particles, top quarks, or any of their decay products are included. An inclusive cross section of 175.2 $\pm$ 2.5 (stat) $\pm$ 6.3 (syst) fb is measured in a signal region with at least one jet coming from the hadronization of a bottom quark and exactly one photon with transverse momentum above 20 GeV. Differential cross sections are measured as functions of several kinematic observables of the photon, leptons, and jets, and compared to standard model predictions. The measurements are also interpreted in the standard model effective field theory framework, and limits are found on the relevant Wilson coefficients from these results alone and in combination with a previous CMS measurement of the $\mathrm{t\bar{t}}\gamma$ production process using the lepton+jets final state.

• Figure 6a

Data corresponding to figure 6a (upper right)

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Observed and predicted event yields as a function of $p_{T}(\gamma)$ in the $e\mu$ channel, after the fit to the data.

• Figure 6b

Data corresponding to figure 6b (lower)

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Observed and predicted event yields as a function of $p_{T}(\gamma)$ in the $ee$ channel, after the fit to the data.

• Figure 6c

Data corresponding to figure 6c (upper left)

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Observed and predicted event yields as a function of $p_{T}(\gamma)$ in the $\mu\mu$ channel, after the fit to the data.

• Figure 7

Data corresponding to figure 7

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Measured inclusive fiducial $tt\gamma$ production cross section in the dilepton final state for the different dilepton-flavour channels and combined.

• Figure 8a

Data corresponding to figure 8a (upper left)

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Absolute differential $tt\gamma$ production cross section as a function of $p_{T}(\gamma)$ .

• Figure 8b

Data corresponding to figure 8b (upper right)

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Absolute differential $tt\gamma$ production cross section as a function of $|\eta |(\gamma)$.

• Figure 8c

Data corresponding to figure 8c (middle left)

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Absolute differential $tt\gamma$ production cross section as a function of min $\Delta R(\gamma, \ell)$.

• Figure 8d

Data corresponding to figure 8d (middle right)

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Absolute differential $tt\gamma$ production cross section as a function of $\Delta R(\gamma, \ell_{1})$.

• Figure 8e

Data corresponding to figure 8e (lower left)

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Absolute differential $tt\gamma$ production cross section as a function of $\Delta R(\gamma, \ell_{2})$.

• Figure 8f

Data corresponding to figure 8f (lower right)

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Absolute differential $tt\gamma$ production cross section as a function of min $\Delta R(\gamma, b)$.

• Figure 9a

Data corresponding to figure 9a (upper left)

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Absolute differential $tt\gamma$ production cross section as a function of $|\Delta\eta(\ell\ell)|$.

• Figure 9b

Data corresponding to figure 9b (upper right)

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Absolute differential $tt\gamma$ production cross section as a function of $\Delta \phi(\ell\ell)$.

• Figure 9c

Data corresponding to figure 9c (middle left)

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Absolute differential $tt\gamma$ production cross section as a function of $p_{T}(\ell\ell)$.

• Figure 9d

Data corresponding to figure 9d (middle right)

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Absolute differential $tt\gamma$ production cross section as a function of $p_{T}(\ell_{1})+p_{T}(\ell_{2})$ .

• Figure 9e

Data corresponding to figure 9e (lower left)

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Absolute differential $tt\gamma$ production cross section as a function of min $\Delta R(\ell, j)$.

• Figure 9f

Data corresponding to figure 9f (lower right)

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Absolute differential $tt\gamma$ production cross section as a function of $p_{T}(j_{1})$ .

• Figure 10a

Data corresponding to figure 10a (upper left)

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Normalized differential $tt\gamma$ production cross section as a function of $p_{T}(\gamma)$ .

• Figure 10b

Data corresponding to figure 10b (upper right)

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Normalized differential $tt\gamma$ production cross section as a function of $|\eta |(\gamma)$.

• Figure 10c

Data corresponding to figure 10c (middle left)

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Normalized differential $tt\gamma$ production cross section as a function of min $\Delta R(\gamma, \ell)$.

• Figure 10d

Data corresponding to figure 10d (middle right)

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Normalized differential $tt\gamma$ production cross section as a function of $\Delta R(\gamma, \ell_{1})$.

• Figure 10e

Data corresponding to figure 10e (lower left)

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Normalized differential $tt\gamma$ production cross section as a function of $\Delta R(\gamma, \ell_{2})$.

• Figure 10f

Data corresponding to figure 10f (lower right)

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Normalized differential $tt\gamma$ production cross section as a function of min $\Delta R(\gamma, b)$.

• Figure 11a

Data corresponding to figure 11a (upper left)

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Normalized differential $tt\gamma$ production cross section as a function of $|\Delta\eta(\ell\ell)|$.

• Figure 11b

Data corresponding to figure 11b (upper right)

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Normalized differential $tt\gamma$ production cross section as a function of $\Delta \phi(\ell\ell)$.

• Figure 11c

Data corresponding to figure 11c (middle left)

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Normalized differential $tt\gamma$ production cross section as a function of $p_{T}(\ell\ell)$.

• Figure 11d

Data corresponding to figure 11d (middle right)

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Normalized differential $tt\gamma$ production cross section as a function of $p_{T}(\ell_{1})+p_{T}(\ell_{2})$ .

• Figure 11e

Data corresponding to figure 11e (lower left)

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Normalized differential $tt\gamma$ production cross section as a function of min $\Delta R(\ell, j)$.

• Figure 11f

Data corresponding to figure 11f (lower right)

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Normalized differential $tt\gamma$ production cross section as a function of $p_{T}(j_{1})$ .

• Syst. correlation for $p_{T}(\gamma)$

Additional material related to figure 8a.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $p_{T}(\gamma)$ .

• Stat. correlation for $p_{T}(\gamma)$

Additional material related to figure 8a.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $p_{T}(\gamma)$ .

• Syst. correlation for $|\eta |(\gamma)$

Additional material related to figure 8b.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $|\eta |(\gamma)$.

• Stat. correlation for $|\eta |(\gamma)$

Additional material related to figure 8b.

10.17182/hepdata.113657.v1/t32

Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $|\eta |(\gamma)$.

• Syst. correlation for min $\Delta R(\gamma, \ell)$

Additional material related to figure 8c.

10.17182/hepdata.113657.v1/t33

Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of min $\Delta R(\gamma, \ell)$.

• Stat. correlation for min $\Delta R(\gamma, \ell)$

Additional material related to figure 8c.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of min $\Delta R(\gamma, \ell)$.

• Syst. correlation for $\Delta R(\gamma, \ell_{1})$

Additional material related to figure 8d.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $\Delta R(\gamma, \ell_{1})$.

• Stat. correlation for $\Delta R(\gamma, \ell_{1})$

Additional material related to figure 8d.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $\Delta R(\gamma, \ell_{1})$.

• Syst. correlation for $\Delta R(\gamma, \ell_{2})$

Additional material related to figure 8e.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $\Delta R(\gamma, \ell_{2})$.

• Stat. correlation for $\Delta R(\gamma, \ell_{2})$

Additional material related to figure 8e.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $\Delta R(\gamma, \ell_{2})$.

• Syst. correlation for min $\Delta R(\gamma, b)$

Additional material related to figure 8f.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of min $\Delta R(\gamma, b)$.

• Stat. correlation for min $\Delta R(\gamma, b)$

Additional material related to figure 8f.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of min $\Delta R(\gamma, b)$.

• Syst. correlation for $|\Delta\eta(\ell\ell)|$

Additional material related to figure 9a.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $|\Delta\eta(\ell\ell)|$.

• Stat. correlation for $|\Delta\eta(\ell\ell)|$

Additional material related to figure 9a.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $|\Delta\eta(\ell\ell)|$.

• Syst. correlation for $\Delta \phi(\ell\ell)$

Additional material related to figure 9b.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $\Delta \phi(\ell\ell)$.

• Stat. correlation for $\Delta \phi(\ell\ell)$

Additional material related to figure 9b.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $\Delta \phi(\ell\ell)$.

• Syst. correlation for $p_{T}(\ell\ell)$

Additional material related to figure 9c.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $p_{T}(\ell\ell)$.

• Stat. correlation for $p_{T}(\ell\ell)$

Additional material related to figure 9c.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $p_{T}(\ell\ell)$.

• Syst. correlation for $p_{T}(\ell_{1})+p_{T}(\ell_{2})$

Additional material related to figure 9d.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $p_{T}(\ell_{1})+p_{T}(\ell_{2})$ .

• Stat. correlation for $p_{T}(\ell_{1})+p_{T}(\ell_{2})$

Additional material related to figure 9d.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $p_{T}(\ell_{1})+p_{T}(\ell_{2})$ .

• Syst. correlation for min $\Delta R(\ell, j)$

Additional material related to figure 9e.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of min $\Delta R(\ell, j)$.

• Stat. correlation for min $\Delta R(\ell, j)$

Additional material related to figure 9e.

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Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of min $\Delta R(\ell, j)$.

• Syst. correlation for $p_{T}(j_{1})$

Additional material related to figure 9f.

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Correlation matrix of the systematic uncertainty in the absolute differential cross section as a function of $p_{T}(j_{1})$ .

• Stat. correlation for $p_{T}(j_{1})$

Additional material related to figure 9f.

10.17182/hepdata.113657.v1/t52

Correlation matrix of the statistical uncertainty in the absolute differential cross section as a function of $p_{T}(j_{1})$ .

• Figure 12a

Data corresponding to figure 12a (upper left)

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Negative log-likelihood difference from the best-fit value for the one-dimensional scans of the Wilson coefficient $c_{tZ}$, using the photon pT...

• Figure 12b

Data corresponding to figure 12b (upper right)

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Negative log-likelihood difference from the best-fit value for the one-dimensional scans of the Wilson coefficient $c_{tZ}$, using the combination of...

• Figure 12c

Data corresponding to figure 12c (lower left)

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Negative log-likelihood difference from the best-fit value for the one-dimensional scans of the Wilson coefficient $c^{I}_{tZ}$, using the photon pT...

• Figure 12d

Data corresponding to figure 12d (lower right)

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Negative log-likelihood difference from the best-fit value for the one-dimensional scans of the Wilson coefficient $c^{I}_{tZ}$, using the combination of...

• Figure 13a

Data corresponding to figure 13a (left)

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Negative log-likelihood difference from the best-fit value as a function of Wilson coefficients $c_{tZ}$ and $c^{I}_{tZ}$ from the interpretation of...

• Figure 13b

Data corresponding to figure 13b (right)

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Negative log-likelihood difference from the best-fit value as a function of Wilson coefficients $c_{tZ}$ and $c^{I}_{tZ}$ from the interpretation of...

• Table 5

Data corresponding to table 5

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One-dimensional 68 and 95% CL intervals obtained for the Wilson coefficients $c_{tZ}$ and $c^{I}_{tZ}$, using the photon $p_{T}$ distribution from...

• Figure 14

Data corresponding to figure 14

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Comparison of observed $95\%$ CL intervals for the Wilson coefficients $c_{tZ}$ and $c^{I}_{tZ}$. Results are shown from a CMS ttZ...