A measurement of the fiducial cross section of the associated production of a Z boson and a high-$p_\mathrm{T}$ photon, where the Z decays to two neutrinos, and a search for anomalous triple gauge couplings are reported. The results are based on data collected by the CMS experiment at the LHC in proton-proton collisions at $\sqrt{s}$ = 13 TeV during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The fiducial Z$γ$ cross section, where a photon with a $p_\mathrm{T}$ greater than 225 GeV is produced in association with a Z, and the Z decays to a $ν\barν$ pair (Z($ν\barν$)$γ$), is measured to be 23.3$^{+1.4}_{-1.3}$ fb, in agreement, within uncertainties, with the standard model prediction. The differential cross section as a function of the photon $p_\mathrm{T}$ has been measured and compared with standard model predictions computed at next-to-leading and at next-to-next-to-leading order in perturbative quantum chromodynamics. Constraints have been placed on the presence of anomalous couplings that affect the ZZ$γ$ and Z$γγ$ vertex using the $p_\mathrm{T}$ spectrum of the photons. The observed 95% confidence level intervals for $CP$-conserving $h_3^γ$ and $h_4^γ$ are determined to be ($-$3.4, 3.5) $\times$ 10$^{-4}$ and ($-$6.8, 6.8) $\times$ 10$^{-7}$, and for $h_3^\mathrm{Z}$ and $h_4^\mathrm{Z}$ they are ($-$2.2, 2.2) $\times$ 10$^{-4}$ and ($-$4.1, 4.2) $\times$ 10$^{-7}$, respectively. These are the strictest limits to date on $h_3^γ$, $h_3^\mathrm{Z}$ and $h_4^\mathrm{Z}$.
Post-fit reconstruction-level photon transverse momentum $p_{T}^{\gamma}$ distribution in the ECAL barrel signal region. The yields correspond to the post-fit expectation from the maximum-likelihood fit used in the analysis, with uncertainties reflecting the post-fit total (stat+syst) uncertainty per bin. Data correspond to the full Run-2 dataset (138 fb$^{-1}$ at $\sqrt{s}=13$ TeV).
Post-fit reconstruction-level photon transverse momentum $p_{T}^{\gamma}$ distribution in the ECAL endcaps signal region. The yields correspond to the post-fit expectation from the maximum-likelihood fit used in the analysis, with uncertainties reflecting the post-fit total (stat+syst) uncertainty per bin. Data correspond to the full Run-2 dataset (138 fb$^{-1}$ at $\sqrt{s}=13$ TeV).
Measured and predicted fiducial cross sections (fb) in the EB, EE, and combined phase space. The fiducial phase space definition follows the analysis selection in the paper. Predictions are shown at NLO (MADGRAPH5_aMC@NLO) and NNLO (MATRIX).
A direct search for new heavy neutral Higgs bosons A and H in the $\mathrm{t\bar{t}}$Z channel is presented, targeting the process pp $\to$ A $\to$ ZH with H $\to$$\mathrm{t\bar{t}}$. For the first time, the channel with decays of the Z boson to muons or electrons in association with all-hadronic decays of the $\mathrm{t\bar{t}}$ system is targeted. The analysis uses proton-proton collision data collected at the CERN LHC with the CMS experiment at $\sqrt{s}$ = 13 TeV, which correspond to an integrated luminosity of 138 fb$^{-1}$. No signal is observed. Upper limits on the product of the cross section and branching fractions are derived for narrow resonances A and H with masses up to 2100 and 2000 GeV, respectively, assuming A boson production through gluon fusion. The results are also interpreted within two-Higgs-doublet models, where A and H are CP-odd and CP-even states, respectively, complementing and substantially extending the reach of previous searches.
Distributions of p_T(Z) × ∆m in the SR after the fit to data with a (mA , mH) signal hypothesis of (1000, 350) GeV. The post-fit signal yields are compatible with zero events in all bins. The pre-fit signal is arbitrarily scaled and therefore omitted.
Distributions of p_T(Z) × ∆m in the SR after the fit to data with a (mA , mH) signal hypothesis of (1000, 350) GeV. The post-fit signal yields are compatible with zero events in all bins. The pre-fit signal is arbitrarily scaled and therefore omitted.
Distributions of p_T(Z) × ∆m in the SR after the fit to data with a (mA , mH) signal hypothesis of (1000, 850) GeV. The pre-fit signal is arbitrarily scaled and therefore omitted.
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.
Observed and predicted event yields as a function of $p_{T}(\gamma)$ in the $e\mu$ channel, after the fit to the data.
Observed and predicted event yields as a function of $p_{T}(\gamma)$ in the $ee$ channel, after the fit to the data.
Observed and predicted event yields as a function of $p_{T}(\gamma)$ in the $\mu\mu$ channel, after the fit to the data.