Measurements of the $$\mathrm {p}\mathrm {p}\rightarrow \mathrm{Z}\mathrm{Z}$$pp→ZZ production cross section and the $$\mathrm{Z}\rightarrow 4\ell $$Z→4ℓ branching fraction, and constraints on anomalous triple gauge couplings at $$\sqrt{s} = 13\,\text {TeV} $$s=13TeV

Four-lepton production in proton-proton collisions, $$\mathrm {p}\mathrm {p}\rightarrow (\mathrm{Z}/ \gamma ^*)(\mathrm{Z}/\gamma ^*) \rightarrow 4\ell $$ , where $$\ell = \mathrm {e}$$ or $$\mu $$ , is studied at a center-of-mass energy of 13 $$\,\text {TeV}$$ with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 $$\,\text {fb}^{-1}$$ . The ZZ production cross section, $$\sigma (\mathrm {p}\mathrm {p}\rightarrow \mathrm{Z}\mathrm{Z}) = 17.2 \pm 0.5\,\text {(stat)} \pm 0.7\,\text {(syst)} \pm 0.4\,\text {(theo)} \pm 0.4\,\text {(lumi)} \text { pb} $$ , measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region $$60< m_{\ell ^+\ell ^-} < 120\,\text {GeV} $$ , is consistent with standard model predictions. Differential cross sections are measured and are well described by the theoretical predictions. The Z boson branching fraction to four leptons is measured to be $$\mathcal {B}(\mathrm{Z}\rightarrow 4\ell ) = 4.83 _{-0.22}^{+0.23} (stat)_{-0.29}^{+0.32} (syst) \pm 0.08 (theo) \pm 0.12 (lumi) \times 10^{-6}$$ for events with a four-lepton invariant mass in the range $$80< m_{4\ell } < 100\,\text {GeV} $$ and a dilepton mass $$m_{\ell \ell } > 4\,\text {GeV} $$ for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ $$\gamma $$ couplings at 95% confidence level: $$-0.0012

Keywords:

• Coupling
• Particle physics
• Gauge (firearms)
• Physics
• Branching fraction
• Quantum chromodynamics
• W and Z bosons
• Invariant mass
• Lepton
• Luminosity
• Standard Model

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