Measurement of the ZZ production cross section and search for anomalous couplings in 2l2l' final states in pp collisions at sqrt(s) = 7 TeV

Abstract

A measurement is presented of the ZZ production cross section in the ZZ to 2l 2l' decay mode with l = e, mu and l' = e, mu, tau in proton-proton collisions at sqrt(s) = 7 TeV with the CMS experiment at the LHC. Results are based on data corresponding to an integrated luminosity of 5.0 inverse femtobarns. The measured cross section sigma(pp to ZZ) = 6.24 [+0.86/-0.80] (stat.) [+0.41/-0.32] (syst.) +/- 0.14 (lumi.) pb is consistent with the standard model predictions. The following limits on ZZZ and ZZ gamma anomalous trilinear gauge couplings are set at 95% confidence level: -0.011 < f[4;Z] < 0.012, -0.012 < f[5;Z] < 0.012, -0.013 < f[4;gamma] < 0.015, and -0.014 < f[5,gamma] < 0.014.

Figures (3)

• Figure 1: Distributions of the four-lepton reconstructed mass for (a) the sum of the $4\mathrm{e}, 4{\mu}$, and $2\mathrm{e}2{\mu}$ channels and (b) the sum of the $2\ell 2\tau$ channels. Points represent the data, and the shaded histograms represent the expected ${Z}{Z}$ signal and the reducible background. The shapes of the signal and background are taken from the MC simulation, with each component normalized to the corresponding estimated value from Table \ref{['table:results']}. The distributions (c) and (d) demonstrate the relationship between the reconstructed ${Z}_1$ and ${Z}_2$ masses.
• Figure 2: Distribution of the four-lepton reconstructed mass for the sum of the $4\mathrm{e}, 4{\mu}$, and the $2\mathrm{e}2{\mu}$ channels. Points represent the data, and the shaded histograms represent the expected ${Z}{Z}$ signal and the reducible background. The dashed and dotted histograms represent the results of the sherpa simulation for the SM ($f_4^{{Z}} = 0$) and in the presence of an ATGC ($f_4^{{Z}}=0.015$), while all the other anomalous couplings are set to zero.
• Figure 3: Expected and observed two-dimensional exclusion limits at 95% CL on the anomalous neutral trilinear ${Z}{Z}{Z}$ ($f_{4,5}^{{Z}}$) and ${Z}{Z}\gamma$ ($f_{4,5}^{\gamma}$) couplings. The green and yellow bands represent the one and two standard-deviation variations from the expected limit. In calculating the limits, the anomalous couplings that are not shown in the figure are set to zero.