We report the first evidence of Z boson pair production at a hadron collider with a significance exceeding 4 standard deviations. This result is based on a data sample corresponding to 1.9fb-1 of integrated luminosity from pp̄ collisions at s=1.96TeV collected with the Collider Detector at Fermilab II detector. In the ′ ′ channel, we observe three ZZ candidates with an expected background of 0.096-0.063+0.092 events. In the νν channel, we use a leading-order calculation of the relative ZZ and WW event probabilities to discriminate between signal and background. In the combination of ′ ′ and νν channels, we observe an excess of events with a probability of 5.1×10-6 to be due to the expected background. This corresponds to a significance of 4.4 standard deviations. The measured cross section is σ(pp̄→ZZ)=1.4-0.6+0.7(stat+syst)pb, consistent with the standard model expectation. © 2008 The American Physical Society.
Publication Source (Journal or Book title)
Physical Review Letters
Aaltonen, T., Adelman, J., Akimoto, T., Albrow, M., Álvarez González, B., Amerio, S., Amidei, D., Anastassov, A., Annovi, A., Antos, J., Aoki, M., Apollinari, G., Apresyan, A., Arisawa, T., Artikov, A., Ashmanskas, W., Attal, A., Aurisano, A., Azfar, F., Azzi-Bacchetta, P., Azzurri, P., Bacchetta, N., Badgett, W., Barbaro-Galtieri, A., Barnes, V., Barnett, B., Baroiant, S., & Bartsch, V. (2008). Strong evidence for ZZ production in pp̄ collisions at s=1.96TeV. Physical Review Letters, 100 (20) https://doi.org/10.1103/PhysRevLett.100.201801