Measurement of the 4` Cross Section at the Z Resonance and Determination of the Branching Fraction of Z → 4` in pp Collisions at √s = 7 and 8 TeV with ATLAS

Aad, G. and Abbott, B. and Abdallah, J. and Abdel, Khalek S. and Abdinov, O. and Aben, R. and Abi, B. and Abolins, M. and Abouzeid, O. S. and Abramowicz, H. and Abreu, H. and Abreu, R. and Abulaiti, Y. and Acharya, B. S. and Adamczyk, L. and Adams, D. L. and Adelman, J. and Adomeit, S. and Adye, T. and Agatonovic-Jovin, T. and Aguilar-Saavedra, J. A. and Agustoni, M. and Ahlen, S. P. and Ahmad, A. and Ahmadov, F. and Aielli, G. and Akerstedt, H. and Åkesson, T. P. A. and Akimoto, G. and Akimov, A. V. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2014) Measurement of the 4` Cross Section at the Z Resonance and Determination of the Branching Fraction of Z → 4` in pp Collisions at √s = 7 and 8 TeV with ATLAS. PHYSICAL REVIEW LETTERS, 112 (23). ISSN 0031-9007

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Abstract

Measurements of four-lepton (4`, ` = e, μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass region m`+`− > 5 GeV and 80 < m4` < 100 GeV, the measured cross sections are 76±18 (stat) ± 4 (syst) ±1.4 (lumi) fb and 107±9 (stat) ±4 (syst) ±3.0 (lumi) fb at √s = 7 and 8 TeV, respectively. By subtracting the non-resonant 4` production contributions and normalizing with Z → μ+μ− events, the branching fraction for the Z boson decay to 4` is determined to be (3.20 ± 0.25 (stat) ± 0.13 (syst)) × 10−6, consistent with the Standard Model prediction.

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