Evidence for the spin-0 nature of the Higgs boson using ATLAS data

Aad, G. and Abajyan, T. and Abbott, B. and Abdallah, J. and AbdelKhalek, S. and Abdinov, O. and Aben, R. and Abi, B. and Abolins, M. and AbouZeid, O. S. and Abramowicz, H. and Abreu, H. and Abulaiti, Y. and Acharya, B. S. and Adamczyk, L. and Adams, D. L. and Addy, T. N. and Adelman, J. and Adomeit, S. and Adye, T. and Aefsky, S. and Aguilar-Saavedra, J. A. and Agustoni, M. and Ahlen, S. P. and Ahmad, A. and Ahsan, M. and Aielli, G. and Åkesson, T. P. A. and Akimoto, G. and Akimov, A. V. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2013) Evidence for the spin-0 nature of the Higgs boson using ATLAS data. PHYSICS LETTERS B, 726 (1-3). pp. 120-144. ISSN 0370-2693

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Abstract

Studies of the spin and parity quantum numbers of the Higgs boson are presented, based on proton–proton collision data collected by the ATLAS experiment at the LHC. The Standard Model spin–parity J P = 0 + hypothesis is compared with alternative hypotheses using the Higgs boson decays H→ γγ, H → ZZ∗ → 4` and H→ WW∗→ `ν`ν, as well as the combination of these channels. The analysed dataset corresponds to an integrated luminosity of 20.7 fb−1 collected at a centre–of–mass energy of √ s = 8 TeV. For the H → ZZ∗ → 4` decay mode the dataset corresponding to an integrated luminosity of 4.6 fb−1 collected at √ s = 7 TeV is added. The data are compatible with the Standard Model J P = 0 + quantum numbers for the Higgs boson, whereas all alternative hypotheses studied in this letter, namely some specific J P = 0 − , 1 + , 1 − , 2 + models, are excluded at confidence levels above 97.8%. This exclusion holds independently of the assumptions on the coupling strengths to the Standard Model particles and in the case of the J P = 2 + model, of the relative fractions of gluon–fusion and quark–antiquark production of the spin-2 particle. The data thus provide evidence for the spin-0 nature of the Higgs boson, with positive parity being strongly preferred.

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