Combination of CDF and D0 measurements of the W boson helicity in top quark decays

Abstract

Aaltonen, T. et al.We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7–5.4  fb-1 of pp¯ collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f0) and right-handed (f+) helicities, we find f0=0.722±0.081[±0.062(stat)±0.052(syst)] and f+=-0.033±0.046[±0.034(stat)±0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f0=0.682±0.057[±0.035(stat)±0.046(syst)] for fixed f+ and f+=-0.015±0.035[±0.018(stat)±0.030(syst)] for fixed f0. The results are consistent with standard model expectations.Acknowledge support from the DOE and NSF (USA); CEA and CNRS/IN2P3 (France); FASI, Rosatom and RFBR (Russia); CNPq, FAPERJ, FAPESP, and FUNDUNESP (Brazil); DAE and DST (India); INFN (Italy); Ministry of Education, Culture, Sports, Science, and Technology (Japan); Colciencias (Colombia); CONACyT (Mexico); World Class University Program, National Research Foundation, NRF (Korea); CONICET and UBACyT (Argentina); Australian Research Council (Australia); FOM (The Netherlands); STFC and the Royal Society (United Kingdom); MSMT and GACR (Czech Republic); CRC Program and NSERC (Canada); Academy of Finland (Finland); BMBF and DFG (Germany); SFI (Ireland); Slovak R&D Agency (Slovakia); Programa Consolider-Ingenio 2010 (Spain); Swedish Research Council (Sweden); Swiss National Science Foundation (Switzerland); NSC (Republic of China); CAS and CNSF (China); and the A. P. Sloan Foundation (USA).Peer Reviewe