Measurement of tt̄ Helicity Fractions and Spin Correlation Using Reconstructed Lepton+Jets Events
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چکیده
Standard model top pair production produces a characteristic spin correlation which can be modified by new production mechanisms such as Z ′ bosons or Kaluza-Klein gluons. In the standard model, top quarks decay weakly before any hadronization processes take effect, enabling top spin information to be transmitted to the top quark decay products. We report on the observation and measurement of the tt̄ helicity fractions and spin correlation in 5.3 fb−1 of reconstructed lepton+jet data. In the helicity basis, we find the opposite helicity fraction FOH = 0.74 ± 0.24(stat)±0.11(syst), and a spin correlation coefficient κhelicity = 0.48± 0.48(stat)±0.22(syst). In the beam basis, we find the opposite spin fraction FOS = 0.86±0.32(stat)±0.13(syst), and a spin correlation coefficient κbeam = 0.72± 0.64(stat)±0.26(syst). http://www-cdf.fnal.gov
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