Measurement of top quark polarization in tt¯ lepton+jets final states

We present a measurement of top quark polarization in tt¯ pair production in pp¯ collisions at s=1.96 TeV using data corresponding to 9.7 fb−1 of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing a lepton and at least three jets. The polarization is measured through the distribution of lepton angles along three axes: the beam axis, the helicity axis, and the transverse axis normal to the tt¯ production plane. This is the first measurement of top quark polarization at the Tevatron using lepton+jet final states and the first measurement of the transverse polarization in tt¯ production. The observed distributions are consistent with standard model predictions of nearly no polarization.