Longitudinal quark polarization in e+e-→t(t)over-bar and chromoelectric and chromomagnetic dipole couplings of the top quark

The effect of anomalous chromomagnetic (mu) and chromoelectric couplings (d) of the gluon to the top quark is considered in e(+)e(-) --> t (t) over bar with unpolarized and longitudinally polarized electron beams. The total cross section, as well as t and (t) over bar polarizations, are calculated to order alpha(s) in the presence of the anomalous couplings. One of the two linear combinations of t and (t) over bar polarizations is CP even, while the other is CP odd. The limits that could be obtained at a typical future linear collider with an integrated luminosity of 50 fb(-1) and a total c.m. energy of 500 GeV on the most sensitive CP-even combination of anomalous couplings, are estimated as -3 < Re(mu) < 2, for Im(mu) = 0 = d, and root Im(mu)(2) + \ d \(2) < 2.25, for Re(mu) = 0. There is an improvement by roughly a factor of 2 at 1000 GeV. On the other hand: from the CP-odd combination. we derive the possible complementary bounds as -3.6 < Im(mu*d) < 3.6, for Im(d) = 0, and -10 < Im(d) < 10, for Im(mu*d) = 0, for a c.m. energy of 500 GeV. The corresponding limit for 1000 GeV is almost an order of magnitude better for Tm(mu*d); though somewhat worse for Im(d). Results for the c.m, energies 500 GeV and 1000 GeV, if combined, would yield independent limits on the two CP-violating parameters of -0.8 < Im(mu*d) < 0.8 and -11 < Im(d) < 11.