The magnetic field for the D0 central tracker is provided by a solenoid with a nominal field of 2.0 T.
If we assume the field is constant, then the following holds for tracks that cross the beamline (i.e. those with zero impact parameter):
phi - phi0 = alpha
= asin(K q/pT r)
= asin(pTmin/pT)
where K = 0.003 GeV/c/cm
phi0 = phi direction at the beamline
phi = angular position at radius r
alpha = difference between the angular direction and position at radius r
pTmin = minimum |pT| which reaches radius r
If we take the outer radius of the tracker to be 50 cm, then the minimum pT which
can reach this radius is
pTmin = 150 MeV/cLower transverse momenta will curl up inside this radius.
Here are some values for alpha at r = 50 cm for charge +1e:
pT alpha (GeV/c) (deg) ------- ----- 0.2 48.6 0.3 30.0 0.5 17.5 1.0 8.6 5.0 1.72 10.0 0.86