Study of non-uniformity of magnetic field Simulation Real data analysis (CR) Summary and outlook

Simulation of electron drift in E and non-uniformed B field Drift velocity of electron in E, B field (Langevin equation) First order Runge-Kutta integration was applied

Strategy of simulation Determine T0 in the case of B=0 (vd=5cm/usec). T0 = L0/ vd(B=0), where L0 is a drift length in z-direction between the pad plane and the source point. Execute Runge-Kutta intergration in non-uniform B Calculate the drift length Lsim (Lsim = zf-zi) Calculate the residual in z-direction (ResZ) ResZ = Lsim-L0 <- corresponding to the resZ in the real data?

Result of simulation tracks of electrons Source point: center of each pad, zi = 40cm Pad plane: z = -35.6cm Deviation is larger at outer pads. Z direction (cm) Radius (cm) Phi-direction (cm)

Electron tracks (Zi =0 cm)

ResZ vs. radius ResZ is decreasing as the radius is increased. In the worst case, the gap is 1.6mm (zi = 40 cm)

Source files saho:/home/uchida/sim/eDrift/ Please check the bugs in the program!

Real data (CR) analysis Run #: 28895, before correction Cut condition: chi2Pad > 0.02, chi2Z > 0.02, -0.4 < lambda (dip angle) <0.4

Correction offset values are added in deriving the z-position. zcorr [ilay] = z0[ilay]+offset[ilay] = vd t + offset[ilay] offset valued are determined to adjust the mean of the residual-Z into zero in each layer at -1400<z<-1300. See the source code (saho:/home/uchida/ana/TPC/TPCana0.41/src/anaCluster.c Function: setHit() )

Run # 28895 after correction Mean values are improved (not perfect), the RMS not!

Summary and outlook Simulation and CR data have the same tendency due to non-uniformity of the magnetic field. Offset correction would be effective for improvement of the mean value of the resZ, but not for the RMS of the resZ. We need the detailed investigation for the optimizations of the offset values. Sawada-kun is now under construction of the frame-work. Z-dependence of resZ will be also studied in his frame-work.