Uncertainties in Electroweak Modelling

All Monte Carlo generators do not model the events in exactly the same manner. There may be some uncertainty introduced by the way that the generators model the fundamental interactions occurring. Samples of fully detector simulated four-fermion Monte Carlo generated by EXCALIBUR are compared to samples generated by grc4f and ERATO.

Figure 10.1 shows the comparison of the SDM elements extracted from a large EXCALIBUR sample to those extracted from a large grc4f sample. Table 10.1 quantifies the systematic uncertainties as a fraction of the statistical uncertainties measured on the data sample.

The systematic uncertainties due to the generator modelling of the events on the helicity fractions were calculated by comparing the measured helicity fractions from the EXCALIBUR to the those from the grc4f and ERATO. The overall difference was taken as the uncertainty. These are shown in table 10.9.

Table 10.1: The systematic uncertainty due to generator modelling. The numbers represent the size of the error as a fraction of the statistical error from the data sample on each bin of each variable used in the TGC fits.

	1	2	3	4	5	6	7	8
$\cos\theta_{\rm W}$	0.07	0.45	0.31	0.07	0.27	0.01	0.12	0.17
$\rho_{++}$	0.43	0.16	0.20	0.05	0.24	0.20	0.24	0.15
$\rho_{--}$	0.55	0.26	0.17	0.07	0.02	0.28	0.04	0.39
$\rho_{00}$	0.61	0.04	0.24	0.08	0.15	0.30	0.10	0.21
Re($\rho_{+-}$)	0.52	0.21	0.25	0.36	0.17	0.23	0.42	0.28
Re($\rho_{+0}$)	0.35	0.31	0.17	0.18	0.53	0.17	0.17	0.10
Re($\rho_{-0}$)	0.47	0.12	0.39	0.16	0.76	0.10	0.09	0.14
Im($\rho_{+-}$)	0.33	0.53	0.43	0.04	0.19	0.16	0.14	0.05
Im($\rho_{+0}$)	0.13	0.15	0.50	0.30	0.10	0.37	0.20	0.04
Im($\rho_{-0}$)	0.10	0.40	0.71	0.52	0.53	0.27	0.20	0.39

Figure 10.1: Single W SDM elements extracted from fully detector simulated four-fermion EXCALIBUR Monte Carlo (closed circles) and grc4f Monte Carlo (open circles).