Figure 5

Fig. 5. Determining the weak isospin of the bottom quark. The blue circle represents the partial Z decay width to bbbar pairs at LEP; blue wedges are the forward-backward asymmetry at LEP; and the green strip is the cross-section at PETRA. All measurements cross the point [I³_L, I³_R] = [-1/2, 0], so an isospin partner to the b-quark with [I³_L, I³_R] = [+1/2, 0] should exist, i.e. the top quark.

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