We use the S U ( 5 ) model to show the presence in grand unified theories of an electroweak monopole and a magnetic dumbbell (“meson”) made up of a monopole-antimonopole pair connected by a Z -magnetic flux tube. The monopole is associated with the spontaneous breaking of the weak S U ( 2 ) L gauge symmetry by the induced vacuum expectation value of a heavy scalar S U ( 2 ) L triplet with zero weak hypercharge contained in the adjoint Higgs 24-plet. This monopole carries a Coulomb magnetic charge of ( 3 / 4 ) ( 2 π / e ) as well as Z -magnetic charge, where 2 π / e denotes the unit Dirac magnetic charge. Its total magnetic charge is 3 / 8 ( 4 π / e ) , which is in agreement with the Dirac quantization condition. The monopole weighs about 700?GeV, but because of the attached Z -magnetic tube it exists, together with the antimonopole, in a magnetic dumbbell configuration whose mass is expected to lie in the TeV range. The presence of these topological structures in S U ( 5 ) and S O ( 10 ) and in their supersymmetric extensions provides an exciting new avenue for testing these theories in high-energy colliders.
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