X and Y bosons  

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the X and Y bosons (sometimes collectively called "X bosons"[1]: 437 ) are hypothetical elementary particles analogous to the W and Z bosons, but corresponding to a new type of force predicted by the Georgi–Glashow model, a grand unified theory. Since the X and Y boson mediate the grand unified force, they would have unusual high mass, which requires more energy to create than the reach of any current particle collider experiment.

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The X and Y bosons couple quarks to leptons (such as a positron), allowing violation of the conservation of baryon number, and thus permitting proton decay.

An X boson would have the following decay modes:[1]: 442 

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where the two decay products in each process have opposite chirality, u is an up quark, d- is a down antiquark and e+ is a positron.

A Y boson would have the following decay modes:[1]: 442 

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where the first decay product in each process has left-handed chirality and the second has right-handed chirality and          is an electron antineutrino. Similar decay products exist for the other quark-lepton generations.

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In these reactions, neither the lepton number (L) nor the baryon number (B) is conserved, but B − L is. Different branching ratios between the X boson and its antiparticle (as is the case with the K-meson) would explain baryogenesis. For instance, if an X⁺⁄X⁻− pair is created out of energy, and they follow the two branches described above:   X⁺→u + u, X⁻ →d + e⁻ ; re-grouping the result ( u + u + d )  + e⁻ = e⁻ + p
shows it to be a hydrogen atom.

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The X± and Y± bosons are defined respectively as the six Q = ± 4⁄3 and the six Q = ± 1⁄3 components of the final two terms of the adjoint 24 representation of SU(5) as it transforms under the standard model's group:

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Thus, the positively-charged X and Y carry anti-color charges (equivalent to having two different color charges), while the negatively-charged X and Y carry normal color charges, and the signs of the Y bosons' weak isospins are always opposite the signs of their electric charges. In terms of their action on {\displaystyle \mathbb {C} ^{5}}, X bosons rotate between a color index and the weak isospin-up index, while Y bosons rotate between a color index and the weak isospin-down index.