X and Y bosons

In particle physics, 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.

Details[]

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

X
⁺ →
u
+
u

X
⁺ →
e⁺
+
d

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

Y
⁺ →
e⁺
+
u

Y
⁺ →
d
+
u

Y
⁺ →
d
+
ν
_e

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

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⁻
=
p
+
e⁻
shows it to be a hydrogen atom.

Origin[]

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:

${\displaystyle \mathbf {24} \rightarrow (8,1)_{0}\oplus (1,3)_{0}\oplus (1,1)_{0}\oplus (3,2)_{-{\frac {5}{6}}}\oplus ({\bar {3}},2)_{\frac {5}{6}}}$.

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.

See also[]

• B − L
• Grand unification theory
• Leptoquark
• Proton decay
• W' and Z' bosons

References[]

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