# X and Y bosons

Composition Elementary particle Bosonic Hypothetical 12 ≈ 1015 GeV/c2 X: two quarks, or one antiquark and one charged antilepton Y: two quarks, or one antiquark and one charged antilepton, or one antiquark and one antineutrino X: ±4/3 e Y: ±1/3 e triplet or antitriplet 1 3 X: ±1/2 Y: ∓1/2 ±5/3 ±2/3 0

In particle physics, the X and Y bosons (sometimes collectively called "X bosons":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.

## Details

The X and Y bosons couple quarks to leptons, allowing violation of the conservation of baryon number, and thus permitting proton decay.

An X boson would have the following decay modes::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::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 BL 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 = ± ​43 and the six Q = ± ​13 components of the final two terms of the adjoint 24 representation of SU(5) as it transforms under the standard model's group:

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

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 $\mathbb {C} ^{5}$ , 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.