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.

This article is about bosons of a hypothetical new interaction. For mesons with the same names, see XYZ particle.
X± and Y± bosons
CompositionElementary particle
StatisticsBosonic
StatusHypothetical
Types12
Mass≈ 1015 GeV/c2
Decays intoX: 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
Electric chargeX: ±4/3 e
Y: ±1/3 e
Color chargetriplet or antitriplet
Spin1
Spin states3
Weak isospin projectionX: ±1/2
Y: ∓1/2
Weak hypercharge±5/6
B − L±2/3
X0

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:

.

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 , 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

References
  1. Ta-Pei Cheng; Ling-Fong Li (1983). Gauge Theory of Elementary Particle Physics. Oxford University Press. ISBN 0-19-851961-3.


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