| Composition | Elementary particle |
|---|---|
| Statistics | Bosonic |
| Status | Hypothetical |
| Types | 12 |
| Mass | ≈ 1015 GeV/c2 |
| Decays into | 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 |
| Electric charge | X: ±4/3 e Y: ±1/3 e |
| Color charge | triplet or antitriplet |
| Spin | 1 |
| Spin states | 3 |
| Weak isospin projection | X: ±1/2 Y: ∓1/2 |
| Weak hypercharge | ±5/6 |
| B − L | ±2/3 |
| X | 0 |
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.
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&fras1;3 and the six Q = ± 1&fras1;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
- B − L
- Grand unification theory
- Leptoquark
- Proton decay
- W' and Z' bosons
References
- ^ a b c Ta-Pei Cheng; Ling-Fong Li (1983). Gauge Theory of Elementary Particle Physics. Oxford University Press. ISBN 0-19-851961-3.