A Mathematica based Version of the CKMfitter Package
A Mathematica based Version of the CKMfitter Package
A Mathematica based Version of the CKMfitter Package
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
8 Chapter 2. Theory<br />
2.4 Neutral Meson Oscillation<br />
The phenomenon <strong>of</strong> quark flavor oscillation is predicted in <strong>the</strong> four neutral meson<br />
systems:<br />
K 0 (¯sd) ↔ ¯ K 0 (s ¯ d) , D 0 (cū) ↔ ¯ D 0 (¯cu) , B 0 d (¯ bd) ↔ ¯ B 0 d (b ¯ d) , B 0 s ( ¯ bs) ↔ ¯ B 0 s (b¯s) .<br />
Since <strong>the</strong> mean life time <strong>of</strong> <strong>the</strong> neutral D mesons is very small compared to <strong>the</strong>ir<br />
oscillation frequency, neutral meson mixing has been only observed in <strong>the</strong> Kaon and<br />
B-meson systems, yet.<br />
The time evolution <strong>of</strong> <strong>the</strong>se transitions is given by <strong>the</strong> Schrödinger Equation for<br />
two-state systems <strong>of</strong> instable particles:<br />
i ˙ ψ(t) = ˆ H ψ(t) , (2.20)<br />
where ψ(t) is <strong>the</strong> two-state system <strong>of</strong> <strong>the</strong> neutral mesons, e. g. for <strong>the</strong> Bd system:<br />
�<br />
|B0 (t)〉<br />
ψ(t) =<br />
| ¯ B0 �<br />
. (2.21)<br />
(t)〉<br />
The Hamilton Operator ˆ H contains <strong>the</strong> two hermitian 2 × 2 mass (Mij) and decay<br />
width (Γij) matrices:<br />
⎛<br />
ˆH = ˆ M − i<br />
2 ˆ ⎜<br />
Γ = ⎝<br />
M11 − i<br />
2 Γ11 M12 − i<br />
2 Γ12<br />
M21 − i<br />
2 Γ21 M22 − i<br />
2 Γ22<br />
⎞<br />
⎟<br />
⎠ . (2.22)<br />
Since CPT symmetry requires equal masses and decay rates for a particle and its<br />
anti-particle, <strong>the</strong> diagonal elements must be equal:<br />
Γ11 = Γ22 = Γ (2.23)<br />
M11 = M22 = m (2.24)<br />
and <strong>the</strong> eight real parameters can be reduced to six independent parameters. The<br />
hermiticity <strong>of</strong> ˆ Γ and ˆ M leads to:<br />
M21 = M ∗ 12 and Γ21 = Γ ∗ 12 . (2.25)<br />
Because <strong>of</strong> an arbitrary global phase, only five observables can be defined<br />
� � � �<br />
Γ12<br />
Γ12<br />
m , Γ , |M12| , Re and Im . (2.26)<br />
M12<br />
The Schrödinger Equation (2.20) has well defined solutions ψ(t) for any ψ(0), but<br />
only two mass eigenstates with time-independent flavor composition for each neutral<br />
meson system.<br />
M12