On the Flavor Problem in Strongly Coupled Theories - THEP Mainz

108 Chapter 3. Solving the Flavor Problem in Strongly Coupled Theories
��Bs � Μ � Μ � � �10 �9 �
30
25
20
15
10
5
95 � excl. � LHCb
95 � CDF
0
0 2 4 6 8 10 12 14
��Bd � Μ � Μ � � �10 �10 �
Figure 3.5: The red points correspond to the parameter set constrained by the Zb ¯ b
couplings and |ɛK| at the 99% and 95% CL, for the custodially protected RS model.
The black star indicates the SM prediction and the black dashed lines denote the
experimental upper limits as measured by LHCb at 95% CL. The blue band shows
the preferred region at 95% CL measured by CDF.
impressive that also rare decays are sufficiently suppressed by the RS-GIM mechanism
even for reasonably small new physics scales with the measurements reaching a stage
which will soon test the SM.
shown
3.3 Limitations of the RS GIM Mechanism
In summary of the previous sections, one can say that the RS-GIM mechanism proves
to be a successful protection from large tree level FCNCs, even if the heavy b quark is
involved. However, already from Table 1.1 it is clear that the most restrictive bound
on new physics from the flavor sector does not come from heavy quarks, but from
K − ¯ K mixing. The reason is twofold, and both aspects are related to the mixed
left-right operators Q4 and Q5 in (3.18). First, the corresponding Wilson coefficients
are subject to a large chiral enhancement from the matrix elements (3.23) (which
translate to the case of K − ¯ K mixing with the obvious replacements), because in
contrast to the B-mesons, the Kaon is much heavier than the sum of its constituents,
� mK
ms + md
� 2
≈ 15 . (3.40)