On the Flavor Problem in Strongly Coupled Theories - THEP Mainz
On the Flavor Problem in Strongly Coupled Theories - THEP Mainz
On the Flavor Problem in Strongly Coupled Theories - THEP Mainz
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(ND)<br />
and all possible<br />
Higgs<br />
<strong>in</strong>sertions<br />
2.3. Profiles of Gauge Bosons 63<br />
This is <strong>the</strong> “messiest” scenario, <strong>in</strong> <strong>the</strong> sense that all possible diagrams <strong>in</strong><br />
Figure 2.7 contribute to <strong>the</strong> propagator, besides <strong>the</strong> pure gauge boson<br />
propagator, because it will be massive due to mix<strong>in</strong>g with a composite<br />
which breaks <strong>the</strong> gauge symmetry. In <strong>the</strong> language of Section 2.2, <strong>the</strong><br />
group I is empty here. The correspond<strong>in</strong>g propagator should have flavordiagonal,<br />
∆F = 1 and additional ∆F = 2 contributions and we f<strong>in</strong>d<br />
D ξ=1<br />
µν (q, t; t ′ ) = ηµν L<br />
4πrc M 2 KK<br />
� t 2 < − t 2 − t ′2 + 1 � . (2.87)<br />
This is not exactly what one would expect. The Higgs corrections to<br />
<strong>the</strong> ∆F = 2 contributions we found for (DD) BCs are absent. This can<br />
not be expla<strong>in</strong>ed by a direct cancellation between diagrams, because<br />
all o<strong>the</strong>r diagrams will not lead to ∆F = 2 effects. Also, <strong>the</strong> flavordiagonal<br />
factor is much larger compared to (NN) BCs, which can only<br />
be expla<strong>in</strong>ed by <strong>the</strong> Higgs <strong>in</strong>sertions <strong>the</strong>re hav<strong>in</strong>g a large effect.<br />
We will close this section with <strong>the</strong> <strong>in</strong>troduction of <strong>the</strong> KK decomposition for <strong>the</strong><br />
different scenarios just <strong>in</strong>troduced and a discussion of <strong>the</strong> behavior of <strong>the</strong> profile<br />
functions for <strong>the</strong> lightest modes.<br />
The generic bulk Lagrangian (2.53) suggests a KK decomposition <strong>in</strong> t-notation<br />
� �<br />
Aµ(xµ, t)<br />
=<br />
A5(xµ, t)<br />
1<br />
�<br />
� An µ(xµ) χn(t)<br />
√<br />
rc<br />
�<br />
. (2.88)<br />
n<br />
MKK A n 5 (xµ) ∂tχn(t)<br />
If this decomposition is <strong>in</strong>serted <strong>in</strong>to equation (2.53), one f<strong>in</strong>ds <strong>the</strong> important relation<br />
(valid <strong>in</strong> Feynman gauge)<br />
iDµν(q, t; t ′ ) =<br />
∞�<br />
n=0<br />
−iηµν<br />
q 2 − x 2 n + iɛ χn(t)χn(t ′ ) , (2.89)<br />
<strong>in</strong> which xn ≡ mn/MKK and mn denotes <strong>the</strong> mass of <strong>the</strong> nth KK mode. This shows<br />
how <strong>the</strong> 5D propagator is equivalent to <strong>the</strong> exchange of <strong>the</strong> whole KK tower and<br />
represents ano<strong>the</strong>r connection to <strong>the</strong> strongly coupled dual <strong>the</strong>ory, compare (2.42). It<br />
also follows that <strong>the</strong> normalization of <strong>the</strong> k<strong>in</strong>etic terms imposes <strong>the</strong> orthonormality<br />
relation<br />
2π<br />
L<br />
� 1<br />
ɛ<br />
dt<br />
t χm(t)χn(t) = δmn . (2.90)<br />
Fur<strong>the</strong>r, all terms <strong>in</strong>clud<strong>in</strong>g derivatives with respect to φ and <strong>the</strong> bulk mass have to<br />
be matched to a 4D mass term for each mode. The result<strong>in</strong>g equations are called<br />
EOM, and read for <strong>the</strong> vector component<br />
�<br />
1<br />
− t∂t<br />
t ∂t + c2 A<br />
t2 �<br />
χn(t) = x 2 nχn(t) . (2.91)