Constraints on B and Higgs physics in minimal low energy supersymmetric models Page: 2 of 45
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The standard model (SM) provides an accurate description of all the results from high energy
physics experiments, in particular precision electroweak measurements and flavor physics
observables. These experiments put strong constraints on extensions of the SM that have
tree-level flavor changing neutral current effects or large custodial symmetry breaking effects.
For renormalizable, weakly interacting theories, where the new exotic particles acquire large
gauge invariant masses so that they decouple from the low energy effective theory, these
constraints can be avoided. Low energy supersymmetry [1, 2] is a particularly attractive
example of this kind of theory. The minimal supersymmetric extension of the Standard
Model or MSSM (with gauge invariant SUSY breaking masses of the order of 1 TeV) predicts
an extended Higgs sector with a light SM-like Higgs boson of mass lower than 135 GeV -
 that agrees well with precision electroweak measurements.
However the structure of supersymmetry breaking parameters is not well defined. If
there are no tree-level flavor changing transitions in any gauge or super-gauge interaction,
then the deviations from SM predictions are naturally small. Such small deviations can be
achieved if the quark and squark mass matrices are block diagonalizable in the same basis.
For instance, this happens when the squark and slepton supersymmetry breaking masses are
flavor independent. For these kinds of models, all flavor violating effects are induced at the
loop-level and are governed by the CKM matrix elements, as in the SM. Many studies have
concentrated on the properties of these minimal flavor violating scenarios (see, for example,
In this article we shall analyze their flavor violating effects in two quite generic cases. In
the first case, we consider a low energy effective theory in which the quark and squark mass
matrices are aligned in flavor space and can be simultaneously diagonalized in blocks, as
described in the next section. We will remain agnostic about how this effective low energy
theory is UV completed. However, since the Yukawa-induced radiative corrections to the
soft supersymmetry breaking parameters tend to destroy the alignment of the squark and
quark mass matrices, this situation may be only naturally realized in models of low energy
supersymmetry breaking, where these radiative corrections are small. We call this low energy
scenario Minimal Flavor Violation.
In order to study the possible effect of Yukawa dependent radiative corrections we study a
second case, in which we assume a departure from the alignment condition by the presence of
flavor violating effects proportional to the CKM matrix elements. These effects are induced
by corrections to the left-handed down squark mass matrices proportional to the product
of the up-quark Yukawa matrix and its hermitian conjugate (or, in general, powers of this
product). We furthermore assume that the right-handed down squark masses are flavor
independent. As we will discuss in more detail in the next section, these conditions at low
energies are achieved, for instance, by Yukawa dependent radiative corrections, if one starts
from flavor independent squark masses at a high energy scale at moderate values of tan #.
One characteristics of this second scenario is that there are flavor violating down-squark-
gluino vertices at tree-level. Since all flavor violating effects are governed by the CKM
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Carena, Marcela; Menon, A.; Noriega-Papaqui, R.; Szynkman, A. & Wagner, C. E. M. Constraints on B and Higgs physics in minimal low energy supersymmetric models, article, March 1, 2006; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc875881/m1/2/: accessed April 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.