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Register a new userSequestering CP Violation and GIM-Violation with Warped Extra Dimensions
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Authors
Clifford Cheung
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We propose a model of spontaneous CP violation to address the strong CP problem in warped extra dimensions that relies on sequestering flavor and CP violation. We assume that brane-localized Higgs Yukawa interactions respect a U(3) flavor symmetry that is broken only by bulk fermion mass and Yukawa terms. All CP violation arises from the vev of a CP-odd scalar field localized in the bulk. To suppress radiative corrections to theta-bar, the doublet quarks in this model are localized on the IR brane. We calculate constraints from flavor-changing neutral currents (FCNCs), precision electroweak measurements, CKM unitarity, and the electric dipole moments in this model and predict theta-bar to be at least about 10^-12.
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We analyze the flavor violation in warped extra dimension due to radion mediation. We show that Delta S=2 and Delta B=2 flavor violating processes impose stringent constraints on radion mass, m_phi and the scale Lambda_phi. In particular, for Lambda_phi ~ O(1) TeV, B_d^0-bar{B}^0_d implies that m_phi ~ 65 GeV. We also study radion contributions to lepton flavor violating processes: tau -> (e,mu) phi, tau -> emu^+mu^- and B -> l_i l_j. We show that BR(B_s -> mu^+ mu^-) can be of order 10^{-8}, which is reachable at the LHCb. The radion search at LHC, through the flavor violation decays into tau mu or top-charm quarks, is also considered.
We explore how to protect extra dimensional models from large flavor changing neutral currents by using bulk and brane flavor symmetries. We show that a GIM mechanism can be built in to warped space models such as Randall-Sundrum or composite Higgs models if flavor mixing is introduced via UV brane kinetic mixings for right handed quarks. We give a realistic implementation both for a model with minimal flavor violation and one with next-to-minimal flavor violation. The latter does not suffer from a CP problem. We consider some of the existing experimental constraints on these models implied by precision electroweak tests.
We introduce the CP violating scalar leptoquark $S_3$ to explain the measured values of the lepton universality ratios $R_{K^{(*)}}$. We derive constraints on the CP-even and CP-odd components of the leptoquark Yukawa couplings stemming from effects in $b to s mu mu$ and $B_s$ mixing. For the $b to s mu mu$ processes we impose $R_{K^{(*)}}$, $mathcal{B}(B_s to mu^+ mu^-)$, as well as CP-sensitive angular asymmetries $A_{7,8,9}$, whereas in the $B_s$ mixing sector $Delta M_s$ and $S_{psiphi}$ are considered. Combining the constraints within the $S_3$ model reveals that a large CP phase with a definite sign is perfectly viable for a leptoquark of mass below a few TeV. For larger mass of the $S_3$ leptoquark the CP phase is suppressed due to the observables pertaining to the $B_s$ system. We provide predictions of direct and mixing-induced CP asymmetries in $B to K mu mu$ that could reveal the presence of the novel CP phase.
We study an effective field theory describing CP-violation in a scalar meson sector. We write the simplest interaction that we can imagine, $${cal L}sim epsilon_{i_1cdots i_5}epsilon^{mu_1cdotsmu_4}phi_{i_1}partial_{mu_1}phi_{i_2}partial_{mu_2}phi_{i_3}partial_{mu_3}phi_{i_4}partial_{mu_4}phi_{i_5}$$ which involves 5 scalar fields. The theory describes CP-violation only when it contains scalar fields representing mesons such as the $K^*_0$, sigma, $f_0$ or $a_0$. If the fields represent pseudo-scalar mesons, such as B, K and $pi$ mesons then the Lagrangian describes anomalous processes such as $KKto pipipi$. We speculate that the field theory contains long lived excitations corresponding to $Q$-ball type domain walls expanding through space-time. In an 1+1 dimensional, analogous, field theory we find an exact, analytic solution corresponding to such solitons. The solitons have a U(1) charge $Q$, which can be arbitrarily high, but oddly, the energy behaves as $Q^{2/3}$ for large charge, thus the configurations are stable under disintegration into elementary charged particles of mass $m$ with $Q=1$. We also find analytic complex instanton solutions which have finite, positive Euclidean action.
We study that a minimal supersymmetric standard model with an extra $U(1)$ gauge symmetry may accommodate the explicit CP violation at the one-loop level through radiative corrections. This model is CP conserving at the tree level and cannot realize the spontaneous CP violation for a wide parameter space at the one-loop level. In explicit CP violation scenario, we calculate the Higgs boson masses and the magnitude of the scalar-pseudoscalar mixings in this model at the one-loop level by taking into account the contributions of top quarks, bottom quarks, exotic quarks, and their superpartners. In particular, we investigate how the exotic quarks and squarks would affect the scalar-pseudoscalar mixings. It is observed that the size of the mixing between the heaviest scalar and pseudoscalar Higgs bosons is changed up to 20 % by a complex phase originated from the exotic quark sector of this model.
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