The current 7 TeV run of the LHC experiment shall be able to probe gluino and squark masses up to values larger than 1 TeV. Assuming that hints for SUSY are found in the jets plus missing energy channel by the end of a 5 fb$^{-1}$ run, we explore the flavour constraints on three models with a CMSSM-like spectrum: the CMSSM itself, a Seesaw extension of the CMSSM, and Flavoured CMSSM. In particular, we focus on decays that might have been measured by the time the run is concluded, such as $B_s\toμμ$ and $μ\to eγ$. We also analyse constraints imposed by neutral meson bounds and electric dipole moments. The interplay between collider and flavour experiments is explored through the use of three benchmark scenarios, finding the flavour feedback useful in order to determine the model parameters and to test the consistency of the different models.
The flavour messenger sectors and their impact on the soft SUSY breaking terms are investigated in SUSY flavour models. In the case when the flavour scale M is below the SUSY breaking mediation scale M_S, the universality of soft terms, even if assumed at M_S, is radiatively broken. We estimate this effect in a broad class of models. In the CKM basis that effect gives flavour off-diagonal soft masses comparable to the tree-level estimate based on the flavour symmetry.
If supersymmetry (SUSY) will be discovered, successful models of flavour not only have to provide an explanation of the flavour structure of the Standard Model fermions, but also of the flavour structure of their scalar superpartners. We discuss aspects of such "SUSY flavour" models, towards predicting both flavour structures, in the context of supergravity (SUGRA). We point out the importance of carefully taking into account SUSY-specific effects, such as 1-loop SUSY threshold corrections and canonical normalization, when fitting the model to the data for fermion masses and mixings. This enta…
The SUSY flavour problem is deeply related to the origin of flavour and hence to the origin of the SM Yukawa couplings themselves. Since all CP-violation in the SM is restricted to the flavour sector, it is possible that the SUSY CP problem is related to the origin of flavour as well. In this work, we present three variations of an SU(3) flavour model with spontaneous CP violation. Such models explain the hierarchy in the fermion masses and mixings, and predict the structure of the flavoured soft SUSY breaking terms. In such a situation, both SUSY flavour and CP problems do not exist. We use e…
We review aspects of the phenomenology of the MSSM with non-minimal flavour violation, including a discussion of important constraints and the sensitivity to fundamental scales.
The so-called supersymmetric flavour problem does not exist in isolation to the Standard Model flavour problem. We show that a realistic flavour symmetry can simultaneously solve both problems without ad hoc modifications of the SUSY model. Furthermore, departures from the SM expectations in these models can be used to discriminate among different possibilities. In particular we present the expected values for the electron EDM in a flavour model solving the supersymmetric flavour and CP problems.
We comment on the power of the 'standard' solutions to the SUSY flavour and CP problem based on supergravity and its derivates like mSUGRA in comparison to the flavour symmetry approach. It is argued that flavour symmetries, and SU(3) in particular, can not only mimic the situation in supergravity frameworks in this respect, but sometimes do even better providing at the same time a further link between the soft and Yukawa sectors, that could be testable at future experimental facilities.
We analyse the complementarity between Lepton Flavour Violation (LFV) and LHC experiments in probing the Supersymmetric (SUSY) Grand Unified Theories (GUT) when neutrinos got a mass via the see--saw mechanism. Our analysis is performed in an SO(10) framework, where at least one neutrino Yukawa coupling is necessarily as large as the top Yukawa coupling. Our study thoroughly takes into account the whole RG running, including the GUT and the right handed neutrino mass scales, as well as the running of the observable neutrino spectrum. We find that the upcoming (MEG, SuperKEKB) and future (PRISM/…
We discuss Lepton-Flavour-Violating phenomena such as $μ\to e γ$, $μ\to eee$, and $μ\to e$ conversion in nuclei in SUSY models with and without R-parity. We stress that experimental searches for all the LFV processes are important to distinguish between the different models.
SUSY_FLAVOUR 2.0 is a FORTRAN code calculating over 30 low-energy flavour- and CP-related observables in the R-parity conserving MSSM. The code admits for the most general flavour structure of the SUSY breaking terms and complex flavour-diagonal couplings. It includes the numerically important resummation of chirally enhanced effects and it is fast enough for scanning over a large SUSY-parameter space. The program can be obtained from http://www.fuw.edu.pl/susy_flavor.
Direct searches and the hints for the Higgs at ~125 GeV put increasing pressure on simple models of SUSY breaking, in particular (but not exclusively) on those that automatically solve the flavour problem, such as gauge mediation. SUSY-breaking parameters are pushed to higher and higher values, increasing the fine-tuning required to achieve electroweak symmetry breaking at the observed scale. In this note we consider the situation for models which do not attempt to solve the flavour problem. To treat them on equal footing, we consider the combined fine-tuning arising from electroweak symmetry …
We discuss how flavour GUT models in the context of supergravity can be completed with a simple SUSY breaking sector, such that the flavour-dependent (non-universal) soft breaking terms can be calculated. As an example, we discuss a model based on an SU(5) GUT symmetry and $A_4$ family symmetry, plus additional discrete "shaping symmetries" and a $\mathbb{Z}_4^\mathrm{R}$ symmetry. We calculate the soft terms and identify the relevant high scale input parameters, and investigate the resulting predictions for the low scale observables, such as flavour violating processes, the sparticle spectrum…
We re-examine the constraints on continuous family symmetries coming from flavour changing neutral current limits on the D-term contributions to squark and slepton masses. We show that, for a restricted choice of the familon sector, continuous family symmetries are consistent with even the most conservative limits both for the case of gauge mediated supersymmetry breaking and the case of gravity mediated supersymmetry breaking.
The SUSY-EW one-loop quantum contributions to flavour-changing MSSM Higgs-boson decays into $b \bar s$ and $s \bar b$ are computed and discussed. We use the full diagrammatic approach that is valid for all $\tan β$ values and do not rely on the mass-insertion approximation for the characteristic flavour-changing parameter. We analyze in full detail the dependence of these flavour-changing partial widths on all the relevant MSSM parameters and also study the non-decoupling behaviour of these widths with the SUSY mass parameters. We find that these contributions are sizable as compared to the SM…
We obtain predictions for the neutrino masses, the effective Majorana mass in neutrinoless double beta decay and for the rates of the lepton flavor violating processes $μ\rightarrow e + γ$, $τ\rightarrow e + γ$ and $ τ\rightarrow μ+ γ$ in a SUSY $SU(5) \times T^{\prime}$ Model of flavour, which gives rise to realistic masses and mixing patterns for quarks and leptons.
In split-family SUSY, one can use a U(2)^3 symmetry to protect flavour observables in the quark sector from SUSY contributions. However, attempts to extend this procedure to the lepton sector by using an analogous U(2)^5 symmetry fail to reproduce the neutrino data without introducing some form of fine-tuning. In this work, we solve this problem by shifting the U(2)^2 symmetry acting on leptons towards the second and third generations. This allows neutrino data to be reproduced without much difficulties, as well as protecting the leptonic flavour observables from SUSY. Key signatures are a $μ\…
In this article I review the consequences of radiative flavor violation (RFV) in the Minimal Supersymmetric Standard Model (MSSM). In this framework the trilinear supersymmetry (SUSY)-breaking terms are the only source of flavor violation. Constraints on the parameter space come from Kaon mixing and b->s+gamma and are satisfied for SUSY masses of the order of 1 TeV. In addition, neutral Higgs penguins significantly contribute to B_s->mu^+mu^- and are capable of explaining the observed CP phase in the B_s system.
Can a theory of flavour capable of describing the spectrum of fermion (including neutrino) masses and mixings also contain within it the seeds for a solution of the SUSY flavour and CP problems? We argue that supergravity together with a non-Abelian family symmetry can completely resolve the SUSY flavour and CP problems in a broad class of theories in which family symmetry and CP is spontaneously broken in the flavon sector. We show that a simple superpotential structure can suppresses the F-terms of the flavons and GUT scale Higgs fields and that, if this mechanism is implemented, the resulti…
We study flavour violation in the minimal SUSY SU(5) GUT assuming all the third generation Yukawa couplings to be due to the renormalizable physics above GUT scale. At large $\tanβ,$ as suggested by Yukawa unification in SU(5), sizable flavour violation in the left (right) slepton (down squark) sector is induced due to renormalization effects of down type Yukawa couplings between GUT and Planck scales in addition to the flavour violation in the right slepton sector. The new flavour physics contribution to $K-\bar K,$ $B-\bar B$ mixing is small but might be of phenomenological interest in the c…
The current 7 TeV run of the LHC experiment shall be able to probe gluino and squark masses up to values of about 1 TeV. Assuming that hints for SUSY are found by the end of a 2 fb$^{-1}$ run, we explore the flavour constraints on the parameter space of the CMSSM, with and without massive neutrinos. In particular, we focus on decays that might have been measured by the time the run is concluded, such as $B_s\toμμ$ and $μ\to eγ$. We also briefly show the impact such a collider--flavour interplay would have on a Flavoured CMSSM.
We show how approximate Minimal Flavour Violation (MFV) can emerge from an SU(5) Supersymmetric Grand Unified Theory (SUSY GUT) supplemented by an S4 x U(1) family symmetry, which provides a good description of all quark and lepton (including neutrino) masses, mixings and CP violation. Assuming a SUSY breaking mechanism which respects the family symmetry, we calculate in full explicit detail the low energy mass insertion parameters in the super-CKM basis, including the effects of canonical normalisation and renormalisation group running. We find that the very simple family symmetry S4 x U(1) i…
We study the direct CP asymmetry in B -> X_s gamma decay in SUSY models with non-universal A-terms. We show that the flavour-dependent phases of the A-terms, unlike the flavour-independent ones, can give rise too large contribution to the CP asymmetry while respecting the experimental bounds on the branching ratio of B -> X_s gamma decay and the electric dipole moments of the electron and neutron. The CP asymmetry of this decay is predicted to be much larger than the standard model prediction in a wide region of the parameter space. In particular, it can be of order 10-15% which can be accessi…
The principle of Minimal Flavour Violation (MFV) provides a natural solution to the SUSY flavour problem, but does not solve the SUSY CP problem as it allows for the presence of new CP-violating phases. If the MFV principle is generalized by the assumption of CP conservation in the limit of flavour blindness, the SUSY CP problem can be solved, predicting at the same time interesting CP violating phenomenology.
We study CP-conserving non-minimal flavour violation in $A_4 \times SU(5)$ inspired Supersymmetric Grand Unified Theories (GUTs), focussing on the regions of parameter space where dark matter is successfully accommodated due to a light right-handed smuon a few GeV heavier than the lightest neutralino. We find that it is necessary to scan over all NMFV parameters simultaneously in order to properly constrain the space of the model.
We study CP asymmetries in rare B decays within supersymmetry with a U(2)^3 flavour symmetry, motivated by the SUSY flavour and CP problems, the hierarchies in the Yukawa couplings and the absence so far of any direct evidence for SUSY. Even in the absence of flavour-blind phases, we find potentially sizable CP violating contributions to b -> s decay amplitudes. The effects in the mixing-induced CP asymmetries in B ->phi K(S) and B -> eta' K(S), angular CP asymmetries in B -> K* mu+ mu- and the direct CP asymmetry in B -> X(s) gamma can be in the region to be probed by LHCb and next generation…
Here we update the predictions for lepton flavour violating tau and muon decays, $l_j \to l_i γ$, $l_j \to 3 l_i$, and $μ-e$ conversion in nuclei. We work within a SUSY-seesaw context where the particle content of the Minimal Supersymmetric Standard Model is extended by three right handed neutrinos plus their corresponding SUSY partners, and where a seesaw mechanism for neutrino mass generation is implemented. Two different scenarios with either universal or non-universal soft supersymmetry breaking Higgs masses at the gauge coupling unification scale are considered. After comparing the predic…
We perform an extensive study of FCNC and CP Violation within Supersymmetric (SUSY) theories with particular emphasis put on processes governed by b->s transitions and of their correlations with processes governed by b->d transitions, s->d transitions, $D^0-\bar D^0$ oscillations, lepton flavour violating decays, electric dipole moments and (g-2)_mu. We first perform a comprehensive model-independent analysis of Delta F=2 observables and we emphasize the usefulness of the R_b-gamma plane in exhibiting transparently various tensions in the present UT analyses. Secondly, we consider a number of …
We discuss the characteristic low energy phenomenological implications of an SU(5) Supersymmetric Grand Unified Theory (SUSY GUT) whose flavour structure is controlled by the family symmetry S4 x U(1), which provides a good description of all quark and lepton masses, mixings as well as CP violation. Although the model closely mimics Minimal Flavour Violation (MFV) as shown in arXiv:1511.07886, here we focus on the differences. We first present numerical estimates of the low energy mass insertion parameters, including canonical normalisation and renormalisation group running, for well-defined r…
In this work we re-examine the correlation between B(d,s)-anti-B(d,s) mixing and Lepton Flavour Violation in the light of recent experimental measurements in the $B_s$ system. We perform a generic SUSY analysis of the allowed down squark mass insertion parameter space. In the SUSY GUT scenario this parameter space is then used to make predictions for LFV branching ratios. We find that the recent measurement for the CP phase $ϕ_s$ excludes the lowest rates for tau --> mu + gamma and provides a lower bound of ~ 3E-9 for tan beta = 10. Future experimental improvements in the bound on tau --> mu +…
Lepton-flavour violating processes, such as $μ\to eγ$, are studied in ordinary (non-SUSY) SU(5) and SUSY SU(5) grand unified theories. First given are some introductory argument on the mechanism of U.V. divergence cancellation in flavour changing neutral current processes and on the decoupling of particles with GUT scale masses . We next see that such general argument is confirmed by an explicit calculation of the amplitude of $μ\to eγ$ in ordinary SU(5), which shows that logarithmic divergence really cancels among diagrams and remaining finite part are suppressed by at least $1/M_{GUT}^2$. In…
We discuss the implications, for general flavour mixing, of the recent results regarding the new allowed range for mixing in the $B_s$ meson system, as well as the new improved bounds on $BR(\bar{B}_s\toμ^+μ^-)$. Constraints on right handed insertions, in particular, improve considerably in the large $\tanb$ regime where the contributions to $B_s$ mixing are dominated by double Higgs penguins. Similarly, the allowed regions of parameter space when varying multiple insertions also decrease significantly.
We address the constraints on the SUSY seesaw parameters arising from Lepton Flavour Violation observables. Working in the Constrained Minimal Supersymmetric Standard Model extended by three right-handed (s)neutrinos, we study the predictions for the branching ratios of $l_j \to l_i γ$ and $l_j \to 3 l_i$ channels. We impose compatibility with neutrino data, electric dipole moment bounds, and further require a successful baryon asymmetry of the Universe (via thermal leptogenesis). We emphasise the interesting interplay between $θ_{13}$ and the LFV muon decays, pointing out the hints on the SUS…
An inverted mass hierarchy in the squark sector, as in so-called "natural supersymmetry", requires non-universal boundary conditions at the mediation scale of supersymmetry breaking. We propose a formalism to define such boundary conditions in a basis-independent manner and apply it to generic scenarios where the third-generation squarks are light, while the first two generation squarks are heavy and near-degenerate. We show that not only is our formalism particularly well-suited to study such hierarchical squark mass patterns, but in addition the resulting soft terms at the TeV scale are mani…
In this work we study the Lepton Flavour Violating semileptonic tau --> mu f0(980) decay within the context of SUSY-Seesaw Models, where the MSSM spectrum is extended by three right handed neutrinos and their SUSY partners, and where the seesaw mechanism is used to generate the neutrino masses. We estimate its decay rate when it proceeds via the Higgs mediated channel tau --> mu H* --> mu f0(980), where H refers to the CP-even MSSM Higgs bosons h^0 and H^0, and the Lepton Flavour Violating tau mu H vertex is radiatively generated via SUSY loops. In order to describe the f0(980) meson we follow…
We present the first complete calculation of flavour violating lepton decays taking into account all supersymmetric (SUSY) and non-SUSY contributions in the context of the supersymmetric inverse seesaw, a specific SUSY low-scale seesaw model. We consider radiative and 3-body lepton decays as well as neutrinoless $μ-e$ conversion in muonic atoms and perform a full one-loop calculation in the mass basis. Taking CMSSM-like boundary conditions for the soft SUSY breaking parameters, we find that cancellations between different contributions are present in several regions, which might reduce the bra…
In 5D SUSY GUTs, wave-function localization permits to reproduce flavour hierarchy. As this mechanism also acts on SUSY breaking parameters, it can potentially solve the SUSY flavour problem. We carry out an analysis of the Holographic Grand Unification framework, where we take properly into account effects of matrix anarchy. In this contribution, we focus on brane-localized SUSY breaking and its consequences.
The atmospheric neutrino anomaly reported by the super-Kamiokande collaboration suggests existence of a large flavour violating Yukawa coupling in the lepton sector. We discuss lepton-flavour violation at low energies in the framework of the supersymmetric SU(5)_{GUT} model with right-handed neutrinos. We find that for a wide range of parameter space suggested from the atmospheric neutrino anomaly, if the tau-neutrino Yukawa coupling is as large as that of top quark, lower bounds of the branching ratios of mu -> e gamma, tau -> mu gamma, and the mu-e conversion rate on $^{48}_{22}Ti$ become ar…
Supersymmetric (SUSY) Grand Unified theories (GUTs) generally predict FCNC and CP violating processes to occur both in the leptonic and hadronic sectors. Assuming an underlying SU(5) group plus right-handed neutrinos (RN), we perform an extensive study of FCNC and CP violation, analyzing the correlations between leptonic and hadronic processes like mu-> e gamma and K-Kbar mixing, tau->mu gamma and b -> s transitions such as B_d -> phi K_s and Bs-Bsbar mixing. Moreover, we examine the impact of the considered scenario on the UT analyses, monitoring the low energy consequences implied by possibl…
The concept of non-abelian horizontal symmetry $SU(3)_H$ can greatly help in understanding the fermion and sfermion flavour structures in supersymmetric grand unification. For the sake of demonstration the $SU(5)\times SU(3)_H$ model, suggested earlier in ref. \cite{PLB85}, is revisited. We show that under very simple and natural assumption it links the sfermion mass pattern to those of fermions in a remarkable way. All dangerous supersymmetric flavour-changing contributions are naturally suppressed in a general case, independently of the concrete texture for fermion mass matrices. Nevertheles…
We propose a 6d model with a SUSY $SU(5)$ gauge symmetry. After compactification, it explains the origin of the $S_4$ Family Symmetry with CSD3 vacuum alignment, as well as $SU(5)$ breaking with doublet-triplet splitting. The model naturally accounts for all quark and lepton (including neutrino) masses and mixings, incorporating the highly predictive Littlest Seesaw structure. It spontaneously breaks CP symmetry, resulting in successful CP violation in the quark and lepton sectors, while solving the Strong CP problem. It also explains the Baryon Asymmetry of the Universe (BAU) through leptogen…
We consider an explicit effective field theory example based on the Bousso-Polchinski framework with a large number N of hidden sectors contributing to supersymmetry breaking. Each contribution comes from four form quantized fluxes, multiplied by random couplings. The soft terms in the observable sector in this case become random variables, with mean values and standard deviations which are computable. We show that this setup naturally leads to a solution of the flavor problem in low-energy supersymmetry if N is sufficiently large. We investigate the consequences for flavor violating processes…
That $μ\to e, γ$ and $τ\to μ,γ$ are sensitive probes of SUSY models with a see-saw mechanism is a well accepted fact. Here we propose a `top-down' approach in a general SUSY SO(10) scheme. In this framework, we show that at least one of the neutrino Yukawa couplings is as large as the top Yukawa coupling. This leads to a strong enhancement of these leptonic flavour changing decay rates. We examine two `extreme' cases, where the lepton mixing angles in the neutrino Yukawa couplings are either small (CKM-like) or large (PMNS-like). In these two cases, we quantify the sensitivity of leptonic radi…
Recent work on flavour changing neutral current effects in supersymmetric models is reviewed. The emphasis is put on new issues related to solutions to the flavour problem through new symmetries: GUTs, horizontal symmetries, modular invariances.
We investigate the generation of the baryon asymmetry of the Universe within a SUSY SU(5) x T' model of flavour, which gives rise to realistic masses and mixing patterns for quarks and leptons. The model employs the see-saw mechanism for generation of the light neutrino masses and the baryon asymmetry is produced via leptogenesis. We perform detailed calculations of both the CP violating lepton asymmetries, originating from the decays of the heavy Majorana neutrinos operative in the see-saw mechanism, and of the efficiency factors which account for the lepton asymmetry wash-out processes in th…
We study the potential of an e+- e- Linear Collider for charged lepton flavour violation studies in a supersymmetric framework where neutrino masses and mixings are explained by a type-I seesaw. Focusing on e-mu flavour transitions, we evaluate the background from standard model and supersymmetric charged currents to the e mu + missing E_T signal. We study the energy dependence of both signal and background, and the effect of beam polarisation in increasing the signal over background significance. Finally, we consider the mu- mu- + missing E_T final state in e- e- collisions that, despite bein…
We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged sector can lead to measurable rates for BR(mu->e gamma) and BR(tau->mu gamma). We consider three different scenarios, the fist one corresponds to the Minimal Supersymmetric Standard Model with non-universal soft terms. In the other two cases the violation of flavor in the leptonic charged sector is associated to the neutrino problem in models with a see-saw mechanism and with R-parity violation respectively.
We present a data-driven analysis of a concrete Supersymmetric (SUSY) Grand Unified Theory (GUT) of flavour, based on $SU(5)\times S_4$, which predicts charged fermion and neutrino mass and mixing, and where the mass matrices of both the Standard Model and the Supersymmetric particles are controlled by a common symmetry at the GUT scale. This framework also predicts non-vanishing non-minimal flavour violating effects, motivating a sophisticated data-driven parameter analysis to uncover the signatures and viability of the model. This computer-intensive Markov-Chain-Monte-Carlo (MCMC) based anal…
We modify the first ISS model (hep-th/0602239) by gauging a diagonal flavour symmetry. We add additional multiplets transforming as fundamentals and anti-fundamentals under the gauged flavour group. Their number is chosen such that the microscopic theory is asymptotically free whereas in the Seiberg dual (w.r.t. the colour group) it changes to an infrared free theory. Non perturbative effects within the flavour group can correct the location of the supersymmetric vacuum. Statements about meta-stability of the susy breaking vacuum would require a two loop calculation. For general couplings, the…
Realistic predictions are made for lepton flavour violating and flavour changing neutral current decays in the large tan beta regime of a SUSY-seesaw model. Lepton flavour violating neutral Higgs decays are discussed within this framework along with the highly constraining charged lepton decays l_i --> l_j + gamma. In the b-s system the important constraint from b --> s + gamma is studied in conjunction with the rare FCNC Bs --> mu mu (tau mu) decays and the recently measured Delta Ms.
From the naturalness point of view, the first LHC results seem to disfavour any constrained MSSM realization with universal conditions at the SUSY-breaking scale. A more motivated scenario is given by split-family SUSY, in which the first two generations of squarks are heavy, compatible with a U(2)^3 flavour symmetry. Here, after reviewing the flavour structures obtained in this framework, we consider the flavour symmetry to be broken at a very high scale, and study the consequences at low energies through its RGE evolution. Initial conditions compatible with a split scenario are found, and th…
By an explicit calculation we show that in ordinary SU(5) logarithmic divergence in the amplitude of $μ\to eγ$ cancels among diagrams and remaining finite part is suppressed by at least $1/M_{GUT}^2$. In SUSY SU(5), when the effect of flavour changing wave function renormalization is taken into account such logarithmic correction disappears, provided a condition is met among SUSY breaking masses. In SUGRA-inspired SUSY GUT the remaining logarithmic effect is argued not to be taken as a prediction of the theory.
We show how the SUSY flavour and CP problems can be solved using gauged SU(3) family symmetry previously introduced to describe quark and lepton masses and mixings, in particular neutrino tri-bimaximal mixing via constrained sequential dominance. The Yukawa and soft trilinear and scalar mass squared matrices and kinetic terms are expanded in powers of the flavons used to spontaneously break the SU(3) family symmetry, and the canonically normalized versions of these matrices are constructed. The soft mass matrices are then expressed in the Super-CKM basis, and the leading order mass insertion p…
In this paper we review our main results for Lepton Flavour Violating (LFV) semileptonic tau decays and muon-electron conversion in nuclei within the context of two Constrained SUSY-Seesaw Models, the CMSSM and the NUHM. The relevant spectrum is that of the Minimal Supersymmetric Standard Model extended by three right handed neutrinos, $ν_{R_i}$ and their corresponding SUSY partners, ${\tilde ν}_{R_i}$, ($i=1,2,3$). We use the seesaw mechanism for neutrino mass generation and choose a parameterisation of this mechanism that allows us to incorporate the neutrino data in our analysis of LFV proc…
The missing VEV solution to the doublet-triplet splitting problem in general SU(N) SUSY GUTs is found. Remarkably enough, it requires a strict equality of numbers of the fundamental colours and flavours in SU(N) and for the even-order groups (N=2k) gives the predominant breaking channel $SU(N) \to SU(k-1)_c\otimes SU(k-1)_f\otimes SU(2)_w\otimes U(1)\otimes U(1)'$ in the parameter natural area. The flavour subsymmetry breaking owing to some generic string inspired extra symmetries of the Higgs superpotential appears not to affect markedly the basic adjoint vacuum configuration in the model. Th…
We propose an SU(5) SUSY GUT of flavour with A_4 family symmetry in 8d where the vacuum alignment is achieved in an elegant way by the use of boundary conditions on orbifolds. The model involves SU(5) living in the 8d bulk, with matter living in 6d (or 4d) subspaces and Yukawa interactions occurring at a 4d point. The GUT group is broken to the Standard Model by the orbifold compactification, setting the GUT scale and leading to low energy supersymmetry and Higgs doublet-triplet splitting. The first two families of 10-plets are doubled resulting in a lack of both desirable and unwanted GUT rel…
We construct a Supersymmetric (SUSY) Grand Unified Theory (GUT) of Flavour based on S4 x SU(5), together with an additional (global or local) Abelian symmetry, and study it to next-to-leading order (NLO) accuracy. The model includes a successful description of quark and lepton masses and mixing angles at leading order (LO) incorporating the Gatto-Sartori-Tonin (GST) relation and the Georgi-Jarlskog (GJ) relations. We study the vacuum alignment arising from F-terms to NLO and such corrections are shown to have a negligible effect on the results for fermion masses and mixings achieved at LO. Tri…
We study CP-conserving non-minimal flavour violation in $A_4 \times SU(5)$ inspired Supersymmetric Grand Unified Theories (GUTs), focussing on the regions of parameter space where dark matter is successfully accommodated due to a light right-handed smuon a few GeV heavier than the lightest neutralino. In this region of parameter space we find that some of the flavour-violating parameters are constrained by the requirement of the dark matter relic density, due to the delicate interplay between the smuon and neutralino masses. By scanning over GUT scale flavour violating parameters, constrained …
In order to satisfy current FCNC and CP violation bounds, SUSY flavour structures cannot be generic. An interesting solution to these SUSY Flavour and CP Problems lies on the use of an SU(3) family symmetry which spontaneously breaks CP symmetry. Typical observables of such a model are electric dipole moments and LFV processes. In addition, these models can give contributions to CP violation in neutral meson mixing. We show how the latter can be used to restrict the allowed SUSY parameter space, and induce correlations between LFV and EDM predictions.
Recent T2K, MINOS and Double CHOOZ results, together with global fits of mixing parameters, indicate a sizeable reactor angle theta13 ~ 8 deg which, if confirmed, would rule out tri-bimaximal (TB) lepton mixing. Recently two of us studied the vacuum alignment of the Altarelli-Feruglio A4 family symmetry model including additional flavons in the 1' and 1" representations, leading to so-called "trimaximal" neutrino mixing and allowing a potentially large reactor angle. Here we show how such a model may arise from a Supersymmetric (SUSY) Grand Unified Theory (GUT) based on SU(5), leading to sum r…
We study FCNC and CP violating processes in the MSSM without a new flavour structure (flavour blind MSSM). The low energy parameters are determined by the running of the soft breaking terms from the GUT scale with SUSY phases consistent with the EDM constraints. We find that the CP asymmetry in b -> s gamma can reach large values potentially measurable at B factories, especially in the low BR(b -> s gamma) region. We analyze the SUSY contributions to the anomalous magnetic moment of the muon pointing out its impact on the b -> s gamma CP asymmetry and on the SUSY spectrum.
We present a general analysis of B_{s,d}-> l^+ l^- and K_L -> l^+ l^- decays in supersymmetric models with non-minimal sources of flavour mixing. In spite of the existing constraints on off-diagonal squark mass terms, these modes could still receive sizeable corrections, mainly because of Higgs-mediated FCNCs arising at large tan(beta). The severe limits on scenarios with large tan(beta) and non-negligible {tilde d}^i_{R(L)}-{d-tilde}^j_{R(L)} mixing imposed by the present experimental bounds on these modes and Delta B=2 observables are discussed in detail. In particular, we show that scalar-c…
