We recalculate the leading one-loop contributions to mu > e gamma and mu -> eee in the Littlest Higgs model with T-parity, recovering previous results for the former. When all the Goldstone interactions are taken into account, the latter is also ultraviolet finite. The present experimental limits on these processes require a somewhat heavy effective scale ~2.5 TeV, or the flavour alignment of the Yukawa couplings of light and heavy leptons at the ~10% level, or the splitting of heavy lepton masses to a similar precision. Present limits on tau decays set no bounds on the corresponding parameters involving the tau lepton
We present the results of an extensive analysis of lepton flavour violating decays in the Littlest Higgs model with T-parity (LHT). As lepton flavour violation is highly suppressed in the Standard Model by small neutrino masses, the LHT effects turn out to be naturally huge and could be seen in the near future experiments.
The Littlest Higgs Model with T parity (LHT) is an interesting alternative model for New Physics at the TeV scale. Although Flavour Physics was not the reason for creating the LHT model, significant effects (such as large CP violation where not predicted by the SM) can be created without violating existing experimental bounds. We study the B-, K- and especially the D-sector.
The Little Higgs model with T-parity (LHT) belongs to the non-minimal flavour violating model. This model has new sources of flavour and CP violation both in quark and leptonic sectors. These new sources of flavour violation originates by the interaction of Standard Model (SM) fermions with heavy gauge bosons and heavy (or mirror) fermions. In this work we will present the impact of the new flavour structure of T-parity models on flavour violations in leptonic sector.
Flavour changing neutral current processes, being strongly suppressed in the Standard Model (SM), provide a unique window to new physics at scales much above the electroweak scale. Here, we summarize the recent progress in flavour physics studies of the Littlest Higgs model with T-parity, both in the quark and lepton sector. Particular emphasis is put on various correlations that could distinguish this model from other extensions of the SM.
The Littlest Higgs model with T-parity (LHT) contains new sources of flavour and CP violation both in the quark and the lepton sector. They originate from the interactions of ordinary fermions with mirror fermions mediated by new gauge bosons: W_H, Z_H and A_H. The most spectacular departures from the Standard Model are found in K_L -> pi^0 nu {bar nu}, K^+ -> pi^+ nu {bar nu}, in the CP-asymmetry S_{psi phi} and in lepton flavour violating decays. In particular, the latter decays offer a clear distinction between the LHT model and the MSSM. We summarize the most interesting results of three e…
We present the results of an extensive analysis of flavour physics in both quark and lepton sectors, in the Littlest Higgs model with T-parity (LHT). In the quark sector, we identify some interesting scenarios for new mirror quark masses and V_Hd mixing matrix that satisfy the existing experimental constraints from K and B physics and simultaneously allow large New Physics effects in rare decays and CP-violating observables. In the lepton sector, where flavour violation in the Standard Model is highly suppressed by small neutrino masses, LHT effects turn out to be naturally huge and could be s…
We first study the hadronic lepton flavor violating tau decays within the littlest Higgs model with T-parity (including one or two pseudoscalars, or a vector resonance). We consider the case where only T-odd particles and partner fermions contribute, and also its extension including Majorana neutrinos coming from an inverse seesaw. In both cases our mean values lie only one order of magnitude below current upper limits, strengthening the case of searching for these decays in the quest for new physics.
In this work pair productions of charged and doubly charged scalars in the framework of littlest Higgs model at $e^+e^-$ colliders are studied. In the allowed parameter space of the littlest Higgs model, the production rates of the scalar pairs are calculated. It is obtained that pair productions of charged and doubly charged scalars are reachable at $e^+ e^-$ colliders with energy $\sqrt{S}\geq 1.7TeV$. Using the lepton flavor violating decays of charged scalars calculated in literature, final state analysis is done for pair production processes. This analysis show that depending on the model…
We discuss the mixing matrix V_Hd that describes the charged and neutral current interactions between ordinary down-quarks and up- and down-mirror quarks in the Littlest Higgs Model with T-parity (LHT). We point out that this matrix in addition to three mixing angles contains three physical complex phases and not only one as used in the present literature. We explain the reason for the presence of two additional phases, propose a new standard parameterization of V_Hd and briefly comment on the relevance of these new phases for the phenomenology of FCNC processes in the LHT model. In a separate…
Inspired by the recent CMS $h \to μτ$ excess, we calculate the lepton flavor violating Higgs decay $h \to μτ$ in the littlest Higgs model with T-parity (LHT). Under the constraints of $\ell_i \to \ell_j γ$, $Z \to \ell_i \bar{\ell}_j$ and Higgs data, we find that the branching ratio of $h \to μτ$ can maximally reach $\mathcal O(10^{-4})$. We also investigate the correlation between $h \to μτ$, $τ\to μγ$ and $Z \to μτ$, which can be used to test LHT model at future $e^+e^-$ colliders.
The results of an extensive flavour physics analysis in the Littlest Higgs model with T-parity are presented. In particular, mixing and CP-violation in K^0 and B^0_{d,s} systems have been studied. Several scenarios defined by the values of mirror quark masses and the parameters of the new flavour mixing matrix V_Hd have been considered. A very interesting scenario is identified, where the well-known kaon constraints are satisfied, the sin(2beta) and Delta M_s issues are improved w.r.t the Standard Model and visible effects could be soon found in A_SL^s and S_{psi phi}.
We discuss spontaneously broken CP symmetry in two right-handed neutrino models based on the idea of having a {\it different residual flavour symmetry}, together with a {\it different residual CP symmetry}, associated with each of the two right-handed neutrinos. The charged lepton sector also has a {\it different residual flavour symmetry}. In such a {\it tri-direct CP approach}, we show that the combination of the three residual flavour and two residual CP symmetries provides a new way of fixing the parameters. To illustrate the approach, we revisit the Littlest Seesaw (LSS) model based on $S…
In this work productions of charged and doubly charged scalars and their lepton flavor violating collider signals in the framework of littlest Higgs model at LHC are studied. In the allowed parameter region of the littlest Higgs model, the production rates of the scalars of littlest Higgs model via $pp \to ϕ^{++}ϕ^{-}$, $pp \to ϕ^+ϕ^-$ and $pp \to ϕ^{++}ϕ^{--}$ processes are calculated. We obtained that charged and doubly charged scalar pairs can be produced at LHC . Considering the possible lepton flavor violating decays of charged scalars found in literature, final state analysis is done. Th…
We investigate the sources of neutrino mass generation in Little Higgs theories, by confining ourselves to the "Littlest Higgs" scenario. Our conclusion is that the most satisfactory way of incorporating neutrino masses is to include a lepton-number violating interaction between the scalar triplet and lepton doublets. The tree-level neutrino masses generated by the vacuum expectation value of the triplet are found to dominate over contributions from dimension-five operators so long as no additional large lepton-number violating physics exists at the cut-off scale of the effective theory. We al…
In this work, the production processes of heavy neutral scalar and pseudo scalar associated with standard model gauge boson $Z_L$ at future $e^{+}e^{-}$ colliders (ILC and CLIC) are examined. The total and differential cross sections are calculated for the processes in the context of the littlest Higgs model. Also dependence of production processes to littlest Higgs model parameters in the range of compatibility with electroweak precision measurements and decays to lepton flavor violating final states are analyzed. We have found that both heavy scalar and pseudoscalar will be produced in $e^+e…
We calculate the rates for the charged lepton flavour violating decays l_i -> l_j gamma, tau -> l pi, tau -> l eta, tau -> l eta', mu^- -> e^- e^+ e^-, the six three body leptonic decays tau^- -> l_i^- l_j^+ l_k^- and the rate for mu-e conversion in nuclei in the Littlest Higgs model with T-Parity (LHT). We also calculate the rates for K_{L,S} -> mu e, K_{L,S} -> pi^0 mu e and B_{d,s} -> l_i l_j. We find that the relative effects of mirror leptons in these transitions are by many orders of magnitude larger than analogous mirror quark effects in rare K and B decays analyzed recently. In particu…
In this paper we consider the effects of the T-parity violating anomalous Wess-Zumino-Witten-Term in the Littlest Higgs model. Apart from tree level processes, the loop induced decays of the heavy mirror particles into light standard model fermions lead to a new and rich phenomenology in particular at breaking scales f below 1 TeV. Various processes are calculated and their signatures at present and future colliders are discussed. As a byproduct we find an alternative production mechanism for the Higgs boson.
Motivated by the first experimental evidence of meson oscillations in the D system, we study D^0 - \bar D^0 mixing in the Littlest Higgs model with T-parity, we investigate its role in constraining the model parameters and its impact on the most interesting flavour observables. We find that the experimental data are potentially strongly constraining but at present limited by large theoretical uncertainties in the long-distance Standard Model contribution to D^0 - \bar D^0 mixing.
We propose a $μ-τ$ reflection symmetric Littlest Seesaw ($μτ$-LSS) model. In this model the two mass parameters of the LSS model are fixed to be in a special ratio by symmetry, so that the resulting neutrino mass matrix in the flavour basis (after the seesaw mechanism has been applied) satisfies $μ-τ$ reflection symmetry and has only one free adjustable parameter, namely an overall free mass scale. However the physical low energy predictions of the neutrino masses and lepton mixing angles and CP phases are subject to renormalisation group (RG) corrections, which introduces further parameters. …
We calculate loop induced lepton flavor violating Higgs decays in the Littlest Higgs model with T-parity. We find that a finite amplitude is obtained only when all contributions from the T-odd lepton sector are included. This is in contrast to lepton flavor violating processes mediated by gauge bosons where the partners of the right-handed mirror leptons can be decoupled from the spectrum. These partners are necessary to cancel the divergence in the Higgs mass introduced by the mirror leptons but are otherwise unnecessary and assumed to be decoupled in previous phenomenological studies. Furthe…
We show that the inverse see-saw is the most natural way of implementing neutrino masses in the Littlest Higgs model with T-parity. The three extra quasi-Dirac neutrinos are needed to cancel the quadratically divergent contributions of the mirror leptons to the Higgs mass. If the T-parity of the heavy neutrino singlets is chosen to be even, their contributions to lepton flavor violating transitions are one-loop finite. The most stringent limits on this scenario result from the non-observation of these transitions. Constraints on neutrino mixing imply an upper bound on the mass of the T-odd mir…
We calculate the most interesting rare and CP-violating K and B decays in the Littlest Higgs model with T-parity. We give a collection of Feynman rules including v^2/f^2 contributions that are presented here for the first time and could turn out to be useful also for applications outside flavour physics. We adopt a model-independent parameterization of rare decays in terms of the gauge independent functions X_i,Y_i,Z_i (i=K,d,s), which is in particular useful for the study of the breaking of the universality between K, B_d and B_s systems through non-MFV interactions. Performing the calculatio…
The flavour symmetry succeeds in explaining the current global fit results. Flavour-symmetry models can be tested by the future experiments that improve the precision of neutrino oscillation parameters, \textit{such as} the MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT). In this work, we consider tri-direct littlest seesaw (TDLS) models for a case study, and analyze how much MOMENT can extend our knowledge on the TDLS model. We find that measurements of $θ_{23}$ and $δ$ are crucial for MOMENT to exclude the model at more than $5σ$ confidence level, if the best fit values in the l…
I present a brief summary of the main results on flavour physics beyond the Standard Model that have been obtained in 2008 by my collaborators and myself at the TUM. In particular I list main messages coming from our analyses of flavour and CP-violating processes in Supersymmetry, the Littlest Higgs model with T-Parity and a warped extra dimension model with custodial protection for flavour violating $Z$ boson couplings.
Flavour symmetries provide an appealing mechanism to stabilize the dark matter particle. I present a simple model of quark flavoured dark matter that goes beyond the framework of minimal flavour violation. I discuss the phenomenological implications for direct and indirect dark matter detection experiments, high energy collider searches as well as flavour violating precision data.
We derive the renormalization group equations for dimensionless couplings and soft supersymmetry breaking (SSB) parameters given arbitrary high scale inputs, incorporating 1-loop thresholds. A program (to be incorporated into ISAJET) has been developed, which includes flavour violating couplings of superparticles based on an arbitrary framework for the high scale flavour structure of SSB parameters. The weak scale flavour structure derived in this way can be applied to the study of SUSY flavour changing decays. As an illustration, we recalculate the branching ratio of the flavour-violating dec…
The Littlest Higgs Model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. We present a new analysis of quark observables in the LHT model in view of the oncoming flavour precision era. We use all available information on the CKM parameters, lattice QCD input and experimental data on quark flavour observables and corresponding theoretical calculations, taking into account new lower bounds on the symmetry breaking scale and the mirror quark masses from the LHC. We investigate by how much the branching ratios for a number of rare $K$ …
I review the physics case for flavour violating axions. In particular, I argue that relaxing the assumption of the universality of the Peccei-Quinn current opens up new pathways, including: the relaxation of the Supernova bound on the axion mass, a possible connection with the Standard Model flavour puzzle and the experimental opportunity of discovering the axion via flavoured axion searches.
We study the effects of dimension six effective operators on the flavour violating production and decay of leptons at the International Linear Collider. Analytic expressions for the cross sections, decay widths and asymmetries of all flavour changing processes will be presented, as well as an analysis of the feasibility of their observation at the ILC.
We study the impact of the inverse seesaw mechanism on several low-energy flavour violating observables such as tau decaying to three muons in the context of the Minimal Supersymmetric Standard Model. As a consequence of the inverse seesaw, the contributions of the right-handed sneutrinos significantly enhance the Higgs-mediated penguin diagrams. We find that different flavour violating branching ratios can be enhanced by as much as two orders of magnitude. We also comment on the impact of the Higgs-mediated processes on the leptonic B-meson decays and on the Higgs flavour violating decays.
We compute the lepton flavour violating couplings of Higgs bosons in the Minimal Supersymmetric Standard Model, and show that they can induce the decays (h,H,A) --> mu tau at non-negligible rates, for large tan(beta) and sizeable smuon-stau mixing. We also discuss the prospects for detecting such decays at LHC and other colliders, as well as the correlation with other flavour violating processes, such as tau --> mu gamma and tau --> 3 mu.
We consider scenarios with large flavour violating entries in the squark mass matrices focusing on the mixing between second and third generation squarks. These entries govern both, flavour violating low energy observables on the one hand and squark and gluino decays on the other hand. We first discuss the constraints on the parameter space due to the recent data on B mesons from the B factories and Tevatron. We then consider flavour violating squark and gluino decays and show that they can still be typically of order 10% despite the stringent constraints from low energy data. Finally we brief…
We investigate a two Higgs doublet model with extra flavour depending $U(1)_X$ gauge symmetry where $Z'$ boson interactions can explain the Atomki anomaly by choosing appropriate charge assignment for the SM fermions. For parameter region explaining the Atomki anomaly we obtain light scalar boson with $\mathcal{O}(10)$ GeV mass, and we explore scalar sector to search for allowed parameter space. We then discuss anomalous magnetic dipole moment of muon and lepton flavour violating processes induced by Yukawa couplings of our model.
Lepton flavor violation in tau and mu processes is studied in the littlest Higgs model with T-parity. We consider various asymmetries defined in polarized tau and mu decays. Correlations among branching ratios and asymmetries are shown in the following lepton flavor violation processes: mu+ --> e+ gamma, mu+ --> e+ e+ e-, mu- A --> e- A (A = Al, Ti, Au and Pb), tau+ --> mu+ gamma, tau+ --> mu+ mu+ mu-, tau+ --> mu+ e+ e-, tau+ --> mu+ P (P = pi0, eta and eta'), tau+ --> mu+ V (V = rho0, omega and phi), tau+ --> e+ gamma, tau+ --> e+ e+ e-, tau+ --> e+ mu+ mu-, tau+ --> e+ P, tau+ --> e+ V, tau…
We implement non-minimal flavour violation (NMFV) in the MSSM at low scale. In this framework, we propose benchmark points for the mSUGRA scenario including non-minimal flavour violation by evaluating a number of experimental low-energy, electroweak precision and cosmological constraints. We finally discuss phenomenological aspects of our NMFV scenario and present a numerical analysis of squark and gaugino production cross sections at the LHC.
Many models for physics beyond the Standard Model predict lepton-flavour violating decays of charged leptons at a level which may become observable very soon. In the present paper we investigate the decays of a Tau into three charged leptons in a generic way, based on effective-field-theory methods, where the relevant operators are classified according to their chirality structure. We work out the decay distributions and discuss phenomenological implications.
We investigate couplings of squarks to gauge and Higgs-bosons within the framework of non-minimal flavour violation in the Minimal Supersymmetric Standard Model. Introducing non-diagonal elements in the mass matrices of squarks, we first study their impact on the self-energies and physical mass eigenvalues of squarks. We then present an extensive analysis of bosonic squark decays for variations of the flavour-violating parameters around the two benchmark scenarios SPS1a' and SPS1b. Signatures, that would be characteristic for a non-minimal flavour structure in the squark sector, can be found i…
In this work, we systematically investigate the one-loop corrections to $t\bar{t}$ production in the littlest Higgs model with T-parity (LHT) at the LHC for $\sqrt{s}=8,14$ TeV. We focus on the effects of LHT particles on $t\bar{t}$ cross section, polarization asymmetries, spin correlation and charge asymmetry at the LHC. We also study the top quark forward-backward asymmetry at Tevatron and its correlations with the LHC observables. We found that: (1) the contributions of the LHT particles to $t\bar{t}$ production can only reach about 1% at the 14 TeV LHC. Meanwhile, the anomalous top quark f…
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 …
The non-minimal flavour violating interactions of mirror quarks and new heavy gauge bosons in the Littlest Higgs model with T-parity (LHT) give rise to naturally large CP-violating effects in the B_s system. In view of a large new CP phase in B_s - anti-B_s mixing hinted by the CDF and D0 data and the recent UTfit analysis, we update our 2006 analysis of particle-antiparticle mixing and rare K and B decays in the LHT model, using the most recent values of a number of input parameters and performing a more careful error analysis. We find that the CP-asymmetry S_{psi phi} can easily reach values…
In supersymmetric extensions of the Standard Model, the Yukawa and/or mass terms of the heavy neutrinos can generate lepton flavour violating slepton mass terms. These new supersymmetric sources of lepton flavour violation may both enhance the rates of charged lepton flavour violating processes, l_a -> l_b y, and generate distinct final states, like l_b l_a + jets + missing E_T, at future colliders. First, we discuss the sensitivity of future e^+e^- colliders to the SLFV independently of the lepton flavour violating mechanism. Second, we study lepton flavour violating slepton pair production a…
A variety of lepton flavour violating effects related to the recent discovery of neutrino oscillations and mixings is here systematically discussed in terms of an S_3-flavour permutational symmetry. After presenting some relevant results on lepton masses and mixings, previously derived in a minimal S_3-invariant extension of the Standard Model, we compute the branching ratios of some selected flavour-changing neutral current processes (FCNC) as well as the contribution of the exchange of neutral flavour-changing scalar to the anomaly of the magnetic moment of the muon. We found that the minima…
Motivated by flavour symmetry models, we construct theories based on a low-energy limit featuring lepton flavour triality that have the flavour-violating decays $τ^\pm \to μ^\pm μ^\pm e^\mp$ and $τ^\pm \to e^\pm e^\pm μ^\mp$ as the main phenomenological signatures of physics beyond the standard model. These decay modes are expected to be probed in the near future with increased sensitivity by the Belle II experiment at the SuperKEKB collider. The simple standard model extensions featured have doubly-charged scalars as the mediators of the above decay processes. The phenomenology of these exten…
We study Yukawa Renormalization Group (RG) running effects in the context of the Standard Model Effective Theory (SMEFT).The Yukawa running being flavour dependent leads to RG-induced off-diagonal entries, so that initially diagonal Yukawa matrices at the high scale have to be rediagonalized at the electroweak (EW) scale. Performing such flavour rotations can lead to flavour violating operators which differ from the ones obtained through SMEFT RG evolution. We show, that these flavour rotations can have a large impact on low-energy phenomenology. In order to demonstrate this effect, we compare…
Treating the MSSM as an effective theory below a threshold scale Lambda, we study the consequences of having dimension-five operators in the superpotential for flavour and CP-violating processes. Below the supersymmetric threshold such terms generate flavour changing and/or CP-odd effective operators of dimension six composed from the Standard Model fermions, that have the interesting property of decoupling linearly with the threshold scale, i.e. as 1/(Lambda m_soft), where m_soft is the scale of soft supersymmetry breaking. The assumption of weak-scale supersymmetry, together with the stringe…
We present a first update on the constraints on general MSSM scenarios with non-minimal sources of flavour violation (NMFV). Using the public code SuperIso, we present an up-to-date computation of the relevant Wilson coefficients related to $b\to s ll$ transitions which manifest tensions with the SM predictions. We present benchmark scenarios compatible with the most recent fits to the Wilson coefficients. We finally discuss the possibility for such scenarios to completely explain the recent flavour anomalies.
We consider a $U(1)'$ extended supersymmetric model with a right-handed neutrino superfield which can generate light neutrino mass by Type I seesaw mechanism. The lighter superpartner of the right-handed neutrino could be the scalar dark matter. These right-handed sneutrinos can come from the decay of $\tilde{Z'}$, superpartner of the extra gauge boson $Z'$. Left-right handed sneutrino mixings affect their decays further, giving rise to displaced "lepton flavour violating" signatures. A wino-like chargino NLSP (next to lightest supersymmetric particle) creates even more interesting decay topol…
A variety of lepton flavour violating effects related to the recent discovery of neutrino oscillations and mixings is here systematically discussed in terms of an S_3-flavour permutational symmetry. After a brief review of some relevant results on lepton masses and mixings, that had been derived in the framework of a Minimal S_3-Invariant Extension of the Standard Model, we derive explicit analytical expressions for the matrices of the Yukawa couplings and compute the branching ratios of some selected flavour changing neutral current (FCNC) processes, as well as, the contribution of the exchan…
We present a general study of a three neutrino flavour transition model based on the supersymmetric interactions which violate R-parity. These interactions induce flavour violating scattering reactions between solar matter and neutrinos. The model does not contain any vacuum mass or mixing angle for the first generation neutrino. Instead, the effective mixing in the first generation is induced via the new interactions. The model provides a natural interpretation of the atmospheric neutrino anomaly, and is consistent with reactor experiments. We determine all R-parity violating couplings which …
In the framework of the minimal ${SU}(3)_C\otimes {SU}(3)_L \otimes {U}(1)_N$ model, the lepton-flavour-violating decay $π^+ \ra μ^- ν_μe^+ e^+ $ is calculated without directly invoking lepton mixing. The branching ratio for this rare pion decay mode is found to be much smaller than the current experimental upper limit. Dropping out anomalous interactions, this result coincides with the previous calculation .
The detection of the flavour content of jets produced from R-parity violating neutralino decays is investigated in the case where one baryon-number violating coupling dominates. Simulations are performed of the ATLAS experiment at the LHC for all couplings, other than lambda"_tjk since neutralino decays through these couplings are very suppressed. Secondary vertex distributions and muons produced by heavy-quark (b- and c-) jets allow discrimination between LSP decay modes. The dominant coupling can be identified at better than 3.5 sigma in almost all cases, with the only remaining ambiguity ca…
We consider lepton flavour violating decays of the top quark, mediated by four-fermion operators. We compile constraints on a complete set of SU(3)*U(1)-invariant operators, arising from their loop contributions to rare decays and from HERA's single top search. The bounds on e-mu flavour change are more restrictive than l-tau; nonetheless the top could decay to a jet $+ e \barμ$ with a branching ratio of order $10^{-3}$. We estimate that the currently available LHC data (20 inverse-fb at 8 TeV) could be sensitive to $BR(t \to e \barμ$+ jet) $ \sim 6\times 10^{-5}$, and extrapolate that 100 inv…
We analyse the top flavour violating decays in general supersymmetric model using the mass insertion approximation. In particular, we discuss the impact of a light right-handed top-squark and large mixing between the first or second and third generation of up-squarks on processes as t -> q gamma,g . We also take into account the relevant experimental constraints from B-physics and the requirements for a successfull electroweak baryogenesis on squark mixings. We show that for general large mixings in squarks mass matrix, the branching ratio of the t -> q gamma, g (q=u,c) can be as large as 10^{…
We study lepton flavour violating signals at a future e+ e- linear collider within the general MSSM, allowing for the most general flavour structure. We demonstrate that there is a large region in parameter space with large signals, while being consistent with present experimental bounds on rare lepton decays such as mu -> e gamma. In our analysis, we include all possible signals from charged slepton, sneutrino, neutralino, and chargino production and decay. We also consider the background from the Standard Model and the MSSM. We find that in general the signature e tau missing energy is the m…
We study the impact of the inverse seesaw mechanism on several leptonic and hadronic low-energy flavour-violating observables in the context of the Minimal Supersymmetric Standard Model. Indeed, the contributions of the light right-handed sneutrinos from the inverse seesaw significantly enhance the Higgs-mediated penguin diagrams. We find that this can increase the different branching ratios by as much as two orders of magnitude.
The solution to the Strong CP problem is analysed within the Minimal Flavour Violation (MFV) context. An Abelian factor of the complete flavour symmetry of the fermionic kinetic terms may play the role of the Peccei-Quinn symmetry in traditional axion models. Its spontaneous breaking, due to the addition of a complex scalar field to the Standard Model scalar spectrum, generates the MFV axion, which may redefine away the QCD theta parameter. It differs from the traditional QCD axion for its couplings that are governed by the fermion charges under the axial Abelian symmetry. It is also distinct …
Analytic expressions of lepton-flavour- and lepton-number-violating decays of charged leptons are derived in the context of general $SU(2)_L\otimes U(1)_Y$ seesaw scenarios that are motivated by grand unified theories (GUT's) or superstring models, in which left-handed and/or right-handed neutral singlets are present. Possible constraints imposed by cosmology and low-energy data are briefly discussed. The violation of the decoupling theorem in flavour-dependent graphs due to the presence of heavy neutral leptons of Dirac or Majorana nature is emphasized. Numerical estimates reveal that the dec…
We use a new weak basis invariant approach to classify all the observable phases in any extension of the Standard Model (SM). We apply this formalism to determine the invariant CP phases in a simplified version of the Minimal Supersymmetric SM with only three non-trivial flavour structures. We propose four experimental measures to fix completely all the observable phases in the model. After these phases have been determined from experiment, we are able to make predictions on any other CP-violating observable in the theory, much in the same way as in the Standard Model all CP-violation observab…
