Higgs singlet superfields, usually present in extensions of the Minimal Supersymmetric Standard Model (MSSM) which address the $μ$-problem, such as the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and the Minimal Nonminimal Supersymmetric Standard Model (mnSSM), can have significant contributions to $B$-meson flavour-changing neutral current observables for large values of $\tanβ\gsim 50$. Illustrative results are presented including effects on the $B_s$ and on the rare decay $B_s\toμ^+μ^-$. In particular, we find that in the NMSSM, the branching ratio for $B_s\toμ^+μ^-$ can be enhanced or even suppressed with respect to the Standard Model prediction by more than one order of magnitude.
Higgs singlet superfields are usually present in most extensions of the Minimal Supersymmetric Standard Model (MSSM) that address the mu-problem, such as the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and the Minimal Nonminimal Supersymmetric Standard Model (MNSSM). Employing a gauge- and flavour-covariant effective Lagrangian formalism, we show how the singlet Higgs bosons of such theories can have significant contributions to B-meson flavour-changing neutral current (FCNC) observables for large values of $\tanβ\stackrel{>}{{}_\sim} 50$ at the 1-loop level. Illustrative results are…
A mechanism for double suppression of flavor-changing neutral currents (FCNCs) and CP violating phases in supersymmetric models is suggested. At M_{SUSY} they are suppressed due to a nonabelian discrete flavor symmetry, and the infrared attractive force of gauge interactions in extra dimensions are used to suppress them at the compactification scale. We present a concrete model, which is a simple extension of S_{3} invariant minimal supersymmetric standard model, where only SU(2)_{L} and SU(3)_{C} gauge multiplets are assumed to propagate in the bulk. We find that a disorder of two orders of m…
A concrete model which can suppress FCNCs and CP violating phenomena is suggested. It is an $S_3$ symmetric extension of the MSSM in extra dimensions, where only SU(2) and SU(3) gauge multiplets are assumed to propagate in the bulk. They are suppressed due to $S_3$ flavor symmetry at $M_{SUSY}$, and the infrared attractive force of gauge interactions in extra dimensions are used to suppress them at the compactification scale. We find that O(1) disorders of the soft parameters are allowed at the cut-off scale to suppress sufficiently FCNCs and CP violating phenomena.
We conduct a general discussion of supersymmetric models with three families in the Higgs sector. We analyse the scalar potential, and investigate the minima conditions, deriving the mass matrices for the scalar, pseudoscalar and charged states. Depending on the Yukawa couplings and the Higgs spectrum, the model might allow the occurrence of potentially dangerous flavour changing neutral currents at the tree-level. We compute model-independent contributions for several observables, and as an example we apply this general analysis to a specific model of quark-Higgs interactions, discussing how …
We consider Flavour Changing Neutral Current processes in the framework of the supersymmetric extension of the Standard Model. FCNC constraints on the structure of sfermion mass matrices are reviewed. Furthermore, we analyze supersymmetric contributions to FCNC transitions which remain in the limit of flavour-conserving sfermion mass matrices. Implications of the FCNC constraints on the structure of sfermion mass matrices for SUSY breaking and sfermion mass generation are discussed. We conclude that the supersymmetric flavour problem is intriguing but perhaps not as severe as it is commonly be…
In the context of the Supersymmetric Standard Model with hierarchical sfermion masses, we re-analyze the QCD corrections to Delta F=2 effective Hamiltonian properly including effects which have been neglected so far. The point is that some Delta F=2 diagrams, involving both the heavy and the light sparticles, exhibit a logarithmic dependence on the ratio between the two masses, signalling a sensitivity to all the momenta between the two scales. In order to properly deal with these terms one has to take into account the mixing between Delta F=1 and Delta F=2 operators. In typical situations thi…
We analyze the production and subsequent decay of the neutral MSSM Higgs bosons (h = h^0, H^0, A^0) mediated by flavor changing neutral currents (FCNC) in the LHC collider. We have computed the h-production cross-section times the FCNC branching ratio, σ(pp -> h -> qq') = σ(pp -> h) B(h -> qq'), in the LHC focusing on the strongly-interacting FCNC sector. Here qq' is an electrically neutral pair of quarks of different flavors, the dominant modes being those containing a heavy quark: tc or bs. We determine the maximum production rates for each of these modes and identify the relevant regions of…
We discuss the production of single top-quark final states by direct supersymmetric flavor-changing interactions at the LHC. The total cross section pp(gg)->t\bar{c}+\bar{t}c is computed at the 1-loop order within the unconstrained MSSM. We prove that SUSY-QCD effects may furnish sizeable production rates amounting up to barely 10^5 t\bar{c}(c\bar{t}) events per 100 fb^{-1} of integrated luminosity, in full compliance with the stringent low-energy constraints from b->s gamma. Furthermore, we show that the cooperative SUSY-EW effects can be sizeable on their own, regardless of the SUSY-QCD cont…
We revise the limits on the FCNC higgses in manifestly left-right symmetric theories. It is shown that the combination of the Kobayashi-Maskawa CP-violation with the tree level $ΔS=2$ higgs exchange gives very large contribution to the CP-violating $ε$ parameter. It leads to the new strong constraint on the FCNC higgs mass, M>50- 100 TeV, enhanced by factor of the order $\sqrt{m_t/m_c}$. Being addressed to the supersymmetric left-right models, FCNC problem requires both right-handed scale and supersymmetric mass parameters be heavier than 50 TeV for $tanβ\sim 1$. The most relaxed case correspo…
I discuss a ``more minimal'' modification of the minimal supersymmetric standard model, in which supersymmetry breaking is connected with the physics of flavor. Flavor Changing Neutral Currents (FCNC) for the first two families are suppressed, and for the third family may be of comparable size to the FCNC in the Standard Model.
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.
Baryon number (B) is automatically conserved in the standard SU(2) X U(1) electroweak gauge model, but not in its supersymmetric extension where it must be imposed as an extra condition. This undesirable feature is avoided in the conventional left-right supersymmetric extension, but then flavor-changing neutral currents (FCNC) are not naturally suppressed. A new version is proposed with automatic B conservation as well as FCNC suppression (except for u quarks through scalar exchange).
Adding singlet neutrinos to the standard model spectrum in general gives rise to Z-induced flavor-changing neutral currents. We study the impact of these currents on matter-induced neutrino oscillations in the sun and in supernovae. While the effects for solar neutrinos are negligible, dramatic effects are possible for supernova neutrinos.
In the supersymmetric models with nontrivial flavour structure in the soft-breaking sector the exchange of neutral Higgses mediates $ΔF=2$ transitions. This mechanism is studied for $ΔS, ΔB=2$ processes and for a generic form of the soft-breaking terms. We find that Higgs-mediated FCNC amplitudes increase very rapidly with $\tanβ$ and can exceed $SUSY$ box contribution by up to two orders of magnitude when $\tanβ\sim m_t/m_b$.
We compute the finite renormalisation of the Cabibbo-Kobayashi-Maskawa (CKM) matrix induced by gluino-squark diagrams in the MSSM with non-minimal sources of flavour violation. Subsequently we derive bounds on the flavour-off-diagonal elements of the squark mass matrices by requiring that the radiative corrections to the CKM elements do not exceed the experimental values. Our constraints on the associated dimensionless quantities delta^{d LR}_{ij}, j>i, are stronger than the bounds from flavour-changing neutral current (FCNC) processes if gluino and squarks are heavier than 500 GeV. Our bound …
These two lectures constitute a reappraisal and an update of the status of the Flavour Changing Neutral Current (FCNC) and CP violation issues in supersymmetry. The first lecture discusses these points in the framework of the Minimal Supersymmetric Standard Model (MSSM), while the second one provides an analysis in a generic low-energy supersymmetric extension of the Standard Model. The goal of these lectures is twofold: on one hand we present a qualitative and quantitative discussion of the threat that FCNC and CP violation represent on supersymmetry model building; on the other hand, we poin…
We construct explicit examples with a horizontal, ``anomalous'' $U(1)$ gauge group, which, in a supersymmetric extension of the standard model, reproduce qualitative features of the fermion spectrum and CKM matrix, and suppress FCNC and proton decay rates without the imposition of global symmetries. We review the motivation for such ``more'' minimal supersymmetric standard models and their predictions for the sparticle spectrum. There is a mass hierarchy in the scalar sector which is the inverse of the fermion mass hierarchy. We show in detail why DeltaS = 2 FCNC are suppressed when compared w…
We compute the partial width of the FCNC top quark decay t->c h in the framework of the Minimal Supersymmetric Standard Model, where h = h0, H0, A0 is any of the neutral Higgs of the MSSM. We include the SUSY electroweak, Higgs, and SUSY-QCD contributions. Our results substantially improve previous estimations on the subject, and we find that there is a possibility that they can be measured at LHC.
We evaluate the top-quark FCNC productions induced by the topcolor assisted technicolor (TC2) model at the LHC. These productions proceed respectively through the parton-level processes g g -> t c_bar, c g->t, c g -> t g, c g -> t Z and c g -> t γ. We show the dependence of the production rates on the relevant TC2 parameters and compare the results with the predictions in the minimal supersymmetric model. We find that for each channel the TC2 model predicts a much larger production rate than the supersymmetric model. All these rare productions in the TC2 model can be enhanced above the 3-sigma…
In the context of Supersymmetric Grand Unified theories with soft breaking terms arising at the Planck scale, it is generally possible to link flavor changing neutral current and CP violating processes occurring in the leptonic and hadronic sectors. We study the correlation between flavor changing squark and slepton mass insertions in models à la SU(5). We show that the constraints coming from lepton flavor violation exhibit a strong impact on CP-violating B decays.
The solution to the supersymmetric FCNC problem may not have a simple field theory interpretation. Here I advocate a possibility based on string selection rules. The requirement of non--trivial Yukawa structures restricts the form of the soft terms such that the FCNC problem often does not arise.
We present results of our study of tan(beta)-enhanced loop corrections in the Minimal Supersymmetric Standard Model (MSSM) with Minimal Flavour Violation (MFV). We demonstrate that these corrections induce flavour changing neutral current (FCNC) gluino couplings which have a large impact on the Wilson coefficient C_8 of the chromomagnetic operator. To illustrate the phenomenological consequences of this gluino-squark contribution to C_8, we briefly discuss its effect on the mixing-induced CP asymmetry in the decay B_d -> phi K_S.
We analyze the maximum branching ratios for the Flavor Changing Neutral Current (FCNC) decays of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) into bottom quarks, h -> b\bar{s} (h=h^0,H^0,A^0). We consistently correlate these decays with the radiative B-meson decays (b-> sγ). A full-fledged combined numerical analysis is performed of these high-energy and low-energy FCNC decay modes in the MSSM parameter space. Our calculation shows that the available data on B(b->s γ) severely restricts the allowed values of B(h->b\bar{s}). While the latter could reach a few per…
Flavor Changing Neutral Current decays of the top quark within the strict context of the Standard Model are known to be extremely rare. In fact, they are hopelessly undetectable at the Tevatron, LHC and LC in any of their scheduled upgradings. Therefore, if a few of these events eventually show up in the future we will have certainly discovered new physics. We argue that this could well be the case for the LHC and the LC both within the Minimal Supersymmetric Standard Model (MSSM) and in a general two-Higgs-doublet model (2HDM), especially if we look for FCNC top quark decays into Higgs bosons…
We examine extensions of the MSSM with more than one generation of Higgs bosons. If one assumes that a symmetry eliminates the tree-level FCNC, then the extra scalar bosons do not acquire VEVs, do not couple to fermions and do not mix with the ordinary Higgs bosons; the lightest is absolutely stable. The two lightest neutral scalars, $ϕ_S$, and $ϕ_P$, are degenerate in mass, and the mass difference between those and the lightest charged scalar, $ϕ_+$, is calculated. For most of the parameter space, the charged scalar is between a hundred MeV and a few GeV heavier than the neutral scalars. The …
Production of (electrically neutral) heavy-quark pairs, such as t{\bar c} and {\bar t}c, is extremely suppressed in the SM. In supersymmetric (SUSY) theories, such as the MSSM, the number of these events can be significantly enhanced thanks (mainly) to the FCNC couplings of gluinos. We compute the efficiency of this mechanism for FCNC production of heavy quarks at the LHC. We find that σ(pp\to t\bar{c}+\bar{t}c) can reach 1 pb, and therefore one can expect up to 10^{5} events per 100 fb^{-1} of integrated luminosity (with no counterpart in the SM). Their detection would be instant evidence of …
We propose a E_6 inspired supersymmetric model with a non-Abelian discrete flavor symmetry; SU(3)_c x SU(2)_W x U(1)_Y x U(1)_X x S_4 x Z_2. In our scenario, the additional abelian gauge symmetry; U(1)_X, not only solves the mu-problem in the minimal Supersymmetric Standard Model(MSSM), but also requires new exotic fields which play an important role in solving flavor puzzles. If our exotic quarks can be embedded into a S_4 triplet, which corresponds to the number of the generation, one finds that dangerous proton decay can be well-suppressed. Hence, it might be expected that the generation st…
We derive the general resummed effective Lagrangian for Higgs-mediated flavour-changing neutral-current (FCNC) interactions in the Minimal Supersymmetric Standard Model (MSSM), without resorting to particular assumptions that rely on the squark-mass or the quark-Yukawa structure of the theory. In our derivation we also include the possibility of explicit CP violation through the Cabibbo--Kobayashi--Maskawa mixing matrix and soft supersymmetry-breaking mass terms. The advantages of our resummed FCNC effective Lagrangian are explicitly demonstrated within the context of phenomenologically motiva…
Consequences of a specific class of two Higgs doublet models in which the Higgs induced tree level flavour changing neutral currents (FCNC) display minimal flavour violation (MFV) are considered. These FCNC are fixed in terms of the CKM matrix elements and the down quark masses. The minimal model in this category with only two Higgs doublets has no extra CP violating phases but such a phase can be induced by adding a complex singlet. Many of the theoretical predictions are similar to other MFV scenario. The FCNC contribute significantly to $B$ meson mixing and CP violation. Detailed numerical …
A supersymmetric extension of the standard model based on the discrete $Q_6$ family symmetry is considered, and we investigate flavor-changing neutral current (FCNC) processes, especially those mediated by heavy flavor-changing neutral Higgs bosons. Because of the family symmetry the number of the independent Yukawa couplings is smaller than that of the observed quantities such as the Cabibbo-Kobayashi-Maskawa matrix and the quark masses, so that the FCNCs can be parametrized only by the mixing angles and masses of the Higgs fields. We focus our attention on the mass differences of the neutral…
We show that the gauge singlet scalar boson in low-energy supersymmetric model may behave as the standard model (SM) Higgs boson if the singlet couples to (heavy) vector-like colored particles. In this case, the SM-Higgs-like signal at the LHC can be mimicked by the singlet production process for wide range of the singlet mass.
The minimal flavor violation hypothesis is presented in the context of the MSSM. Its fundamental principles are introduced and motivated, and its phenomenological consequences for FCNC and CP-violating observables as well as for R-parity violating processes are briefly described.
It has been argued that the squarks and sleptons of the first and second generations can be relatively heavy without destabilizing the weak scale, thereby improving the situation with too-large flavor-changing neutral current (FCNC) and CP violating processes. In theories where the soft supersymmetry breaking parameters are generated at a high scale (such as the Planck scale), we show that such a mass spectrum tends to drive the scalar top mass squared $m_{\tilde{Q}_3}^2$ negative from two-loop renormalization group evolution. Even ignoring CP violation and allowing $O(λ) \sim .22$ alignment, …
We re-examine resonant massless-neutrino conversions in a dense medium induced by flavour changing neutral current (FCNC) interactions. We show how the observed $\barν_e$ energy spectra from SN1987a and the supernova $r$-process nucleosynthesis provide constraints on supersymmetric models with $R$ parity violation, which are much more stringent than those obtained from the laboratory. We also suggest that resonant massless-neutrino conversions may play a positive role in supernova shock reheating. Finally, we examine the constraints on explicit $R$-parity-violating FCNCs in the presence of non…
We study the FCNC top quark decays t -> c h in the framework of the MSSM, where h= h^0,H^0,A^0 is any of the supersymmetric neutral Higgs bosons. We include the leading set of SUSY-QCD and SUSY electroweak contributions. While the FCNC top quark decay into the SM Higgs boson has such a negligible rate that will not be accessible to any presently conceivable accelerator, we find that there is a chance that the potential rates in the MSSM can be measured at the high luminosity colliders round the corner, especially at the LHC and possibly at a future LC, but we deem it difficult at the upgraded …
A generalization of the Next-to-Minimal Supersymmetric Model (NMSSM) is studied in which an explicit μ-term as well as a small supersymmetric mass term for the singlet superfield are incorporated. We study the possibility of raising the Standard Model-like Higgs mass at tree level through its mixing with a light, mostly-singlet, CP-even scalar. We are able to generate Higgs boson masses up to 145 GeV with top squarks below 1.1 TeV and without the need to fine tune parameters in the scalar potential. This model yields light singlet-like scalars and pseudoscalars passing all collider constraints…
Extensions of the MSSM generically feature gauge singlet Higgs bosons. These singlet Higgs bosons have tan(beta)-enhanced Yukawa couplings to down-type quarks and leptons at the one-loop level. We present an effective Lagrangian incorporating these Yukawa couplings and use it to study their effect on singlet Higgs boson phenomenology within both the mnSSM and NMSSM. It is found that the loop-induced couplings represent an appreciable effect for the singlet pseudoscalar in particular, and may dominate its decay modes in some regions of parameter space.
We study the Minimal Supersymmetric Standard Model with Minimal Flavour Violation for the case of a large parameter tanbeta and arbitrary values of the supersymmetric mass parameters. We derive several resummation formulae for tanbeta-enhanced loop corrections, which were previously only known in the limit of supersymmetric masses far above the electroweak scale. Studying first the renormalisation-scheme dependence of the resummation formula for the bottom Yukawa coupling, we clarify the use of the sbottom mixing angle in the supersymmetric loop factor Delta_b. As a new feature, we find tan-be…
We discuss the Higgs sector of the supersymmetric standard model extended by a gauge singlet for the range of parameters, which is compatible with universal soft supersymmetry breaking terms at the GUT scale. We present results for the masses, couplings and decay properties of the lightest Higgs bosons, in particular with regard to Higgs boson searches at LEP. The prospects differ significantly from the ones within the MSSM.
A non-Abelian flavour symmetry in a minimal supersymmetric standard model can explain the flavour structures in the Yukawa couplings and simultaneously solve the SUSY flavour problem. Similarly the SUSY CP problem can be solved if CP is spontaneously broken in the flavour sector. In this work, we present an explicit example of these statements with a SU(3) flavour symmetry and spontaneous CP violation. In addition, we show that it is still possible to find some significant deviation from the SM expectations as far as FCNC and CP violation are concerned. We find that large contributions can be …
We consider the renormalisation of a softly-broken supersymmetric theory with singlet fields and a superpotential with a linear term. We show that there exist exact beta-functions for both the linear term in the superpotential and the associated linear term in the Lagrangian. We also construct exact renormalisation group invariant trajectories for these terms, corresponding to the conformal anomaly solution for the soft masses and couplings.
We present the results of the influence of the minimal supersymmetric standard model extended by an additional Higgs singlet N, with vacuum expectation value $v_N$, on the anomalous magnetic moment of the muon. This gives different mass matrices for the charginos and neutralinos, which are taken into account within the relevant penguin diagrams leading to a contribution $Δa_μ$\ to the anomalous magnetic moment of the muon. We show that a large vacuum expectation value for the Higgs singlet leads to a suppression of the supersymmetric contribution making it difficult to see in an experiment in …
We analyze the FCNC semileptonic decay $B \to X_s l^+l^-$ in a fully left-right supersymmetric model. We give explicit expressions for all the amplitudes involved in the process, and compare the numerical results with experimental bounds, in both the constrained case (where the only flavor violation comes from the Cabibbo-Kobayashi-Maskawa matrix) and the unconstrained case (including soft breaking supersymmetry terms). Stringent constraints on the parameter space of the model are obtained. We also include constraints from $b \to s γ$.
The neutron electric dipole moment is investigated in a supersymmetric electroweak model admitting $ {\rm SU(2)}_W $ singlet and $ Q = -1/3 $, say $ D $-type, quarks. Significant $ CP $ violating phases appear in the coupling between the singlet $ D $-type quarks and the ordinary $ d $-type quarks. Then, through the $ d $-$ D $ mixing effects on the squark mass terms the gluino one-loop diagrams provide naturally the contributions $ \sim 10^{-26} e~{\rm cm} $ comparable to the current experimental bound on the neutron electric dipole moment. The $ CP $ violation in the $ d $-$ D $ coupling wou…
The loop corrections to the couplings of Higgs bosons to quarks and charged leptons are calculated within supersymmetric versions of the Standard Model, extended by a gauge singlet. The effective couplings of the $SU(2)_L$ doublet and singlet Higgs bosons to quarks and leptons, induced by sfermion loops, are derived. Analytic expressions for the case of generic sfermion flavour mixing, including the complete resummation of all chirally-enhanced contributions are presented. These results are important in scenarios in which the mixing between singlet and doublet components of Higgs bosons is sma…
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…
Higgs boson decays mediated by flavor changing neutral currents (FCNC) are very much suppressed in the Standard Model, at the level of 10^{-15} for Higgs boson masses of a few hundred GeV. Therefore, any experimental vestige of them would immediately call for new physics. In this paper we consider the FCNC decays of Higgs bosons into a top quark in a general two-Higgs-doublet model (2HDM). The isolated top quark signature, unbalanced by any other heavy particle, should help to identify the potential FCNC events much more than any other final state. We compute the maximum branching ratios and t…
It is generally assumed that the dynamical generation of the Higgs mass parameter of the superpotential, $μ$, implies the existence of a light singlet at or below the supersymmetry breaking scale, $\msusy$. We present a counter-example in which the singlet field can receive an arbitrarily heavy mass (\eg, of the order of the Planck scale, $M_{\rm P}\approx 10^{19}~\gev$). In this example, a non-zero value of $μ$ is generated through soft supersymmetry breaking parameters and is thus naturally of the order of $\msusy$.
We search for supersymmetric standard model realizations with extra singlets and extra $ U(1)$ using the heterotic string compactification on the $ Z_{6-II}$ orbifold with two Wilson lines. We analyze the vacuum restabilization mechanism for three representative Pati-Salam string models obtained in the literature and present detailed results for the effective superpotential compatible with the string selection rules. An automated selection of semi-realistic vacua along flat directions in the non-Abelian singlet modes field space is performed by requiring the presence of massless pairs of elect…
A supersymmetric standard model with two Higgs doublets and two Higgs singlets is investigated if it can accommodate the possibility of spontaneous CP violation. Assuming the degeneracy of the scalar quark masses of the third generation, we find that spontaneous CP violation in the Higgs sector is viable in our model. In the case of spontaneous CP violation, the masses of the lightest two neutral Higgs bosons are estimated to be 80 and 125 GeV for some parameter values in our model, which, are consistent with LEP2 data.
An upper bound on the tree-level mass of the lightest Higgs boson of the Supersymmetric Singlet Majoron Model is obtained. Contrary to some recent claims, it is shown to be of the same form as the general mass bound previously calculated for supersymmetric models with an extended Higgs sector. Soft-breaking masses or exotic vacuum expectation values do not enter in the tree-level bound [which is only controlled by the electroweak scale (M_Z)] and also decouple from the most important radiative corrections to the bound (the ones coming from the top-stop sector). The derivation of the upper boun…
The supersymmetric extension of the standard model with an additional gauge singlet is analysed in detail in the light of the recent experimental bounds on supersymmetric particles. The useful part of the parameter space and the particle spectrum are displayed. We find that once the recent bounds on the chargino mass are imposed, all other new particles practically satisfy the present experimental limits. Special attention is given to particles to be searched for in the future experiments. The singlet fields tend to decouple and give rise to an effective MSSM, enlarging the validity of many ph…
Singlet Higgs bosons present in extensions of the MSSM can have sizable Yukawa couplings to the b quark and the tau lepton for large values of tan(beta) at the 1-loop level. We present an effective Lagrangian which incorporates these tan(beta)-enhanced Yukawa couplings and which enables us to study their effect on singlet Higgs-boson phenomenology within the context of both the mnSSM and the NMSSM. In particular, we find that the loop-induced coupling can be a significant effect for the singlet pseudoscalar, and may dominate its decay modes. Further implications of the tan(beta)-enhanced Yukaw…
In the minimal supersymmetric model the R-parity violating top quark interactions, which are so far weakly constrained, can induce various flavor-changing neutral-current (FCNC) productions for the top quark at the Large Hadron Collider (LHC). In this work we assume the presence of the B-violating couplings and examine their contributions to the FCNC productions proceeding through the parton processes cg -> t, gg -> t c_bar, cg -> tγ, cg -> t Z and cg -> t h. We find that all these processes can be greatly enhanced relative to the R-parity preserving predictions. In the parameter space allowed…
We examine cosmological constraints on the lepton number breaking scale in supersymmetric singlet majoron models. Special attention is drawn to the model dependence arising from the particular choice of a certain majoron extension and a cosmological scenario. We find that the bounds on the symmetry breaking scale can vary substantially. Large values of this scale can be allowed if the decoupling temperature of smajoron and majorino exceeds the reheating temperature of inflation. In the opposite case an upper bound depending on the majoron model can be obtained which, however, is unlikely to be…
In this lectures, we give a review about the Minimal Supersymmetric Standard Model (MSSM) and the General Singlet Extensions of the MSSM (GSEMSSM). We, first introduce the minimal set of fields to built both models. Then we introduce their superfields and using them we build the lagrangian of those models in the superspace formalism. We show how to get the mass spectrum of those model in the $R$-parity scenarios and we also show how to get some Feynman Rules with the Gauge Bosons.
We consider the supersymmetric seesaw mechanism induced by the exchange of heavy SU(2)_W triplet states, rather than `right-handed' neutrino singlets, to generate neutrino masses. We show that in this scenario the neutrino flavour structure tested at low-energy in the atmospheric and solar neutrino experiments is directly inherited from the neutrino Yukawa couplings to the triplets. This allows us to predict the ratio of the tau --> mu gamma (or tau --> e gamma) and mu --> e gamma decay rates in terms of the low-energy neutrino parameters. Moreover, once the model is embedded in a grand unifie…
