We present an application of the reduction of couplings program in the minimal supersymmetric Standard Model (MSSM). We investigate if a functional relation between $α_1$ and $α_2$ gauge couplings can be realized which is Renormalization Group Invariant (RGI). Following the same procedure for the top and bottom Yukawa couplings we end up with a prediction of a narrow window for tan$β$, which is one of the basic parameters that determine the light Higgs mass.
The evaluation of three-loop contributions to the MSSM Higgs-boson mass is considered at the orders enhanced by the strong gauge coupling and top or bottom Yukawa couplings, i.e. at the orders $O(α_{t,b}α_s^2,α_{t,b}^2α_s,α_{t,b}^3)$. We prove that regularization by dimensional reduction preserves supersymmetry at the required level. Thus generating counterterms by multiplicative renormalization is correct. Technically, we extend a previous two-loop analysis to the three-loop level. The extension covers not only the genuine three-loop Higgs potential counterterms but also a large sector of two…
Using dimensional reduction we construct an effective 3D theory of the Minimal Supersymmetric Standard Model at finite temperature. The final effective theory is obtained after three successive stages of integration out of massive particles. We obtain the full 1-loop relation between the couplings of the reduced theory and the underlying 4D couplings and masses. The procedure is also applied to a general two Higgs doublet model and the Next to Minimal Supersymmetric Standard Model.
I briefly summarize the main features related to the unification of gauge and Yukawa couplings in the MSSM, emphasizing the predictions derived in this framework, which are of special interest in the light of present and near--future experiments
For MSSM phenomenology, soft SUSY breaking dimension-three operators are important, in particular the couplings between Higgs bosons and squarks. In scattering processes, perturbative unitarity is violated at modest center-of-mass energy if these couplings are much larger than the masses of the scalar particles involved. Assuming perturbative unitarity, constraints on the trilinear couplings can be determined using a computer program that we have developed.
We extend the already existing two-loop calculation of the effective bottom-Yukawa coupling in the MSSM. In addition to the resummation of the dominant corrections for large values of tg$β$, we include the subleading terms related to the trilinear Higgs coupling $A_b$ and contributions induced by the electroweak gauge couplings. This calculation has been extended to the NNLO corrections to the MSSM strange-Yukawa coupling. Our analysis leads to residual theoretical uncertainties of the effective Yukawa couplings at the per-cent level.
The evaluation of Yukawa-enhanced two-loop contributions to the MSSM Higgs-boson mass is considered. We prove the common assumption that regularization by dimensional reduction preserves supersymmetry at the required level. Thus generating counterterms by multiplicative renormalization is correct. Technically, we identify a suitable Slavnov-Taylor identity, use a recently developed method to evaluate it at the two-loop level, and show that it is valid in dimensional reduction.
We consider the measurement of the trilinear couplings of the neutral Higgs bosons~($H^0, h^0$) in the minimal supersymmetric standard model~(MSSM) at a high energy $e^+$ $e^-$ linear collider in the light of the discovery of a Higgs boson at the CERN Large Hadron Collider~(LHC). We identify the state observed at the LHC with the lightest CP-even Higgs boson of the MSSM. We implement this constraint, as well as all the other relevant experimental constraints, on the parameter space of the MSSM in order to study the feasibility of measuring the trilinear couplings of the neutral Higgs bosons. F…
We apply the method of reduction of couplings in a Finite Unified Theory and in the MSSM. The method consists on searching for renormalization group invariant relations among couplings of a renormalizable theory holding to all orders in perturbation theory. It has a remarkable predictive power since, at the unification scale, it leads to relations between gauge and Yukawa couplings in the dimensionless sectors and relations involving the trilinear terms and the Yukawa couplings, as well as a sum rule among the scalar masses and the unified gaugino mass in the soft breaking sector. In both the …
The FeynArts model file MSSMdreg2dred.mod implements MSSM transition counterterms which can convert one-loop Green functions from dimensional regularization to dimensional reduction. They correspond to a slight extension of the well-known Martin/Vaughn counterterms, specialized to the MSSM, and can serve also as supersymmetry-restoring counterterms. The paper provides full analytic results for the counterterms and gives one- and two-loop usage examples. The model file can simplify combining MSbar-parton distribution functions with supersymmetric renormalization or avoiding the renormalization …
The anomalous couplings of the top quark and the Higgs boson has been studied in an effective theory resulting in the framework of the minimal supersymmetric extension of the standard model (MSSM) when the heavy fields are integrated out. Constraints on the parameters of the model from the experimental data on the ratio $R_b={Γ(Z\to b\bar{b})/Γ(Z\to hadrons)}$ are derived.
A detailed analysis of the top-quark/squark quantum corrections to the lightest CP-even Higgs boson (h^0) self-couplings is presented in the MSSM. By considering the leading one-loop Yukawa-coupling contributions of O(m_t^4), we discuss the decoupling behaviour of these corrections when the top-squarks are heavy compared to the electroweak scale. As shown analytically and numerically, the large corrections can almost completely be absorbed into the h^0-boson mass. Our conclusion is that the h^0 self-couplings remain similar to the coupling of the SM Higgs boson for a heavy top-squark sector.
In this article we compute the two-loop SQCD corrections to Higgs-quark-quark couplings in the generic MSSM generated by diagrams involving squarks and gluinos. We give analytic results for the two-loop contributions in the limit of vanishing external momenta for general SUSY masses valid in the MSSM with general flavour-structure. Working in the decoupling limit (M_SUSY >> v) we resum all chirally enhanced corrections (related to Higgs-quark-quark couplings) up to order α_s^(n+1) tan(β)^n. This resummation allows for a more precise determination of the Yukawa coupling and CKM elements of the …
We consider tan(beta)-enhanced quantum effects in the minimal supersymmetric standard model (MSSM) including those from the Higgs sector. To this end, we match the MSSM to an effective two-Higgs doublet model (2HDM), assuming that all SUSY particles are heavy, and calculate the coefficients of the operators that vanish or are suppressed in the MSSM at tree-level. Our result clarifies the dependence of the large-tan(beta) resummation on the renormalization convention for tan(beta), and provides analytic expressions for the Yukawa and trilinear Higgs interactions. The numerical effect is analyze…
We show that the effects of heavy Higgs particles and heavy top-squarks in the one-loop self-couplings of the lightest CP-even MSSM Higgs boson decouple from the low energy theory when the self-couplings are expressed in terms of the Higgs boson mass M_h0. Our conclusion is that the h^0 self-interactions become very close to those of the SM Higgs boson and, therefore, MSSM quantum effects could only be revealed by very high precision experiments.
The top-Yukawa-coupling enhanced two-loop corrections to the charged Higgs-boson mass in the real MSSM are presented. The contributing two-loop self-energies are calculated in the Feynman- diagrammatic approach in the gaugeless limit with vanishing external momentum and bottom mass, within a renormalization scheme comprising on-shell and $\overline{\text{DR}}$ conditions. Numerical results illustrate the effect of the $\mathcal{O}{(α_t^2)}$ contributions and the importance of the two-loop corrections to the mass of the charged Higgs bosons.
The Higgs boson effective self-couplings $λ_{hhh}$ and $λ_{HHH}$ are calculated in the framework of the Minimal Supersymmetric Standard Model (MSSM) for the complete set of one-loop diagrams with one of the Higgs bosons off-shell. The comparison with previous results, where only the leading correction terms in the limiting case of large masses of virtual particles were calculated, is carried out. We analyse the dependence of the self-couplings on the energy and ${\tt tan} β$; it is demonstrated that the tree-level self-couplings could acquire substantial one-loop corrections, which could be ph…
We recalculate the branching ratios for $t\to cV$ ($V=g,γ,Z$) induced by SUSY FCNC couplings within the general unconstrained MSSM framework using mass eigenstate approach. Our results show that the branching ratios for these decays are larger than ones reported in previous literatures in the MSSM with R-parity conservation, and they can reach $\sim 10^{-4}$, $\sim 10^{-6}$, and $\sim 10^{-6}$, respectively, for favorable parameter values allowed by current precise experiments. Thus, the branching ratios for $t\to cg$ and $t\to cγ$ may be measurable at the LHC.
Results for the leading two-loop corrections of $\mathcal{O}{\left(α_t^2\right)}$ from the Yukawa sector to the Higgs-boson masses of the MSSM with complex parameters are presented. The corresponding self-energies and their renormalization have been obtained in a Feynman-diagrammatic approach. A numerical analysis of the new contributions is performed for the mass of the lightest Higgs boson, supplemented by the full one-loop result and the $\mathcal{O}{\left(α_t α_s\right)}$ terms including complex phases. In the limit of the real MSSM a previous result is confirmed.
Recent results for the leading $\mathcal{O}{\left(α_t^2\right)}$ two-loop corrections to the Higgs-boson masses of the MSSM with complex parameters are presented. The strategy of the Feynman-diagrammatic, analytical calculation is illustrated. Numerical analyses show agreement with a previous result in the limit of real parameters. Furthermore, the newly available dependence on complex MSSM parameters is investigated. Mass shifts by $\approx 1$GeV for different phases underline the importance of this contribution for a precise prediction of the Higgs-boson mass spectrum in the MSSM.
We present the two-loop SUSY-QCD corrections to the effective bottom Yukawa couplings within the minimal supersymmetric extension of the Standard Model. The effective Yukawa couplings include the resummation of the non-decoupling corrections Delta m_b for large values of tg(beta). We have derived the two-loop SUSY-QCD corrections to the leading SUSY-QCD and top-induced SUSY-electroweak contributions to Delta m_b. The scale dependence of the resummed Yukawa couplings is reduced from O(10%) to the per-cent level. These results reduce the theoretical uncertainties of the MSSM Higgs branching rati…
We calculate ~$\sin^2θ(M_Z)$ ~in the MSSM in terms of ~ $α_{EM}$, ~$G_F$, ~$m_t$, ~$\tanβ$ ~and SUSY mass parameters with the same accuracy as the present calculations of ~$\sin^2θ(M_Z)$ ~in the SM. We compare the results with the standard leading logarithmic approximation used for SUSY threshold corrections and find important differences in the case of light sparticles. We give approximate formulae connecting coupling constants in the SM and in the MSSM and comment on process dependence of such formulae. The obtained values of the MSSM couplings ~$α_i(M_Z)$ ~are used to investigate gauge coup…
Higgs Yukawa couplings to down-type fermions receive, in the MSSM, supersymmetric quantum corrections that can be of order 1 for large values of tanβ, provided μ\sim MSUSY. Therefore, a sensitive prediction for observables driven by any of these couplings can only be obtained after an all-order resummation of the large corrections. We perform this necessary step and show, as an example, the effect of the resummation on the computation of the p\bar{p},pp \to t\bar{b}H^{-} + X cross-section and on the branching ratio BR(b\to sγ) at the next-to-leading order.
The four self-couplings $λ_{hhh}$, $λ_{hhH}$, $λ_{hHH}$, $λ_{HHH}$ and decay width $Γ(H \to hh)$ are calculated taken into account one-loop $t,b,c$ - (s)quarks, $τ$ - (s)lepton corrections in the framework of the Minimal Supersymmetric Standard Model (MSSM). By the example of self-couplings dependencies from $ \tg β$ and \textrm{$M_A$}, it is shown, that calculated corrections can give the essential contribution to self-couplings and decay width determined at one-loop level. The radiative corrections account becomes necessary condition for performance of Higgs potential reconstruction procedur…
Trilinear couplings of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) can be measured through the multiple production of the lightest CP-even Higgs boson (h) at high-energy e^+e^- colliders. This includes the production of the heavier CP-even Higgs boson (H) via e^+e^- \to ZH, in association with the CP-odd Higgs boson (A) in e^+e^- \to AH, or via e^+e^- \to ν_e \barν_e H, with H subsequently decaying through H \to hh. These processes can enable one to measure the trilinear Higgs couplings λ_{Hhh} and λ_{hhh}, which can be used to theoretically reconstruct…
The possibility of generating a large trilinear $A_t$ soft supersymmetry breaking coupling at low energies through renormalisation group evolution in the 5D MSSM is investigated. Using the power law running in five dimensions and a compactification scale in the 10-$10^3$ TeV range, to show that gluino mass may drive a large enough $A_t$ to reproduce the measured Higgs mass and have a light stop superpartner below $\sim 1$ TeV as preferred by the fine tuning argument for the Higgs mass.
In the MSSM extended by a complete vectorlike family, precise top, bottom and tau Yukawa coupling unification can be achieved assuming SUSY threshold corrections which are typical for comparable superpartner masses. Furthermore, the unification is possible with a large unified coupling, implying that all three fermion masses can be simultaneously close to their IR fixed points. Assuming unified Yukawa couplings of order one or larger, the preferred common scale of new physics (superpartners and vectorlike matter) is in the 3 TeV to 30 TeV range, with larger couplings favoring smaller scales. S…
The evolution equations of the Yukawa couplings and quark mixings are derived for the one-loop renormalization group equations in the 5D Minimal Supersymmetric Standard Model on an {$S^1 / Z_2$} orbifold. Different possibilities for the matter fields are discussed such as the cases of bulk propagating or brane localised fields. We discuss in both cases the evolution of the mass ratios and the implications for the mixing angles.
In a theory with broken supersymmetry, gaugino couplings renormalize differently from gauge couplings, as do higgsino couplings from Higgs boson couplings. As a result, we expect the gauge (Higgs boson) couplings and the corresponding gaugino (higgsino) couplings to evolve to different values under renormalization group evolution. We re-examine the renormalization group equations (RGEs) for these couplings in the Minimal Supersymmetric Standard Model (MSSM). To include threshold effects, we calculate the $β$-functions using a sequence of (non-supersymmetric) effective theories with heavy parti…
The 100+ free parameters of the minimal supersymmetric standard model (MSSM) make it computationally difficult to compare systematically with data, motivating the study of specific parameter reductions such as the cMSSM and pMSSM. Here we instead study the reductions of parameter space implied by using minimal flavour violation (MFV) to organise the R-parity conserving MSSM, with a view towards systematically building in constraints on flavour-violating physics. Within this framework the space of parameters is reduced by expanding soft supersymmetry-breaking terms in powers of the Cabibbo angl…
This talk consists of two parts. In the first, the present experimental bounds on the anomalous couplings of the gauge bosons, based mainly on the LEP and Tevatron experiments, are reviewed. In the second part, the theorem of helicity conservation (HC) is presented, which should be valid in either the Standard Model (SM) or MSSM, for any two-body process at high energies and fixed angles. The energy-range for the HC validity is discussed and, under certain conditions, it should well be within the LHC or ILC range. Since all known anomalous couplings violate HC, its testing may provide a way fo…
We discuss the associated production of a light Higgs boson and a light chargino pair in the process e+e- -> h chi+ chi- in the Minimal Supersymmetric Standard Model (MSSM) at linear colliders (LC) with \sqrt s=500 GeV. This process gives direct informations about the Higgs-boson coupling to light charginos, that cannot be analyzed in decay processes due to phase-space restrictions. We compute total cross sections in the regions of the MSSM parameter space where the process cannot proceed via on-shell production and subsequent decay of either heavier charginos or pseudoscalar Higgs bosons A. C…
We present a detailed analysis of multiple production of the lightest CP-even Higgs boson (h) of the Minimal Supersymmetric Standard Model (MSSM) at high-energy e^+ e^- colliders. We consider the production of the heavier CP-even Higgs boson (H) via Higgs-strahlung e^+e^- \to ZH, in association with the CP-odd Higgs boson (A) in e^+e^- \to AH, or via the fusion mechanism e^+e^- \to ν_e \barν_e H, with H subsequently decaying through H \to hh, thereby resulting in a pair of lighter Higgs bosons (h) in the final state. These processes can enable one to measure the trilinear Higgs couplings λ_{Hh…
We propose a new mechanism for producing a Higgs boson mass near 125 GeV within the MSSM. By coupling the MSSM Higgs boson to a set of strongly interacting fields, large corrections to the Higgs quartic coupling are induced. Although the Higgs doublets do not participate in the strong dynamics, they feel the effects of the strongly coupled sector via (semi-)perturbative interactions. These same strong dynamics are also capable of generating the $μ$-term. Additionally, this strong sector is in the conformal window, which drives the couplings to an infrared fixed point and naturally generates mo…
In this paper we compute the $\mathcal{O}(α_s α_t)$ threshold corrections to the running strong coupling constant, the top-Yukawa coupling and the top-quark mass within the MSSM. These parameters present a non-decoupling behaviour with the supersymmetry scale $M_{\rm SUSY}$. Our numerical analysis shows that the mixed QCD-Yukawa corrections can amount to few GeV for the running top-quark mass and range at the percent level for the top-Yukawa coupling.
We evaluate the $t\bar{c}$ and $t\bar{u}$ productions at the LHC within the general unconstrained MSSM framework. We find that these single top quark productions induced by SUSY-QCD FCNC couplings have remarkable cross sections for favorable parameter values allowed by current low energy data, which can be as large as a few pb. Once large rates of the $t\bar{c}$ and $t\bar{u}$ productions are detected at the LHC, they may be induced by SUSY FCNC couplings. We show that the precise measurement of single top quark production cross sections at the LHC is a powerful probe for the details of the SU…
g g \to γ\bar{f}f scattering is discussed in the strongly interacting phase of the MSSM. The rate for the decay h \to γ\bar{f} f is computed in the MSSM and SM, and values of the Higgs-sfermion coupling needed for the former to dominate on the latter are identified. It is found that the MSSM signal dominates on the SM one for Higgs-sfermion couplings well below the one needed for developing stopponium bound states via Higgs mediation.
Run I of the LHC has not revealed any sign of new physics beyond the Standard Model (BSM). However, the discovery of an SM-like Higgs boson with mass around 125 GeV opens up new possibilities for probing various BSM scenarios with enlarged Higgs sectors and/or new particles affecting the loop-induced processes or opening new decay modes. We will present how we derive constraints on new physics from the Higgs measurements performed by the ATLAS and CMS collaborations. The impact of these measurements will then be assessed in the context of the general phenomenological Minimal Supersymmetric Sta…
When relating the strong coupling $α_s$, measured at the scale of the $Z$ boson mass, to its numerical value at some higher energy, for example the scale of Grand Unification, it is important to include higher order corrections both in the running of $α_s$ and the decoupling of the heavy particles. We compute the two-loop matching coefficients for $α_s$ within the Minimal Supersymmetric Standard Model (MSSM) which are necessary for a consistent three-loop evolution of the strong coupling constant. Different scenarios for the hierarchy of the supersymmetric scales are considered and the numeric…
We examined Z\ell^+\ell^- and Zb\bar b couplings in the minimal supersymmetric model (MSSM) with explicit R-parity violating interactions. We found the top quark L-violating couplings λ'_{i3k} and B-violating couplings λ''_{3j3} could give significant contributions through the top quark loops. To accomadate the latest R_{\ell} data, λ'_{i3k} are suject to stringent bounds, some of which can be much stronger than the current bounds. Within the current perturbative unitarity bound of 1.25 for λ''_{3j3}, the R_b value in R-violating MSSM agrees well with the experimental data at $2σ$ level, but m…
In this paper, we first demonstrate the existence of renormalization group invariant relations among the top, bottom Yukawa and the gauge colour couplings in the minimal supersymmetric SM. Based on this observation and assuming furthermore the existence of a renormalization group invariant relation among the trilinear couplings in the superpotential and the soft supersymmetry breaking sector, we obtain predictions for the Higgs masses and the supersymmetric spectrum.
We present a new geometric approach to the flavour decomposition of an arbitrary soft supersymmetry-breaking sector in the MSSM. Our approach is based on the geometry that results from the quark and lepton Yukawa couplings, and enables us to derive the necessary and sufficient conditions for a linearly-independent basis of matrices related to the completeness of the internal [SU(3) x U(1)]^5 flavour space. In a second step, we calculate the effective Yukawa couplings that are enhanced at large values of tan(beta) for general soft supersymmetry-breaking mass parameters. We highlight the contrib…
We present the full two-loop beta-functions for the MSSM including R-parity violating couplings. We analyse the effect of two-loop running on the bounds on R-parity violating couplings, on the nature of the LSP and on the stop masses.
We compute the one-loop radiative corrections to the masses of the top quark, the stop squarks and the gluino in the Minimal Supersymmetric Standard Model. We include the loops controlled by the strong coupling constant and the top Yukawa coupling, neglecting those controlled by the $SU(2) \times U(1)$ gauge couplings and by other Yukawa couplings. We find that the significant scale-dependence of the renormalization-group-improved tree-level expressions is almost completely removed. Even for natural choices of the renormalization scale, corrections can be numerically relevant. Our results shou…
In the MSSM, the presence of CP phases can have a significant impact on the neutralino relic abundance. These phase effectsare on the one hand due to shifts in the masses, on the other hand due to modifications of the couplings. Typical variations in Omega h^2 solely from modifications in the couplings are of order 10%-100%.
We present several advances in the effective field theory calculation of the Higgs mass in MSSM scenarios with heavy superparticles. In particular, we compute the dominant two-loop threshold corrections to the quartic Higgs coupling for generic values of the relevant SUSY-breaking parameters, including all contributions controlled by the strong gauge coupling and by the third-family Yukawa couplings. We also study the effects of a representative subset of dimension-six operators in the effective theory valid below the SUSY scale. Our results will allow for an improved determination of the Higg…
Including contributions of scale-dependent vacuum expectation values of Higgs scalars, we derive new one-loop formulas analytically for running quark-lepton masses at higher scales in MSSM. Apart from the gauge-coupling dependence being different from earlier formulas, the third-generation- Yukawa-coupling effects are absent in the masses of the first two generations. While predicting the masses and $\tanβ$ numerically, we also include two-loop effects.
We consider the leading one-loop Yukawa-coupling corrections to the h^0 b b-bar coupling at O(m_t^2)in the MSSM in the decoupling limit. The decoupling behavior of the corrections from the various MSSM sectors is analyzed in the case of having some or all of the supersymmetric mass parameters and/or the CP-odd Higgs mass large as compared to the electroweak scale.
Results for the leading two-loop corrections of $\mathcal{O}{\left(α_t^2\right)}$ from the Yukawa sector to the Higgs-boson mass spectrum of the MSSM with complex parameters are presented, with details of the analytical calculation performed in the Feynman-diagrammatic approach using a mixed $\left.\text{on-shell}\middle/\,\overline{\text{DR}}\right.$ scheme that can be directly matched onto the higher-order terms in the code ${\tt FeynHiggs}$. Numerical results are shown for the masses and mixing effects in the neutral Higgs-boson sector and their variation with the phases of the complex para…
In the light of the gathering evidence for $ν_μ-ν_τ$ neutrino oscillations, coming in particular from the Super-Kamiokande data on atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa couplings within the minimal supersymmetric extension of the Standard Model (MSSM). Guided by a range of different grand-unified models, we stress the relevance of large mixing in the lepton sector for the question of bottom-tau Yukawa coupling unification. We also discuss the dependence of the favoured value of $\tanβ$ on the characteristics of the high-energy quark and lepton mass matrices. …
In the decoupling limit, $M^2_{A^0} \gg M^2_Z$, the heavy CP-even, CP-odd and charged Higgs boson masses are nearly degenerate, $\sin(β-α)$ approaches 1, and the lightest CP-even Higgs boson almost displays the same properties as the Standard Model Higgs boson. But the stop and sbottom sector can change this pattern through radiative corrections. We find that there are parameter regions at small, moderate and large $\tanβ$ in MSSM under experimental constraints of $(g-2)_μ$ and $b\to sγ$, where $\sin^2(β-α)$ is damped (say below 0.8), which has a significant effect on Higgs couplings $g_{h^0VV…
We present the calculation of the light neutral CP-even Higgs mass in the MSSM for a heavy SUSY spectrum by resumming enhanced terms through fourth logarithmic order (N$^3$LL), keeping terms of leading order in the top Yukawa coupling $α_t$, and NNLO in the strong coupling $α_s$. To this goal, the three-loop matching coefficient for the quartic Higgs coupling of the SM to the MSSM is derived to order $α_t^2α_s^2$ by comparing the perturbative EFT to the fixed-order expression for the Higgs mass. The new matching coefficient is made available through an updated version of the program Himalaya. …
We improve the determination of the Higgs-boson mass in the MSSM with heavy superpartners, by computing the two-loop threshold corrections to the quartic Higgs coupling that involve both the strong and the electroweak gauge couplings. Combined with earlier results, this completes the calculation of the two-loop QCD corrections to the quartic coupling at the SUSY scale. We also compare different computations of the relation between the quartic coupling and the pole mass of the Higgs boson at the EW scale. We find that the numerical impact of the new corrections on the prediction for the Higgs m…
In the "intense--coupling" regime all Higgs bosons of the Minimal Supersymmetric extension of the Standard Model (MSSM) are rather light and have comparable masses of O(100 GeV). They couple maximally to electroweak gauge bosons, and for large ratios of the vacuum expectation values of the two Higgs doublet fields, tanβ, they interact strongly with the standard third generation fermions. We present in this note a comprehensive study of this scenario. We summarize the main phenomenological features, and the accordance with the direct constraints from Higgs boson searches at LEP2 and the Tevatro…
We analyze the implications of the infrared quasi fixed point solution for the top quark mass in the Minimal Supersymmetric Standard Model. This solution could explain in a natural way the relatively large value of the top quark mass and, if confirmed experimentally, may be suggestive of the onset of nonperturbative physics at very high energy scales. In the framework of grand unification, the expected bottom quark - tau lepton Yukawa coupling unification is very sensitive to the fixed point structure of the top quark mass. For the presently allowed values of the electroweak parameters and the…
Supersymmetric extensions of the standard model generically contain additional sources of CP violation. We discuss how at one loop a potentially large CP violating coupling of the lightest Higgs, h^0, to leptons is induced in the minimal supersymmetric standard model (MSSM). The CP violating couplings of h^0 in extensions of the MSSM, such as the next-to-minimal supersymmetric standard model (NMSSM) are also considered. We indicate how this CP violation might be observed; in particular a polarization-dependent production asymmetry, in the context of a muon collider, provides a means to access …
We show that the upper bound on the lightest Higgs mass in the MSSM is relaxed by introducing a singlet which couples to the Higgs fields, even at a large tan beta region, preferable for explaining the muon anomalous magnetic moment. In the models of a singlet extension, it is known that the upper bound is relaxed by a tree-level contribution, especially at small tan beta region. For large tan beta, however, the requirement for the perturbativity on the singlet-Higgs coupling up to the GUT scale prevents the lightest Higgs from obtaining a large tree-level mass. We construct an explicit UV com…
We consider the renormalisation of the Fayet-Iliopoulos D-term in a softly-broken supersymmetric gauge theory with a non-simple gauge group containing an abelian factor, and present the associated beta-function through three loops. We also include in an appendix the result for several abelian factors. We specialise to the case of the minimal supersymmetric standard model (MSSM), and investigate the behaviour of the Fayet-Iliopoulos coupling for various boundary conditions at the unification scale. We focus particularly on the case of non-standard soft supersymmetry breaking couplings, for whic…
An elementary Higgs boson, which is the remnant of the spontaneous symmetry breaking mechanism in the Standard Model, remains one of the most elusive particles. If a Higgs boson candidate is found at future accelerators, it becomes necessary to determine its properties, beyond the mass, production cross section and decay rates. The other crucial properties relate to the self-couplings of the Higgs boson, which are necessary to reconstruct the Higgs potential, and thereby confirm the mechanism of spontaneous symmetry breaking. In this paper we review the question of the measurability of some of…
The decoupling properties of the Higgs sector in the Minimal Supersymmetric Standard Model (MSSM) imply that a light CP-even Higgs boson discovered at the Tevatron or LHC may closely resemble the Standard Model (SM) Higgs boson. In this paper, we investigate how precision measurements of Higgs properties at a Linear Collider (LC) can distinguish between a CP-even Higgs boson of the MSSM and the SM Higgs boson. We review the expected theoretical behavior of the partial widths and branching ratios for decays of the neutral MSSM Higgs bosons with significant couplings to the W and Z bosons, inclu…
We consider the Minimal Supersymmetric extension of the Standard Model in the regime where the supersymmetric breaking scale is extermely large. In this MSSM, not only the Higgs masses will be affected by large radiative corrections, the dominant part of which is provided by the third generation quark/squark sector, but also the various self-couplings among the Higgs states. In this note, assuming that squarks are extremely heavy, we evaluate the next-to-leading order radiative corrections to the two neutral CP-even Higgs self-couplings $λ_{H h h}$ and $λ_{h h h}$ and to the partial decay widt…
