Indirect information about the possible scale of supersymmetry (SUSY) breaking can be obtained from the comparison of precisely measured observables (and also of exclusion limits) with accurate theory predictions incorporating SUSY loop corrections. Recent results are reviewed obtained from a combined analysis of the most sensitive electroweak precision observables (EWPO), M_W, sin^2_theta^eff, Gamma_Z, (g-2)_μand M_h, and B-physics observables (BPO), BR(b -> s γ), BR(B_s -> μ^+μ^-), BR(B_u -> τν_τ) and ΔM_{B_s}. Assuming that the lightest supersymmetric particle (LSP) provides the cold dark matter density preferred by WMAP and other cosmological data, χ^2 fits are performed to the parameters of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the SUSY-breaking parameters are universal at the GUT scale, and the non-universal Higgs model (NUHM), in which this constraint is relaxed for the soft SUSY-breaking contributions to the Higgs masses. Within the CMSSM indirect bounds on the mass of the lightest CP-even Higgs boson are derived.
I present applications of a master formula for next-to-next-to-leading order soft and virtual QCD corrections to various electroweak, Higgs, and supersymmetric processes. They include Drell-Yan and charged Higgs production, single-top production in flavor-changing neutral-current processes, and squark and gluino production.
SUSY models with a gauge singlet easily allow for a strongly first order electroweak phase transition (EWPT). We discuss the wall profile, in particular transitional CP violation during the EWPT. We calculate CP violating source terms for the charginos in the WKB approximation and solve the relevant transport equations to obtain the generated baryon asymmetry.
These lectures are a very brief introduction to low energy supersymmetry (SUSY). The approach to the construction of SUSY Lagrangians based on the superfield formalism is considered. The minimal supersymmetric standard model (MSSM) is specified. The breakdown of gauge symmetry and Higgs phenomenology within the simplest SUSY extensions of the standard model (SM) are briefly reviewed. The upper bound on the mass of the lightest Higgs boson and little hierarchy problem in SUSY models are discussed.
Enhanced radiative corrections generated in SUSY extensions of the Standard Model make the fit of the precision data ($Z$-boson decay parameters and $W$-boson mass) worse. This negative effect is washed out for heavy enough squarks due to decoupling property of SUSY models. We find that even for light squarks the enhanced radiative corrections can be small. In this case substantial $\tilde{t}_L \tilde{t}_R$ mixing is necessary.
We compute the MSSM one-loop contributions to the asymptotic energy behaviour of fermion-antifermion pair production at future lepton-antilepton colliders. Besides the conventional logarithms of Renormalization Group origin, extra SUSY linear logarithmic terms appear of "Sudakov-type". In the TeV range their overall effect on a variety of observables can be quite relevant and drastically different from that obtained in the SM case.
Large top quark mass is responsible for the enhancement of the oblique radiative corrections in SUSY models. We present the analytical formulas for these corrections to the $W$-boson mass $m_W$ and to $Z$ $l^+ l^-$ coupling constants. The comparison with the result of the Standard Model fit is made.
We review the mechanism of radiative electroweak symmetry breaking taking place in SUSY versions of the standard model. We further discuss different proposals for the origin of SUSY-breaking and the corresponding induced SUSY-breaking soft terms. Several proposals for the understanding of the little hierarchy problem are critically discussed.
We present a global $χ^2$ analysis of electroweak data, including fermion masses and mixing angles, in SO(10) SUSY GUTs. Just as precision electroweak data is used to test the Standard Model, the well determined Standard Model parameters are the precision electroweak data for testing theories beyond the Standard Model. In this talk we use the latest experimentally measured values for these parameters. We study several models discussed in the literature. One of these models provides an excellent fit to the low energy data with $χ^2 \sim 1$ for 3 degrees of freedom. We present our predictions fo…
In collaboration with G.D. Moore, the electroweak phase transition in the minimal supersymmetric standard model is studied using the two-loop effective potential. We make a comprehensive search of the MSSM parameter space consistent with electroweak baryogenesis, taking into account various factors: the latest experimental constraints on the Higgs boson mass and the rho parameter, the possibility of significant squark and Higgs boson mixing, and the exact rate of bubble nucleation and sphaleron transitions. Most of the baryogenesis-allowed regions of parameter space will be probed by LEP 200, …
We consider the production of neutralino, chargino, and charged Higgs boson pairs in the MSSM framework at future $e^+e^-$ colliders. We show that, for c.m. energies in the one TeV range and in a ``moderately'' light SUSY scenario, a combined analysis of the slopes of these production cross sections could lead to a strong consistency test involving the soft supersymmetric breaking parameters $M_1$, $M_2$, the Higgsino parameter $μ$, and $\tanβ$.
A $χ^2$ analysis of several SUSY GUTs recently discussed in the literature is presented. We obtain global fits to electroweak data, which include gauge couplings, gauge boson masses, BR($b\to sγ$) and masses of fermions of all three generations and their mixing angles. Thus we are able to test gauge unification, radiative electroweak symmetry breaking, SUSY sector (- in the context of supergravity induced SUSY breaking) and the Yukawa sector in each particular model self-consistently. One of the models studied provides a very good fit with $χ^2 \sim 1$ for 3 degrees of freedom, in a large regi…
We present the details of a global $χ^2$ analysis of electroweak data, including fermion masses and mixing angles, in SO(10) SUSY GUTs. Just as precision electroweak data is used to test the Standard Model, the well determined Standard Model parameters are the precision electroweak data for testing theories beyond the Standard Model. In this paper we use the latest experimentally measured values for these parameters. We study several models discussed in the literature. One of these models provides an excellent fit to the low energy data with $χ^2 \sim 1$ for 3 degrees of freedom. We present gr…
We propose a new electroweak baryogenesis scenario in high-scale supersymmetric (SUSY) models. We consider a singlet extension of the minimal SUSY standard model introducing additional vector-like multiplets. We show that the strongly first-order phase transition can occur at a high temperature comparable to the soft SUSY breaking scale. In addition, the proper amount of the baryon asymmetry of the universe can be generated via the lepton number violating process in the vector-like multiplet sector. The typical scale of our scenario, the soft SUSY breaking scale, can be any value. Thus our new…
We introduce the idea of bosonic see-saw mechanism in analogy with the see-saw mechanism. Bosonic see-saw is a new symmetry breaking mechanism and we apply it to explain electroweak symmetry breaking as an inevitable consequence of supersymmetry breaking. The breaking of electroweak symmetry occurs at tree level once supersymmetry is broken. Absence of color/charge breaking in this model is related to doublet-triplet splitting in grand unified theory. An extension of MSSM with a weak triplet shows very interesting results especially when mu =0. It provides the most natural understanding of why…
We analyze the effective 3 dimensional theory previously constructed for the MSSM and multi-Higgs models to determine the regions of parameter space in which the electroweak phase transition is sufficiently strong for a $B+L$ asymmetry to survive in the low temperature phase. We find that the inclusion of all supersymmetric scalars and all 1-loop corrections has the effect of enhancing the strength of the phase transition. Without a light stop or extension of the MSSM the phase transition is sufficiently first order only if the lightest Higgs mass $M_{h}\lsi 70$ GeV and $tanβ\lsi 1.75$.
The MSSM with a light right-handed stop and supersymmetric models with a singlet whose vev is comparable to that of the SU(2)_W Higgs allow for a strongly first-order electroweak phase transition even for a mass of the lightest Higgs around 100 GeV. After a short review of the standard model situation we discuss these supersymmetric models. We also compare perturbative calculations based on the dimensionally reduced 3-dimensional action with lattice results and present an analytic procedure based on an analogue of the stochastic vacuum model of QCD to estimate the nonperturbative contributions…
SUSY models with a gauge singlet easily allow for a strong first order electroweak phase transition (EWPT) if the vevs of the singlet and Higgs fields are of comparable size. We discuss the profile of the stationary expanding bubble wall and CP-violation in the effective potential, in particular transitional CP-violation inside the bubble wall during the EWPT. The dispersion relations for charginos contain CP-violating terms in the WKB approximation. These enter as source terms in the Boltzmann equations for the (particle--antiparticle) chemical potentials and fuel the creation of a baryon asy…
The two-loop QCD corrections to the $ρ$ parameter are derived in the Minimal Supersymmetric Standard Model. They turn out to be sizable and modify the one-loop result by up to 30%. Furthermore exact results for the gluonic corrections to $Δr$ are presented and compared with the leading contribution entering via the $ρ$ parameter.
The SUSY-EW one-loop quantum contributions to flavour-changing MSSM Higgs-boson decays into $b \bar s$ and $s \bar b$ are computed and discussed. We use the full diagrammatic approach that is valid for all $\tan β$ values and do not rely on the mass-insertion approximation for the characteristic flavour-changing parameter. We analyze in full detail the dependence of these flavour-changing partial widths on all the relevant MSSM parameters and also study the non-decoupling behaviour of these widths with the SUSY mass parameters. We find that these contributions are sizable as compared to the SM…
We explore the phenomenological predictions of a supersymmetric standard model, with a large extra dimension and unifying gauge couplings. The modified five dimensional renormalisation group equations make it possible to obtain light, maximally mixed stops, with a low scale of supersymmetry breaking and a low unification scale. This allows the fine-tuning to be lowered right down to the barrier coming directly from experimental lower limits on the stop masses. We also show that attempts at modifying the SUSY breaking pattern to obtain more natural soft terms at the high scale do not give the e…
We consider the production of squarks and gluinos at hadronic colliders. An overview over the class of processes is given. We investigate in detail the tree-level and higher order EW contributions to the cross sections. Special care has to be taken to obtain infrared finite observables. We study numerically stop--anti-stop and squark--gluino production at the LHC.
One-loop contributions to the Higgs potential at finite temperatures are discussed in the supersymmetric standard model with four Higgs doublet chiral superfields as well as a pair of charged singlet chiral superfields. The mass of the lightest Higgs boson $h$ is determined only by the D-term at the tree-level in this model, while the triple Higgs boson coupling for $hhh$ can receive a significant radiative correction. The same nondecoupling effect can also contribute to realize the sufficient first order electroweak phase transition, which is required for a successful scenario of electroweak …
We compute supersymmetric QCD and supersymmetric electroweak corrections to the b and t quark masses and to the $τ$ lepton mass in the presence of CP phases valid for all $\tanβ$. The analysis includes one loop diagrams arising from the exchange of gluinos, charginos and neutralinos. We find that the CP effects can change both the magnitude as well as the sign of the supersymmetric loop correction. In the region of parameter space studied we found that the numerical size of the correction to the b quark mass can be as large as 30 percent and to the $τ$ lepton mass as much as 5 percent. For the…
The light slepton-sneutrino scenario with non-universal scalar masses at the GUT scale is preferred by the electroweak precision data. Though a universal soft breaking mass at or below the Plank scale can produce the required non-universality at the GUT scale through running, such models are in conflict with the stability of the electroweak symmetry breaking vacuum. If the supergravity motivated idea of a common scalar mass at some high scale along with light sleptons is supported by future experiments that may indicate that we are living in a false vacuum. In contrast SO(10) D-terms, which ma…
We consider the production of SUSY scalar pairs at lepton colliders, for c.m. energies much larger than the mass of the heaviest SUSY (real or virtual) particle involved in the process. In that energy regime, we derive the leading and subleading terms of the electroweak Sudakov logarithms in the MSSM, first working at one loop with physical states and then resumming to all orders with asymptotic expansions. We show that the first order of the resummed expression reproduces the physical one loop approximation, and compute systematically the possible effects on various observables both at one lo…
We present the full $\mathcal{O}(α_s)$ supersymmetric QCD corrections for stop-anti-stop annihilation into electroweak final states within the Minimal Supersymmetric Standard Model (MSSM). We also incorporate Coulomb corrections due to gluon exchange between the incoming stops. Numerical results for the annihilation cross sections and the predicted neutralino relic density are presented. We show that the impact of the radiative corrections on the cosmologically preferred region of the parameter space can become larger than the current experimental uncertainty, shifting the relic bands within t…
The absence of any signal of supersymmetry (SUSY) at the LHC has raised the SUSY particle mass scale compared to $Z$ boson mass $M_Z$. We investigate the naturalness of the electroweak symmetry breaking after considering radiative symmetry breaking along with 125 GeV Higgs mass. We find that the important quantity to measure the naturalness of the hierarchy between the SUSY scale and $M_Z$ is the separation between the radiative symmetry breaking scale, i.e., where $m_{H_u}^2+μ^2$ turns negative for large $\tanβ$ case ($μ$ is the Higgsino mass and $m_{H_u}$ is the SUSY breaking up-type Higgs b…
We consider an extended Higgs sector that arises as a low-energy description of a strongly-coupled SUSY gauge theory. This model predicts the presence of extra superfields that couple with the Higgs superfields through large coupling constants. Large radiative corrections involving the extra fields can realize strongly first order electroweak phase transition, which is a vital requirement for electroweak baryogenesis scenario. At the same time, the large radiative corrections lead to significant deviations in the Higgs boson triple coupling and Higgs-to-diphoton branching ratio, which are test…
For superpartner masses not much heavier than the weak scale $M=M_{\rm W}$, large logarithmic corrections of the Sudakov type arise at TeV energies. In this paper we summarize recent results of supersymmetric (susy) electroweak radiative corrections for sfermion and charged Higgs production at $e^+e^-$ colliders in the MSSM. The results are given to subleading logarithmic (SL) accuracy to all orders in perturbation theory in the ``light'' susy-mass scenario. Prospects for the determination of $\tan β\geq 10$ are discussed which is independent of soft susy-breaking terms to SL accuracy.
In a class of supersymmetric gauge theories with asymptotic freedom, the low energy effective theory below the confinement scale is described by the composite superfields of the fundamental representation fields. Based on the supersymmetric gauge theory with N_c=2 and N_f=3 with an additional unbroken Z_2 symmetry, we propose a new model where neutrino masses, dark matter, and baryon asymmetry of the Universe can be simultaneously explained by physics below the confinement scale. This is an example for the ultraviolet complete supersymmetric extension of so-called radiative seesaw scenarios wi…
The electroweak (EW) symmetry breaking in the simplest supersymmetric (SUSY) extensions of the standard model (SM), i.e. minimal and next-to-minimal supersymmetric standard models (MSSM and NMSSM), is considered. The spectrum of the Higgs particles, upper bound on the mass of the lightest Higgs boson and little hierarchy problem are discussed. The breakdown of gauge symmetry and Higgs phenomenology within the E6 inspired SUSY models with extra U(1)' factor are briefly reviewed.
In a recent paper, we proposed a new class of supersymmetric SO(10) models for neutrino masses where the TeV scale electroweak symmetry is SU(2)_L\times SU(2)_R\times U(1)_{B-L} making the associated gauge bosons W_R and Z' accessible at the Large Hadron Collider. We showed that there exists a domain of Yukawa coupling parameters and symmetry breaking patterns which give an excellent fit to all fermion masses including neutrinos. In this sequel, we discuss an alternative Yukawa pattern which also gives good fermion mass fit and then study the predictions of both models for proton lifetime. Con…
We evaluate the supersymmetric (SUSY) electroweak corrections to the effect of parity nonconservation in $q {\bar q} \to t {\bar t}$ production at the Fermilab Tevatron predicted by the Minimal Supersymmetric Model (MSSM). We find that the parity nonconserving asymmetry from the SUSY electroweak and SUSY Yukawa loop corrections predicted by the minimal supergravity (mSUGRA) model and the MSSM models with scenarios motivated by current data is about one percent. It will be challenging to observe such a small asymmetry at the Tevatron with 10 fb^{-1} of luminosity. It could however be observable…
In the framework of the Constrained Minimal Supersymmetric Standard Model (CMSSM) we evaluate the electroweak fine tuning measure that provides a quantitative test of supersymmetry as a solution to the hierarchy problem. Taking account of current experimental constraints we compute the fine tuning at two-loop order and determine the limits on the CMSSM parameter space and the measurements at the LHC most relevant in covering it. Without imposing the LEPII bound on the Higgs mass, it is shown that the fine tuning computed at two-loop has a minimum $Δ=8.8$ corresponding to a Higgs mass $m_h=114\…
We calculate the region of the MSSM parameter space (i.e. $M_{1/2}$, $m_{0}$, $μ$, \ldots) compatible with a correct electroweak breaking and a realistic top-quark mass. To do so we have included {\em all} the one-loop corrections to the effective potential $V_{1}$ and checked their importance in order to obtain consistent results. We also consider the fine-tuning problem due to the enormous dependence of $M_{Z}$ on $h_{t}$ (the top Yukawa coupling), which is substantially reduced when the one-loop effects are taken into account. We also explore the reliability of the so-called "standard" crit…
We construct a calculable model of electroweak symmetry breaking in which the Higgs doublet emerges from the meta-stable SUSY breaking sector as a pseudo Nambu-Goldstone boson. The Higgs boson mass is further protected by the little Higgs mechanism, and naturally suppressed by a two-loop factor from the SUSY breaking scale of 10 TeV. Gaugino and sfermion masses arise from standard gauge mediation, but the Higgsino obtains a tree-level mass at the SUSY breaking scale. At 1 TeV, aside from new gauge bosons and fermions similar to other little Higgs models and their superpartners, our model predi…
In supersymmetric scenarios with a low scale of SUSY breaking [sqrt{F}=O(TeV)] the conventional MSSM Higgs sector can be substantially modified, mainly because the Higgs potential contains additional effective quartic terms. The Higgs spectrum can be dramatically changed, and the lightest state can be much heavier than in usual SUSY scenarios. Novel opportunities for electroweak breaking arise, and the electroweak scale may be obtained in a less fine-tuned way for wide ranges of tan(beta) and the Higgs mass, offering a possible solution to the MSSM fine-tuning problem.
For the search for electroweak particles in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We review the evaluation of the cross sections for the chargino, neutralino and scalar lepton production at e+e- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the various production mechanisms, including soft and hard photon radiation. The dependence of the chargino/neutralino/slepton cross sections on…
For the search for electroweak (EW) particles in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We evaluate the cross sections for the chargino, neutralino and slepton production at e+e- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of all possible production channels including soft and hard photon radiation. The dependence of the cross sections on the relevant cMSSM parameters is analyzed nume…
Some possible tests of physics beyond the Standard Model in the next generation collider experiments are considered. The main emphasis is put on the processes which may be studied in the non-conventional $e^-e^-$, $e^-γ$ and $γγ$ operation modes of the next linear collider (NLC). In particular, sensitivity of the NLC for testing the gauge boson self-interactions through the reaction $e^-γ\to W^-ν$ is investigated. High energy tests of the susy and non-susy left-right symmetric models are analysed.
We study the stability of the neutral- and charged-current Drell-Yan process in association with a jet as a standard candle at the LHC under the inclusion of O(alpha_s) supersymmetric QCD (SQCD) corrections within the MSSM. We include the decay of the electroweak gauge boson into dileptons, i.e. we consider the production of charged lepton--anti-lepton or lepton-neutrino final states with one hard jet. We find that the SQCD corrections are negligible for the integrated cross section. Only at high lepton transverse momentum can they induce effects of the percent level.
This lecture discusses the Higgs boson sector of the SM and the MSSM, including their connection to electroweak precision physics and the searches for SM and SUSY Higgs bosons at the LHC.
We present results for Delta I=3/2 and Delta S=2 matrix elements relevant for CP violation in K->Pi Pi decays and for the K_S-K_L mass difference in the standard model and beyond. They were obtained with Neuberger fermions on quenched gauge configurations generated with the Wilson plaquette action at beta=6.0 on an 18^3x64 lattice.
After motivation and short presentation of the minimal supersymmetric model with R-symmetry (MRSSM), we address the question of accomodating the measured Higgs boson mass in accordance with electroweak precision observables and LHC constraints.
We show that the present LEPI lower bound on the Standard Model Higgs boson mass ($M_H\gsim60\GeV$) applies as well to the lightest Higgs boson ($h$) of the minimal $SU(5)$ and no-scale flipped $SU(5)$ supergravity models. This result would persist even for the ultimate LEPI lower bound ($M_H\gsim70\GeV$). We show that this situation is a consequence of a decoupling phenomenon in the Higgs sector driven by radiative electroweak breaking for increasingly larger sparticle masses, and thus it should be common to a large class of supergravity models. A consequence of $m_h\gsim60\GeV$ in the minima…
Indirect information about the possible scale of supersymmetry (SUSY) breaking is provided by B physics observables (BPO) as well as electroweak precision observables (EWPO). We review the combination of the constraints imposed by recent measurements of the BPO BR(b -> s gamma), BR(B_s -> mu+ mu-), BR(B_u -> tau nu_tau) and Delta M_{B_s} with those obtained from the experimental measurements of the EWPO M_W, sin^2 theta_eff, Gamma_Z, (g-2)_mu and M_h. We perform a chi^2 fit to the parameters of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the SUSY-br…
Considerations from electroweak naturalness and stringy naturalness imply a little hierarchy in supersymmetric models where the superpotential higgsino mass parameter mu is of order the weak scale whilst the soft SUSY breaking terms may be in the (multi-) TeV range. In such a case, discovery of SUSY at LHC may be most likely in the higgsino pair production channel. Indeed, ATLAS and CMS are performing searches in the higgsino mass discovery plane of m(chi_2^0) vs. Δm^0 = m(chi_2^0)-m(chi_1^0). We examine several theoretical aspects of this discovery plane in both the gravity-mediation NUHM2 mo…
Electroweak precision tests of the SM and MSSM as well as searches for Supersymmetric Particles and Higgs bosons at LEP II and their significance within the MSSM are discussed. Invited talk presented at the EPIPHANY Conf. in Cracow, Jan. 3-7, 1997.
Weak scale supersymmetry (SUSY) remains a prime explanation for the radiative stability of the Higgs field. A natural account of the Higgs boson mass, however, strongly favors extensions of the Minimal Supersymmetric Standard Model (MSSM). A plausible option is to introduce a new supersymmetric sector coupled to the MSSM Higgs fields, whose associated states resolve the little hierarchy problem between the third generation squark masses and the weak scale. SUSY also accomodates a weakly interacting cold dark matter (DM) candidate in the form of a stable neutralino. In minimal realizations, the…
Direct searches and the hints for the Higgs at ~125 GeV put increasing pressure on simple models of SUSY breaking, in particular (but not exclusively) on those that automatically solve the flavour problem, such as gauge mediation. SUSY-breaking parameters are pushed to higher and higher values, increasing the fine-tuning required to achieve electroweak symmetry breaking at the observed scale. In this note we consider the situation for models which do not attempt to solve the flavour problem. To treat them on equal footing, we consider the combined fine-tuning arising from electroweak symmetry …
I discuss some essential features of the electroweak hierarchy problem and the ensuing motivation for weak-scale supersymmetry. Taking the hierarchy problem seriously, null results in searches for SUSY at the LHC favor specific regions of SUSY parameter space. More broadly, they suggest investigating a variety of alternative approaches to the hierarchy problem with diverse experimental signatures.
We address the compatibility of a light sbottom (mass $2\sim 5.5 \gev$) and a light gluino (mass $12\sim 16 \gev$) with electroweak precision measurements. Such light particles have been suggested to explain the observed excess in the $b$ quark production cross section at the Tevatron. The electroweak observables may be affected by the sbottom and gluino through the SUSY-QCD corrections to the $Zbb$ vertex. We examine, in addition to the SUSY-QCD corrections, the electroweak corrections to the gauge boson propagators from the stop which are allowed to be light from the SU(2)$_L$ symmetry. We f…
(Abridged) We report on a complete study of the single top-quark production by direct supersymmetric flavor-changing neutral-current (FCNC) processes at the LHC. The total cross section for pp(gg)->t\bar{c}+\bar{t}c is computed at the 1-loop order within the unconstrained Minimal Supersymmetric Standard Model (MSSM). The present study extends the results of the supersymmetric strong effects (SUSY-QCD), which were advanced by some of us in a previous work, and includes the computation of the full supersymmetric electroweak corrections (SUSY-EW). Our analysis of pp(gg)->t\bar{c}+\bar{t}c in the …
If weak scale supersymmetry (SUSY) is to somehow explain the radiative stability of the Higgs boson mass, it is likely that non-minimal variants of SUSY models should be considered. Under the assumption that the dark matter of the universe is comprised of neutralinos, recent limits from direct detection experiments as well as dark matter abundance measurements place stringent bounds on the naturalness of minimal supersymmetric models. We show that even non-minimal models introducing moderately decoupled new physics in order to address the Higgs boson mass problem face similar issues, with one …
We present a complete 1-loop study of the electroweak corrections to the process $ug\to dW^+$ in MSSM and SM. The occurrence of a number of remarkable properties in the behavior of the helicity amplitudes at high energies is stressed, and the crucial role of the virtual SUSY contributions in establishing them, is emphasized. The approach to asymptopia of these amplitudes is discussed, comparing the effects of the logarithmic and constant contributions to the mass suppressed ones, which are relevant at lower energies. Applying crossing to $ug\to d W^+$, we obtain all subprocesses needed for the…
R-symmetry is a fundamental symmetry which can solve the SUSY flavor problem and relax the search limits on SUSY masses. Here we provide a complete next-to-leading order computation and discussion of the lightest Higgs boson mass, the W boson mass and muon decay in the minimal R-symmetric SUSY model (MRSSM). This model contains non-MSSM particles including a Higgs triplet, Dirac gauginos and higgsinos, and leads to significant new tree-level and one-loop contributions to these observables. We show that the model can accommodate the measured values of the observables for interesting regions of …
Particle physics models with Peccei-Quinn (PQ) symmetry breaking as a consequence of supersymmetry (SUSY) breaking are attractive in that they solve the strong CP problem with a SUSY DFSZ-like axion, link the SUSY breaking and PQ breaking intermediate mass scales and can resolve the SUSY mu problem with a naturalness-required weak scale mu term whilst soft SUSY breaking terms inhabit the multi-TeV regime as required by LHC sparticle mass limits and the Higgs mass measurement. On the negative ledger, models based on global symmetries suffer a generic gravity spoliation problem. We present a mod…
We assume that the scale of the soft supersymmetry breaking masses, m_SUSY, sliding at tree level, is fixed by the minimization of the potential, but without a significant contribution of the cosmological term. Under these assumptions the electroweak breaking scale gets related to m_SUSY by a loop factor. Applied to specific models of supersymmetry breaking, this mechanism naturally gives sparticles slightly above all present accelerator bounds.
Precision measurements, now and at a future linear electron-positron collider (ILC), can provide indirect information about the possible scale of supersymmetry. Performing a chi^2 analysis, we illustrate the present-day and possible future ILC sensitivities within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), varying the parameters so as to obtain the cold dark matter density allowed by WMAP and other cosmological data. The current data are in very good agreement with the CMSSM prediction for tan beta = 10, with a clear preference for relatively small values o…
