We consider the fully constrained version of the next-to-minimal supersymmetric extension of the standard model (cNMSSM) in which a singlet Higgs superfield is added to the two doublets that are present in the minimal extension (MSSM). Assuming universal boundary conditions at a high scale for the soft supersymmetry-breaking gaugino, sfermion and Higgs mass parameters as well as for the trilinear interactions, we find that the model is more constrained than the celebrated minimal supergravity model. The phenomenologically viable region in the parameter space of the cNMSSM corresponds to a small value for the universal scalar mass m_0: in this case, one single input parameter is sufficient to describe the phenomenology of the model once the available constraints from collider data and cosmology are imposed. We present the particle spectrum of this very predictive model and discuss how it can be distinguished from the MSSM.
The code NMSDECAY allows to compute widths and branching ratios of sparticle decays in the Next-to-Minimal Supersymmetric Standard Model. It is based on a generalization of SDECAY, to include the extended Higgs and neutralino sectors of the NMSSM. Slepton 3-body decays, possibly relevant in the case of a singlino-like lightest supersymmetric particle, have been added. NMSDECAY will be part of the NMSSMTools package, which computes Higgs, sparticle masses and Higgs decays in the NMSSM.
The Next-to-Minimal Supersymmetric Standard Model (NMSSM) includes a Higgs iso-singlet superfield in addition to the two Higgs doublet superfields of the minimal supersymmetric extension. The Higgs sector and neutralino sectors of this model are examined within the context of a future linear collider.
The next-to-minimal supersymmetric extension of the Standard Model (NMSSM) is one of the most favored supersymmetric models. After an introduction to the model, the Higgs sector and the neutralino sector are discussed in detail. Theoretical, experimental, and cosmological constraints are studied. Eventually, the Higgs potential is investigated in the approach of bilinear functions. Emphasis is placed on aspects which are different from the minimal supersymmetric extension.
The effective bottom Yukawa couplings are analyzed for the minimal supersymmetric extension of the Standard Model at two-loop accuracy within SUSY-QCD. They include the resummation of the dominant corrections for large values of tg(beta). In particular the two-loop SUSY-QCD corrections to the leading SUSY-QCD and top-induced SUSY-electroweak contributions are addressed. The residual theoretical uncertainties range at the per-cent level.
We discuss the domain wall problem in the Next-to-Minimal Supersymmetric Standard Model, with particular attention to the usual solution of explicit breaking of the discrete symmetry by non-renormalisable operators. This ``solution'' leads to a contradiction between the requirements of cosmology and those of avoiding the destabilisation of the hierarchy.
We discuss the upper bound on the lightest CP-even Higgs boson mass in the next-to-minimal supersymmetric standard model within the framework of a low energy renormalisation group analysis. We find $m_h$ < 146 GeV for $m_t$ = 90 GeV, decreasing to $m_h$ < 123 GeV for $m_t$ = 180 GeV.
We explore the possibility of spontaneous CP violation within the Next to Minimal Supersymmetric Standard Model. In the most general form of the model, without a discrete $Z_3$ symmetry, we find that even at tree level spontaneous CP violation can occur, while also permitting Higgs masses consistent with experiment.
We compute the total cross section for the production of a light CP even Higgs boson within the framework of supersymmetric QCD up to next-to-next-to-leading order. Technical subtleties in connection to the evaluation of three-loop Feynman integrals with many mass scales are discussed in detail and explicit results for the counterterms of the evanescent couplings are provided. The new results are applied to several phenomenological scenarios which are in accordance with the recent discovery at the LHC. In a large part of the still allowed parameter space the $K$ factor of the supersymmetric th…
So far the squarks have not been detected at the LHC indicating that they are heavier than a few hundred GeVs, if they exist. The lighter stop can be considerably lighter than the other squarks. We study the possibility that a supersymmetric partner of the top quark, stop, is the next-to-lightest supersymmetric particle in the constrained supersymmetric standard model. Various constraints, on top of the mass limits, are taken into an account, and the allowed parameter space for this scenario is determined. Observing stop which is the next-to-lightest supersymmetric particle at the LHC may be d…
We analyze the experimental data from the search for new particles at LEP 100 and obtain mass bounds for the neutralinos of the Next--To--Minimal Supersymmetric Standard Model (NMSSM). We find that for $\tanβ\gsim 5.5$ a massless neutralino is still possible, while the lower mass bound for the second lightest neutralino corresponds approximately to that for the lightest neutralino in the Minimal Supersymmetric Standard Model (MSSM).
We study the mass, the mixing and the coupling with $Z$ boson of the lightest Higgs boson in the next-to-minimal supersymmetric standard model. The vacuum structure of the Higgs potential is analyzed and the new false vacua are discussed. The significant parameter region can be excluded by requiring that the realistic vacuum is deeper than false vacua, which result in constraints on the properties of the lightest Higgs boson.
Supersymmetric unified models in which the Z' couples to the Higgs doublets, as in the E6 class of models, have large fine tuning dominated by the experimental mass limit on the Z'. To illustrate this we investigate the degree of fine tuning throughout the parameter space of the Constrained Exceptional Supersymmetric Standard Model (cE6SSM) that is consistent with a Higgs mass m_h ~ 125 GeV. Fixing tan beta = 10, and taking specific values of the mass of the Z' boson, with M_Z' ~ 2-4 TeV. We find that the minimum fine tuning is set predominantly from the mass of Z' and varies from ~ 200-400 as…
We review the theoretical and phenomenological aspects of the Next-to-Minimal Supersymmetric Standard Model: the Higgs sector including radiative corrections and the 2-loop beta-functions for all parameters of the general NMSSM; the tadpole and domain wall problems, baryogenesis; NMSSM phenomenology at colliders, B physics and dark matter; specific scenarios as the constrained NMSSM, Gauge Mediated Supersymmetry Breaking, U(1)'-extensions, CP and R-parity violation.
We consider spontaneous CP violation in the Next to Minimal Supersymmetric Standard Model (NMSSM), without the usual $Z_3$ discrete symmetry. CP violation can occur at tree level, raising a potential conflict with the experimental bounds on the electric dipole moments of the electron and neutron. One escape from this is to demand that the CP violating angles are small, but we find that this entails an unacceptably light neutral Higgs.
We perform a detailed analysis of the next-to-minimal supersymmetric standard model (NMSSM), imposing the constraints of two-loop gauge coupling unification, universal soft supersymmetry breaking and the correct pattern of electroweak symmetry breaking. We compare our results with those for the minimal supersymmetric standard model (MSSM) using closely related techniques and, as far as possible, a common set of input and output variables. In general, in the constrained NMSSM, there are much stronger correlations between parameters than in the constrained MSSM, and we map out the allowed parame…
Prospects for direct dark matter detection are considered in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The effective neutralino-quark Lagrangian is obtained and event rates are calculated for Ge-73. Accelerator and cosmological constraints on the NMSSM are included in our numerical analysis, which allows us to conclude that the lightest neutralino from NMSSM could be detected in future dark matter experiments.
We discuss the possible enhancement of the tau lepton events at LHC when the left-handed stau doublet becomes light (which can be even lighter than the right-handed stau). This is illustrated in the constrained supersymmetric seesaw model where the slepton doublet mass is suppressed by the effects of a large neutrino Yukawa coupling. We study a few representative parameter sets in the sneutrino coannihilation regions where the tau sneutrino is NLSP and the stau coannihilation regions where the stau is NLSP both of which yield the thermal neutralino LSP abundance determined by WMAP.
We discuss how the experimental neutrino oscillation data can be realized in the framework of the baryon triality ($B_3$) constrained supersymmetric Standard Model (cSSM). We show how to obtain phenomenologically viable solutions, which are compatible with the recent WMAP observations. We present results for the hierarchical, inverted and degenerate cases which illustrate the possible size and structure of the lepton number violating couplings. We work with a new, as yet unpublished version of SOFTSUSY, where we implemented full one--loop neutrino masses. Finally, we shortly discuss some pheno…
The problems of the standard model are briefly reviewed and the motivations for introducing supersymmetry are discussed. Two realistic supersymmetric models; the Minimal SuperSymmetric Model, MSSM, and its proposed extension NMSSM are introduced briefly and then some details of the Higgs sector of NMSSM are stated and some constraints on parameters are described. I then explore the Higgs boson masses and couplings for some interesting scenarios, including a few different ways of taking the limit where NMSSM reduces to MSSM.
We perform a renormalisation group analysis of the next-to-minimal supersymmetric standard model (NMSSM) based on the following constraints: two-loop gauge coupling unification at a variable scale $M_X$, running the gauge couplings through the low energy thresholds; universal soft supersymmetry breaking parameters; correct electroweak symmetry breaking. The phenomenological implications of our results include a standard model-like Higgs boson of mass in the range 70-140 GeV.
We review the most important aspects of the NMSSM, discussing the impact of the NMSSM on low-energy observables, for dark matter, as well as NMSSM specific signatures at colliders. We also briefly consider constrained realisations of the NMSSM.
The purpose of this paper is to present a complete and consistent list of the Feynman rules for the vertices of neutralinos and Higgs bosons in the Next-To-Minimal Supersymmetric Standard Model (NMSSM), which does not yet exist in the literature. The Feynman rules are derived from the full expression for the Lagrangian and the mass matrices of the neutralinos and Higgs bosons in the NMSSM. Some crucial differences between the vertex functions of the NMSSM and the Minimal Supersymmetric Standard Model (MSSM) are discussed.
Direct dark matter detection is considered in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The effective neutralino-quark Lagrangian is obtained and event rates are calculated for the Ge-73 isotope. Accelerator and cosmological constraints on the NMSSM parameter space are included. By means of scanning the parameter space at the Fermi scale we show that the lightest neutralino could be detected in dark matter experiments with sizable event rate.
A simple extension of the minimal renormalizable supersymmetric SO(10) grand unified theory by adding a 120-dimensional Higgs representation is examined. This brings new antisymmetric contributions to the relevant quark and lepton mass sum rules and leads to a better fit of the measured values of lepton masses and mixings together with a natural completion of the renormalizable Higgs sector within the SUSY SO(10) framework.
We examine the observed diphoton excess at 750 GeV in the framework of constrained Minimal Supersymmetric Standard Model (cMSSM). The consistency of cMSSM with the discovery of a 125 GeV Higgs boson and PLANCK/WMAP data for dark matter relic density (RD) demands large mixing in the scalar top (stop) sector and consequently, the existence of a light stop quasi-degenerate with the lightest neutralino. Small decay width due to kinematic and loop suppression of such a stop allows for the existence of stop-antistop bound states (stoponia). Identifying the particular part of cMSSM parameter space co…
We present a supersymmetric left-right model which predicts gauge coupling unification close to the string scale and extra vector bosons at the TeV scale. The subtleties in constructing a model which is in agreement with the measured quark masses and mixing for such a low left-right breaking scale are discussed. It is shown that in the constrained version of this model radiative breaking of the gauge symmetries is possible and a SM-like Higgs is obtained. Additional CP-even scalars of a similar mass or even much lighter are possible. The expected mass hierarchies for the supersymmetric states …
We study the implications of the triviality problem for the Higgs masses and other relevant parameters in the Next to Minimal Supersymmetric Standard Model (NMSSM). By means of triviality, a new way to constrain parameters is proposed, and therefore we are able to derive triviality bounds on the heaviest-Higgs mass, the lightest-Higgs mass, the soft SUSY- breaking parameters, and the vacuum expectation value of the Higgs gauge singlet through a thorough examination of the parameter space. The triviality upper bound on the lightest-Higgs mass predicted by NMSSM is indeed larger than the upper b…
The Higgs boson discovery stirred interest in next-to-minimal supersymmetric models, due to the apparent fine-tuning required to accommodate it in minimal theories. To assess their naturalness, we compare fine-tuning in a $\mathbb{Z}_3$ conserving semi-constrained Next-to-Minimal Supersymmetric Standard Model (NMSSM) to the constrained MSSM (CMSSM). We contrast popular fine-tuning measures with naturalness priors, which automatically appear in statistical measures of the plausibility that a given model reproduces the weak scale. Our comparison shows that naturalness priors provide valuable ins…
We analyze the possibility of detecting one of the three scalar Higgs bosons in the next-to-minimal supersymmetric model at the future $e^+e^-$ linear collider, by examining their productions via the Higgsstrahlung process. The production cross sections of the three scalar Higgs bosons in $e^+e^-$ collisions are evaluated for the proposed c.m. energies of the future $e^+e^-$ colliders, for the whole space of relevant parameters. We find that at least one of the three production cross sections is not smaller than 16 fb, 4 fb, and 1 fb for ${\sqrt s} = 500$ GeV, 1000 GeV, and 2000 GeV, respectiv…
We study constraints to avoid deep unrealistic minima in the next-to-minimal supersymmetric standard model. We analyze a scalar potential along directions where all of and one of the three Higgs fields develop their vacuum expectation values, and find unrealistic minima deeper than the electroweak symmetry breaking (EWSB) vacuum. These unrealistic minima threaten the realization of the successful EWSB and therefore should be avoided. Necessary conditions to avoid these minima result in constraints of parameters. We show that a wide and significant region of the parameter space, especially larg…
We study the possibility of spontaneous CP violation in the next-to-minimal supersymmetric standard model (NMSSM). It is shown that the spontaneous CP violation is induced by the radiative effects of top, stop, bottom and sbottom superfields. The available regions of parameters, which are obtained by imposing the constraints from experiments, are rather narrow. We also obtain strong constraints for light Higgs masses such as m_H \le 36 GeV numerically. Sum of masses of two light neutral Higgs should set around 93 GeV and charged Higgs boson has a rather higher mass larger than 700 GeV.
We examine the possibilities for constructing models with Dirac gaugino masses and unification of gauge couplings. We identify one promising model, and discuss to what extent it can have a "natural SUSY" spectrum. We then determine the low-energy constraints upon it, and propose a constrained set of boundary conditions at the unification scale. We describe the implementation of these boundary conditions in the spectrum-generator generator \SARAH and we perform a first exploration of the parameter space, specifically searching for points where the spectrum is relatively light. It is shown that …
We discuss the unification of the bottom quark and tau lepton Yukawa couplings within the framework of the next-to-minimal supersymmetric standard model. We compare the allowed regions of the $m_t$-$\tan β$ plane to those in the minimal supersymmetric standard model, and find that over much of the parameter space the deviation between the predictions of two models is small, and nearly always much less than the effect of current theoretical and experimental uncertainties in the bottom quark mass and the strong coupling constant. However over some regions of parameter space top-bottom Yukawa uni…
The Higgs boson spectrum of the Next-to-Minimal Supersymmetric Standard Model is examined. The model includes a singlet Higgs field S in addition to the two Higgs doublets of the minimal extension. `Natural' values of the parameters of the model are motivated by their renormalization group running and the vacuum stability. The qualitative features of the Higgs boson masses are dependent on how strongly the Peccei-Quinn U(1) symmetry of the model is broken, measured by the self-coupling of the singlet field in the superpotential. We explore the Higgs boson masses and their couplings to gauge bo…
In the electroweak phase transition there arises the problem of baryon number washout by sphaleron transitions, which can be avoided if the phase transition is strongly enough first order. The minimal supersymmetric standard model has just two Higgs doublets H1 and H2, while the next to minimal model, NMSSM, has an additional singlet, N, this latter giving rise to the helpful feature that the Higgs potential contains a tree level trilinear field term. We use the tunneling criterion for the existence of a first order electroweak phase change. A quantitative statistical analysis indicates that w…
We analyse the electric dipole moment of the neutron in the MSSM, induced by the renormalisation of the soft-susy breaking terms. We run the RGEs using two-loop expressions for gauge and Yukawa couplings and retaining family dependence. The $μ$ and $B$ parameters were determined by minimising the full one-loop Higgs potential, and we find that the neutron EDM lies in the range $10^{-33}<|d_n| < 10^{-29} {\; e\;\mbox{cm}} $.
We present a complete next-to-leading-order calculation of the QCD corrections to $B^0-\bar{B}^0$ ($K^0-\bar{K}^0$) mixing in the framework of the minimal flavor violating (MFV) supersymmetry. We take into account the contributions from the gluino and find that the gluino-mediated corrections modify the LO result obviously even when the mass of gluino $m_{\tilde{g}} \gg m_{\rm w}$. In general, one cannot neglect gluino contributions.
The electroweak symmetry is nonlinearly realized in an extension of the minimal supersymmetric standard model (MSSM) through an additional pair of constrained Higgs doublet superfields. The superpotential couplings of this constrained Higgs doublet pair to the MSSM Higgs doublet pair catalyze their vacuum expectation values. The Higgs and Higgsino-gaugino mass spectrum is presented for several choices of supersymmetry (SUSY) breaking and Higgs superpotential mass parameters. The additional vacuum expectation values provided by the constrained fields can produce a phenomenology quite different …
We study phenomenologically the scenario in which the scalar top quark is lighter than any other standard supersymmetric partner and also lighter than the top quark, so that it decays to the gravitino via stop -> W^+ b G. In this case, scalar top quark events would seem to be very difficult to separate from top quark pair production. However, we show that, even at a hadron collider, it is possible to distinguish these two reactions. We show also that the longitudinal polarization of the final $W^+$ gives insight into the scalar top and wino/Higgsino mixing parameters.
A Fortran-program for the production cross-sections of squarks and gluinos at hadron colliders is described. It includes full next-to-leading order SUSY-QCD corrections to all possible final states ($\squark\squarkbar, \gluino\gluino, \squark\gluino, \squark\squark$). The program allows to calculate total cross-sections as well as differential distributions in the transverse momentum p_t and the rapidity y of one of the outgoing particles. In addition cuts in p_t and y can easily be implemented.
The present work investigates the possibility that both dark matter and the anomalous magnetic moment of the muon may be explained within the context of the inverse seesaw extended Next-to-Minimal Supersymmetric Standard Model (ISS-NMSSM). In ISS-NMSSM, the newly introduced Higgs-neutrino Yukawa coupling $Y_ν$ provides additional Higgsino-sneutrino loop contribution to $(g-2)_μ$. If the deviation between the experimental observations and the Standard Model predictions of the anomalous muon magnetic moment is confirmed by the further experimental and theoretical studies, it can be explained nat…
We assess the extent to which the NMSSM can allow for light dark matter in the $2\gev\lsim \mcnone\lsim 12\gev$ mass range with correct relic density and large spin-independent direct-detection cross section, $\sigsi$, in the range suggested by \cogent\ and DAMA. For standard assumptions regarding nucleon $s$-quark content and cosmological relic density, $ρ$, we find that the NMSSM falls short by a factor of about 10 to 15 (3 to 5) without (with) significant violation of the current $(g-2)_μ$ constraints.
The next-to-leading order (NLO) QCD corrections to the production and decay rate of a Higgs boson are computed within the framework of the Minimal Supersymmetric Standard Model (MSSM). The calculation is based on an effective theory for light and intermediate mass Higgs bosons. We provide a Fortran routine for the numerical evaluation of the coefficient function. For most of the MSSM parameter space, the relative size of the NLO corrections is typically of the order of 5% smaller than the Standard Model value. We exemplify the numerical results for two scenarios: the benchmark point SPS1a, and…
Within the context of an effective potential formalism we calculate the contribution to Higgs boson masses in the next--to--minimal supersymmetric standard model from squark loops. We then supplement a previously performed renormalisation group analysis of the Higgs sector of this model with these results in order to determine the shift in the bound on the lightest CP-even Higgs boson mass as a result of squark effects. The improved bound on the lightest neutral CP-even Higgs boson mass, including squark contributions, is $m_h \leq 146 \ \ (139, 149)$ GeV for $m_t = 90 \ \ (140, 190)$ GeV. For…
The motivations for the NMSSM are reviewed, and possible unconventional signals for Higgs and sparticle production at the LHC are discussed. In the presence of a light pseudoscalar, the SM-like Higgs scalar can decay dominantly into a 4-tau final state. In the fully constrained NMSSM with mSUGRA-like soft SUSY breaking terms, the correct dark matter relic density is obtained for a singlino-like LSP which modifies considerably all sparticle decay chains.
We discuss two striking Large Hadron Collider (LHC) signatures of the constrained version of the exceptional supersymmetric standard model (cE6SSM), based on a universal high energy soft scalar mass m_0, soft trilinear coupling A_0 and soft gaugino mass M_{1/2}. The first signature we discuss is that of light exotic colour triplet charge 1/3 fermions, which we refer to as D-fermions. We calculate the LHC production cross section of D-fermions, and discuss their decay patterns. Secondly we discuss the E6 type U(1)_N spin-1 Z' gauge boson and show how it may decay into exotic states, increasing …
We analyze CP violation in the supersymmetric standard model (MSSM) embedded minimally into a left-right symmetric gauge structure with the seesaw mechanism for neutrino masses. With the plausible assumption of universal scalar masses it is shown that CP violation in the hadron sector of the MSSM is described by a single phase residing in the supersymmetry breaking Lagrangian. This improves the CP properties of the MSSM by providing a natural solution to the SUSY CP problem. Furthermore, $ε'/ε$ vanishes in this model above the seesaw scale; extrapolation to the weak scale then leads to a predi…
We consider next-to-minimal supersymmetric standard model (NMSSM) which has a gauge singlet superfield. In the scale invariant superpotential we do not have the mass terms and the whole Lagrangian has an additional $Z_3$ symmetry. This model can have light scalar and/or pseudoscalar allowed by the recent data from LHC and the old data from LEP. We investigate the situation where a relatively light charged Higgs can decay to such singlet-like pseudoscalar and a $W^\pm$ boson giving rise to final state containing $τ$ and/or $b$-jets and lepton(s). Such decay evades the recent bounds on charged H…
We consider the production of baryon number from collapsing domain walls, and in particular examine the magnitude of CP violation which is required in such schemes. Taking the conventional solution to the domain wall problem in the Next-to-Minimal Supersymmetric Standard Model as an example, we show that the observed baryon assymmetry of the universe may have been generated, even if the initial {\em explicit} CP violation in the Lagrangian were so small ({\em i.e.} gravitational) that it could never be experimentally detected. This is possible by having the {\em explicit} CP violation affect t…
We study the explicit $CP$ violation of the Higgs sector in the minimal supersymmetric standard model with a gauge singlet Higgs field. The magnitude of $CP$ violation is discussed in the limiting cases of $x\gg v_1,\ v_2$ and $x\ll v_1,\ v_2$, where $x$ and $v_{1,2}$ denote VEV of singlet and doublet Higgs scalars, respectively. Our numerical predictions of the electric dipole moments of electron and neutron lie around the present experimental upper limits. It is found that the large $CP$ violation effect reduces the magnitude of the lightest Higgs boson mass in the order of a few ten GeV.
Within the framework of the Next-To-Minimal Supersymmetric Standard Model (NMSSM) we study neutralino production $e^+e^- \longrightarrow \tildeχ^0_i \tildeχ^0_j$ ($i,j=1,\ldots ,5$) at center-of-mass energies between 100 and 600 GeV and the decays of the heavier neutralinos into the LSP plus a fermion pair, a photon or a Higgs boson. For representative gaugino/higgsino mixing scenarios, where the light neutralinos have significant singlet components, we find some striking differences between the NMSSM and the minimal supersymmetric model. Since in the NMSSM neutralino and Higgs sector are stro…
We discuss the predictions of a constrained version of the exceptional supersymmetric standard model (cE6SSM), based on a universal high energy soft scalar mass m_0, soft trilinear coupling A_0 and soft gaugino mass M_1/2. We predict a supersymmetry (SUSY) spectrum containing a light gluino, a light wino-like neutralino and chargino pair and a light bino-like neutralino, with other sparticle masses except the lighter stop being much heavier. In addition, the cE6SSM allows the possibility of light exotic colour triplet charge 1/3 fermions and scalars, leading to early exotic physics signals at …
The minimal supersymmetric standard model (MSSM) is extended by including an additional pair of constrained Higgs doublet superfields through which the electroweak symmetry is nonlinearly realized. The superpotential couplings of this constrained Higgs doublet pair to the MSSM Higgs doublet pair catalyze the later nontrivial vacuum expectation values. The mass spectrum of the Higgs scalars and Higgsino-gaugino sector is presented for several choices of supersymmetry (SUSY) breaking and Higgs superpotential mass parameters. The effect of the the additional constrained fields and multiple vacuum…
If the scalar tau $\stau$ is the next lightest supersymmetric particle and decays into a gravitino ($\gravitino$) being the lightest supersymmetric particle, it will have generally a very long lifetime. In this paper, we investigate the possibility to study the decay of such a long lived scalar tau at the LHC. If we can add to the present LHC experiments additional detectors which are able to stop the stau particles and measure the produced decay products, the decay characteristics can be studied precisely at the LHC. We identify a maximum "stopper detector" that could be added in the CMS cave…
The complete matrix element for $e^+e^-\rightarrow b\bar b W^+W^-$ is computed at tree-level within the Minimal Supersymmetric Standard Model. Rates of interest to phenomenological analyses at the Next Linear Collider are given. In particular, we study: - $t\bar t$ production and decay $t\bar t\ar (bW^+)(\bar bW^-)$; - $ZH$ production followed by $Z\ar b\bar b$ and $H\ar W^+W^-$; - $AH$ production followed by $A\ar b\bar b$ and $H\ar W^+W^-$; - $hW^+W^-$ production followed by $h\ar b\bar b$. Top and Higgs finite width effects are included, as well as all those of the irreducible backgrounds.
We present a self--consistent $E_6$ inspired supersymmetric model with an extra $U(1)_{N}$ gauge symmetry under which right-handed neutrinos have zero charge. We explore the particle spectrum within the constrained version of this exceptional supersymmetric standard model (E$_6$SSM) and discuss its possible collider signatures.
In the Next--To--Minimal Supersymmetric Standard Model (NMSSM), the Higgs and neutralino/chargino sectors are strongly correlated by four common parameters at tree level. Therefore we analyze the experimental data from both the search for Higgs bosons as well as for neutralinos and charginos at LEP 100 in order to constrain the parameter space and the masses of the neutral Higgs particles in the NMSSM. We find that small singlet vacuum expectation values are ruled out, but a massless neutral Higgs scalar and pseudoscalar is not excluded for most of the parameter space of the NMSSM. Improved li…
The neutral Higgs sector of the next-to-minimal supersymmetric standard model (NMSSM) with explicit CP violation is investigated at the 1-loop level, using the effective potential method; not only the loops involving the third generation of quarks and scalar quarks, but also the loops involving $W$ boson, charged Higgs boson, and chargino are taken into account. It is found that for some parameter values of the NMSSM the contributions from the $W$ boson, charged Higgs boson, and chargino loops may modify the masses of the neutral Higgs bosons and the mixings among them significantly, depending…
New NLO b->sgamma calculations have become available using resummed radiative corrections. Using these calculations we perform a global fit of the supergravity inspired constrained minimal supersymmetric model (CMSSM). We find that the resummed calculations show similar constraints as the LO calculations, namely that only with a relatively heavy supersymmetric mass spectrum of the order of 1 TeV the b-τYukawa unification and the b->sgamma rate can coexist in the large tanb scenario. The resummed b->sgamma calculations are found to reduce the renormalization scale uncertainty considerably. The …
