The upper limit on the mass of the lightest CP-even neutral Higgs in the minimal supersymmetric standard model is around 135 GeV for soft supersymmetry breaking masses in the 1 TeV range. We demonstrate that this upper limit may be sizably relaxed if supersymmetry is embedded in extra dimensions. We calculate, using the effective potential technique, the radiative corrections to the lightest Higgs mass induced by the Kaluza-Klein towers of quarks and squarks with one and two compactified directions. We observe that the lightest Higgs may comfortably weigh around 200 GeV (300 GeV) with one (two) extra dimension(s).
Within the framework of the constrained Minimal Supersymmetric extension of the Standard Model we show that recent LEP I limits on the invisible Z width exclude the possibility that the lightest sparticle is the sneutrino.
We consider the neutralino sector in the Minimal Non--minimal Supersymmetric Standard Model (MNSSM). We argue that there exists a theoretical upper bound on the lightest neutralino mass in the MNSSM. An approximate solution for the mass of the lightest neutralino is obtained.
The problem of the lightest Higgs boson mass in the next-to-minimal supersymmetric standard model (NMSSM) is investigated. Assuming the validity of the perturbation theory up to unification scales and using the recent experimental results for the top quark mass, the restrictions on the NMSSM coupling constants are obtained. These restrictions are used to make the predictions for the lightest Higgs mass, which are compared to those of the minimal supersymmetric standard model (MSSM).
We present cross sections for the production of the lightest supersymmetric particle as a neutralino state in the minimal supersymmetric standard model at electron-photon colliders. The lightest supersymmetric particle mass is taken at a value of 30 GeV which is slightly higher than its lowest experimental bound of 20 GeV, and the masses of the scalar electron are varied. We show partial cross sections of the energy and angular distribution of the outgoing electron for different values of the centre of mass energy. As a result we show that electron-photon collider experiments could be quite se…
Given the conservation of baryon number as well as electron and muon numbers, all present data can be explained without the need of a conserved quantum number for the tau lepton and its neutrino. A supersymmetric extension of the standard model naturally allows for such a scenario. One consequence is that the tau neutrino becomes the lightest supersymmetric particle.
Supersymmetric models with broken R-parity induced by lepton number violating terms provide a calculable framework for neutrino masses and mixings. Within models with bilinear R-parity breaking six new physical phases appear which are potential sources of novel CP-violating phenomena compared to the minimal supersymmetric extension of the standard model. We consider CP-violating observables in the decays of the lightest supersymmetric particle in this class of models. We show that: (i) Neutrino physics requires a strong correlation between three different pairs of phases, thus reducing the eff…
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…
In this talk the question of what is the upper bound on the lightest supersymmetric Higgs mass, m_h is addressed. This question is relevant since experimental lower bounds on m_h might implement, in the near future, exclusion of supersymmetry. By imposing (perturbative) unification of the gauge couplings at some high scale \simgt 10^{17} GeV, we have found that for a top-quark mass M_t=175 GeV, and depending on the supersymmetric parameters, this bound can be as high as 205 GeV.
We calculate an upper bound on the lightest Higgs boson mass in the supersymmetric singlet majoran model containing SU(2) X U(1) singlet right handed neutrino fields and a chiral singlet having two units of lepton number. We show that although the singlet vacuum expectation values and supersymmetry breaking masses do not decouple from the upper bound, even at the tree level, their effect is small, thereby reducing the bound to the corresponding bound in the Minimal Supersymmetric Standard Model. Radiative corrections to the bound are similar to those in the minimal model. We also show that the…
The cosmological relic density of the lightest supersymmetric particle of the minimal supersymmetric standard model is calculated under the assumption of gauge and Yukawa coupling unification. We employ radiative electroweak breaking with universal boundary conditions from gravity-mediated supersymmetry breaking. Coannihilation of the lightest supersymmetric particle, which turns out to be an almost pure bino, with the next-to-lightest supersymmetric particle (the lightest stau) is crucial for reducing its relic density to an acceptable level. Agreement with the mixed or the pure cold (in the …
We review the phenomenology of light Higgs scalars in supersymmetric left-right models. We consider models with minimal particle content (with and without non-renormalizable higher-dimensional terms) and with additional Higgs superfields. The upper bound on the lightest CP-even neutral Higgs boson in these models is larger than in the minimal supersymmetric standard model, and the Higgs couplings to fermions approach those of the Standard Model. Possibly light doubly charged Higgs boson may provide the best signature of these models.
We consider the neutralino mass matrix in a supersymmetric theory based on SU(2) $\times$ U(1) gauge group with arbitrary number of singlet, doublet and triplet Higgs superfields. We derive an upper bound on the mass of the lightest neutralino, and a lower bound on the mass of the heaviest neutralino, in such a theory. Assuming grand unification of the gauge couplings, the upper bound on the mass of the lightest neutralino can be expressed in terms of the gluino mass. For a gluino mass of 200 GeV, the tree level upper bound on the mass of the lightest neutralino is 92 GeV, which increases to 1…
We consider minimal supergravity (mSUGRA) models with an additional R-parity violating operator at the grand unification scale. This can change the supersymmetric spectrum leading on the one hand to a sneutrino, smuon or squark as the lightest supersymmetric particle (LSP). On the other hand, a wide parameter region is reopened, where the scalar tau is the LSP. It is vital to know the nature of the LSP, because supersymmetric particles normally cascade decay down to the LSP at collider experiments. We investigate in detail the conditions leading to non-neutralino LSP scenarios. We also present…
In the minimal supersymmetric model (MSSM), the upper limit of the lightest Higgs boson mass, $\mhl$, depends strongly on the top quark mass, $m_t$. We have computed the dominant two-loop radiative corrections to this upper limit of $\mhl$ in order to eliminate large uncertainties due to QCD and $m_t^6$ corrections. It is shown that the QCD corrections significantly reduce the one-loop corrections. As a result, the SUSY parameter space accessible to LEP experiments is significantly increased.
We examine the radiative corrections to the mass of the lightest Higgs boson in the minimal supersymmetric extension of the standard model. We use the renormalization-group improved effective potential which includes the next-to-leading-order contributions. We find that, contrary to the result of Espinosa and Quirós, the higher-order corrections to the lightest Higgs boson mass are non-negligible, adding $3-11$ GeV ($3-9$ GeV) to the result in the leading logarithm approximation for the range of top quark mass $100 {\rm GeV} < m_t < 200 {\rm GeV}$ and for the supersymmetric breaking scale $M_{…
Supersymmetric (SUSY) QCD corrections to the lightest neutral Higgs boson associated production with top quark pair are studied in the minimal supersymmetric standard model (MSSM) at Linear colliders. Our calculations show that the SUSY QCD effects generally are very moderate (say 10%) and under control, except for some rescattering effects which lead to a breakdown of perturbation theory and require a more detailed study. In the vicinity of the production threshold for the favorable model parameters under the framework of the on-shell renormalization scheme, SUSY QCD can be as large as about …
In supersymmetric models extended with a gauge singlet the mass of the lightest Higgs boson has contributions proportional to the adimensional coupling $λ$. In minimal scenarios, the requirement that this coupling remains perturbative up to the unification scale constrains $λ$ to be smaller than $\approx 0.7$. We study the maximum value of $λ$ consistent with a perturbative unification of the gauge couplings in models containing nonstandard fields at intermediate scales. These fields appear in scenarios with gauge mediation of supersymmetry breaking. We find that the presence of extra fields c…
An upper bound on the tree-level mass of the lightest Higgs boson of the Supersymmetric Singlet Majoron Model is obtained. Contrary to some recent claims, it is shown to be of the same form as the general mass bound previously calculated for supersymmetric models with an extended Higgs sector. Soft-breaking masses or exotic vacuum expectation values do not enter in the tree-level bound [which is only controlled by the electroweak scale (M_Z)] and also decouple from the most important radiative corrections to the bound (the ones coming from the top-stop sector). The derivation of the upper boun…
We consider the lightest Higgs boson in naturally R-parity conserving supersymmetric left-right models. We obtain an upper bound on the tree level mass of this lightest Higgs boson. This upper bound depends on the $SU(2)_L$ and $SU(2)_R$ gauge couplings, and the vacuum expectation values of bidoublet Higgs fields, which are needed to break $SU(2)_L\times U(1)_Y$. The upper bound does not depend on either the $SU(2)_R$ breaking scale or the supersymmetry breaking scale. We evaluate the bound numerically by assuming that the theory remains perturbative upto some scale $Λ$. We find that the bound…
In the Minimal Supersymmetric Standard Model with conserved R-parity, the decays of the next-to-lightest neutralino into the lightest neutralino and two leptons are always involved in each supersymmetric particle decay chain. In this thesis we calculate one-loop corrections to the two-body decays of the next-to-lightest neutralino into a lepton and a slepton, which again decays into another lepton and the lightest neutralino. We also investigate a scenario where the next-to-lightest neutralino can undergo three-body decays. Not only the branching ratios of leptonic decay modes, but also the di…
The cross sections for the lightest neutral Higgs pair production at the one-loop level in photon-photon collisions are calculated in the Minimal Supersymmetric Standard Model(MSSM). We find that the contributions to the lightest Higgs boson pair production cross sections arising from the genuine supersymmetric virtual particles dominate over that arising from the virtual particles in the two-Higgs-doublet model (2HDM) if there are mixing between the right- and left-handed stops, otherwise, the contributions from ones in the 2HDM are dominant. We present the detailed numerical results of the c…
We have considered a supersymmetric scenario in which the minimal supersymmetric standard model is augmented with a right-chiral neutrino superfield for each generation. Such a scenario can have a lightest supersymmetric particle (LSP) dominated by the right-chiral sneutrino state and the lighter stau as the next-to-lightest supersymmetric particle (NLSP). This can easily be motivated by assuming a high scale framework of supersymmetry breaking like minimal supergravity (mSUGRA). Due to the extremely small neutrino Yukawa coupling, the decay of the NLSP to the LSP is suppressed and consequentl…
We investigate focus points of the renormalization group equations of the Minimal Supersymmetric Standard Model. We show that within this model the up- and down-type Higgs mass soft supersymmetry breaking parameters have focus point behavior at the electroweak scale simultaneously when appropriate conditions are fulfilled. The focus point scenario is holding for large $\tan β$. This two focus point scenario allows to fix the pole top-quark mass which is within the experimentally allowed interval. The main goal of the present paper is the investigation of the influence of the existence of focus…
Supersymmetry with broken R-parity can explain the neutrino mass squared differences and mixing angles observed in neutrino oscillation experiments. In the minimal model, where R-parity is broken only by bilinear terms, certain decay properties of the lightest supersymmetric particle (LSP) are correlated with neutrino mixing angles. Here we consider charginos, squarks, gluinos and sneutrinos being the LSP and calculate their decay properties in bilinear R-parity breaking supersymmetry. Together with the decays of charged scalars and neutralinos calculated previously this completes the proof th…
An upperbound on the mass of the lightest neutral scalar Higgs boson is calculated in an extended version of the minimal supersymmetric standard model that contains an additional Higgs singlet. We integrate the renormalization group equations of the model, and impose low energy boundary conditions consistent with present experimental results, and ultra-violet conditions following from triviality. Radiative corrections induced by a large top quark Yukawa coupling are included in our analysis, and we find the allowed values for the mass of the Higgs boson as a function of the mass of the top qua…
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…
After reviewing briefly the upper bounds on the mass of the lightest Higgs boson in the most general unconstrained minimal supersymmetric extension of the Standard Model, we discuss various arguments which reduce the parameter space of the model and give stronger predictions for $M_{h^0}$. First, the constraints from the presently available experimental data are summarized. Next, the role of of several additional theoretical assumptions is studied, after extrapolating the model to high energy scales. The most important ones are: perturbative validity up to the GUT scale and the electroweak sym…
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 supersymmetric version of the $SU(3)_L \otimes U(1)_X$ gauge model is presented. The model is embedded in a $SU(6)_L \otimes U(1)_X$ gauge group and it has been built up completely quiral anomaly free and without any exotic charges in the fermionic content. The Minimal Supersymmetric Standard Model can be seen as an effective theory of this larger symmetry. We analyze how the spectrum of the new model can shift the upper bound on the CP-even Higgs boson and we find that it can be moved up to 143 GeV.
We quantify and examine the uncertainties in predictions of the lightest $CP$ even Higgs boson pole mass $M_h$ in the Minimal Supersymmetric Standard Model (MSSM), utilising current spectrum generators and including some three-loop corrections. There are two broadly different approximations being used: effective field theory (EFT) where an effective Standard Model (SM) is used below a supersymmetric mass scale, and a fixed order calculation, where the MSSM is matched to QCD$\times$QED at the electroweak scale. The uncertainties on the $M_h$ prediction in each approach are broken down into loga…
In an R-parity violating supersymmetric scenario, the lightest neutralino $\tilde χ^0_1$ is no longer a stable particle. We calculate the branching ratio for the decay mode $\tilde χ^0_1 \longrightarrow νγ$ which occurs at the one-loop level. Taking into account bilinear as well as trilinear lepton number violating interactions as the sources of R-parity violation, we make a detailed scan of the parameter space, both with and without gaugino mass unification and including the constraints on the neutrino sector from the recent Superkamiokande results. This study enables one to suggest interesti…
The cosmological relic density of the lightest supersymmetric particle of the minimal supersymmetric standard model is calculated under the assumption of gauge and Yukawa coupling unification. We employ radiative electroweak breaking with universal boundary conditions from gravity-mediated supersymmetry breaking. Further constraints are imposed by the experimental bounds on the b-quark mass and the BR(b -> s gamma). We find that coannihilation of the lightest supersymmetric particle, which turns out to be an almost pure bino, with the next-to-lightest supersymmetric particle (the lightest stau…
In the four-dimensional supersymmetric standard model extended with gauge singlets the lightest Higgs boson mass, $M_H$, has an important contribution proportional to the squared of the superpotential coupling $λ$ of singlets to Higgs fields, $λSH_1\cdot H_2$. The requirement of perturbativity up to the unification scale yields an upper bound on $M_H\sim 140$ GeV. In extensions to theories with (longitudinal) extra dimensions at the TeV where such coupling exists and massive Kaluza-Klein states fall into N=2 representations, if either of the Higgs or singlet fields live in the bulk of the extr…
To escape the current LHC supersymmetry (SUSY) search constraints while preserve the naturalness condition, we propose the heavy Lightest Supersymmetric Particle (LSP) SUSY. According to the different dependence on the LSP mass, we systematically classify the discriminating variables into three categories. We find the strong dependence of all current SUSY searches on variables in the first category render the weak sensitivity for the heavy LSP SUSY. Especially, all the current LHC SUSY search constraints can be evaded if the LSP mass is around 600 GeV or higher. In the Minimal Supersymmetric S…
In extended supersymmetric models with additional singlet Higgs fields displaced vertices could be observed if the decay width of the next-to-lightest supersymmetric particle becomes very small due to a singlino dominated LSP. We study the supersymmetric parameter space where displaced vertices of the second lightest neutralino exist in the NMSSM and an E6 inspired model. For a mass difference between LSP and NLSP of more than 10 GeV the singlet vacuum expectation value has to be at least of the order of 100 TeV in order to obtain a lightest neutralino with a singlino component large enough fo…
We show that the $B-L$ Supersymmetric Standard Model with Inverse Seesaw (BLSSMIS) provides new Dark Matter (DM) candidates (lightest right-handed sneutrino and lightest $B-L$ neutralino) with mass of order few hundreds GeV, while most of other SUSY spectrum can be quite heavy, consistently with the current Large Hadron Collider (LHC) constraints. We emphasize that the thermal relic abundance and direct detection experiments via relic neutralino scattering with nuclei impose stringent constraints on the $B-L$ neutralinos. These constraints can be satisfied by few points in the parameter space …
We show that there is a calculable upper limit on the mass of the lightest Higgs boson in any supersymmetric theory that remains perturbative up to a high scale . There are no restrictions on the Higgs sector, or the gauge group or particle content. We estimate the value of the upper limit to be $m_{\hcirc} < 146$ GeV for 100 GeV < $M_t$ < 145 GeV, from all effects except possibly additional heavy fermions beyond top (which could increase the limit by 0-20 GeV if any existed); for $M_t$ > 145 GeV the limit decreases monotonically. We expect to be able to decrease the value of the upper limit b…
Inspired by split supersymmetry, we study a minimal supersymmetric scenario with only the Higgsino mass parameter $μ$ below the TeV scale. The motivation is to satisfy the gauge coupling unification and dark matter constraints with the minimal particle contents at the electroweak scale in supersymmetric models. With the neutral Higgsino as the lightest supersymmetric particle, we discuss the dark matter signals in both direct and indirect detection. We also discuss collider phenomenology associated with the two lightest neutralinos and the lightest chargino, which are almost degenerate in mass…
We study the production of the lightest neutralinos in the radiative process $e^+e^- \to \tildeχ^0_1 \tildeχ^0_1γ$ in supersymmetric models with grand unification. We consider models wherein the standard model gauge group $SU(3)_c \times SU(2)_L \times U(1)_Y$ is unified into the grand unified gauge groups SU(5), or SO(10). We study this process at energies that may be accessible at a future International Linear Collider. We compare and contrast the dependence of the signal cross section on the grand unified gauge group, and different representations of the grand unified gauge group, into whic…
We analyze the constrained minimal supersymmetric standard model with mu>0 supplemented by a generalized `asymptotic' Yukawa coupling quasi-unification condition, which allows an acceptable b-quark mass. We impose constraints from the cold dark matter abundance in the universe, B physics, and the mass of the lightest neutral CP-even Higgs boson. We find that, in contrast to previous results obtained for a more restrictive Yukawa quasi-unification condition, the lightest neutralino can act as a cold dark matter candidate in a relatively wide parameter range. In this range, the lightest neutrali…
I summarize results of two-loop effective potential calculations of the lightest CP-even Higgs boson mass in the minimal supersymmetric standard model.
In supersymmetric extensions of the Standard Model, the lightest neutralino, the gravitino, and the axino can appear as the lightest supersymmetric particle and as such provide a compelling explanation of the non-baryonic dark matter in our Universe. For each of these dark matter candidates, I review the present status of primordial production mechanisms, cosmological constraints, and prospects of experimental identification.
We consider supersymmetric models in which the lightest Higgs scalar can decay invisibly consistent with the constraints on the $126$~GeV state discovered at the CERN LHC. We consider the invisible decay in the minimal supersymmetric standard model~(MSSM), as well its extension containing an additional chiral singlet superfield, the so-called next-to-minimal or nonminimal supersymmetric standard model~(NMSSM).We consider the case of MSSM with both universal as well as nonuniversal gaugino masses at the grand unified scale, and find that only an $E_6$ grand unified model with unnaturally large …
We calculate the averaged number νof the lightest supersymmetric particles (LSPs) in a shower from the decay of superheavy particle X by generalized DGLAP equations. If the primary decayed particles have color charges and the virtuality is around 10^13-10^14 GeV, the averaged number of the LSPs can become O(100). As the result, the upper limit of the mass of the superheavy particle, whose decay can produce the observed abundance of the dark matter, can increase from 10^12 GeV to 10^14 GeV. Since the typical scale of the inflaton mass of the chaotic inflation is around 10^13 GeV, the decay of t…
The measurement of sparticle masses in the Minimal Supersymmetric Standard Model at the LHC is analysed, in the scenario where the lightest neutralino decays into three quarks. Such decays, occurring through the baryon-number violating coupling lambda"\_ijk, pose a severe challenge to the capability of the LHC detectors since the final state has no missing energy signature and a high jet multiplicity. We focus on the case of non-zero lambda"\_212 which is the most difficult experimentally. The proposed method is valid over a wide range of SUGRA parameter space with lambda"\_212 between 10^{-5}…
We calculate QCD correction to the neutralino annihilation cross section into quark anti-quark final state and discuss its implications to the calculation of neutralino relic density. We see that the QCD correction enhances the pair-annihilation cross section by O(10 %) when final-state quarks are non-relativistic. Consequently, when the lightest neutralinos dominantly annihilate into a t\bar{t} pair, the relic density of the lightest neutralino is significantly affected by the QCD correction, in particular when the lightest-neutralino mass is close to the top-quark mass.
Upper bounds on the three neutral scalar Higgs masses are considered in the supersymmetric standard model with a gauge singlet Higgs field. When the lightest Higgs is singlet-dominated the second lightest Higgs is shown to lie near or below the theoretical upper bound on the lightest Higgs mass. We also consider detectability of these Higgs bosons at a future $e^+ e^-$ linear collider with $\sqrt{s}\sim 300 $ GeV and show that at least one of the neutral scalar Higgs has a production cross section larger than 0.04~pb.
We argue, based on typical properties of known solutions of string/$M$-theory, that the lightest supersymmetric particle of the visible sector will not be stable. In other words, dark matter is {\em not} a particle with Standard Model quantum numbers, such as a WIMP. The argument is simple and based on the typical occurrence of a) hidden sectors, b) interactions between the Standard Model (visible) sector and these hidden sectors, and c) the lack of an argument against massive neutral hidden sector particles being lighter than the lightest visible supersymmetric particle. These conclusions do …
In a general supersymmetric standard model there is an upper bound $m_h$ on the tree level mass of the $CP=+1$ lightest Higgs boson which depends on the electroweak scale, $\tan β$ and the gauge and Yukawa couplings of the theory. When radiative corrections are included, the allowed region in the $(m_h,m_t)$ plane depends on the scale $Λ$, below which the theory remains perturbative, and the supersymmetry breaking scale $Λ_s$, that we fix to $1\ TeV$. In the minimal model with $Λ=10^{16}\ GeV$: $m_h<130\ GeV$ and $m_t<185\ GeV$. In non-minimal models with an arbitrary number of gauge singlets …
We consider B3 mSUGRA models where we have one lepton number violating LQD operator at the GUT scale. This can alter the supersymmetric mass spectrum leading to a sneutrino as the lightest supersymmetric particle in a large region of parameter space. We take into account the restrictions from neutrino masses, the muon anomalous magnetic moment, b -> s gamma and other precision measurements. We furthermore investigate existing restrictions from direct searches at LEP, the Tevatron and the CERN p\bar p collider. We then give examples for characteristic signatures at the LHC.
High energy electron-photon colliders provide unique opportunities for probing physics beyond the standard model. We have studied the experimental signatures for two supersymmetric scenarios, with the lightest supersymmetric particle (LSP) being either the lightest neutralino or the gravitino. In the ``neutralino LSP'' scenario favored by the minimal supersymmetric standard model (MSSM), it is found that some basic parameters of the model, $μ$, $\tanβ$, $M_1$ and $M_2$, may be uniquely determined from the outgoing electron energy spectrum without assuming high scale unification of the masses o…
We investigate, which lightest supersymmetric particles can be obtained via a non-vanishing lepton- or baryon-number violating operator at the grand unification scale within the R-parity violating minimal supergravity model. We employ the full one-loop renormalization group equations. We take into account restrictions from the anomalous magnetic moment of the muon and b -> s gamma, as well as collider constraints from LEP and the Tevatron. We also consider simple deformations of minimal supergravity models.
The lightest Higgs boson mass of the Minimal Supersymmetric Standard Model has been recently computed diagrammatically at the three-loop order in the whole supersymmetric parameters space of the SUSY-QCD sector. The code FeynHiggs combines one- and two-loop fixed-order with the effective-field-theory calculations for the same Higgs mass. The two numerical predictions agree considering the scenario of only one SUSY-scale and vanishing stop mixing parameter below 10 TeV. The agreement is improved by introducing an additional supersymmetric scale and a non-zero stop mixing. Additionally, the comb…
A review of the Higgs and neutralino sectors of supersymmetric models is presented. This includes the upper limit on the mass of the lightest Higgs boson in the Minimal Supersymmetric Standard Model, as well as models based on the Standard Model gauge group $SU(2)_L \times U(1)_Y$ with extended Higgs sectors. We then discuss the Higgs sector of left-right supersymmetric models, which conserve R-parity as a consequence of gauge invariance, and present a calculable upper bound on the mass of the lightest Higgs boson in these models. We also discuss the neutralino sector of general supersymmetric…
One of the main features of the Minimal Supersymmetric Standard Model (MSSM) is the existence of an absolute tree-level upper bound $m_h$ on the mass of the $CP=+1$ lightest Higgs boson, equal to $m_Z$, that could affect detectability at future colliders. The above bound is spoiled by {\bf radiative corrections} and by an {\bf enlarged Higgs sector}, as {\em e.g.} a gauge singlet. Radiative corrections in the MSSM can push the upper bound up to $115\ GeV$ for $m_t \simlt 150\ GeV$. The presence of an enlarged Higgs sector changes the previous upper bound to one depending on the electroweak sca…
We present a detailed discussion of the particle spectrum of the Non-Minimal Supersymmetric Standard Model (NMSSM), containing two Higgs doublets and a singlet, in the limit $\tanβ\simeq m_t/m_b$. This is compared with the corresponding particle spectrum of the Minimal Supersymmetric Standard Model (MSSM). In this limit the singlet vacuum expectation value is forced to be large, of the order of $10$ TeV, and the singlet decouples from the lightest scalar Higgs boson and the neutralinos. With the exception of the lightest Higgs boson, the particle spectrum in the model turns out to be heavy. Th…
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.
Contrary to common expectation, a left-sneutrinos can occasionally be the lightest supersymmet- ric particle. This has important implications in both collider and dark matter studies. We show that same-sign tri-lepton (SS3L) events at the Large Hadron Collider, with any lepton having opposite sign vetoed, distinguish such scenarios, up to gluino masses exceeding 2 TeV. The jets + M ET signal rate is somewhat suppressed in this case, thus enhancing the scope of leptonic signals.
