The lightest neutralino in the minimal supersymmetric extension of the Standard Model can be, in principle, massless. If super-light neutralinos are the dark matter, structure formation constrains their mass to be above a few keV. We show that relaxing the assumption of radiation domination and entropy conservation prior to Big Bang Nucleosynthesis, the relic abundance of very light neutralinos can be consistent with the inferred cold dark matter density. We study how we can hunt for light neutralino dark matter, with a mass at or below a GeV, focusing on both direct and indirect searches. We argue that the two most promising channels are spin-dependent direct detection and the search for monochromatic gamma rays from the prompt pair-annihilation of neutralinos into photons with GLAST. Our study indicates that the lightest lightest neutralinos can be detected as long as their mass is above a few tenth of a GeV, a mass range where a future linear collider could provide important information on the details of the particle dark matter model.
We argue that the allowed range of the mass of the lightest neutralino in the MNSSM is limited. We establish the theoretical upper bound on the lightest neutralino mass and obtain an approximate solution for this mass.
We examine the allowed mass range of the lightest neutralino within the Minimal Non--minimal Supersymmetric Standard Model. Being absolutely stable if R-parity is conserved this lightest neutralino is a candidate for the dark matter of the universe. We establish the theoretical upper bound on the lightest neutralino mass and obtain an approximate solution for this mass.
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.
We study neutralino sectors in extensions of the MSSM that dynamically generate the mu-term. The extra neutralino states are superpartners of the Higgs singlets and/or additional gauge bosons. The extended models may have distinct lightest neutralino properties which can have important influences on their phenomenology. We consider constraints on the lightest neutralino from LEP, Tevatron, and (g-2)_mu measurements and the relic density of the dark matter. The lightest neutralino can be extremely light and/or dominated by its singlino component which does not couple directly to SM particles ex…
We study neutralino sectors in extensions of the MSSM that dynamically generate the mu-term. The extra neutralino states are superpartners of the Higgs singlets and/or additional gauge bosons. The extended models may have distinct lightest neutralino properties which can have important influences on their phenomenology. We consider constraints on the lightest neutralino from LEP, Tevatron, and (g-2)_mu measurements and the relic density of the dark matter. The lightest neutralino can be extremely light and/or dominated by its singlino component, which does not couple directly to SM particles e…
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…
In this talk we summarize previous work on mass bounds of a light neutralino in the Minimal Supersymmetric Standard Model. We show that without the GUT relation between the gaugino mass parameters M_1 and M_2, the mass of the lightest neutralino is essentially unconstrained by collider bounds and precision observables. We conclude by considering also the astrophysics and cosmology of a light neutralino.
In a minimal supersymmetric extension of the standard model (MSSM) with explicit CP violation a mass of the lightest Higgs boson H_1 in the range 7 GeV} < M_{H_1} < 10 GeV is experimentally allowed by present accelerator limits. In the same scenario a lightest neutralino as light as 2.9 GeV can be a viable dark matter candidate, provided that a departure from the usual GUT relation among gaugino masses is assumed.
Though LEP II direct searches still cannot exclude a chargino nearly degenerate with the lightest neutralino if its mass is only slightly above half of the Z boson mass and the sneutrino is light, it can be excluded indirectly analyzing precision data. In this particular limit simple analytical formulas for oblique electroweak radiative corrections are presented.
We show that in the Minimal Supersymmetric Standard Model, the mass of the lightest neutralino is experimentally unconstrained if the GUT relation between the gaugino mass parameters M_1 and M_2 is dropped. We discuss what the impact of light or massless neutralinos would be on their production at LEP, as well as on electroweak precision data and rare decays.
Most ongoing supersymmetry searches have concentrated on the high-energy frontier. High-intensity fixed target beamlines, however, offer an opportunity to search for supersymmetric particles with long lifetimes and low cross-sections in regions complementary to the ones accessible to collider experiments. In this paper, we consider R-parity violating supersymmetry searches for the lightest neutralino and use the NuTeV experiment as an example for the experimental sensitivity which can be achieved.
Though LEP II direct searches still cannot exclude a chargino nearly degenerate with the lightest neutralino if their mass is only slightly above half of the Z boson mass, it can be excluded indirectly analyzing precision data. In this particular limit simple analytical formulas for oblique electroweak radiative corrections are presented.
We study the toroidal dipole moment of the lightest neutralino in the constrained Minimal Supersymmetric Standard Model. The toroidal dipole moment is the only electromagnetic property of the neutralino. Since the neutralino is the LSP in many versions of the MSSM and therefore a candidate for dark matter, its characterization through its electromagnetic properties is important both for particle physics and for cosmology. We perform a scan in the parameter space of the cMSSM and find that the toroidal dipole moment is different from zero, albeit very small, in all the parameter space, and reac…
Decays of the lightest neutralino are studied in R_p-violating models with operators lambda^{prime} L Q D^c and lambda L L E^c involving third-generation matter fields and with dominant lambda^{prime} and lambda couplings. Generalizations to decays of the lightest neutralino induced by subdominant lambda^{prime} and lambda couplings are straightforward. Decays with the top-quark among the particles produced are considered, in addition to those with an almost massless final state. Phenomenological analyses for examples of both classes of decays are presented. No specific assumption on the compo…
We derive the general upper bounds on the mass of the lightest neutralino, as a function of the gluino mass, in different supersymmetry breaking models with minimal particle content and the standard model gauge group. This includes models with gravity mediated supersymmetry breaking (SUGRA), as well as models with anomaly mediated supersymmetry breaking (AMSB). We include the next-to-leading order corrections in our evaluation of these bounds. We then expand the mass matrix in powers of M_Z/mu, and find the upper bound on the mass of the lightest neutralino from this expansion. By scanning ove…
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.
We discuss neutrino parameters in addition with the effects of a Higgs boson of mass $\sim$ 125 GeV in Split Supersymmetry with Bilinear R-Parity Violation. This model allows for the explanation of neutrino masses and mixing angles, and has the gravitino as Dark Matter candidate. We find constraints on the parameters in the neutrino sector of the model by performing a numerical study of the parameter space, and by fitting neutrino oscillation observables and the Higgs mass. In addition, we study in detail the decay of the lightest neutralino in this model and we realize the importance of the e…
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…
Bounds on cross section measurements of chargino pair production at LEP yield a bound on the chargino mass. If the GUT relation is assumed, the lightest neutralino must be heavier than $\approx 45 -50\GeV$. If no GUT relation is assumed, no lower bound on the neutralino mass exists. I derive mass bounds on the lightest neutralino from relic density measurements for relativistic and non-relativistic neutralinos and I derive bounds on the selectron mass from the observed limits on the cross section of the neutralino pair production process $e^+e^-\to \x{1}\x{2}$ at LEP, if the lightest neutralin…
We study the anapole moment of the lightest neutralino in the constrained Minimal Supersymmetric Standard Model (cMSSM). The electromagnetic anapole is the only allowed electromagnetic form factor for Majorana fermions, such as the neutralino. Since the neutralino is the LSP in many versions of the MSSM and therefore a candidate for dark matter, its characterization through its electromagnetic properties is important both for particle physics and for cosmology. We perform a scan in the parameter space of the cMSSM and find that the anapole moment is different from zero albeit very small ($< 10…
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…
Pair production of light top squarks at the 8-TeV LHC can be used to probe the gaugino-Higgsino sector of the Minimal Supersymmetric Standard Model. The case where the lightest neutralino is a mixture of Bino and Higgsino, satisfying the thermal dark matter relic density, is investigated. In such a scenario, the lightest top squark decays mostly into $(i)$ a top quark plus the second or third lightest neutralino, and $(ii)$ a bottom quark plus the lightest chargino, instead of a decay scenario of the lightest top squark into a top quark and the lightest neutralino. Final states with $\geq 2$ j…
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}…
The Split SUSY scenario with light Higgsino states is treated as an application to the Dark Matter problem. We have considered the structure of the neutralino-nucleon interaction and calculated cross-section of the neutralino-nucleon scattering. The decay properties of the lightest chargino and next lightest neutralino are analyzed in details.
We study the decays of the lightest supersymmetric particle (LSP) in models with spontaneously broken R-parity. We focus on the two cases that the LSP is either a bino or a neutral singlet lepton. We work out the most important phenomenological differences between these two scenarios and discuss also how they might be distinguished from explicit R-Parity breaking models. In both cases we find that certain ratios of decay branching ratios are correlated with either the solar or the atmospheric (and reactor) neutrino angle. The hypothesis that spontaneous R-Parity violation is the source of the …
We study the inclusive production of the next-to-lightest neutralino chi2, decaying directly, or via slepton, into two leptons and the lightest neutralino. The dilepton invariant mass spectrum in these decays has a characteristic sharp edge near the kinematical upper limit. We propose to exploit this feature as a search strategy for the chi2, and thereby for SUSY. The possibilities to determine neutralinos and slepton masses are also discussed.
We consider supersymmetric (SUSY) models in which a very light gravitino is the lightest SUSY particle. Assuming that a neutralino is the next-to-lightest SUSY particle, we present a measurement of the neutralino mass at the LHC in two photons + missing energy events, which is based on the MT2 method. It is a direct measurement of the neutralino mass itself, independent of other SUSY particle masses and patterns of cascade decays before the neutralino is produced.
We perform a comprehensive analysis of the decays of charginos and neutralinos in the Minimal Supersymmetric Standard Model where the neutralino $χ_1^0$ is assumed to be the lightest supersymmetric particle. We focus, in particular, on the three-body decays of the next-to-lightest neutralino and the lightest chargino into the lightest neutralino and fermion-antifermion pairs and include vector boson, Higgs boson and sfermion exchange diagrams, where in the latter contribution the full mixing in the third generation is included. The radiative corrections to the heavy fermion and SUSY particle m…
We discuss the phenomenology of the lightest neutralino in models where an effective bilinear term in the superpotential parametrizes the explicit breaking of R-parity. We consider supergravity scenarios where the lightest supersymmetric particle (LSP) is the lightest neutralino and which can be explored at LEP2. We present a detailed study of the LSP decay properties and general features of the corresponding signals expected at LEP2. We also contrast our model with gauge mediated supersymmetry breaking.
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 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 calculate one-loop corrections to the decays of the next-to-lightest neutralino $\tildeχ_2^0$ into the lightest neutralino $\tildeχ_1^0$ and two leptons; this includes diagrams where a real photon is emitted. In cases where two-body decays $\tildeχ_2^0 \to \tilde{l}^\pm_1 l^\mp \to \tildeχ_1^0 l^- l^+$ are kinematically allowed, we calculate these decays both with and without the single-pole approximation, and find consistent results. For example, for the minimal supergravity parameter set SPS1a, the integrated partial widths (the branching ratios) for $\tildeχ_2^0\to \tildeχ_1^0 l^- l^+ (l…
We study a distinct supersymmetric signal of multi-photons in association with jets and missing transverse energy. At least one of these photons has the origin in displaced vertex, thus delayed and non-pointing. We consider a supersymmetric scenario in which the gravitino is the lightest supersymmetric particle (LSP) (with a mass $\sim 1~{keV}$) and the lightest neutralino is the next-to-lightest supersymmetric particle (NLSP). The NLSP decays dominantly into a photon and a gravitino within the detector with a decay length ranging from $cτ_{\tildeχ}\sim$ 50-100 cm. In addition, we assume that …
In my diploma thesis I calculate a lower mass bound of the lightest nutralino assuming an additional supernova cooling mechanism. I consider elektron-positron annihilation and nucleon-nucleon bremsstrahlung as cooling processes. These cooling processes must not be too effective because they would destroy the neutrino signal (SN 1987a). From this requirement I derive an upper bound for the emitted energy and as a consequence I get a lower bound for the mass of the lightest neutralino.
Prospects are examined for the detection of a slow decay of the lightest neutralino (or any other longlived particles) at the CERN LHC and at Very Large Hadron Collider (VLHC). We first point out that such hadron colliders will become the ``neutralino factory'' producing 10^6--10^9 neutralinos/yr, if gluinos and/or squarks actually exist below O(1) TeV. The lightest neutralino (\neu), usually assumed to be stable, will be unstable if lighter superparticles such as the gravitino (\gra) or axino (\axi) exist, or R-parity is not conserved. The decay signal would, however, be missed in usual colli…
Using the latest LHC data, we analyse and compare the lower limits on the masses of gluinos and the lightest stop in two natural supersymmetric motivated scenarios: one with a neutralino being the lightest supersymmetric particle (LSP) and the other one with gravitino as the LSP and neutralino as the next-to-lightest supersymmetric particle. In the second case our analysis applies to neutralinos promptly decaying to very light gravitinos, which are of cosmological interest, and are generic for low, of order O(100) TeV, messenger scale in gauge mediation models. We find that the lower bounds on…
We study the neutralino sector of the Minimal Non-minimal Supersymmetric Standard Model (MNSSM) where the $μ$ problem of the Minimal Supersymmetric Standard Model (MSSM) is solved without accompanying problems related with the appearance of domain walls. In the MNSSM as in the MSSM the lightest neutralino can be the absolutely stable lightest supersymmetric particle (LSP) providing a good candidate for the cold dark matter component of the Universe. In contrast with the MSSM the allowed range of the mass of the lightest neutralino in the MNSSM is limited. We establish the theoretical upper bou…
We investigate the correlated predictions of singlet extended MSSM models for direct detection of the lightest neutralino with its cosmological relic density. To illustrate the general effects of the singlet, we take heavy sleptons and squarks. We apply LEP, $(g-2)_μ$ and perturbativity constraints. We find that the WMAP upper bound on the cold dark matter density limits much of the parameter space to regions where the lightest neutralino can be discovered in recoil experiments. The results for the NMSSM and UMSSM are typically similar to the MSSM since their light neutralinos have similar com…
Relatively light sneutrinos, which are experimentally allowed, may significantly affect the currently popular search strategies for supersymmetric particles by decaying dominantly into an invisible channel. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy -- in addition to the lightest supersymmetric particle (LSP) \zi\ -- the virtual LSPs (VLSPs). It is shown that these VLSPs are allowed in supergravity models with common scalar and gaugino masses at the unification scale for a sizable region of parameter space and are co…
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 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 study properties of the lightest neutralino (χ) and calculate its cosmological relic density in a supersymmetric U(1)' model with a secluded U(1)' breaking sector (the S-model). The lightest neutralino mass is smaller than in the minimal supersymmetric standard model; for instance, m_χ< 100 GeV in the limit that the U(1)' gaugino mass is large compared to the electroweak scale. We find that the Z-χ-χcoupling can be enhanced due to the singlino components in the extended neutralino sector. Neutralino annihilation through the Z-resonance then reproduces the measured cold dark matter density o…
The neutralino sector of the semi-constrained next-to-minimal supersymmetric standard model is explored under recent experimental constraints, with special attention to dark matter (DM) limits. The effects of the upper and lower bounds of dark matter relic density and recent direct detection constraints on spin-independent and -dependent cross-sections are thoroughly analyzed. Particularly, we show which regions of the parameter space are ruled out due to the different dark matter constraints and the corresponding model-specific parameters: $λ, κ, A_λ$, and $A_κ$. We analyze all annihilation a…
Neutralino as the lightest supersymmetric particle (LSP) is a candidate for supersymmetric dark matter. It is known that coannihilation effects could be important in neutralino relic density calculation. Here we present some results on neutralino-stop coannihilation in the CMSSM. In this model, the lighter stop can be degenerate with the lightest neutralino chi when |A_0| is not equal to 0 and large, more specifically when the lighter stop mass is suppressed by large off-diagonal terms in the stop square mass matrix. In the region where the stop is slightly heavier than the neutralino, the coa…
If $R$-parity is not conserved, the lightest supersymmetric particle (LSP) could decay via lepton number violating or baryon number violating interactions. The latter case is particularly insidious since it leads to a reduction of the $\eslt$ as well as leptonic signals for supersymmetry. We evaluate cross sections for jets plus $\eslt$, 1$\ell$, $2\ell$ (same-sign and opposite sign) and $3\ell$ event topologies that result from the simultaneous production of all sparticles at the CERN Large Hadron Collider (LHC), assuming that the lightest supersymmetric particle $\tz_1$ decays hadronically i…
We study the production of the lightest neutralinos in the process $e^+ e^- \rightarrow χ_1^0 χ_1^0 γ$ in supersymmetric grand unified models for the International Linear Collider Energies with longitudinally polarized beams. We consider cases where the standard model gauge group is unified into the grand unified gauge groups SU(5), or SO(10). We have carried out a comprehensive study of this process in the SU(5) and SO(10) grand unified theories which includes the QED radiative corrections. We compare and contrast the dependence of the signal cross section on the grand unified gauge group, an…
Indirect limits on the mass of the lightest neutralino are derived from the results of searches for charginos, neutralinos, and sleptons performed with data taken by the ALEPH Collaboration at centre-of-mass energies near the Z peak and at 130 and 136 GeV. Within the context of the Minimal Supersymmetric Standard Model and when $M_{\tildeν}\ge 200$ GeV/c^2, the bound $M_χ>12.8$ GeV/c^2 at the 95\% confidence level applies for any $\tanβ$. The impact of lighter sneutrinos is presented in the framework of SUSY grand unified theories; a massless neutralino is allowed only for a narrow range of $\…
We examine in detail the neutrino masses and mixing patterns in an extension of the minimal supersymmetric standard model with three gauge-singlet neutrinos and R-parity violation. The Majorana masses for the gauge-singlet neutrinos as well as the usual $μ$-term for the Higgs superfields are generated at the electroweak scale through the vacuum expectation values of the singlet sneutrinos. The resulting effective mass matrix for the three light neutrinos have contributions from the seesaw mechanism involving the singlet neutrinos as well as due to the mixing with the heavy neutralinos. This mo…
We perform a study of neutrinoless double beta ($0νββ$) decay mediated by the lightest neutralino of arbitrary mass in the Minimal Supersymmetric Standard Model (MSSM) under the presence of R-parity violating trilinear interactions. In this scenario, the exchange of the lightest neutralino can result in $0νββ$ decay of either long-range or short-range behaviour, depending on the neutralino mass. Using nuclear matrix elements calculated in the Interacting Boson Model, we use an interpolation between the long- and short-range behaviours with an approximate formula. The non-observation of $0νββ$ …
We analyse the mass reach for electroweakinos at future hadron colliders and their interplay with direct detection experiments. Motivated by the LHC data, we focus on split supersymmetry models with different electroweakino spectra. We find for example that a 100 TeV collider may explore Winos up to ~ 7 TeV in low scale gauge mediation models or thermal Wino dark matter around 3 TeV in models of anomaly mediation with long-lived Winos. We show moreover how collider searches and direct detection experiments have the potential to cover large part of the parameter space even in scenarios where th…
We give an overview of our precise calculation of the relic density of the lightest neutralino, in which we included relativistic Boltzmann averaging, subthreshold and resonant annihilations, and coannihilation processes with charginos and neutralinos.
In this work, we propose a search for a single photon at \texttt{FASER} and \texttt{FASER2}, produced from decays of bino-like, sub-GeV lightest neutralinos in the theoretical framework of the R-parity-violating (RPV) Minimal Supersymmetric Standard Model (MSSM). We consider a list of representative benchmark scenarios with one or two non-vanishing RPV couplings. The photon has an energy $\mathcal{O}\left(0.1\right)-\mathcal{O}\left(1\right)$ TeV. We find a sensitivity reach for RPV couplings beyond the current bounds by orders of magnitude at \texttt{FASER} and \texttt{FASER2}.
I consider the prospect to use the outer layer of the Moon as a detector volume for ultra-high energy (UHE) neutrino fluxes and the flux of the lightest neutralino which I assume is the lightest supersymmetric particle (LSP). For this purpose, I calculate the event rates of these fluxes for top-down scenarios. I show that a suitable experiment for the detection of radio waves might be able to detect sufficient event rates after a measurement period of one year.
If a light gaugino sector exists in the supersymmetric standard model then the mass of lightest neutralino may be of the order of 1 GeV or less. As a consequence of neutral flavor violation in supersymmetric theories $B_s$-meson may decay into a pair of lightest neutralinos in such a case. It is found that the parameter space for such light neutralinos can be appreciably constrained by looking for such decays. We also show how a rare B-decays ($B \longrightarrow K(K^{*}) + invisible$ channels) can help us in probing a light neutralino in B-factories in a reasonably model- independent manner. F…
We investigate the production of charginos and neutralinos at a 500 GeV e^+e^- collider (NLC) and study their decays to the lightest neutralino, which then decays into multi-fermion final states through couplings which do not conserve R-parity. These couplings are assumed to affect only the decay of the lightest neutralino. Detailed analyses of the possible signals and backgrounds are performed for five selected points in the parameter space.
The $U(1)_X$ extension of the minimal supersymmetric standard model(MSSM) is called as $U(1)_X$SSM with the local gauge group $SU(3)_C\times SU(2)_L \times U(1)_Y \times U(1)_X$. $U(1)_X$SSM has three singlet Higgs superfields beyond MSSM. In $U(1)_X$SSM, the mass matrix of neutralino is $8\times8$, whose lightest mass eigenstate possesses cold dark matter characteristic. Supposing the lightest neutralino as dark matter candidate, we study the relic density. For dark matter scattering off nucleus, the cross sections including spin-independent and spin-dependent are both researched. In our nume…
We discuss the lower bound to the lightest Higgs boson H_1 in the minimal supersymmetric extension of the standard model (MSSM) with explicit CP violation, and the phenomenology of the lightest relic neutralino in the same scenario. In particular, adopting the CPX benchmark scenario, we find that the combination of experimental constraints coming from LEP, Thallium Electric Dipole Moment (EDM) measurements, quorkonium decays, and B_s -> mu mu decay favours a region of the parameter space where the mass of H_1 is in the range 7 GeV < M_{H_1} < 10 GeV, while 3 < tan(beta) < 5. Assuming a departu…
We provide the next-to-leading order (NLO) predictions for the neutralino pair production via quark-antiquark annihilation and gluon-gluon fusion at the CERN Large Hadron Collider, focusing on the lightest neutralino which is likely to be the lightest supersymmetric particle. The dependence of total LO, NLO cross sections, and $K$ factor on the center-of-mass energy, the $M_2$-$μ$ mass plane, the squark mass, and the factorization and renormalization scales is comprehensively analyzed for three different scenarios in the minimal supersymmetric standard model and the constrained minimal supersy…
