Precise Predictions for Higgs Production in Neutralino Decays
A. C. Fowler
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4 pages, 3 figures; to appear in the proceedings of the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY09), Boston, USA, 5-10 Jun 2009
Complete one-loop results, supplemented by two-loop Higgs propagator-type corrections, are obtained for the class of processes chi^0_i->chi^0_j h_a in the MSSM with CP-violating phases for parameters entering the process beyond lowest order. The parameter region of the CPX benchmark scenario where a very light Higgs boson is unexcluded by present data is analysed in detail. We find that the decay chi^0_2->chi^0_1 h_1 may offer good prospects to detect such a light Higgs boson.
The lightest neutralino is a compelling candidate to account for cold dark matter in the universe in supersymmetric theories with $R$--parity. In the CP-invariant theory, the neutralino relic density can be found in accord with recent WMAP data if neutralino annihilation in the early universe occurs via the s-channel $A$ funnel. In contrast, in the CP-noninvariant theory two heavy neutral Higgs bosons can contribute to the Higgs funnel mechanism significantly due to a CP-violating {\it complex} mixing between two heavy states, in particular, when they are almost degenerate. With a simple analy…
We show that the Higgs boson exchange contribution can be large in three-body decays of neutralinos even in the case of small tan(beta). This enlarges the branching ratios for the decays neutralino_2 -> neutralino_1 b \bar{b} and neutralino_2 -> neutralino_1 tau- tau+. This is the case in the region of the parameter space where the two lightest neutralinos are gaugino-like, the sfermions are heavier than 300 GeV, and m_A0 = 200 GeV or smaller.
We study the interference of resonant Higgs boson exchange in neutralino production in μ^+ μ^- annihilation with longitudinally polarized beams. We use the energy distribution of the decay lepton in the process \neutralino_j \to \ell^\pm \slepton^\mp to determine the polarization of the neutralinos. In the CP conserving Minimal Supersymmetric Standard Model a non-vanishing asymmetry in the lepton energy spectrum is caused by the interference of Higgs boson exchange channels with different CP eigenvalues. The contribution of this interference is large if the heavy neutral bosons H and A are nea…
We present the one-loop corrected decay widths of a neutral (charged) Higgs boson into a chargino or neutralino pair (chargino and neutralino) in the CP-conserving MSSM. The chargino and neutralino parameters are renormalized in the on-shell scheme and it is shown that the correction due to the chargino/neutralino mass matrix renormalization is comparable to the conventional vertex correction. The full corrections are typically of the order of 10%.
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.
In the Minimal Supersymmetric Standard Model, neutralinos lighter than 50 GeV are compatible with all accelerator, precision, and cosmological bounds. Such neutralinos might constitute a relevant decay channel for the Higgs boson, modifying its expected signatures at hadron colliders. We study the branching ratio h --> χχand determine the region in the supersymmetric parameter space where it is sizable. We have found that, in fact, the Higgs may dominantly decay into neutralino pairs. Besides, as a result of this new channel, the branching ratio into visible modes, such as h --> γγ, gets suppr…
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…
The neutralino-nucleon (\tildeχ^0-N) scattering is an important process for direct dark matter searches. In this paper we discuss one-loop contributions to the cross section in the wino-like and Higgsino-like LSP cases. The neutralino-nucleon scattering mediated by the Higgs \tildeχ^0\tildeχ^0 and Z\tildeχ^0\tildeχ^0 couplings at tree level is suppressed by the gaugino-Higgsino mixing at tree level when the neutralino is close to a weak eigenstate. The one-loop contribution to the cross section, generated by the gauge interaction, is not suppressed by any SUSY particle mass or mixing in the wi…
We show that a supersymmetric neutral Higgs boson with a mass of about 115 GeV and with the other prerequisites required by the LEP Higgs events would be compatible with the detection of relic neutralinos in current set-ups for WIMP direct search. Thus this putative Higgs would fit remarkably well in an interpretation in terms of relic neutralinos of the annual-modulation effect recently measured in a WIMP direct experiment. We also show that the cosmological abundance of the relevant neutralinos reaches values of cosmological interest.
We analyze the charge-parity (CP) asymmetry in the charged Higgs boson decays to chargino-neutralino pairs, H^- -> chargino_i + neutralino_j. We show first that these modes have a large branching ratio for m_H^- > 600 GeV. We use Cutkosky rules to obtain the analytical formulas needed for the evaluation of the asymmetry under consideration. We then calculate the CP asymmetry in chargino-neutralino decays by including supersymmetric mass bounds, as well as constraints from b -> s gamma, (g-2)_mu, Deltaρand electric dipole moments. Finally, we discuss observability of the asymmetry at the LHC by…
A calculus for the derivatives of the eigen values of the neutralino mass matrix with respect to the CP violating background fields is developed and used to compute the mixings among the CP even and the CP odd Higgs sectors arising from the inclusion of the neutralino sector consisting of the neutralino, the Z boson, and the neutral Higgs bosons ($χ^0_i-Z-h^0-H^0$) exchange in the loop contribution to the effective potential including the effects of large CP violating phases. Along with the stop, sbottom, stau and chargino-W-charged Higgs ($χ^+-W-H^+$) contributions computed previously the pre…
We examine prospects for detecting the neutral Higgs bosons of minimal supersymmetric models (MSSM) when their decays into neutralino pairs are kinematically allowed. The best signature appears to be $H_h,H_p\to\tz_2\tz_2\to 4\ell +\eslt$. We argue that Standard Model contributions to this signature are negligible, and examine regions of MSSM parameter space where the four lepton mode should be observable at the Large Hadron Collider. The same signal can also come from continuum neutralino pair production. We propose a set of cuts to illustrate that the neutralino decay mode of the Higgs boson…
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.
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.
In the CP-violating Minimal Supersymmetric Standard Model, we study the pair production of neutralinos at center-of-mass energies around the heavy neutral Higgs boson resonances. For longitudinally polarized muon beams, we analyze CP asymmetries which are sensitive to the interference of the two heavy neutral Higgs bosons. Due to radiatively induced scalar-pseudoscalar transitions, the CP asymmetries can be strongly enhanced when the resonances are nearly degenerate, as in the Higgs decoupling limit. The Higgs couplings to the neutralino sector can then be analyzed in the presence of CP violat…
We consider the production of neutralino, chargino, and charged Higgs boson pairs in the MSSM framework at future $e^+e^-$ colliders. We show that, for c.m. energies in the one TeV range and in a ``moderately'' light SUSY scenario, a combined analysis of the slopes of these production cross sections could lead to a strong consistency test involving the soft supersymmetric breaking parameters $M_1$, $M_2$, the Higgsino parameter $μ$, and $\tanβ$.
We study the neutralino relic density in the minimal supersymmetric standard model with natural light Higgs sector in which all Higgs masses, the supersymmetry (SUSY) breaking parameters, and the higgsino mass parameter mu are of order the weak scale. To realize this situation we adopt nonuniversal Higgs masses at the grand unified scale. We show that in some parameter space in which the SUSY breaking parameters are comparatively small, not only the constraint from the observed relic density of dark matter but also the LEP Higgs bound and the constraint from the b ->s gamma process are satisfi…
We present a complete calculation of the QCD and SUSY-QCD corrections to neutralino pair annihilation into bottom quark-antiquark pairs through exchange of a pseudoscalar Higgs boson, which is the dominant process in the cosmological A-funnel region of the mSUGRA model. We present numerical predictions for the annihilation cross section and discuss the influence of the correction terms on the cold dark matter relic density with respect to recent cosmological data.
We present the one-loop corrected decay widths for the decays of the neutral Higgs bosons h^0, H^0, and A^0 into a neutralino pair neu_m neu_n (m, n = 1, >..., 4) and to the decay neu_m -> (h^0, H^0, A^0) + neu_n. The corrections contain the one-loop contributions of all fermions and sfermions. All parameters are taken on-shell. This requires a proper treatment of the neutralino mass and mixing matrix. The dependence on the SUSY parameters is discussed. The corrections can be large in certain regions of the parameter space.
Recently, the CoGeNT collaboration reported the WIMP candidate signal events exceeding the known backgrounds where the light WIMP with large cross section is supported. Motivated by this issue, we analyze a light neutralino dark matter scenario with a very light CP-even Higgs mediation in the elastic scattering process, which provides the mass and direct detection cross section to explain the CoGeNT result. To be compatible with the result of LEP experiments, the light CP-even Higgs is favored to be in 9 to 10 GeV. Such a scenario can be realized in the "Beyond the MSSM" context. The relic abu…
Recently, the CoGeNT collaboration reported the WIMP candidate signal events exceeding the known backgrounds where the light WIMP with large cross section is supported. Motivated by this issue, we analyze a light neutralino dark matter scenario with a very light CP-even Higgs mediation in the elastic scattering process, which provides the mass and direct detection cross section to explain the CoGeNT result. To be compatible with the result of other experiments such as LEP and B-factories, the light CP-even Higgs is favored to be in 9 to 10 GeV. Such a scenario can be realized in the "Beyond th…
Next-to-Minimal Supersymmetric Standard Model neutralino dark matter candidates in the (1-15) GeV range are found with a Markov Chain Monte Carlo scanning code. A very light, singlet-like Higgs and/or CP-odd Higgs is needed in order to achieve such light masses. Light scalar Higgses can yield large direct detection cross sections, suitable for an account of the recent claims for signals. Neutralino annihilations via resonant light pseudoscalar Higgs exchanges can overproduce the indirect yield of gamma-rays from dwarf spheroidal galaxies. Hence, direct and indirect detection experiments probe …
We consider the Minimal Supersymmetric Standard Model (MSSM) with varying amounts of non-universality in the soft supersymmetry-breaking contributions to the Higgs scalar masses. In addition to the constrained MSSM (CMSSM) in which these are universal with the soft supersymmetry-breaking contributions to the squark and slepton masses at the input GUT scale, we consider scenarios in which both the Higgs masses are non-universal by the same amount (NUHM1), and scenarios in which they are independently non-universal (NUHM2). As the lightest neutralino is a dark matter candidate, we demand that th…
We consider the production of chargino, neutralino and charged Higgs boson pairs at future linear colliders for c. m. energies in the one TeV range within the MSSM. We compute the leading (double) and next-to leading (linear) supersymmetric logarithmic terms of the so-called "Sudakov expansion" at one-loop level. We show that a combined analysis of the slopes of the chargino, neutralino, and charged Higgs boson pair production cross sections would offer a simple possibility for determining \tanβfor large (\gsim 10) values, and the parameters M_1, M_2, and μ. This test could provide a strong co…
We compute the full O(alpha_s) supersymmetric QCD corrections for neutralino-stop co-annihilation into electroweak gauge and Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). We show that these annihilation channels are phenomenologically relevant within the so-called phenomenological MSSM, in particular in the light of the observation of a Higgs-like particle with a mass of about 126 GeV at the LHC. We present in detail our calculation, including the renormalization scheme, the infrared treatment, and the kinematical subtleties to be addressed. Numerical results for the co-ann…
Phenomenology of neutralino dark matter in the minimal supersymmetric model is discussed for a scenario where the lightest Higgs boson mass is lighter than 114.4 GeV. We show that the scenario is consistent not only with many collider experiments but also with the observed relic abundance of dark matter. The allowed region may be probed by experiments of Bs to mu^+ mu^- in near future. The scenario predicts a large scattering cross section between the dark matter and ordinary matter and thus it may be tested in present direct detection experiments of dark matter.
We examine a possibility to explain the signals of dark matter direct detection from DAMA and CoGeNT experiments, under the framework of supersymmetric extension of the standard model. For this purpose, we introduce four Higgs doublet fields and assume that one pair of Higgs fields which have very small vacuum expectation values gives sizable effects for annihilation and scattering processes of dark matter. We show that the preferred parameter regions for DAMA and CoGeNT results can be simultaneously explained by supersymmetric four-Higgs doublet model with the parameters consistent with the o…
In view of the latest LEP data we consider the effects of charginos and neutralinos on the two-photon and bbbar signatures of the Higgs at the LHC. Assuming the usual GUT inspired relation between M_1 and M_2 we show that there are only small regions with moderate tanbeta and large stop mixings that may be dangerous. Pathological models not excluded by LEP which have degeneracy between the sneutrino and the chargino are however a real danger because of large branching fraction of the Higgs into invisibles. We have also studied models where the gaugino masses are not unified at the GUT scale. W…
We examine the prospects for the detection of Higgs mediated lepton flavor violation at LHC and at a photon collider in the minimal supersymmetric standard model with large lepton flavor violating mass insertions in the $μ-τ$ sector constraining the parameter space with several experimental bounds. We find rates probably too small to be observed at future experiments if models have to accommodate for a neutralino relic density as measured by WMAP and explain the $(g-2)_μ$ anomaly: better prospects are found if these two constraints are applied only as upper bounds. The spin-independent neutral…
We study the decays of a standard model-like MSSM Higgs boson to pairs of neutralinos, each of which subsequently decays promptly to a photon and a gravitino. Such decays can arise in supersymmetric scenarios where supersymmetry breaking is mediated to us by gauge interactions with a relatively light gauge messenger sector (M_{mess} < 100 TeV). This process gives rise to a collider signal consisting of a pair of photons and missing energy. In the present work we investigate the bounds on this scenario within the minimal supersymmetric standard model from existing collider data. We also study t…
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…
The Minimal Supersymmetric Extension of the Standard Model (MSSM) is a well motivated theoretical framework, which contains an extended Higgs sector, including a light Higgs with Standard Model-like properties in most of the parameter space. Due to the large QCD background, searches for such a Higgs, decaying into a pair of bottom quarks, is very challenging at the LHC. It has been long realized that the situation may be ameliorated by searching for Higgs bosons in supersymmetric decay chains. Moreover, it has been recently suggested that the bobber decay channel may be observed in standard pr…
The electroweak corrections to the partial widths of the $H^+ \to \tildeχ^+_i \tildeχ_j^0 (i=1,j=1,2)$ decays including one-loop diagrams of the third generation quarks and squarks, are investigated within the Supersymmetric Standard Model. The relative corrections can reach the values about 10%, therefore they should be taken into account for the precise experimental measurement at future colliders.
We study implications of two dark matter candidate events at CDMS-II on the neutralino dark matter scenario in the supersymmetric standard model, in light of the recent lattice simulation on the strange quark content of a nucleon. The scattering rate of neutralino-nucleon is dominated by Higgs exchange processes and the mass of heavy Higgs boson is predicted for the neutralino of Bino-Higgsino mixing state. In the case of Wino-Higgsino mixing, the Higgs sector may not be constrained.
The ATLAS and CMS collaborations have recently reported tantalizing hints of the existence of a 125 GeV Higgs--like particle, whose couplings appear to match well the Standard Model (SM) expectations. In this work, we study implications of this observation for the neutralino sector of supersymmetric models, assuming that the Higgs signal gets confirmed. In general, the Higgs decay into neutralinos can be one of its dominant decay channels. Since a large invisible Higgs decay branching ratio would be in conflict with the data, this possibility is now constrained. In particular, we find that mos…
The region of low neutralino masses as low as (5-10) GeV has attracted attention recently due to the possibility of excess events above background in dark matter detectors. An analysis of spin independent neutralino-proton cross sections $\SI$ which includes this low mass region is given. The analysis is done in MSSM with radiative electroweak symmetry breaking (REWSB). It is found that cross sections as large as $10^{-40}$ cm$^2$ can be accommodated in MSSM within the REWSB framework. However, inclusion of sparticle mass limits from current experiments, as well as lower limits on the Higgs se…
In this work, the following reactions have been studied: $e^- e^+ \to H^- \widetildeχ_{1}^+ \widetildeχ_{1}^o$, $e^{-}e^{+}\to h\widetildeχ_{1}^{+}\widetildeχ_{1}^{-}$, $e^{-}e^{+}\to h\widetildeχ_{1}^{o}\widetildeχ_{1}^{o}$, $e^{-}e^{+}\to h H^{+} H^{-}$, where $\widetildeχ_{1}^{\pm}$ is the chargino and $\widetildeχ_{1}^{0}$ is the neutralino. $h$ represent the lightest neutral Higgs boson, and $H_3$ (sometimes refered to as $A$) is the pseudoscalar Higgs boson. The work went to calculate the differential cross section due to each Feynman diagram, then, the total cross section for each react…
We study the spin-independent neutralino Dark Matter scattering off heavy nuclei in the MSSM. We identify analytically the blind spots in direct detection for intermediate values of $m_A$. In the region where $μ$ and $M_{1,2}$ have opposite signs, there is not only a reduction of the lightest CP-even Higgs coupling to neutralinos, but also a destructive interference between the neutralino scattering through the exchange of the lightest CP-even Higgs and that through the exchange of the heaviest CP-even Higgs. At critical values of $m_A$, the tree-level contribution from the light Higgs exchang…
We study the radiative electroweak symmetry breaking and the relic abundance of neutralino dark matter in the supersymmetric type I seesaw model. In this model, there exist threshold corrections to Higgs bilinear terms coming from heavy singlet sneutrino loops, which make the soft supersymmetry breaking (SSB) mass for up-type Higgs shift at the seesaw scale and thus a minimization condition for the Higgs potential is affected. We show that the required fine-tuning between the Higgsino mass parameter mu and the SSB mass for up-type Higgs may be reduced at the electroweak scale, due to the thres…
We perform for the Large Hadron Collider (LHC) a detailed study of charged Higgs boson production via the top-bottom quark associated mode followed by decays into a chargino and a neutralino, with masses and couplings as given by the general Minimal Supersymmetric Standard Model (MSSM). We focus our attention on the region of parameter space where the charged Higgs is heavier than the top quark, with intermediate values of tan beta. In this region, the identification of charged Higgs bosons via decays into Standard Model (SM) particles has proven to be ineffective. Modelling the CMS detector, …
We explore the collider signatures of the Higgs sectors in singlet-extended MSSM models. We find that even with reduced couplings due to singlet mixing, a significant portion of the parameter spaces have a discoverable Higgs via traditional decay modes or via invisible decays (directly to neutralinos or through cascade decays to neutralinos and neutrinos). For illustrative points in parameter space we give the likelihood of Higgs discovery. In cases where neither traditional nor invisible modes can discover the Higgs, the neutralino sector may provide evidence for the extended models.
Neutralino can be the dark matter candidate in the gauge-mediated supersymmetry breaking models if the conformal sequestered mechanism is assumed in the hidden sector. In this paper, we study this mechanism by using the current experimental results after the run I of LHC and LUX. By adding new Yukawa couplings between the messenger fields and Higgs fields, we find that this mechanism can predict a neutralino dark matter with correct relic density and a Higgs boson with mass around 125 GeV. All our survived points have some common features. Firstly, the Higgs sector falls into the decoupling li…
Spin-independent cross-section for neutralino dark matter scattering off nuclei is investigated in the NMSSM. Several classes of blind spots for direct detection of singlino-Higgsino dark matter are analytically identified, including such that have no analog in the MSSM. It is shown that mixing of the Higgs doublets with the scalar singlet has a big impact on the position of blind spots in the parameter space. In particular, this mixing allows for more freedom in the sign assignment for the parameters entering the neutralino mass matrix, required for a blind spot to occur, as compared to the M…
In the Minimal Supersymmetric Extension of the Standard Model (MSSM) the higgsino mass parameter $μ$ appears both in the masses of the Higgs bosons and in the neutralino mass matrix. Electroweak finetuning therefore prefers small values of $|μ|$. On the other hand, bino--like neutralinos make a good dark matter candidate. We show that current direct search limits then impose a strong lower bound on $|μ|$, in particular for $μ> 0$ or if the masses of the heavy Higgs bosons of the MSSM are near their current limit from LHC searches. There is therefore some tension between finetuning and neutrali…
Among the possible decay modes of Higgs particles into supersymmetric states, neutralino and chargino decays play a prominent rôle. The experimental opportunities of observing such decay modes at LEP2 and at future e+e- linear colliders are analyzed within the frame of the Minimal Supersymmetric extension of the Standard Model. For heavy Higgs particles, the chargino/neutralino decay modes can be very important, while only a small window is open for the lightest CP-even Higgs particle. If charginos/neutralinos are found at LEP2, such decay modes can be searched for in a small area of the param…
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 compute the one loop corrected effective Lagrangian for the neutralino-neutralino-neutral Higgs interactions $χ^{0}_{\ell} χ^{0}_kH^{0}_m$. The analysis completes the previous analyses where similar corrections were computed for the $\bar{f} f H^{0}_m$ couplings, where $f$ stands for Standard Model quarks and leptons and for the chargino-chargino-neutral Higgs couplings $χ^{+}_l χ^{-}_kH^{0}_m$ within the minimal supersymmetric standard model MSSM. The effective one loop Lagrangian is then applied to the computation of the neutral Higgs decays. The sizes of the supersymmetric loop correctio…
We point out another important production channel of a light pseudoscalar Higgs boson $a_1$ via the decays of neutralinos, including $\widetildeχ_{2,3}^0 \to \widetildeχ_{1}^0 a_1$, in the framework of the NMSSM. We scan the whole parameter space using the most up-to-date version of NMHDECAY and search for regions where $B(\widetildeχ_{2,3}^0 \to \widetildeχ_{1}^0 a_1) > 0.5$. If the gluino and squarks are light enough for copious production of SUSY events at the LHC, there would be numerous number of $\widetildeχ_{2,3}^0$ in subsequent decays of gluinos and squarks. Therefore, the production …
In supersymmetric models the lightest Higgs boson may decay with a sizable branching ratio into a pair of light neutralinos. We analyze such decays within the context of the minimal supersymmetric standard model with R-parity violation, where the neutralino itself is unstable and decays into Standard Model fermions. We show that the R-parity violating couplings induce novel Higgs decay signals that might facilitate the discovery of the Higgs boson at colliders. At the LHC, the Higgs may be observed, for instance, through its decay -via two neutralinos- into final states containing missing ener…
The ATLAS and CMS experiments have recently claimed discovery of a Higgs boson-like particle at ~5 sigma confidence and are beginning to test the Standard Model predictions for its production and decay. In a variety of supersymmetric models, a neutralino NLSP can decay dominantly to the Higgs and the LSP. In natural SUSY models, a light third generation squark decaying through this chain can lead to large excess Higgs production while evading existing BSM searches. Such models can be observed at the 8 TeV LHC in channels exploiting the rare diphoton decays of the Higgs produced in the cascade …
We consider the minimal supersymmetric standard model within a scenario of large $\tanβ$ and heavy squarks and gluinos, with masses of the heavy neutral Higgs bosons below the TeV scale. We allow for the presence of a large, model independent, source of lepton flavor violation (LFV) in the slepton mass matrix in the $τ-μ$ sector by the mass insertion approximation. We constrain the parameter space using the $τ$ LFV decays together with the $B$-mesons physics observables, the anomalous magnetic moment of the muon and the dark matter relic density. We further impose the exclusion limit on spin-i…
We study the decay of 125 GeV Higgs boson to light LSP neutralino in the phenomenological minimal supersymmetric standard model in the context of collider searches and astrophysical experiments. We consider the parameter space for light neutralinos that can be probed via the invisible Higgs decays and higgsino searches at the ILC. We consider the cases where the light neutralino is compatible with the observed relic density or where the thermal relic is over-abundant, pointing to non-standard cosmology. In the former case, when the neutralino properties give rise to under-abundant relic densit…
We have investigated charged Higgs boson production via the gluon-bottom quark mode, gb -> tH+, followed by its decay into a chargino and a neutralino. The calculations are based on masses and couplings given by the Minimal Supersymmetric Standard Model (MSSM) for a specific choice of MSSM parameters. The signature of the signal is characterized by three hard leptons, a substantial missing transverse energy due to the decay of the neutralino and the chargino and three hard jets from the hadronic decay of the top quark. The possibility of detecting the signal over the Standard Model (SM) and no…
In the minimal supersymmetric standard model (MSSM), the neutralinos, the spin--1/2 Majorana superpartners of the neutral gauge and Higgs bosons, are expected to be among the light supersymmetric particles that can be produced copiously at future high--energy colliders. We analyze two--body neutralino decays into a neutralino plus a $Z$ boson or a lightest neutral Higgs boson $h$, allowing the relevant parameters to have complex phases. We show that the two--body tree--level decays of neutralinos are kinematically allowed in a large region of the MSSM parameter space and they can provide us wi…
It is pointed out that a bino-dominated well-tempered bino-higgsino in the Minimal Supersymmetric Standard Model (MSSM) with heavy non-SM- like scalars can satisfy the 2016 LUX constraints on the scattering cross-section of dark matter on nuclei only if $\tanβ$ is smaller than about 3. This, together with the Higgs mass constraint, sets a lower bound on the stops masses of about 25 TeV. The LUX constraints can be satisfied for larger $\tanβ$ if the non-SM-like Higgs bosons are light enough. However, this region of parameter space is strongly constrained by recent LHC results of the Higgs boson…
Heavy neutral Higgs boson production and decay into neutralino and chargino pairs is studied at the Large Hadron Collider in the context of the Minimal Supersymmetric Standard Model. Higgs boson decays into the heavier neutralino and chargino states, i.e., H^0 or A^0 to tilde{chi}_i^0 tilde{chi}_j^0 (i,j = 2,3,4) as well as H^0 or A^0 to tilde{chi}_1^{pm} tilde{chi}_2^{mp}, tilde{chi}_2^+ tilde{chi}_2^- (all leading to four-lepton plus missing transverse energy final states), is found to improve the possibilities of discovering such Higgs states beyond those previously identified by considerin…
Complete one-loop results are obtained for the class of processes chi^0_i->chi^0_j h_a in the MSSM where all parameters entering this process beyond lowest order are allowed to have arbitrary CP-violating phases. An on-shell renormalisation scheme is worked out for the chargino-neutralino sector that properly takes account of imaginary parts arising from complex parameters and from absorptive parts of loop integrals. The genuine vertex contributions to the neutralino decay amplitudes are combined with two-loop propagator-type corrections for the outgoing Higgs boson. In this way the currently …
Unlike its minimal counterpart, the Next to Minimal supersymmetric Standard Model (NMSSM) allows the possibility that the lightest neutralino could have a mass as small as $\sim 1 {\rm GeV}$ while still providing a significant component of relic dark matter (DM). Such a neutralino can provide an invisible decay mode to the Higgs as well. Further, the observed SM-like Higgs boson ($H_{125}$) could also have an invisible branching fraction as high as $\sim 19\%$. Led by these facts, we first delineate the region of parameter space of the NMSSM with a light neutralino ($M_{{\tildeχ}_{1}^{0}} < 62…
