LSP Dark Matter Research Articles

Reheating after inflation by supersymmetry breaking

We study reheating after the end of inflation in models where the inflaton is the superpartner of goldstino and is charged under a gauged U(1) R-symmetry. We consider two classes of models – one is small field characterized by an almost flat Kähler space, and the other large field characterized by a hyperbolic Kähler space SU(1, 1)/U(1), while in both cases the inflaton superpotential is linear due to the R-symmetry. The inflationary observables of our models fit within 2sigma CMB values. Upon coupling the inflaton sector to the (supersymmetric) Standard Model, we compute the MSSM parameters, mass spectrum, and decay modes of the inflaton, with the resulting reheating temperature around 10^8 GeV. We also find that both models can accommodate superheavy LSP dark matter, depending on the parameter choice.

B \u2212 \u03c4 Yukawa unification in SUSY SU(5) with mirage mediation: LHC and dark matter implications

We consider a class of b − τ Yukawa unified Supersymmetric (SUSY) SU(5) GUTs, in which the asymptotic gaugino M1,2,3 masses are generated through the mirage mediated supersymmetry breaking, which is a combination of the gravity and anomaly mediation. Due to the contributions from the anomaly contribution, M3 is always lighter than M1 and M2, and consequently for the range of asymptotic masses considered, the gluino mass {m}_{tilde{g}} at low scale is bounded from above at about 4 TeV. We realize two different regions, in one of which the MSSM μ−term is less than about 3 TeV. This region yields a stop mass up to 5 TeV, and the stop mass is nearly degenerate with the LSP neutralino for mass around 0.8 to 1.7 TeV. A stau mass can be realized up to about 5 TeV, and the stau mass is approximately degenerate with the LSP neutralino for mass around 2 to 3 TeV. In addition, an A-funnel solution with {m}_Aapprox 2{m}_{{tilde{chi}}_1^0} and {m}_{{tilde{chi}}_1^0}sim 700-900 GeV is realized. These three cases yield LSP dark matter abundance in accordance with observations. A second region, on the other hand, arises for {m}_{tilde{g}}lesssim 1.1{m}_{{tilde{chi}}_1^0} . The μ−term is rather large (≳20 TeV), and the LSP neutralino is a bino-wino mixture. The gluino mass (∼ 0.8−1.2 TeV) is nearly degenerate with the LSP neutralino mass and hence, the gluino-neutralino coannihilation processes play a role in reducing the relic abundance of LSP neutralino down to ranges allowed by the current WMAP measurements. The two regions above can be distinguished through the direct detection experiments. The first region with relatively low μ values yields Higgsino-like DM, whose scattering on the nucleus typically has a large cross-section. We find that such solutions are still allowed by the current results from the LUX experiment, and they will be severely tested by the LUX-Zeplin (LZ) experiment. The second region contains bino-wino DM whose scattering cross-section is relatively low. These solutions are harder to rule out in the foreseeable future.

Confronting SUSY GUT With Dark Matter, Sparticle Spectroscopy and Muon (g − 2)

We explore the implications of LHC and cold dark matter searches for supersymmetric particle mass spectra in two different grand unified models with left-right symmetry, $SO(10)$ and $ SU(4)_c \times SU(2)_L \times SU(2)_R$ (4-2-2). We identify characteristic differences between the two scenarios, which imply distinct correlations between experimental measurements and the particular structure of the GUT group. The gauge structure of 4-2-2 enhances significantly the allowed parameter space as compared to $SO(10)$, giving rise to a variety of coannihilation scenarios compatible with the LHC data, LSP dark matter and the ongoing muon g-2 experiment.

Dark matter, sparticle spectroscopy and muon (g \u2212 2) in SU(4)c \xd7 SU(2)L \xd7 SU(2)R

We explore the sparticle mass spectra including LSP dark matter within the framework of supersymmetric SU(4)c × SU(2)L × SU(2)R (422) models, taking into account the constraints from extensive LHC and cold dark matter searches. The soft supersymmetry-breaking parameters at MGUT can be non-universal, but consistent with the 422 symmetry. We identify a variety of coannihilation scenarios compatible with LSP dark matter, and study the implications for future supersymmetry searches and the ongoing muon g-2 experiment.

Multiverse dark matter: SUSY or axions

The observed values of the cosmological constant and the abundance of Dark Matter (DM) can be successfully understood, using certain measures, by imposing the anthropic requirement that density perturbations go non-linear and virialize to form halos. This requires a probability distribution favoring low amounts of DM, i.e. low values of the PQ scale f for the QCD axion and low values of the superpartner mass scale $$ \tilde{m} $$ for LSP thermal relics. In theories with independent scanning of multiple DM components, there is a high probability for DM to be dominated by a single component. For example, with independent scanning of f and $$ \tilde{m} $$ , TeV-scale LSP DM and an axion solution to the strong CP problem are unlikely to coexist. With thermal LSP DM, the scheme allows an understanding of a Little SUSY Hierarchy with multi-TeV superpartners. Alternatively, with axion DM, PQ breaking before (after) inflation leads to f typically below (below) the projected range of the current ADMX experiment of f = (3 − 30) × 1011 GeV, providing strong motivation to develop experimental techniques for probing lower f.

Grand unification and intermediate scale supersymmetry

With minimal field content and for an interesting range of the supersymmetric Higgs mixing parameter, 0.5 < tan^2 \beta < 2, the superpartner mass scale, \tilde{m}, is found to be at the intermediate scale, ~ 10^{10 \pm 1} GeV, near where the Standard Model Higgs quartic coupling passes through zero. For any 4d supersymmetric grand unified symmetry spontaneously broken by a vacuum expectation value <\Sigma>, if superpotential interactions for \Sigma are forbidden e.g. by R symmetries, the uneaten color octet, \Sigma_8, and weak triplet, \Sigma_3, have masses of order \tilde{m}. The combination of superpartner and \Sigma_{8,3} states leads to successful gauge coupling unification, removing the disastrously high proton decay rate of minimal Standard Model unification. Proton decay could be seen in future experiments if \tilde{m} ~ 10^{11} GeV, but not if it is lower. If the reheating temperature after inflation, T_R, is less than \tilde{m} dark matter may be axions. If T_R > \tilde{m}, thermal LSP dark matter may lead to the environmental selection of a TeV-scale LSP, either wino or Higgsino, which could comprise all or just one component of dark matter. In the Higgsino case, the dark matter is found to behave inelastically in direct detection experiments, and gauge coupling unification occurs accurately without the need of any threshold corrections.

LHC Signals of Pure Gravity Mediation

Evidence is mounting that natural supersymmetry at the weak scale is not realized in nature. This evidence comes from collider searches, a lack of new flavor changing neutral current e ects, and now also the size of the measured Higgs mass. On the other hand, string theory suggests that supersymmetry might be present at some energy scale, and gauge coupling unification and dark matter imply that that energy scale may be relatively low. The simplest model to address all of these hints is arguably gravity mediation, in which the scalar superpartner masses are taken to be perhaps 100 TeV, with gauginos automatically acquiring loop factor suppressed masses of order TeV. The gauginos might then be the only superpartners accessible to the LHC. Unification and LSP dark matter are maintained (with a wino LSP) at the cost of a 10 5 or 10 6 fine tuning. Here I will discuss the structure and LHC phenomenology of pure gravity mediation.

LHC constraints on NLSP gluino and dark matter neutralino in Yukawa unified models

The ATLAS experiment has recently presented its search results for final states containing jets and/or b-jet(s) and missing transverse momentum, corresponding to an integrated luminosity of 165 pb−1. We employ this data to constrain a class of supersymmetric SU(4)c×SU(2)L×SU(2)R models with t−b−τ Yukawa unification, in which the gluino is the next to lightest supersymmetric particle (NLSP). The NLSP gluino is slightly (∼10–30%) heavier than the LSP dark matter neutralino, and it primarily decays into the latter and a quark–antiquark pair or gluon. We find that NLSP gluino masses below ∼300 GeV are excluded by the ATLAS data. For LSP neutralino mass ∼200–300 GeV and μ>0, where μ is the coefficient of the MSSM Higgs bilinear term, the LHC constraints in some cases on the spin-dependent (spin-independent) neutralino–nucleon cross section are significantly more stringent than the expected bounds from IceCube DeepCore (Xenon 1T/SuperCDMS). For μ<0, this also holds for the spin-dependent cross sections.

Dark Matter in SuperGUT Unification Models

After a brief update on the prospects for dark matter in the constrained version of the MSSM (CMSSM) and its differences with models based on minimal supergravity (mSUGRA), I will consider the effects of unifying the supersymmetry-breaking parameters at a scale above MGUT . One of the consequences of superGUT unification, is the ability to take vanishing scalar masses at the unification scale with a neutralino LSP dark matter candidate. This allows one to resurrect no-scale supergravity as a viable phenomenological model.

Predictive signatures of supersymmetry: Measuring the dark matter mass and gluino mass with early LHC data

We present a focused study of a predictive unified model whose measurable consequences are immediately relevant to early discovery prospects of supersymmetry at the LHC. ATLAS and CMS have released their analysis with $35\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of data and the model class we discuss is consistent with this data. It is shown that with an increase in luminosity, the LSP dark matter mass and the gluino mass can be inferred from simple observables such as kinematic edges in leptonic channels and peak values in effective mass distributions. Specifically, we consider cases in which the neutralino is of low mass and where the relic density consistent with WMAP observations arises via the exchange of Higgs bosons in unified supergravity models. The magnitudes of the gaugino masses are sharply limited to focused regions of the parameter space, and, in particular, the dark matter mass lies in the range $\ensuremath{\sim}(50--65)\text{ }\text{ }\mathrm{GeV}$ with an upper bound on the gluino mass of 575 GeV, with a typical mass of 450 GeV. We find that all model points in this paradigm are discoverable at the LHC at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$. We determine lower bounds on the entire sparticle spectrum in this model based on existing experimental constraints. In addition, we find the spin-independent cross section for neutralino scattering on nucleons to be generally in the range of ${\ensuremath{\sigma}}_{{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}p}^{\mathrm{SI}}={10}^{\ensuremath{-}46\ifmmode\pm\else\textpm\fi{}1}\text{ }\text{ }{\mathrm{cm}}^{2}$ with much higher cross sections also possible. Thus, direct detection experiments such as CDMS and XENON already constrain some of the allowed parameter space of the low mass gaugino models and further data will provide important cross-checks of the model assumptions in the near future.

Minimal gaugomaly mediation

Mixed anomaly and gauge mediation (“gaugomaly” mediation) gives a natural solution to the SUSY flavor problem with a conventional LSP dark matter candidate. We present a minimal version of gaugomaly mediation where the messenger masses arise directly from anomaly mediation, automatically generating a messenger scale of order 50 TeV. We also describe a simple relaxation mechanism that gives rise to realistic μ and Bμ terms. B is naturally dominated by the anomaly-mediated contribution from top loops, so the μ-Bμ sector only depends on a single new parameter. In the minimal version of this scenario the full SUSY spectrum is determined by two continuous parameters (the anomaly-and gauge-mediated SUSY breaking masses) and one discrete parameter (the number of messengers). We show that these simple models can give realistic spectra with viable dark matter.

Nearly degenerate gauginos and dark matter at the LHC

Motivated by dark-matter considerations in supersymmetric theories, we investigate in a fairly model-independent way the detection at the LHC of nearly degenerate gauginos with mass differences between a few GeV and about 30 GeV. Due to the degeneracy of gaugino states, the conventional leptonic signals are likely lost. We first consider the leading signal from gluino production and decay. We find that it is quite conceivable to reach a large statistical significance for the multi-jet plus missing energy signal with an integrated luminosity about 50 pb^-1 (50 fb^-1) for a gluino mass of 500 GeV (1 TeV). If gluinos are not too heavy, less than about 1.5 TeV, this channel can typically probe gaugino masses up to about 100 GeV below the gluino mass. We then study the Drell-Yan type of gaugino pair production in association with a hard QCD jet, for gaugino masses in the range of 100-150 GeV. The signal observation may be statistically feasible with about 10 fb^-1, but systematically challenging due to the lack of distinctive features for the signal distributions. By exploiting gaugino pair production through weak boson fusion, signals of large missing energy plus two forward-backward jets may be observable at a 4-6\sigma level above the large SM backgrounds with an integrated luminosity of 100-300 fb^-1. Finally, we point out that searching for additional isolated soft muons in the range p_T ~3-10 GeV in the data samples discussed above may help to enrich the signal and to control the systematics. Significant efforts are made to explore the connection between the signal kinematics and the relevant masses for the gluino and gauginos, to probe the mass scales of the superpartners, in particular the LSP dark matter.

PAMELA satellite data as a signal of non-thermal wino LSP dark matter

We argue there is a very well motivated theoretical framework (which existed before data) consistent with the interpretation that dark matter annihilation is being observed by the PAMELA satellite detector. The dark matter is (mainly) the neutral W boson superpartner, the wino. Using the program GALPROP extensively we study the annihilation products and the backgrounds together. A wino mass approximately in the 180–200 GeV range gives a good description of the PAMELA data, with antimatter and gammas from annihilating winos contributing or dominating the data below this energy range but not contributing above it. We explain why PAMELA data does not imply no antiproton signal was observed by PAMELA or earlier experiments, and explain why the antiproton analysis was misunderstood by earlier papers. Normalizing the wino density to the local relic density, no “boost factors” are needed. At higher energies we expect astrophysical mechanisms to contribute, and we simply parameterize them, and check that the combination can describe all the data. We emphasize several predictions for satellite data to test the wino interpretation, particularly the flattening or turndown of the positron and antiproton spectra above 100 GeV, and predictions for the Fermi detector. We emphasize that interpretations also depend very strongly on assumptions about the cosmological history of the universe, and that it is crucial to have independent criteria to define the background for any given process.

PAMELA satellite data as a signal of non-thermal wino LSP dark matter

Satellite and astrophysical data is accumulating that suggests and constrains interpretations of the dark matter of the universe. We argue there is a very well motivated theoretical framework (which existed before data) consistent with the interpretation that dark matter annihilation is being observed by the PAMELA satellite detector. The dark matter is (mainly) the neutral W boson superpartner, the wino. Using the program GALPROP extensively we study the annihilation products and the backgrounds together. A wino mass approximately in the 180–200 GeV range gives a good description of the PAMELA data, with antimatter and gammas from annihilating winos dominating the data below this energy range but not contributing above it. We explain why PAMELA data does not imply no antiproton signal was observed by PAMELA or earlier experiments, and explain why the antiproton analysis was misunderstood by earlier papers. Wino annihilation does not describe the Fermi e++e− data (except partially below ∼100 GeV). At higher energies we expect astrophysical mechanisms to contribute, and we simply parameterize them without a particular physical interpretation, and check that the combination can describe all the data. We emphasize several predictions for satellite data to test the wino interpretation, particularly the flattening or turndown of the positron and antiproton spectra above 100 GeV. It should be emphasised that most other interpretations require a large rise in the positron and antiproton rates above 100 GeV. We focus on studying this well-motivated and long predicted wino interpretation, rather than comparisons with other interpretations. We emphasize that interpretations also depend very strongly on assumptions about the cosmological history of the universe, on assumptions about the broader underlying theory context, and on propagation of antiprotons and positrons in the galaxy. The winos PAMELA is observing arose from moduli decay or other non-thermal sources rather than a universe that cooled in thermal equilibrium after the big bang. Then it is appropriate to normalize the wino density to the local relic density, and no “boost factors” are needed to obtain the reported PAMELA rates.

Implications of the Muon Anomalous Magnetic Moment for Direct Detection of Neutralino Dark Matter

We investigate the implications of the recent measurement of muon anomalous magnetic moment for the direct detection of neutralino dark matter in the three different SUSY models: mSUGRA, a model with non-universal Higgs mass, and an SO(10) GUT model. We consider two extreme scenario for $\Delta a_\mu$ bound, i.e. $27 \times 10^{-10} < \Delta a_\mu < 59 \times 10^{-10}$ (1$\sigma$ bound) and $0 < \Delta a_\mu < 11 \times 10^{-10}$ ($2\sigma$ below). In mSUGRA model, the counting ratio may be above the sensitivity of the future experiments when parameters are within $1\sigma$ bound of $\Delta a_{\mu}$. However, the $\Omega_{\chi}$ tends to be high compared to the currently favored value $\Omega=0.3$. For models with the non-universal scalar masses, the possibility to have the consistent $\Omega_{\chi}$ and the high counting ratio is open up in the region of parameter space where Higgsino mass $\mu$ is smaller than mSUGRA prediction. In particular, in the SO(10) model, the LSP dark matter detection rate may be enhanced by almost one order of magnitude compared to mSUGRA and the model with non-universal Higgs mass, for cosmologically acceptable $\Omega_{\chi} h^2$. The highest detection rate of LSP dark matter occurs in the region where the LSP constitutes a subdominant part of local halo DM. Implication of SUSY mass parameter measurement under the cosmological constraint is also discussed.

LSP dark matter and LHC

LSP dark matter and LHC

MSSM dark matter constraints and decaying B-balls

In the MSSM, LSP dark matter could arise from the decay of B-balls rather than from thermal relics, with a quite different dependence on the MSSM parameters and a natural correlation with the baryon asymmetry. We discuss the constraints imposed on the properties of B-balls and the MSSM spectrum by experimental constraints and show that B-balls cannot form from an Affleck-Dine condensate with 100% efficiency in the absence of LSP annihilations after they decay. For likely formation efficiencies the LSP and slepton masses are typically constrained to be light. The effects of LSP annihilations after the B-balls decay are discussed; for sufficiently small decay temperatures annihilations will play no role, opening up the possibility of experimentally testing the scenario.

SupersymmetricD-Term Inflation andB-Ball Baryogenesis

We consider the B-ball cosmology of the MSSM in the context of D-term inflation models where the reheating temperature is determined by the Affleck-Dine mechanism to be of the order of 1 GeV. We show that such a low reheating temperature can arise quite naturally as the result of a symmetry which is required to maintain the flatness of the inflaton potential. In this case the B-balls will decay well after the freeze-out temperature of the LSP, allowing baryons and cold dark matter to originate primarily from B-ball decays.