Supergravity Parameter Research Articles

Linearized supergravity with a dynamical preferred frame

We study supersymmetric extension of the Einstein-aether gravitational model where local Lorentz invariance is broken down to the subgroup of spatial rotations by a vacuum expectation value of a timelike vector field called aether. Embedding aether into a chiral vector superfield, we construct the most general action which describes dynamics of linear perturbations around the Lorentz-violating vacuum and is invariant under the linearized supergravity transformations. The analysis is performed both in the off-shell non-minimal superfield formulation of supergravity and in the “on-shell” approach invoking only physical component fields. The resulting model contains a single free coupling, in addition to the standard supergravity parameters. The spectrum of physical excitations features an enhanced on-shell gravity multiplet comprising four states with helicities 2, 3/2, 3/2 and 1 propagating with superluminal velocity. The remaining excitations propagate with the speed of light. We outline the observational constraints on the model following from its low-energy phenomenology.

Euclidean black saddles and AdS4 black holes

We find new asymptotically locally AdS4 Euclidean supersymmetric solutions of the STU model in four-dimensional gauged supergravity. These “black saddles” have an S1× {Sigma}_{mathfrak{g}} boundary at asymptotic infinity and cap off smoothly in the interior. The solutions can be uplifted to eleven dimensions and are holographically dual to the topologically twisted ABJM theory on S1× {Sigma}_{mathfrak{g}} . We show explicitly that the on-shell action of the black saddle solutions agrees exactly with the topologically twisted index of the ABJM theory in the planar limit for general values of the magnetic fluxes, flavor fugacities, and real masses. This agreement relies on a careful holographic renormalization analysis combined with a novel UV/IR holographic relation between supergravity parameters and field theory sources. The Euclidean black saddle solution space contains special points that can be Wick-rotated to regular Lorentzian supergravity backgrounds that correspond to the well-known supersymmetric dyonic AdS4 black holes in the STU model.

Supergravity models with 50–100 TeV scalars, supersymmetry discovery at the LHC, and gravitino decay constraints

We investigate the possibility of testing supergravity unified models with scalar masses in the range 50-100 TeV and much lighter gaugino masses at the Large Hadron Collider. The analysis is carried out under the constraints that models produce the Higgs boson mass consistent with experiment and also produce dark matter consistent with WMAP and PLANCK experiments. A set of benchmarks in the supergravity parameter space are investigated using a combination of signal regions which are optimized for the model set. It is found that some of the models with scalar masses in the 50-100 TeV mass range are discoverable with as little as 100 fb$^{-1}$ of integrated luminosity and should be accessible at the LHC RUN II. The remaining benchmark models are found to be discoverable with less than 1000 fb$^{-1}$ of integrated luminosity and thus testable in the high luminosity era of the LHC, i.e., at HL-LHC. It is shown that scalar masses in the 50-100 TeV range but gaugino masses much lower in mass produce unification of gauge coupling constants, consistent with experimental data at low scale, with as good an accuracy (and sometimes even better) as models with low ($\mathcal{O}(1)$ TeV) weak scale supersymmetry. Decay of the gravitinos for the supergravity model benchmarks are investigated and it is shown that they decay before the Big Bang Nucleosynthesis (BBN). Further, we investigate the non-thermal production of neutralinos from gravitino decay and it is found that the non-thermal contribution to the dark matter relic density is negligible relative to that from the thermal production of neutralinos for reheat temperature after inflation up to $10^9$ GeV. An analysis of the direct detection of dark matter for SUGRA models with high scalar masses is also discussed.

Constraints on the dark matter neutralinos from the radio emissions of galaxy clusters

By assuming the dark matter to be composed of neutralinos, we used the detection of upper limit on diffuse radio emission in a sample of galaxy clusters to put constraint on the properties of neutralinos. We showed the upper limit constraint on 〈σv〉–mχ space with neutralino annihilation through bb¯ and μ+μ− channels. The best constraint is from the galaxy clusters A2199 and A1367. We showed the uncertainty due to the density profile and cluster magnetic field. The largest uncertainty comes from the uncertainty in dark matter spatial distribution. We also investigated the constraints on minimal Supergravity (mSUGRA) and minimal supersymmetric standard model (MSSM) parameter space by scanning the parameters using the darksusy package. By using the current radio observation, we managed to exclude 40 combinations of mSUGRA parameters. On the other hand, 573 combinations of MSSM parameters can be excluded by current observation.

Light stops and observation of supersymmetry at LHC run II

Light stops consistent with the Higgs boson mass of $\sim126\,{\rm GeV}$ are investigated within the framework of minimal supergravity. It is shown that models with light stops which are also consistent with the thermal relic density constraints require stop coannihilation with the neutralino LSP. The analysis shows that the residual set of parameter points with light stops satisfying both the Higgs mass and the relic density constraints lie within a series of thin strips in the $m_0-m_{1/2}$ plane for different values of $A_0/m_0$. Consequently, this region of minimal supergravity parameter space makes a number of very precise predictions. It is found that light stops of mass down to 400~GeV or lower can exist consistent with all constraints. A signal analysis for this class of models at LHC RUN-II is carried out and the dominant signals for their detection identified. Also computed is the minimum integrated luminosity for $5\sigma$ discovery of the models analyzed. If supersymmetry is realized in this manner, the stop masses can be as low as 400~GeV or lower, and the mass gap between the lightest neutralino and lightest stop will be approximately 30-40~GeV. We have optimized the ATLAS signal regions specifically for stop searches in the parameter space and find that a stop with mass $\sim 375\,{\rm GeV}$ can be discovered with as little as $\sim$ 60~fb$^{-1}$ of integrated luminosity at RUN-II of the LHC; the integrated luminosity needed for discovery could be further reduced with more efficient signature analyses. The direct detection of dark matter in this class of models is also discussed. It is found that dark matter cross sections lie close to, but above, coherent neutrino scattering and would require multi-ton detectors such as LZ to see a signal of dark matter for this class of models.

Indirect probes of the MSSM after the Higgs discovery

AbstractWe study the minimal supersymmetric standard model (MSSM) with minimal flavor violation (MFV), imposing constraints from flavor physics observables and MSSM Higgs searches, in light of the recent discovery of a 125 GeV Higgs boson by ATLAS and CMS. We analyze the electroweak vacuum stability conditions to further restrict the MSSM parameter space. In addition, a connection to ultraviolet physics is shown via an implementation of renormalization group running, which determines the TeV-scale spectrum from a small set of minimal supergravity parameters. Finally, we investigate the impact from dark matter direct detection searches. Our work highlights the complementarity of collider, flavor and dark matter probes in exploring the MSSM, and shows that even in a MFV framework, flavor observables constrain the MSSM parameter space well beyond the current reach of direct SUSY particle searches.

A two-tiered correlation of dark matter with missing transverse energy: reconstructing the lightest supersymmetric particle mass at the LHC

We suggest that non-trivial correlations between the dark matter particle mass and collider based probes of missing transverse energy H_T^miss may facilitate a two tiered approach to the initial discovery of supersymmetry and the subsequent reconstruction of the LSP mass at the LHC. These correlations are demonstrated via extensive Monte Carlo simulation of seventeen benchmark models, each sampled at five distinct LHC center-of-mass beam energies, spanning the parameter space of No-Scale F-SU(5).This construction is defined in turn by the union of the Flipped SU(5) Grand Unified Theory, two pairs of hypothetical TeV scale vector-like supersymmetric multiplets with origins in F-theory, and the dynamically established boundary conditions of No-Scale Supergravity. In addition, we consider a control sample comprised of a standard minimal Supergravity benchmark point. Led by a striking similarity between the H_T^miss distribution and the familiar power spectrum of a black body radiator at various temperatures, we implement a broad empirical fit of our simulation against a Poisson distribution ansatz. We advance the resulting fit as a theoretical blueprint for deducing the mass of the LSP, utilizing only the missing transverse energy in a statistical sampling of >= 9 jet events. Cumulative uncertainties central to the method subsist at a satisfactory 12-15% level. The fact that supersymmetric particle spectrum of No-Scale F-SU(5) has thrived the withering onslaught of early LHC data that is steadily decimating the Constrained Minimal Supersymmetric Standard Model and minimal Supergravity parameter spaces is a prime motivation for augmenting more conventional LSP search methodologies with the presently proposed alternative.

B s →μ+μ− decay in the R-parity violating minimal supergravity

We study B s →μ + μ − in the context of the R-parity violating minimal supergravity in the high-tan β regime. We find that the lowest value of the branching ratio can go well below the present LHCb sensitivity and hence B s →μ + μ − can even be invisible to the LHC. We also find that the present upper bound on Br (B s →μ + μ −) puts strong constraint on the minimal supergravity parameter space. The constraints become more severe if the upper bound is close to its standard model prediction.

Stringy WIMP detection and annihilation

We calculate the direct dark matter detection spin-independent and proton spin-dependent cross sections for a semirealistic intersecting $D6$-brane model. The cross sections are compared to the latest constraints of the current dark matter direct detection experiments, as well as the projected results of future dark matter experiments. The allowed parameter space of the intersecting $D6$-brane model is shown with all current experimental constraints, including those regions satisfying the WMAP and supercritical string cosmology limits on the dark matter density in the Universe. Additionally, we compute the indirect detection gamma-ray flux resulting from neutralino annihilation for the $D6$-brane model and compare the flux to the projected sensitivity of the Fermi Gamma-ray Space Telescope. Finally, we compute the direct and indirect detection cross sections as well as the gamma-ray flux resulting from weakly interacting massive particle annihilations for the one-parameter model for comparison, where the one-parameter model is a highly constrained subset of the minimal supergravity parameter space such that the soft-supersymmetry-breaking terms are functions of the common gaugino mass, which is common to many string compactifications.

Neutralino reconstruction in supersymmetry with long-lived staus

We consider a supergravity (SUGRA) scenario, with universal scalar and gaugino masses at high scale, with a right-chiral neutrino superfield included in the spectrum. Such a scenario can have a lightest supersymmetric particle (LSP) dominated by the right sneutrino and a stau as the next-to lightest supersymmetric particle (NLSP). Since decays of all particles into the LSP are suppressed by the neutrino Yukawa coupling, the signal of supersymmetry consists in charged tracks of stable particles in the muon chamber. We demonstrate how a neutralino decaying into a tau and the stau-NLSP can be fully reconstructed over substantial areas in the SUGRA parameter space. We also suggest event selection criteria for eliminating backgrounds, including combinatorial ones, and use a new method for the extraction of the mass of the stau-NLSP, using its three-momentum as obtained from the curvature of the charged track.

τ˜1lightest supersymmetric particle phenomenology: Two- versus four-body decay modes and resonant single slepton production at the LHC as an example

We investigate ${\mathrm{B}}_{3}$ minimal supergravity models, where the lightest stau ${\stackrel{\texttildelow{}}{\ensuremath{\tau}}}_{1}$ is the lightest supersymmetric particle. ${\mathrm{B}}_{3}$ models allow for lepton number and R-parity violation; the lightest supersymmetric particle can thus decay. We assume one nonzero ${\mathrm{B}}_{3}$ coupling ${\ensuremath{\lambda}}_{ijk}^{\ensuremath{'}}$ at ${M}_{\mathrm{GUT}}$, which generates further ${\mathrm{B}}_{3}$ couplings at ${M}_{Z}$. We study the renormalization group equations and give numerical examples. The new couplings lead to additional ${\stackrel{\texttildelow{}}{\ensuremath{\tau}}}_{1}$ decays, providing distinct collider signatures. We classify the ${\stackrel{\texttildelow{}}{\ensuremath{\tau}}}_{1}$ decays and describe their dependence on the minimal supergravity parameters. We exploit our results for single slepton production at the LHC. As an explicit numerical example, we investigate single-smuon production, focussing on like-sign dimuons in the final state. Also considered are final states with three or four muons.

Lepton flavors at the early CERN LHC experiments as the footprints of the dark matter producing mechanisms

The minimal supergravity (mSUGRA) parameter space corresponding to light sleptons well within the reach of LHC and relatively light squarks and gluinos (mass {<=}1 TeV) has three regions consistent with the Wilkinson Microwave Anisotropy Probe data on dark matter relic density and direct mass bounds from LEP 2. Each region can lead to distinct leptonic signatures from squark-gluino events during the early LHC experiments (integrated luminosity {approx}10 fb{sup -1} or even smaller) due to the distinct features of the 2-body leptonic decay modes of the electroweak gauginos, produced in squark-gluino decay cascades, in each region. In the much studied stau-LSP coannihilation region with a vanishing common trilinear coupling (A{sub 0}) at the grand unified theory scale, a large fraction of the final states contains electrons and/or muons and e-{mu}-{tau} universality holds to a good approximation. In the not so well-studied scenarios with nonvanishing A{sub 0} both lightest supersymmetric particle (LSP) pair annihilation and stau-LSP coannihilation could contribute significantly to the dark matter relic density for even smaller squark-gluino masses. Our simulations using Pythia indicate that the corresponding signatures are final states rich in {tau}-leptons while final states with electrons and muons are suppressed leading to a violation of lepton universality.more » These features may be observed to a lesser extent even in the modified parameter space (with nonzero A{sub 0}) where the coannihilation process dominates. We also show that the generic m-leptons+n-jets+Ee{sub T} signatures without flavor tagging can also discriminate among the three scenarios. However, the signals become more informative if the {tau} and b-jet tagging facilities at the LHC experiments are utilized.« less

Probing bilinear R-parity violating supergravity at the LHC

We study the collider phenomenology of bilinear R-parity violating supergravity, the simplest effective model for supersymmetric neutrino masses accounting for the current neutrino oscillation data. At the CERN Large Hadron Collider the center-of-mass energy will be high enough to probe directly these models through the search for the superpartners of the Standard Model (SM) particles. We analyze the impact of R-parity violation on the canonical supersymmetry searches—that is, we examine how the decay of the lightest supersymmetric particle (LSP) via bilinear R-parity violating interactions degrades the average expected missing momentum of the reactions and show how this diminishes the reach in the usual channels for supersymmetry searches. However, the R-parity violating interactions lead to an enhancement of the final states containing isolated same-sign di-leptons and trileptons, compensating the reach loss in the fully inclusive channel. We show how the searches for displaced vertices associated to LSP decay substantially increase the coverage in supergravity parameter space, giving the corresponding reaches for two reference luminosities of 10 and 100 fb−1 and compare with those of the R-parity conserving minimal supergravity model.

Higgs searches in SUSY cascade with the ATLAS detector

In the context of Supersymmetric extensions of the Standard Model, the lightest Higgs boson can be produced via cascade decays of supersymmetric particles. We investigated the possibility of observing such events with the ATLAS detector at the LHC. We showed that, for some regions of the Minimal Super-Gravity parameter space compatibles with the last LEP searches, the lightest Higgs boson can be discovered with less than 10 fb−1, giving results competitive with standard Higgs production channels. The possibility of reconstructing the supersymmetric particles mass spectrum in these scenarios has also been studied.

Determining spins of metastable sleptons at the CERN Large Hadron Collider

We investigate models in minimal supergravity parameter space which contain metastable sleptons. We find the luminosity required to determine the slepton spin in these scenarios, and apply our analysis to two benchmark models. We show that the spin of the slepton in one of the benchmark models can be determined with less than $30\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data, while the slepton spin in the other model can be determined with roughly $40\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data. We show how our analysis can be applied to other models, and give an estimate of the luminosity needed for a spin determination as a function of the slepton mass. This analysis can be used to distinguish supersymmetry and extra dimensions.

Discovering supersymmetry withm02&lt;0in the first CERN LHC physics run

In minimal supergravity, the parameter space where the slepton is the lightest superpartner is usually neglected, because of strong constraints on charged dark matter. When the gravitino is the true lightest superpartner, this region avoids these constraints and offers spectacular collider signals. We investigate this scenario for the Large Hadron Collider and find that a large portion of the ignored minimal supergravity parameter space can lead to discovery within the first physics run, with $1--4\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data. We find that there are regions where discovery is feasible with only 1 d of running.

One-loop calculations of the decay of the next-to-lightest neutralino in the MSSM

We calculate one-loop corrections to the decays of the next-to-lightest neutralino $\tilde{\chi}_2^0$ into the lightest neutralino $\tilde{\chi}_1^0$ and two leptons; this includes diagrams where a real photon is emitted. In cases where two-body decays $\tilde{\chi}_2^0 \to \tilde{l}^\pm_1 l^\mp \to \tilde{\chi}_1^0 l^- l^+$ 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 $\tilde{\chi}_2^0\to \tilde{\chi}_1^0 l^- l^+ (l = e, \mu)$ are enhanced by about 15.5 (13.6) percent by the one-loop corrections. We also study a scenario where $\tilde \chi_2^0$ cannot undergo two-body decays, and find corrections to these branching ratios of about 13.6 percent. Moreover, we study the dilepton invariant mass ($M_{l^+ l^-}$) distribution, whose endpoint is often used in analyses that aim to reconstruct (differences of) supersymmetric particle masses at the LHC. The shape of this distribution is altered significantly by the emission of hard photons. For example, for the SPS1a parameter set the peak of the $M_{l^+ l^-}$ distribution is shifted by several GeV when these contributions are included.

Testing supersymmetry with lepton flavor violatingτandμdecays

In this work the following lepton flavor violating $\ensuremath{\tau}$ and $\ensuremath{\mu}$ decays are studied: ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}{\ensuremath{\mu}}^{\ensuremath{-}}{\ensuremath{\mu}}^{+}$, ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{e}^{\ensuremath{-}}{e}^{+}$, ${\ensuremath{\mu}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{e}^{\ensuremath{-}}{e}^{+}$, ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}\ensuremath{\gamma}$, ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}\ensuremath{\gamma}$, and ${\ensuremath{\mu}}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}\ensuremath{\gamma}$. We work in a supersymmetric scenario consisting of the minimal supersymmetric standard model particle content, extended by the addition of three heavy right-handed Majorana neutrinos and their supersymmetric partners, and where the generation of neutrino masses is done via the seesaw mechanism. Within this context, a significant lepton flavor mixing is generated in the slepton sector due to the Yukawa neutrino couplings, which is transmitted from the high to the low energies via the renormalization group equations. This slepton mixing then generates via loops of supersymmetric particles significant contributions to the rates of ${l}_{j}\ensuremath{\rightarrow}3{l}_{i}$ and the correlated ${l}_{j}\ensuremath{\rightarrow}{l}_{i}\ensuremath{\gamma}$ decays. We analyze here in full detail these rates in terms of the relevant input parameters, which are the usual minimal supergravity parameters and the seesaw parameters. For the ${l}_{j}\ensuremath{\rightarrow}3{l}_{i}$ decays, a full one-loop analytical computation of all the contributing supersymmetric loops is presented. This completes and corrects previous computations in the literature. In the numerical analysis compatibility with the most recent experimental upper bounds on all these $\ensuremath{\tau}$ and $\ensuremath{\mu}$ decays, with the neutrino data, and with the present lower bounds on the supersymmetric particle masses are required. Two typical scenarios with degenerate and hierarchical heavy neutrinos are considered. We will show here that the minimal supergravity and seesaw parameters do get important restrictions from these $\ensuremath{\tau}$ and $\ensuremath{\mu}$ decays in the hierarchical neutrino case.

Bs→μ+μ−and the upward-going muon flux from the WIMP annihilation in the sun or the earth

We consider the upward-going muon flux due to the WIMP annihilations in the cores of the sun and the earth, including the upper bound on the branching ratio for $B_s \to \mu^+ \mu^-$ decay. We find that the constraint from $B_s \to \mu^+ \mu^-$ is very strong in most parameter space, and exclude the supergravity parameter space regions where the expected upward-going muon fluxes are within the expected reach of AMANDA II.

Supersymmetric dark matter and the reheating temperature of the universe

Since the thermal history of the Universe is unknown before the epoch of primordial nucleosynthesis, the largest temperature of the radiation dominated phase (the reheating temperature) might have been as low as 1 MeV. We perform a quantitative study of supersymmetric dark matter relic abundance in cosmological scenarios with low reheating temperature. We show that, for values of the reheating temperature smaller than about 30 GeV, the domains of the supergravity parameter space which are compatible with the hypothesis that dark matter is composed by neutralinos are largely enhanced. We also find a lower bound on the reheating temperature: if the latter is smaller than about 1 GeV neutralinos cannot be efficiently produced in the early Universe and then they are not able to explain the present amount of dark matter.