Minimal Supergravity Model Research Articles

Causality constraints on nonlinear supersymmetry

It is well-known that gravitino propagation in standard supergravities is free of any causality problems. However, two issues related to gravitino propagation were recently uncovered in specific supergravities with nonlinear supersymmetry. One of them concerns potential acausality/superluminality, whereas the second one arises from the vanishing of the sound speed at specific points during inflation. The former is famously related to positivity constraints on specific EFT operators, derived from dispersion relations on the energy-growing part of scattering amplitudes, and indeed we show that subluminality constraints for the gravitino are related via the equivalence theorem to positivity bounds in low-energy goldstino actions. However, the former are stronger, in the sense that they apply to functions of the scalar fields not only in the ground state, but for any field values such as those scanned by time-dependent solutions, unlike bounds derived from 2 → 2 scattering amplitudes in the vacuum. We also argue that nontrivial causality constraints arise only in the case where nonlinear supersymmetry in the matter sector is encoded into superfield constraints which do not seem to arise from microscopic two-derivative lagrangians, in particular for the orthogonal constraint used to build minimal models of inflation in supergravity. This allows us to propose simple alternatives which maintain the minimality of the spectra and are causal in all points of the theory parameter space. We also discuss minimal supergravity models of inflation along these lines.

A novel way of constraining the α-attractor chaotic inflation through Planck data

Defining a scale of k-modes of the quantum fluctuations during inflation through the dynamical horizon crossing condition k = aH we go from the physical t variable to k variable and solve the equations of cosmological first-order perturbations self consistently, with the chaotic α-attractor type potentials. This enables us to study the behaviour of ns , r, nt and N in the k-space. Comparison of our results in the low-k regime with the Planck data puts constraints on the values of the α parameter through microscopic calculations. Recent studies had already put model-dependent constraints on the values of α through the hyperbolic geometry of a Poincaré disk: consistent with both the maximal supergravity model \U0001d4a9 = 8 and the minimal supergravity model \U0001d4a9 = 1, the constraints on the values of α are 1/3, 2/3, 1, 4/3, 5/3, 2, 7/3. The minimal \U0001d4a9 = 1 supersymmetric cosmological models with B-mode targets, derived from these supergravity models, predicted the values of r between 10-2 and 10-3. Both in the E-model and the T-model potentials, we have obtained, in our calculations, the values of r in this range for all the constrained values of α stated above, within 68% CL. Moreover, we have calculated r for some other possible values of α both in low-α limit, using the formula r = 12α/N 2, and in the high-α limit, using the formula r = 4n/N, for n = 2 and 4. With all such values of α, our calculated results match with the Planck-2018 data with 68% or near 95% CL.

PeV scale supersymmetry breaking and the IceCube neutrino flux

The observation of very high energy neutrino events at IceCube has grasped a lot of attention in the fields of both astrophysics and particle physics. It has been speculated that these high energy neutrinos might originate either from purely conventional astrophysical sources or from the late decay of a super heavy (PeV scale) dark matter (DM) particle. In order for decaying DM to be a dominant source of the IceCube high-energy neutrinos, it would require an unusually suppressed value of the coupling of DM to neutrinos. We attempt to explain this small coupling in the context of an R-parity conserving minimal supergravity model which has right-handed neutrino superfields. With the main assumptions of super-partner masses at the PeV scale and also a reheating temperature not much larger than the PeV scale, we find in our model several natural order-of-magnitude “miracles”, (i) the gravitino is produced via freeze-in as a DM candidate with the correct relic density (ii) the right-handed (RH) sneutrino makes up only a tiny fraction (10−6), of the present day energy density of the universe, yet its decay lifetime to the gravitino and neutrinos is such that it naturally predicts the right order-of-magnitude for the IceCube neutrino flux. The long lifetime of the RH sneutrino is explained by the existence of a global R-symmetry which is only broken due to supersymmetry breaking effects. Our model also predicts a flux of 100 TeV gamma rays from the decaying RH sneutrino which are within the current observational constraints.

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.

Minimal constrained supergravity

We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called "de Sitter" supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

Constraining natural SUSY via the Higgs coupling and the muon anomalous magnetic moment measurements

We use the Higgs coupling and the muon anomalous magnetic moment measurements to constrain the parameter space of the natural supersymmetry (SUSY) in the Generalized Minimal Supergravity (GmSUGRA) model. We scan the parameter space of the GmSUGRA model with small electroweak fine-tuning measure ($\Delta_{\rm EW} \leq 100$). The parameter space after applying various sparticle mass bounds, Higgs mass bounds, B-physics bounds, the muon magnetic moment constraint, and the Higgs coupling constraint from measurements at HL-LHC, ILC, and CEPC, is shown in the planes of various interesting model parameters and sparticle masses. Our study indicates that the Higgs coupling and muon anomalous magnetic moment measurements can constrain the parameter space effectively. It is shown that $\Delta_{\rm EW}\sim$ 30, consistence with all constraints, and having supersymmetric contributions to the muon anomalous magnetic moment within 1$\sigma$ can be achieved. The precision of $k_b$ and $k_{\tau}$ measurements at CEPC can bound $m_A$ to be above 1.2 TeV and 1.1 TeV respectively. The combination of the Higgs coupling measurement and muon anomalous magnetic moment measurement constrain $\tilde{e}_R$ mass to be in the range from 0.6 TeV to 2 TeV. The range of both $\tilde{e}_L$ and $\tilde{\nu}_e$ masses is 0.4 TeV $\sim$ 1.2 TeV. In all cases, the $\tilde{\chi}_1^0$ mass needs to be small (mostly $\leq$ 400 GeV). The comparison of bounds in the $\tan\beta - m_A$ plane shows that the Higgs coupling measurement is complementary to the direct collider searches for heavy Higgs when constraining the natural SUSY. A few mass spectra in the typical region of parameter space after applying all constraints are shown as well.

Constrained superfields in supergravity

We analyze constrained superfields in supergravity. We investigate the consistency and solve all known constraints, presenting a new class that may have interesting applications in the construction of inflationary models. We provide the superspace Lagrangians for minimal supergravity models based on them and write the corresponding theories in component form using a simplifying gauge for the goldstino couplings.

Minimal scalar-less matter-coupled supergravity

We build the minimal supergravity model where the nilpotent chiral goldstino superfield is coupled to a chiral matter superfield, realising a different non-linear representation through a mixed nilpotency constraint. The model describes the spontaneous breaking of local supersymmetry in the presence of a generically massive Majorana fermion, but in the absence of elementary scalars. The sign and the size of the cosmological constant, the spectrum and the four-fermion interactions are controlled by suitable parameters.

Electroweak supersymmetry from the generalized minimal supergravity model in the MSSM

Considering the Generalized Minimal Supergravity Model (GmSUGRA) in the Minimal Supersymmetric Standard Model (MSSM), we study the Electroweak Supersymmetry (EWSUSY), where the squarks and/or gluino are heavy around a few TeVs while the sleptons, sneutrinos, Bino, Winos, and/or Higgsinos are light within one TeV. We resolves the $(g_{\mu}-2)/2$ discrepancy for the muon anomalous magnetic moment in the Standard Model (SM) successfully and identifies a parameter space where such solutions also have the electroweak fine-tuning measures $\Delta_{EW}~16.5$ (6$\%$) and $\Delta_{EW}~25$ (4$\%$) without and with the WMAP bounds, respectively. We find that the allowed mass ranges consistent within 3$\sigma$ of the $g-2$ discrepancy for the lightest neutralino, charginos, stau, stau neutrinos, and first two-family sleptons are $[44,390]$ GeV, $[100,700]$ GeV, $[100,700]$, and $[52,700]$ GeV, respectively. Moreover, our solutions satisfy the latest bounds reported by the ATLAS and CMS Collaborations on electroweakinos and sleptons. The colored sparticles such as light stop, gluinos, and the first two-generation squark masses have been found in the mass ranges of $[500, 3000]$ GeV,[1300, 4300] GeV, and $[1800, 4200]$ GeV, respectively. To obtain the observed dark matter relic density for the Lightest Supersymmetric Particle (LSP) neutralino, we have the bino-wino, LSP neutralino-stau, and LSP neutralino-tau sneutrinos coannihilation scenarios, and the resonance solutions such as $A$-pole, Higgs-pole, and $Z$-pole. We identify the higgsino-like LSP neutralino and display its spin-independent and spin-dependent cross sections with nucleons. We present ten benchmark points which can be tested at the up coming collider searches as well.

KK-monopoles and G-structures in M-theory/type IIA reductions

We argue that M-theory/massive IIA backgrounds including KK-monopoles are suitably described in the language of G-structures and their intrinsic torsion. To this end, we study classes of minimal supergravity models that admit an interpretation as twisted reductions in which the twist parameters are not restricted to satisfy the Jacobi constraints $\omega\, \omega=0$ required by an ordinary Scherk-Schwarz reduction. We first derive the correspondence between four-dimensional data and torsion classes of the internal space and, then, check the one-to-one correspondence between higher-dimensional and four-dimensional equations of motion. Remarkably, the whole construction holds regardless of the Jacobi constraints, thus shedding light upon the string/M-theory interpretation of (smeared) KK-monopoles.

A no-scale inflationary model to fit them all

The magnitude of B-mode polarization in the cosmic microwave background as measured by BICEP2 favours models of chaotic inflation with a quadratic m2 ϕ2/2 potential, whereas data from the Planck satellite favour a small value of the tensor-to-scalar perturbation ratio r that is highly consistent with the Starobinsky R +R2 model. Reality may lie somewhere between these two scenarios. In this paper we propose a minimal two-field no-scale supergravity model that interpolates between quadratic and Starobinsky-like inflation as limiting cases, while retaining the successful prediction ns ≃ 0.96.

On the topology of the inflaton field in minimal supergravity models

We consider global issues in minimal supergravity models where a single field inflaton potential emerges. In a particular case we reproduce the Starobinsky model and its description dual to a certain formulation of R + R 2 supergravity. For definiteness we confine our analysis to spaces at constant curvature, either vanishing or negative. Five distinct models arise, two flat models with respectively a quadratic and a quartic potential and three based on the $ \frac{{\mathrm{SU}\left( {1,1} \right)}}{{\mathrm{U}(1)}} $ space where its distinct isometries, elliptic, hyperbolic and parabolic are gauged. Fayet-Iliopoulos terms are introduced in a geometric way and they turn out to be a crucial ingredient in order to describe the de Sitter inflationary phase of the Starobinsky model.

On the gauged Kähler isometry in minimal supergravity models of inflation

AbstractIn this paper we address the question how to discriminate whether the gauged isometry group ��Σ of the Kähler manifold Σ that produces a D‐type inflaton potential in a Minimal Supergravity Model is elliptic, hyperbolic or parabolic. We show that the classification of isometries of symmetric cosets can be extended to non symmetric Σ.s if these manifolds satisfy additional mathematical restrictions. The classification criteria established in the mathematical literature are coherent with simple criteria formulated in terms of the asymptotic behavior of the Kähler potential ��(C) = 2 J(C) where the real scalar field C encodes the inflaton field. As a by product of our analysis we show that phenomenologically admissible potentials for the description of inflation and in particular α‐attractors are mostly obtained from the gauging of a parabolic isometry, this being, in particular the case of the Starobinsky model. Yet at least one exception exists of an elliptic α‐attractor, so that neither type of isometry can be a priori excluded. The requirement of regularity of the manifold Σ poses instead strong constraints on the α‐attractors and reduces their space considerably. Curiously there is a unique integrable α‐attractor corresponding to a particular value of this parameter.

Higher order corrections in minimal supergravity models of inflation

We study higher order corrections in new minimal supergravity models of a single scalar field inflation. The gauging in these models leads to a massive vector multiplet and the D-term potential for the inflaton field with a coupling g2 ∼ 10−10. In the de-Higgsed phase with vanishing g2, the chiral and vector multiplets are non-interacting, and the potential vanishes. We present generic manifestly supersymmetric higher order corrections for these models. In particular, for a supersymmetric gravity model −R+R2 we derive manifestly supersymmetric corrections corresponding to Rn. The dual version corresponds to a standard supergravity model with a single scalar and a massive vector. It includes, in addition, higher Maxwell curvature/scalar interaction terms of the Born-Infeld type and a modified D-term scalar field potential. We use the dual version of the model to argue that higher order corrections do not affect the last 60 e-foldings of inflation; for example the ξR4 correction is irrelevant as long as ξ < 1024.

Minimal supergravity models of inflation

We present a superconformal master action for a class of supergravity models with one arbitrary function defining the Jordan frame. It leads to a gauge-invariant action for a real vector multiplet, which upon gauge fixing describes a massive vector multiplet, or to a dual formulation with a linear multiplet and a massive tensor field. In both cases the models have one real scalar, the inflaton, naturally suited for single-field inflation. Vectors and tensors required by supersymmetry to complement a single real scalar do not acquire vev's during inflation, so there is no need to stabilize the extra scalars which are always present in the theories with chiral matter multiplets. The new class of models can describe any inflaton potential which vanishes at its minimum and grows monotonically away from the minimum. In this class of supergravity models one can fit any desirable choice of inflationary parameters n_s and r.

Peccei-Quinn violating minimal supergravity and a 126 GeV Higgs boson

In a Peccei-Quinn extension of supergravity the $h\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ detection rate can be significantly enhanced due to the reduction of the total Higgs decay width. To assess the viability of various Peccei-Quinn extensions of minimal supergravity we perform a Bayesian analysis on three such scenarios. The main constraints on these models come from the currently observed Higgs-boson like state by the Large Hadron Collider and from the Wilkinson Microwave Anisotropy Probe observation of dark matter abundance. Our comparative study reveals that under these constraints the Peccei-Quinn violating scenarios with axino dark matter are clearly preferred over the minimal supergravity model with the lightest neutralino as a dark matter candidate.

Many faces of low mass neutralino dark matter in the unconstrained MSSM, LHC data and new signals

If all strongly interacting sparticles (the squarks and the gluinos) in an unconstrained minimal supersymmetric standard model (MSSM) are heavier than the corresponding mass lower limits in the minimal supergravity (mSUGRA) model, obtained by the current LHC experiments, then the existing data allow a variety of electroweak (EW) sectors with light sparticles yielding dark matter (DM) relic density allowed by the WMAP data. Some of the sparticles may lie just above the existing lower bounds from LEP and lead to many novel DM producing mechanisms not common in mSUGRA. This is illustrated by revisiting the above squark-gluino mass limits obtained by the ATLAS Collaboration, with an unconstrained EW sector with masses not correlated with the strong sector. Using their selection criteria and the corresponding cross section limits, we find at the generator level using Pythia, that the changes in the mass limits, if any, are by at most 10-12% in most scenarios. In some cases, however, the relaxation of the gluino mass limits are larger ($\approx 20%$). If a subset of the strongly interacting sparticles in an unconstrained MSSM are within the reach of the LHC, then signals sensitive to the EW sector may be obtained. This is illustrated by simulating the $blj$$\etslash$, $l= e and \mu $, and $b\tau j$$\etslash$ signals in i) the light stop scenario and ii) the light stop-gluino scenario with various light EW sectors allowed by the WMAP data. Some of the more general models may be realized with non-universal scalar and gaugino masses.

Neutralino dark matter in mSUGRA/CMSSM with a 125 GeV light Higgs scalar

The minimal supergravity (mSUGRA or CMSSM) model is an oft-used frame- work for exhibiting the properties of neutralino (WIMP) cold dark matter (CDM). How- ever, the recent evidence from Atlas and CMS on a light Higgs scalar with mass $ {m_h} \simeq 125 $ GeV highly constrains the superparticle mass spectrum, which in turn constrains the neutralino annihilation mechanisms in the early universe. We find that stau and stop co-annihilation mechanisms — already highly stressed by the latest Atlas/CMS re- sults on SUSY searches — are nearly eliminated if indeed the light Higgs scalar has mass $ {m_h} \simeq 125 $ GeV. Furthermore, neutralino annihilation via the A-resonance is nearly ruled out in mSUGRA so that it is exceedingly difficult to generate thermally-produced neutralino-only dark matter at the measured abundance. The remaining possibility lies in the focus-point region which now moves out to $ {m_0} \sim 10 - 20 $ TeV range due to the required large trilinear soft SUSY breaking term A0. The remaining HB/FP region is more fine-tuned than before owing to the typically large top squark masses. We present updated direct and indirect detection rates for neutralino dark matter, and show that ton scale noble liquid detectors will either discover mixed higgsino CDM or essentially rule out thermally-produced neutralino-only CDM in the mSUGRA model.

Implications of a 125 GeV Higgs scalar for the LHC supersymmetry and neutralino dark matter searches

The ATLAS and CMS collaborations have reported an excess of events in the $\ensuremath{\gamma}\ensuremath{\gamma}$, $Z{Z}^{*}\ensuremath{\rightarrow}4\ensuremath{\ell}$ and $W{W}^{*}$ search channels at an invariant mass $m\ensuremath{\simeq}125\text{ }\text{ }\mathrm{GeV}$, which could be the first evidence for the long-awaited Higgs boson. We investigate the consequences of requiring ${m}_{h}\ensuremath{\simeq}125\text{ }\text{ }\mathrm{GeV}$ in both the minimal supergravity and 2-parameter nonuniversal Higgs supersymmetric models. In minimal supergravity, large values of trilinear soft breaking parameter $|{A}_{0}|$ are required, and universal scalar ${m}_{0}\ensuremath{\gtrsim}0.8\text{ }\text{ }\mathrm{TeV}$ is favored so that we expect squark and slepton masses typically in the multi-TeV range. This typically gives rise to an ``effective supersymmetric'' type of sparticle mass spectrum. In this case, we expect gluino pair production as the dominant sparticle creation reaction at LHC. For ${m}_{0}\ensuremath{\lesssim}5\text{ }\text{ }\mathrm{TeV}$, the superpotential parameter $\ensuremath{\mu}\ensuremath{\gtrsim}2\text{ }\text{ }\mathrm{TeV}$ and ${m}_{A}\ensuremath{\gtrsim}0.8\text{ }\text{ }\mathrm{TeV}$, greatly restricting neutralino annihilation mechanisms. These latter conclusions are softened if ${m}_{0}\ensuremath{\sim}10--20\text{ }\text{ }\mathrm{TeV}$ or if one proceeds to the 2-parameter nonuniversal Higgs model. The standard neutralino abundance tends to be far above WMAP-measured values unless the neutralino is Higgsino-like. We remark upon possible nonstandard (but perhaps more attractive) cosmological scenarios which can bring the predicted dark matter abundance into accord with the measured value, and discuss the implications for direct and indirect detection of neutralino cold dark matter.

Nonuniversal gaugino masses, the supersymmetric little hierarchy problem, and dark matter

We study a class of supersymmetric models with nonuniversal gaugino masses that could arise from $F$-terms in a general combination of the singlet and adjoint representations of $SU(5)$. We explore models that satisfy present Large Hadron Collider and other bounds, showing how the allowed parameter space is divided into distinct ``continents.'' Regions of parameter space that ameliorate the supersymmetric little hierarchy problem with a small $\ensuremath{\mu}$ parameter include the usual focus-point scenario, but also natural areas with much lighter squarks and sleptons. These models are continuously connected in parameter space to regions in which stau coannihilation or Higgs exchange is mostly responsible for dark matter annihilation, and to models in which the thermal relic abundance is achieved by slepton-mediated annihilation, reviving the bulk region that is severely restricted in minimal supergravity models. In hybrid or confluence regions, several mechanisms combine to give the requisite dark matter annihilation rate. In each case, we study the prospects for direct detection of dark matter. We also comment briefly on the impact of recent hints for ${M}_{h}$ near 125 GeV from the LHC.