Search

Electroweak loop corrections to the matrix elements for the spin-independent scattering of cold dark matter particles on nuclei are generally small, typically below the uncertainty in the local density of cold dark matter. However, as shown in this paper, there are instances in which the electroweak loop corrections are relatively large, and change significantly the spin-independent dark matter scattering rate. An important example occurs when the dark matter particle is a wino, e.g., in anomaly-mediated supersymmetry breaking (AMSB) and pure gravity mediation (PGM) models. We find that the one-loop electroweak corrections to the spin-independent wino LSP scattering cross section generally interfere constructively with the tree-level contribution for AMSB models with negative Higgsino mixing, μ < 0 , and in PGM-like models for both signs of μ , lifting the cross section out of the neutrino fog and into a range that is potentially detectable in the next generation of direct searches for cold dark matter scattering. [ABSTRACT FROM AUTHOR]

We revisit the calculation of the electron, neutron, and proton electric dipole moments (EDMs) in the constrained minimal supersymmetric standard model (CMSSM). The relatively large mass of the Higgs boson, mH ≃ 125 GeV coupled with the (as yet) lack of discovery of any supersymmetric particle at the LHC, has pushed the supersymmetry breaking scale to several TeV or higher. Though one might expect this decoupling to have relaxed completely any bounds on the two CP violating phases in the CMSSM (θμ and θA), the impressive experimental improvements in the limits on the EDMs (particularly the electron EDM) still allow us to set constraints of order (0.01−0.1)π on θA and (0.001−0.1)π on θμ. We also discuss the impact of future improvements in the experimental limits on supersymmetric models. [ABSTRACT FROM AUTHOR]

We revisit the viability of the CMSSM, searching for regions of parameter space that yield a neutralino dark matter density compatible with Planck measurements, as well as LHC constraints including sparticle searches and the mass of the Higgs boson, recent direct limits on spin-independent and -dependent dark matter scattering from the LUX-ZEPLIN (LZ) experiment, the indirect constraints from Fermi-LAT and H.E.S.S. on dark matter annihilations to photons in dwarf spheroidal galaxies and the Galactic Centre, and the IceCube limits on muons from annihilations to neutrinos in the Sun. For representative values of tan β and A 0 we map in detail the Planck-compatible strips in CMSSM parameter planes, which exhibit multiple distinctive features for large tan β , A 0 = 0 and μ > 0 , and identify portions of the strips that survive all the phenomenological constraints. We find that the most powerful constraint is that from m h , followed by the LZ limit on spin-independent scattering, whereas sparticle searches at the LHC and indirect dark matter searches are less restrictive. Most of the surviving CMSSM parameter space features a Higgsino-like dark matter particle with a mass ∼ 1000 - 1100 GeV, which could best be probed with future direct searches for dark matter scattering. [ABSTRACT FROM AUTHOR]

We show that a minimal scenario, utilizing only the graviton as an intermediate messenger between the inflaton, the dark sector and the Standard Model (SM), is able to generate simultaneously the observed relic density of dark matter (DM), the baryon asymmetry through leptogenesis, as well as a sufficiently hot thermal bath after inflation. We assume an inflaton potential of the form V(ϕ) ∝ ϕk about the minimum at the end of inflation. The possibility of reheating via minimal gravitational interactions has been excluded by constraints on dark radiation for excessive gravitational waves produced from inflation. We thus extend the minimal model in several ways: i) we consider non-minimal gravitational couplings — this points to the parameter range of DM masses M N 1 ≃ 2–10 PeV, and right-handed neutrino masses M N 2 ≃ (5–20) × 1011 GeV, and TRH ≲ 3 × 105 GeV (for k ≤ 20); ii) we propose an explanation for the PeV excess observed by IceCube when the DM has a direct but small Yukawa coupling to the SM; and iii) we also propose a novel scenario, where the gravitational production of DM is a two-step process, first through the production of two scalars, which then decay to fermionic DM final states. In this case, the absence of a helicity suppression enhances the production of DM and baryon asymmetry, and allows a great range for the parameters including a dark matter mass below an MeV where dark matter warmness can be observable by cosmic 21-cm lines, even when gravitational interactions are responsible for reheating. We also show that detectable primordial gravitational wave signals provide the opportunity to probe this scenario for TRH ≲ 5 × 106 GeV in future experiments, such as BBO, DECIGO, CE and ET. [ABSTRACT FROM AUTHOR]

We consider proton decay and g μ - 2 in flipped SU(5) GUT models. We first study scenarios in which the soft supersymmetry-breaking parameters are constrained to be universal at some high scale M in above the standard GUT scale where the QCD and electroweak SU(2) couplings unify. In this case the proton lifetime is typically ≳ 10 36 years, too long to be detected in the foreseeable future, and the supersymmetric contribution to g μ - 2 is too small to contribute significantly to resolving the discrepancy between the experimental measurement and data-driven calculations within the Standard Model. However, we identify a region of the constrained flipped SU(5) parameter space with large couplings between the 10- and 5-dimensional GUT Higgs representations where p → e + π 0 decay may be detectable in the Hyper-Kamiokande experiment now under construction, though the contribution to g μ - 2 is still small. A substantial contribution to g μ - 2 is possible, however, if the universality constraints on the soft supersymmetry-breaking masses are relaxed. We find a 'quadrifecta' region where observable proton decay co-exists with a (partial) supersymmetric resolution of the g μ - 2 discrepancy and acceptable values of m h and the relic LSP density. [ABSTRACT FROM AUTHOR]

We analyze the possible magnitude of the supersymmetric contribution to g μ - 2 in a flipped SU(5) GUT model. Unlike other GUT models which are severely constrained by universality relations, in flipped SU(5) the U(1) gaugino mass and the soft supersymmetry-breaking masses of right-handed sleptons are unrelated to the other gaugino, slepton and squark masses. Consequently, the lightest neutralino and the right-handed smuon may be light enough to mitigate the discrepancy between the experimental measurement of g μ - 2 and the Standard Model calculation, in which case they may be detectable at the LHC and/or a 250 GeV e + e - collider, whereas the other gauginos and sfermions are heavy enough to escape detection at the LHC. [ABSTRACT FROM AUTHOR]

We explore a missing-partner model based on the minimal SU(5) gauge group with 75 , 50 and 50 ¯ Higgs representations, assuming a super-GUT CMSSM scenario in which soft supersymmetry-breaking parameters are universal at some high scale M in above the GUT scale M GUT . We identify regions of parameter space that are consistent with the cosmological dark matter density, the measured Higgs mass and the experimental lower limit on τ (p → K + ν) . These constraints can be satisfied simultaneously along stop coannihilation strips in the super-GUT CMSSM with tan β ∼ 3.5–5 where the input gaugino mass m 1 / 2 ∼ 15–25 TeV, corresponding after strong renormalization by the large GUT Higgs representations between M in and M GUT to m LSP , m t ~ 1 ∼ 2.5–5 TeV and m g ~ ∼ 13–20 TeV, with the light-flavor squarks significantly heavier. We find that τ (p → K + ν) ≲ 3 × 10 34 years throughout the allowed range of parameter space, within the range of the next generation of searches with the JUNO, DUNE and Hyper-Kamiokande experiments. [ABSTRACT FROM AUTHOR]

We analyze nucleon decay modes in a no-scale supersymmetric flipped SU(5) GUT model, and contrast them with the predictions for proton decays via dimension-6 operators in a standard unflipped supersymmetric SU(5) GUT model. We find that these GUT models make very different predictions for the ratios Γ(p → π0μ+)/Γ(p → π0e+), Γ(p → π + ν ¯ )/Γ(p → π0e+), Γ(p → K0e+)/Γ(p → π0e+) and Γ(p → K0μ+)/Γ(p → π0μ+), and that predictions for the ratios Γ(p → π0μ+)/Γ(p → π0e+) and Γ(p → π + ν ¯ )/Γ(p → π0e+) also differ in variants of the flipped SU(5) model with normal- or inverse-ordered light neutrino masses. Upcoming large neutrino experiments may have interesting opportunities to explore both GUT and flavour physics in proton and neutron decays. [ABSTRACT FROM AUTHOR]

Encouraged by the advent of a new generation of underground detectors – JUNO, DUNE and Hyper-Kamiokande – that are projected to improve significantly on the present sensitivities to various baryon decay modes, we revisit baryon decay in the minimal supersymmetric SU(5) GUT. We discuss the phenomenological uncertainties associated with hadronic matrix elements and the value of the strong coupling α s – which are the most important – the weak mixing angle θ W , quark masses including one-loop renormalization effects, quark mixing and novel GUT phases that are not visible in electroweak interaction processes. We apply our analysis to a variety of CMSSM, super- and sub-GUT scenarios in which soft supersymmetry-breaking parameters are assumed to be universal at, above and below the GUT scale, respectively. In many cases, we find that the next generation of underground detectors should be able to probe models with sparticle masses that are O (10) TeV, beyond the reach of the LHC. [ABSTRACT FROM AUTHOR]

We reconsider the minimal SU(5) grand unified theory (GUT) in the context of no-scale supergravity inspired by string compactification scenarios, assuming that the soft supersymmetry-breaking parameters satisfy universality conditions at some input scale Min above the GUT scale MGUT. When setting up such a no-scale super-GUT model, special attention must be paid to avoiding the Scylla of rapid proton decay and the Charybdis of an excessive density of cold dark matter, while also having an acceptable mass for the Higgs boson. We do not find consistent solutions if none of the matter and Higgs fields are assigned to twisted chiral supermultiplets, even in the presence of Giudice-Masiero terms. However, consistent solutions may be found if at least one fiveplet of GUT Higgs fields is assigned to a twisted chiral supermultiplet, with a suitable choice of modular weights. Spin-independent dark matter scattering may be detectable in some of these consistent solutions. [ABSTRACT FROM AUTHOR]

Many supersymmetric models such as the constrained minimal supersymmetric extension of the Standard Model (CMSSM) feature a strip in parameter space where the lightest neutralino $$\chi $$ is identified as the lightest supersymmetric particle, the lighter stop squark $${\tilde{t}_1}$$ is the next-to-lightest supersymmetric particle (NLSP), and the relic $$\chi $$ cold dark matter density is brought into the range allowed by astrophysics and cosmology by coannihilation with the lighter stop squark $${\tilde{t}_1}$$ NLSP. We calculate the stop coannihilation strip in the CMSSM, incorporating Sommerfeld enhancement effects, and we explore the relevant phenomenological constraints and phenomenological signatures. In particular, we show that the $${\tilde{t}_1}$$ may weigh several TeV, and its lifetime may be in the nanosecond range, features that are more general than the specific CMSSM scenarios that we study in this paper. [ABSTRACT FROM AUTHOR]

Successful models of pure gravity mediation (PGM) with radiative electroweak symmetry breaking can be expressed with as few as two free parameters, which can be taken as the gravitino mass and $$\tan \beta $$ . These models easily support a 125-126 GeV Higgs mass at the expense of a scalar spectrum in the multi-TeV range and a much lighter wino as the lightest supersymmetric particle. In these models, it is also quite generic that the Higgs mixing mass parameter, $$\mu $$ , which is determined by the minimization of the Higgs potential is also in the multi-TeV range. For $$\mu >0$$ , the thermal relic density of winos is too small to account for the dark matter. The same is true for $$\mu <0$$ unless the gravitino mass is of order 500 TeV. Here, we consider the origin of a multi-TeV $$\mu $$ parameter arising from the breakdown of a Peccei-Quinn (PQ) symmetry. A coupling of the PQ-symmetry breaking field, $$P$$ , to the MSSM Higgs doublets, naturally leads to a value of $$\mu \sim \langle P \rangle ^2 /M_P \sim {\mathcal O}(100)$$ TeV and of the order that is required in PGM models. In this case, axions make up the dark matter or some fraction of the dark matter with the remainder made up from thermal or non-thermal winos. We also provide solutions to the problem of isocurvature fluctuations with axion dark matter in this context. [ABSTRACT FROM AUTHOR]

We consider the effects of non-universalities among sfermion generations in models of Pure Gravity Mediation (PGM). In PGM models and in many models with strongly stabilized moduli, the gravitino mass may be O(100) TeV, whereas gaugino masses, generated through anomalies at one loop, remain relatively light O(1) TeV. In models with scalar mass universality, input scalar masses are generally very heavy ( $$m_0 \simeq m_{3/2}$$ ), resulting in a mass spectrum resembling that in split supersymmetry. However, if one adopts a no-scale or partial no-scale structure for the Kähler manifold, sfermion masses may vanish at the tree level. It is usually assumed that the leading order anomaly mediated contribution to scalar masses appears at two loops. However, there are at least two possible sources for one-loop scalar masses. These may arise if Pauli-Villars fields are introduced as messengers of supersymmetry breaking. We consider the consequences of a spectrum in which the scalar masses associated with the third generation are heavy (order $$m_{3/2}$$ ) with one-loop scalar masses for the first two generations. A similar spectrum is expected to arise in GUT models based on $$E_7/\mathrm{SO}(10)$$ where the first two generations of scalars act as pseudo-Nambu-Goldstone bosons. Explicit breaking of this symmetry by the gauge couplings then generates one-loop masses for the first two generations. In particular, we show that it may be possible to reconcile the $$g_\mu - 2$$ discrepancy with potentially observable scalars and gauginos at the LHC. [ABSTRACT FROM AUTHOR]

The last 2 years has seen an immense amount of activity and results from the Large Hadron Collider (LHC). Most notable is the discovery of a new particle which may very well be the long sought Higgs boson associated with electroweak symmetry breaking. There have also been many (up to now) unsuccessful searches for new particles associated with supersymmetry. One of the most attractive candidates for dark matter is the lightest supersymmetric particle (LSP). The recent results from the LHC have had a dramatic impact on our expectations for the properties of the LSP. These results can be used to revise expectations for both direct and indirect detection of dark matter. [ABSTRACT FROM AUTHOR]

The simplest model of pure gravity mediation contains only two free parameters: the gravitino mass and tan β. Scalar masses are universal at some high energy renormalization scale and gaugino masses are determined through anomalies and depend on the gravitino mass and the gauge couplings. This theory requires a relatively large gravitino mass ( m3/2≳300 TeV) and a limited range in tan β≃1.7–2.5. Here we generalize the theory to allow for non-universality in the Higgs soft masses. This introduces zero, one or two new free parameters associated with Higgs soft masses. This generalization allows us to greatly increase the allowed range in tan β and it allows one to find viable solutions with lower m3/2. The latter is important if we hope to find a low energy signal from gluinos. Some special cases of these non-universalities are suggestive of Higgs bosons as Nambu–Goldstone bosons or a partial no-scale structure for the Higgs doublets. Thus, we probe signatures at the weak scale and structures at the GUT and/or Planck scale. [ABSTRACT FROM AUTHOR]

The apparent discovery of a Higgs boson with mass ∼125 GeV has had a significant impact on the constrained minimal supersymmetric extension of the Standard Model (the CMSSM). Much of the low-mass parameter space in the CMSSM has been excluded by supersymmetric particle searches at the LHC as well as by the Higgs mass measurement and the emergent signal for B→ μ μ. Here, we consider the impact of these recent LHC results on several variants of the CMSSM with a primary focus on obtaining a Higgs mass of ∼125 GeV. In particular, we consider the one- and two-parameter extensions of the CMSSM with one or both of the Higgs masses set independently of the common sfermion mass, m (the NUHM1,2). We also consider the one-parameter extension of the CMSSM in which the input universality scale M is below the GUT scale (the sub-GUT CMSSM). Finally, we reconsider mSUGRA models with sub-GUT universality, which have the same number of parameters as the CMSSM. We find that when M< M large regions of parameter space open up where the relic density of neutralinos can successfully account for dark matter with a Higgs boson mass ∼125 GeV. Interestingly, we find that the preferred range of the A-term in sub-GUT mSUGRA models straddles that predicted by the simplest Polonyi model. [ABSTRACT FROM AUTHOR]

We describe the resulting phenomenology of string theory/supergravity models with strong moduli stabilization. The KL model with F-term uplifting, is one such example. Models of this type predict universal scalar masses equal to the gravitino mass. In contrast, A-terms receive highly suppressed gravity mediated contributions. Under certain conditions, the same conclusion is valid for gaugino masses, which like A-terms, are then determined by anomalies. In such models, we are forced to relatively large gravitino masses (30-1000 TeV). We compute the low-energy spectrum as a function of m. We see that the Higgs masses naturally takes values between 125-130 GeV. The lower limit is obtained from the requirement of chargino masses greater than 104 GeV, while the upper limit is determined by the relic density of dark matter (wino-like). [ABSTRACT FROM AUTHOR]

While the constrained minimal supersymmetric standard model (CMSSM) with universal gaugino masses, m, scalar masses, m, and A-terms, A, defined at some high energy scale (usually taken to be the GUT scale) is motivated by general features of supergravity models, it does not carry all of the constraints imposed by minimal supergravity (mSUGRA). In particular, the CMSSM does not impose a relation between the trilinear and bilinear soft supersymmetry breaking terms, B= A− m, nor does it impose the relation between the soft scalar masses and the gravitino mass, m= m. As a consequence, tan β is computed given values of the other CMSSM input parameters. By considering a Giudice-Masiero (GM) extension to mSUGRA, one can introduce new parameters to the Kähler potential which are associated with the Higgs sector and recover many of the standard CMSSM predictions. However, depending on the value of A, one may have a gravitino or a neutralino dark matter candidate. We also consider the consequences of imposing the universality conditions above the GUT scale. This GM extension provides a natural UV completion for the CMSSM. [ABSTRACT FROM AUTHOR]

Taking into account the available accelerator and astrophysical constraints, the mass of the lightest neutral Higgs boson h in the minimal supersymmetric extension of the Standard Model with universal soft supersymmetry-breaking masses (CMSSM) has been estimated to lie between 114 and ~130 GeV. Recent data from ATLAS and CMS hint that mh ~ 125 GeV, though mh ~ 119 GeV may still be a possibility. Here we study the consequences for the parameters of the CMSSM and direct dark matter detection if the Higgs hint is confirmed, focusing on the strips in the (m1/2,m0) planes for different tan β and A0 where the relic density of the lightest neutralino ? falls within the range of the cosmological cold dark matter density allowed by WMAP and other experiments. We find that if mh ~ 125 GeV focus-point strips would be disfavoured, as would the low-tan β ῖ-? and t~1-? coannihilation strips, whereas the ῖ-? coannihilation strip at large tan β and A0 > 0 would be favoured, together with its extension to a funnel where rapid annihilation via direct-channel H/A poles dominates. On the other hand, if mh ~ 119 GeV more options would be open. We give parameterisations of WMAP strips with large tan β and fixed A0/m0 > 0 that include portions compatible with mh = 125 GeV, and present predictions for spin-independent elastic dark matter scattering along these strips. These are generally low for models compatible with mh = 125 GeV, whereas the XENON100 experiment already excludes some portions of strips where mh is smaller. [ABSTRACT FROM AUTHOR]

In the context of phenomenological models in which the soft supersymmetry-breaking parameters of the MSSM become universal at some unification scale, M, above the GUT scale, M, it is possible that all the scalar mass parameters m, the trilinear couplings A and the bilinear Higgs coupling B vanish simultaneously, as in no-scale supergravity. Using these no-scale inputs in a renormalisation-group analysis of the minimal supersymmetric SU(5) GUT model, we pay careful attention to the matching of parameters at the GUT scale. We delineate the region of M, m and tan β where the resurrection of no-scale supergravity is possible, taking due account of the relevant phenomenological constraints such as electroweak symmetry breaking, m, b→ s γ, the neutralino cold dark matter density Ω h and g−2. No-scale supergravity survives in an L-shaped strip of parameter space, with one side having m≳200 GeV, the second (orthogonal) side having M≳5×10 GeV. Depending on the relative signs and magnitudes of the GUT superpotential couplings, these may be connected to form a triangle whose third side is a hypotenuse at larger M, m and tan β, whose presence and location depend on the GUT superpotential parameters. We compare the prospects for detecting sparticles at the LHC in no-scale supergravity with those in the CMSSM and the NUHM. [ABSTRACT FROM AUTHOR]

We study models in which soft supersymmetry-breaking parameters of the MSSM become universal at some unification scale, M, above the GUT scale, M. We assume that the scalar masses and gaugino masses have common values, m and m respectively, at M. We use the renormalisation-group equations of the minimal supersymmetric SU(5) GUT to evaluate their evolutions down to M, studying their dependences on the unknown parameters of the SU(5) superpotential. After displaying some generic examples of the evolutions of the soft supersymmetry-breaking parameters, we discuss the effects on physical sparticle masses in some specific examples. We note, for example, that near-degeneracy between the lightest neutralino and the lighter stau is progressively disfavoured as M increases. This has the consequence, as we show in ( m, m) planes for several different values of tan β, that the stau-coannihilation region shrinks as M increases, and we delineate the regions of the ( M,tan β) plane where it is absent altogether. Moreover, as M increases, the focus-point region recedes to larger values of m for any fixed tan β and m. We conclude that the regions of the ( m, m) plane that are commonly favoured in phenomenological analyses tend to disappear at large M. [ABSTRACT FROM AUTHOR]

Dark matter in variations of constrained minimal supersymmetric standard models will be discussed. Particular attention will be given to the comparison between accelerator and direct detection constraints. [ABSTRACT FROM AUTHOR]

Direct and indirect dark matter detection relies on the scattering of the dark matter candidate on nucleons or nuclei. Here, attention is focused on dark matter candidates (neutralinos) predicted in the minimal supersymmetric standard model and its constrained version with universal input soft supersymmetry-breaking masses. Current expectations for elastic scattering cross sections for neutralinos on protons are discussed with particular attention to satisfying all current accelerator constraints as well as insuring a sufficient cosmological relic density to account for the dark matter in the universe. [ABSTRACT FROM AUTHOR]

Discusses astrophysical 7Li as a product of Big Bang nucleosynthesis and galactic cosmic-ray spallation. Abundances of beryllium (Be) and boron (B) in a number of hot population II halo stars; Observed Be and Li (Lithium) and extracted Big Bang abundances of 7Li; Observed B and Li and extracted Big Bang abundance of 2Li; The stellar models of Pinsonneault et al; More.

We show the uniqueness of superpotentials leading to Minkowski vacua of single-field no-scale supergravity models, and the construction of dS/AdS solutions using pairs of these single-field Minkowski superpotentials. We then extend the construction to two- and multifield no-scale supergravity models, providing also a geometrical interpretation. We also consider scenarios with additional twisted or untwisted moduli fields, and discuss how inflationary models can be constructed in this framework. [ABSTRACT FROM AUTHOR]

The lack of evidence for low-scale supersymmetry suggests that the scale of supersymmetry breaking may be higher than originally anticipated. However, there remain many motivations for supersymmetry including gauge coupling unification and a stable dark matter candidate. Models like pure gravity mediation (PGM) evade LHC searches while still providing a good dark matter candidate and gauge coupling unification. Here, we study the effects of PGM if the input boundary conditions for soft supersymmetry breaking masses are pushed beyond the unification scale and higher dimensional operators are included. The added running beyond the unification scale opens up the parameter space by relaxing the constraints on tan β . If higher dimensional operators involving the SU(5) adjoint Higgs are included, the mass of the heavy gauge bosons of SU(5) can be suppressed leading to proton decay, p → π 0 e + , that is within reach of future experiments. Higher dimensional operators involving the supersymmetry breaking field can generate additional contributions to the A- and B-terms of order m 3 / 2 . The threshold effects involving these A- and B-terms significantly impact the masses of the gauginos and can lead to a bino LSP. In some regions of parameter space the bino can be degenerate with the wino or gluino and give an acceptable dark matter relic density. [ABSTRACT FROM AUTHOR]

We revisit the uncertainties in the calculation of spin-independent scattering matrix elements for the scattering of WIMP dark matter particles on nuclear matter. In addition to discussing the uncertainties due to limitations in our knowledge of the nucleonic matrix elements of the light quark scalar densities ⟨N|u¯u,d¯d,s¯s|N⟩, we also discuss the importances of heavy quark scalar densities ⟨N|c¯c,b¯b,t¯t|N⟩, and comment on uncertainties in quark mass ratios. We analyze estimates of the light-quark densities made over the past decade using lattice calculations and/or phenomenological inputs. We find an uncertainty in the combination ⟨N|u¯u+d¯d|N⟩ that is larger than has been assumed in some phenomenological analyses, and a range of ⟨N|s¯s|N⟩ that is smaller but compatible with earlier estimates. We also analyze the importance of the O(αs3) calculations of the heavy-quark matrix elements that are now available, which provide an important refinement of the calculation of the spin-independent scattering cross section. We use for illustration a benchmark CMSSM point in the focus-point region that is compatible with the limits from LHC and other searches. [ABSTRACT FROM AUTHOR]

Stop coannihilation may bring the relic density of heavy supersymmetric dark matter particles into the range allowed by cosmology. The efficiency of this process is enhanced by stop-antistop annihilations into the longitudinal (Goldstone) modes of the W and Z bosons, as well as by Sommerfeld enhancement of stop annihilations and the effects of bound states. Since the couplings of the stops to the Goldstone modes are proportional to the trilinear soft supersymmetry-breaking A-terms, these annihilations are enhanced when the A-terms are large. However, the Higgs mass may be reduced below the measured value if the A-terms are too large. Unfortunately, the interpretation of this constraint on the stop coannihilation strip is clouded by differences between the available Higgs mass calculators. For our study, we use as our default calculator FeynHiggs 2.13.0, the most recent publicly available version of this code. Exploring the CMSSM parameter space, we find that along the stop coannihilation strip the masses of the stops are severely split by the large A-terms. This suppresses the Higgs mass drastically for μ and A0>0, whilst the extent of the stop coannihilation strip is limited for A0<0 and either sign of μ. However, in sub-GUT models, reduced renormalization-group running mitigates the effect of the large A-terms, allowing larger LSP masses to be consistent with the Higgs mass calculation. We give examples where the dark matter particle mass may reach ≳8 TeV. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate that the inclusion of right-handed neutrino superfields in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) makes it possible to impose universality conditions on the soft supersymmetry-breaking parameters at the Grand Unification scale, alleviating many of the problems of the so-called Constrained NMSSM. We have studied the renormalization group equations of this model, showing that right-handed neutrinos greatly contribute to driving the singlet Higgs mass-squared parameter negative, which makes it considerably easier to satisfy the conditions for radiative electroweak symmetry breaking. The new fields also lead to larger values of the Standard Model Higgs mass, thus making it easier to reproduce the measured value. As a consequence, all bounds from colliders and low-energy observables can be fulfilled in wide areas of the parameter space. However, the relic density in these regions is generally too high requiring some form of late entropy production to dilute the density of the lightest supersymmetric particle. [ABSTRACT FROM AUTHOR]