We study soft leptogenesis in gauge mediated supersymmetry breaking models with an enhanced A-term for the right-handed neutrino. We find that this scenario can explain the baryon asymmetry of the present universe, consistently with the gravitino dark matter for a wide range of gravitino mass m_{3/2}=O(MeV)-O(GeV). We also propose an explicit model which induces the necessary A-term for the right-handed neutrino.
We discuss the SM-like Higgs boson mass in the MSSM in an R-invariant direct gauge mediation model with the gravitino mass in the O(1) keV range. The gravitino dark matter scenario in this mass range is a good candidate for a slightly warm dark matter. We show that the Higgs boson mass around 125 GeV suggested by the ATLAS and CMS experiments can be easily achieved in the direct gauge mediation model with this gravitino mass range.
In the present work we discuss baryon asymmetry in the non-thermal leptogenesis scenario and gravitino cosmology for an unstable gravitino with inflaton decay. We take into account two production mechanisms for gravitino, namely thermal production and inflaton decay. We wish to show in plots the allowed parameter space so that the BBN constraint and the requirement for the right baryon asymmetry are satisfied at the same time. However our analysis shows that it is impossible to achieve both goals simultaneously.
We discuss a class of gauge mediated supersymmetry breaking models with conformal invariance above the messenger mass scale (conformal gauge mediation). The spectrum of the supersymmetric particles including the gravitino is uniquely determined by the messenger mass. When the conformal fixed point is strongly interacting, it predicts a light gravitino of mass m_{3/2}<O(10) eV, which is attractive since such a light gravitino causes no problem in cosmology.
In the supersymmetric extensions of the standard model, neutrino masses and leptogenesis requires existence of new particles. We point out that if these particles with lepton number violating interactions have standard model gauge interactions, then they may not be created after reheating because of the gravitino problem. This will rule out all existing models of neutrino masses and leptogenesis, except the one with right-handed singlet neutrinos.
We study implications of thermal leptogenesis for the superparticle mass spectrum. A consistent picture is obtained if the lightest superparticle is the gravitino, which can be the dominant component of cold dark matter. In the case of a long-lived charged scalar lepton as next-to-lightest superparticle, supergravity can be tested at the next generation of colliders, LHC and ILC.
We revisit low-scale gauge mediation models in light of recent observations of CMB Lensing and Cosmic Shear which put a severe upper limit on the gravitino mass, $m_{3/2} \lesssim 4.7$eV. With such a stringent constraint, many models of low-scale gauge mediation are excluded when the squark masses are required to be rather large to explain the observed Higgs boson mass. In this note, we discuss a type of low-scale gauge mediation models which satisfy both the observed Higgs boson mass and the upper limit on the gravitino mass. We also show that the gravitino mass cannot be smaller than about 1…
Gravitinos and hidden sector fields often cause a cosmological disaster in supersymmetric models. We find that a model with gravitational gauge mediation solves such a problem quite naturally. The mu-problem is also absent in the model. Moreover, the abundance of gravitinos explains correct amount of dark matter of the universe. The dark matter abundance can be calculated without detailed information on the thermal history of the universe such as the reheating temperature after inflation.
We comment on a statement made in arXiv:1107.0403, which implies that the model of gravitino dark matter from Q-ball decay we presented in arXiv:1101.5328 is generally ruled out by the effect of NLSP decay on BBN. We explain why this statement is incorrect.
We consider the simplest class of the R-invariant gauge mediation model with the gravitino mass in the one to ten keV range. We show that the entropy production from the supersymmetry breaking sector makes the gravitino into a warm dark matter candidate. We also discuss that the gluino mass can be lighter than the wino mass even when the messenger sector satisfies the GUT relations at the GUT scale.
We examine stabilities of our supersymmetry-breaking false vacuum in a low-energy direct gauge mediation model of SUSY breaking. The stability required in the high-temperature early universe leads to upperbounds on masses of squarks and gluino as m_\tilde{q} \lesssim 1 TeV and m_\tilde{g} \lesssim 1 TeV for the light gravitino of mass m_{3/2} \lesssim 16 eV.
We show that gravitinos produced by decays of a supersymmetry breaking scalar field (the pseudo-moduli field) can naturally explain the observed abundance of dark matter in a certain class of the gauge mediation models. We study the decay processes as well as cosmological constraints on this scenario in detail, particularly focusing on different behavior of the real and imaginary components of the pseudo-moduli field. Cosmologically viable scenario emerges when the gravitino and the pseudo-moduli masses are O(10-100) MeV and O(100) GeV, respectively.
We provide a gauge-mediation model of dynamical supersymmetry breaking where the gravitino mass takes a value in a wide range from 0.1 eV to 10 GeV. The lower mass region of order 100 keV or less deserves experimental and cosmological interests. The vacuum of our model is a true one without runaway instability, which may be desirable in a cosmological evolution of the universe.
We show that for gaugino mediated supersymmetry breaking the gravitino mass is bounded from below. For a size of the compact dimensions of order the unification scale and a cutoff given by the higher-dimensional Planck mass, we find $m_{3/2} \gtrsim 10 GeV$. In a large domain of parameter space, the gravitino is the lightest superparticle with a scalar $\tildeτ$-lepton as the next-to-lightest superparticle.
In this paper, we revisit the gravitino dark matter scenario in the presence of the bilinear $R$-parity violating interaction. In particular, we discuss a consistency with the thermal leptogenesis. For a high reheating temperature required for the thermal leptogenesis, the gravitino dark matter tends to be overproduced, which puts a severe upper limit on the gluino mass. As we will show, a large portion of parameter space of the gravitino dark matter scenario has been excluded by combining the constraints from the gravitino abundance and the null results of the searches for the superparticles …
We study general conditions for the gravitino to be the lightest supersymmetric particle (LSP) in models with gravity mediated supersymmetry breaking. We find that the decisive quantities are the Kaehler potential K and the gauge kinetic function f. In constrained MSSM (CMSSM) type models, the gravitino LSP occurs if the gaugino mass at the GUT scale is greater than approximately 2.5 gravitino masses. This translates into \sqrt{K"}/f' < 0.2, where the derivatives are taken with respect to the dominant SUSY breaking field. This requirement can easily be satisfied in string-motivated setups.
We present a new scenario of gravitino dark matter which is compatible with the thermal leptogenesis. We confirm by an explicit calculation in supergravity that the relic abundance of thermally produced gravitino becomes insensitive to the reheating temperature once the temperature of the Universe exceeds the mass scale of the messenger fields. In such a situation, the correct baryon to dark matter ratio can be obtained by thermal leptogenesis when the reheating temperature after inflation is high enough. We demonstrate in a concrete model of gauge mediation that the correct abundance of gravi…
It was recently found that the decay of inflaton and the SUSY breaking field produces many gravitinos in the gravity mediation scenario. These discoveries led to an exclusion of many inflation models such as chaotic, (smooth) hybrid, topological and new inflation models. Under these circumstances we searched for a successful inflation model and found that the ``inverted'' hybrid inflation models can solve the gravitino overproduction problem by their distinctive shape of the potential. Furthermore, we found that this inflation model simultaneously can explain the observed baryon asymmetry thro…
We discuss sneutrino inflation in the brane-world scenario. We work in the Randall-Sundrum type II brane-world, generalized with the introduction of the Gauss-Bonnet term, a correction to the effective action in string theories. We find that a viable inflationary model is obtained with a reheating temperature appropriate to lead to the right baryon asymmetry and render the gravitino safe for cosmology. In specific realizations we satisfy all the observational constaints without the unnaturally small Yukawa couplings required in other related approaches.
The seesaw mechanism that explains the small neutrino masses comes naturally with supersymmetric (SUSY) grand unification and leptogenesis. However, the framework suffers from the SUSY flavor and CP problems, and has a severe cosmological gravitino problem. We propose anomaly mediation as a simple solution to all these problems, which is viable once supplemented by the D-terms for U(1)_Y and U(1)_{B-L}. Even though the right-handed neutrino mass explicitly breaks U(1)_{B-L} and hence reintroduces the flavor problem, we show that it lacks the logarithmic enhancement and poses no threat to the f…
We consider the situation in which $m_{3/2}\sim O(100{\rm TeV})$ for solving the gravitino problem and the other supersymmetry(SUSY) breaking parameters are $O(1{\rm TeV})$ for the naturalness. We point out that the anomaly mediation cancels out the renormalization group contribution to the gaugino masses and the sfermion masses other than the stop masses at a scale which is called the mirage scale. The situation is similar to the mirage mediation, in which special boundary conditions for the SUSY breaking parameters are required, though for the stop masses and the up-type Higgs mass, such can…
We study gaugino-mediated supersymmetry breaking in a six-dimensional SO(10) orbifold GUT model where quarks and leptons are mixtures of brane and bulk fields. The couplings of bulk matter fields to the supersymmetry breaking brane field have to be suppressed in order to avoid large FCNCs. We derive bounds on the soft supersymmetry breaking parameters and calculate the superparticle mass spectrum. If the gravitino is the LSP, the stau_1 or the tau sneutrino turns out to be the NLSP, with characteristic signatures at future colliders and in cosmology.
Supersymmetric scenarios where the lightest superparticle (LSP) is the gravitino are an attractive alternative to the widely studied case of a neutralino LSP. A strong motivation for a gravitino LSP arises from the possibility of achieving higher reheating temperatures and thus potentially allow for thermal leptogenesis. The predictions for the primordial abundances of light elements in the presence of a late decaying next-to-LSP (NSLP) as well as the currently measured dark matter abundance allow us to probe the cosmological viability of such a scenario. Here we consider a gravitino-stau scen…
We show a calculable example of stable supersymmetry (SUSY) breaking models with O(10) eV gravitino mass based on the combination of D-term gauge mediation and U(1)' mediation. A potential problem of the negative mass squared for the SUSY standard model (SSM) sfermions in the D-term gauge mediation is solved by the contribution from the U(1)' mediation. On the other hand, the splitting between the SSM gauginos and sfermions in the U(1)' mediation is circumvented by the contributions from the D-term gauge mediation. Since the U(1)' mediation does not introduce any new SUSY vacua, we achieve a c…
We show that a mini-thermal inflation occurs naturally in a class of gauge mediation models of supersymmetry (SUSY) breaking, provided that the reheating temperature T_R of the primary inflation is much higher than the SUSY-breaking scale, say T_R > 10^{10} GeV. The reheating process of the thermal inflation produces an amount of entropy, which dilutes the number density of relic gravitinos. This dilution renders the gravitino to be the dark matter in the present universe. The abundance of the gravitinos is independent of the reheating temperature T_R, once the gravtinos are thermally produced…
Models of leptogenesis are constrained by the low reheat temperature at the end of reheating associated with the gravitino bound. However a detailed view of reheating, in which the maximum temperature during reheating, $\Tmax$, can be orders of magnitude higher than the reheat temperature, allows for the production of heavy Majorana neutrinos needed for leptogenesis. But then one must also consider the possibility of enhanced gravitino production in such scenarios. In this article we consider gravitino production during reheating, its dependence on $\Tmax$, and its relevance for leptogenesis. …
The AMS-02 collaboration has recently reported an excess of cosmic-ray positron fractions, which is consistent with previous results at PAMELA and Fermi-LAT experiments. The result indicates the existence of new physics phenomena to provide the origin of the energetic cosmic-ray positron. We pursue the possibility that the enhancement of the positron fraction is due to the decay of gravitino dark matter. We discuss that such a scenario viably fits into the models in which the soft SUSY breaking parameters are dominantly from gauge-mediation mechanism with superparticle masses of around 10 TeV.…
Thermal leptogenesis requires the reheating temperature $T_R \gsim 3\times 10^{9}$ GeV, which contradicts a recently obtained constraint on the reheating temperature, $T_R \lsim 10^6$ GeV, for the gravitino mass of 100 GeV-10 TeV. This stringent constraint comes from the fact that the hadronic decays of gravitinos destroy very efficiently light elements produced by the Big-Bang nucleosynthesis. However, it is not applicable if the gravitino is the lightest supersymmetric particle (LSP). We show that this solution to the gravitino problem works for the case where the next LSP is a scalar charge…
In this talk, we studied the implication of the constraint on the reheating temperature coming from the gravitino problem on models of leptogenesis. We point out that in supersymmetric extensions of the standard model, all existing models of neutrino masses and leptogenesis, except the one with right-handed singlet neutrinos are ruled out for a large range of the gravitino mass.
We reinvestigate the scenario that the amount of the baryons and the gravitino dark matter is naturally explained by the decay of the Q balls in the gauge-mediated SUSY breaking. Equipped by the more correct decay rates into gravitinos and baryons recently derived, we find that the scenario with the direct production of the gravitino dark matter from the Q-ball decay works naturally.
Considering gravitino dark matter scenarios, we obtain the full gauge-invariant result for the relic density of thermally produced gravitinos to leading order in the Standard Model gauge couplings. For the temperatures required by thermal leptogenesis, we find gaugino mass bounds which will be probed at future colliders. We show that a conceivable determination of the gravitino mass will allow for a unique test of the viability of thermal leptogenesis in the laboratory.
We propose a new framework of low-scale gauge-mediated supersymmetry (SUSY) breaking with a gravitino mass of O(100) TeV. The usual 4D gauge mediation models predict a light gravitino and suffer from cosmological problems. In our framework, a heavy gravitino in gauge mediation is realized with a flat extra-dimension, whose compactification scale is around the grand unified theory scale. Superparticle masses of the visible sector from gravity/anomaly mediation are suppressed, and they are purely generated by usual gauge mediation on the visible brane. Importantly, the Higgs Bmu-term vanishes at…
We reconsidered leptogenesis scenario from right-handed (s)neutrino produced by the decay of inflaton. Besides the well-investigated case that the neutrino decays instantaneously after the production, leptogenesis is possible if neutrino decays after it dominates the universe. In the latter case, right-handed (s)neutrino can decay either while it is relativistic or after it becomes non-relativistic. Especially, the first case has not been discussed seriously in literatures. Resultant lepton asymmetry and constraints from the gravitino problem are studied in broad parameter region, including al…
We study low-scale gauge mediated supersymmetry breaking models with a very light gravitino of mass $\mathcal{O}(1)$ eV. The cosmological upper bound on the gravitino mass and the collider constraints on the sparticle masses give a significant impact on such models. We apply the latest results of the LHC to these models and obtain the current constraints. We find that perturbatively calculable classes of low-scale gauge mediation models can be largely excluded.
We consider the possibility that the Peccei-Quinn charged dynamical supersymmetry breaking (DSB) of m_{3/2}=O(eV) for the Intriligator-Seiberg-Shih model, an axion, converted from a Nambu-Goldstone boson, could become a dark matter candidate, while the QCD anomaly and a sizable μvalue are naturally generated. We also stress that rather minimal DSB content is sufficient to yield the observed mass of the lightest Higgs boson, other than the acceptable soft mass of sparticles in the observable sector.
We study the phenomenology of generic supergravity models in which gravity mediation naturally competes with gauge mediation as the origin of supergravity-breaking. This class of hybrid models has been recently motivated in string inspired constructions and differs from usual gauge mediated supersymmetry breaking models in having messenger masses of order of the GUT scale. In these scenarios the gravitino can be the lightest supersymmetric particle in wide regions of the parameter space and therefore a potential candidate for dark matter. We investigate this possibility, imposing the WMAP boun…
In the light of recent experimental data on gaugino searches, we revisit the direct-transmission model of dynamical supersymmery breaking with the gravitino mass m_{\tilde{G}}\leq 16 eV, which does not have any cosmological or astrophysical problems. We find that in the consistent regions of parameter space, the model predicts not only upper bounds on superparticle masses (1.1 TeV, 320 GeV, 160 GeV, 5 TeV, 1.5 TeV and 700 GeV for gluino, Wino, Bino, squarks, left-handed sleptons and right-handed sleptons, respectively), but also a mass of the lightest messenger particle in the range of 10-50 T…
We study dark matter for gaugino-mediated supersymmetry breaking and compact dimensions of order the grand unification scale. Higgs fields are bulk fields, and in general their masses differ from those of squarks and sleptons at the unification scale. As a consequence, at different points in parameter space, the gravitino, a neutralino or a scalar lepton can be the lightest (LSP) or next-to-lightest (NLSP) superparticle. We investigate the constraints from primordial nucleosynthesis on the different scenarios. While neutralino and gravitino dark matter with a sneutrino NLSP are consistent for …
We propose a retrofitted gravity mediation model which alleviates the gravitino overproduction from decays of an inflaton and a supersymmetry breaking field. In the model, we introduce an approximate U(1) symmetry under which the supersymmetry breaking field is charged, although it is broken by a mass term of messenger fields to generate gaugino masses of order the weak scale. In a low-scale inflation model, we find regions in which the gravitino overproduction problem is avoided.
We study models with contributions of similar size to the soft masses from anomaly- and gravity mediation, thereby curing the tachyonic slepton problem of anomaly mediation. A possible origin of this hybrid setup in a 5-dimensional brane world is briefly discussed. The absence of excessive flavor violation is explained by alignment. The gravitino can be heavy enough so that the gravitino problem of supersymmetric theories with leptogenesis is avoided. The model has a characteristic signature: It predicts the distinctive gaugino mass pattern of anomaly mediation and, at the same time, O(1) slep…
We investigate the leptogenesis via decays of heavy Majorana neutrinos which are produced non-thermally in inflaton decays. We make a comprehensive study on the leptogenesis assuming various supersymmetric (SUSY) models for hybrid, new and topological inflations. For an estimation of the lepton asymmetry we adopt the Froggatt-Nielsen mechanism for mass matrices of quarks and leptons. We find that all of these models are successful to produce the lepton asymmetry enough to explain the baryon number in the present universe. Here we impose low reheating temperatures such as $T_R \lesssim 10^8$ Ge…
We present an inflationary scenario based on a phenomenologically viable model with direct gauge mediation of low-scale supersymmetry breaking. Inflation can occur in the supersymmetry-breaking hidden sector. Although the reheating temperature from the inflaton decay is so high that the gravitino problem seems to be severe, late time entropy production from the decay of the pseudomoduli field associated with the supersymmetry breaking can dilute gravitinos sufficiently. We show that gravitinos are also produced from the pseudomoduli decay and there is a model parameter space where gravitinos c…
We study the Yukawa unification, in particular, the unification of the Yukawa coupling constants of $b$ and $τ$, in the framework of supersymmetric (SUSY) model. We concentrate on the model in which the SUSY breaking scalar masses are of the order of the gravitino mass while the gaugino masses originate from the effect of anomaly mediation and hence are one-loop suppressed relative to the gravitino mass. We perform an accurate calculation of the Yukawa coupling constants of $b$ and $τ$ at the grand unified theory (GUT) scale, including relevant renormalization group effects and threshold corre…
Anomaly mediation is a ubiquitous source of supersymmetry (SUSY) breaking which appears in almost every theory of supergravity. In this paper, we show that anomaly mediation really consists of two physically distinct phenomena, which we dub "gravitino mediation" and "Kahler mediation". Gravitino mediation arises from minimally uplifting SUSY anti-de Sitter (AdS) space to Minkowski space, generating soft masses proportional to the gravitino mass. Kahler mediation arises when visible sector fields have linear couplings to SUSY breaking in the Kahler potential, generating soft masses proportional…
We point out that there is no cosmological gravitino problem in a certain class of gauge-mediated supersymmetry-breaking (GMSB) models. The constant term in the superpotential naturally causes small mixings between the standard-model and messenger fields, which give rise to late-time decays of the lightest messenger fields. This decay provides an exquisite amount of entropy, which dilutes the thermal relics of the gravitinos down to just the observed mass density of the dark matter. This remarkable phenomenon takes place naturally, irrespective of the gravitino mass and the reheating temperatu…
Gravitino dark matter, together with thermal leptogenesis, implies an upper bound on the masses of superparticles. In the case of broken R-parity the constraints from primordial nucleosynthesis are naturally satisfied and decaying gravitinos lead to characteristic signatures in high energy cosmic rays. We analyse the implications for supergravity models with universal boundary conditions at the grand unification scale. Together with low-energy observables one obtains a window of superparticle masses, which will soon be probed at the LHC, and a range of allowed reheating temperatures.
We study the moduli-induced gravitino problem within the framework of the phenomenologically attractive mirage mediations. The huge amount of gravitino generated by the moduli decay can be successfully diluted by introducing an extra light modulus field which does not induce the supersymmetry breaking. Since the lifetime of extra modulus field becomes longer than usually considered modulus field, our proposed mechanism is applied to both the low- and high-scale supersymmetry breaking scenarios. We also point out that such an extra modulus field appears in the flux compactification of type II s…
We investigate in detail the leptogenesis by the decay of coherent right-handed sneutrino $\widetilde{N}$ having dominated the energy density of the early universe, which was originally proposed by HM and TY. Once the $\widetilde{N}$ dominant universe is realized, the amount of the generated lepton asymmetry (and hence baryon asymmetry) is determined only by the properties of the right-handed neutrino, regardless of the history before it dominates the universe. Moreover, thanks to the entropy production by the decay of the right-handed sneutrino, thermally produced relics are sufficiently dilu…
We consider low scale gauge mediation models with a very light gravitino m_{3/2}~16 eV, in the light of recent experimental hints on the Higgs boson mass. The light gravitino is very interesting since there is no gravitino over-production problem, but it seems difficult to explain the Higgs boson mass of ~125 GeV. This is because of the conflict between the light gravitino mass and heavy SUSY particle masses needed for producing the relatively heavy Higgs boson mass. We consider two possible extensions in this paper: a singlet extension of the Higgs sector, and strongly coupled gauge mediation…
For supersymmetric theories with gravitino dark matter, the maximal reheating temperature consistent with big bang nucleosynthesis bounds arises when the physical gaugino masses are degenerate. We consider the cases of a stau or sneutrino next-to-lightest superpartner, which have relatively less constraint from big bang nucleosynthesis. The resulting parameter space is consistent with leptogenesis requirements, and can be reached in generalized gauge mediation models. Such models illustrate a class of theories that overcome the well-known tension between big bang nucleosynthesis and leptogenes…
Successful soft leptogenesis requires small B-terms for the right-handed sneutrinos and a large CP violating phase between the A- and B-terms. We show that this situation is realized naturally within the framework of gauge mediated supersymmetry breaking. The A-term is dominated by contribution from gauge mediation, while supergravity effects are more important for the B-term. The different origins naturally explain simultaneously the smallness of the B-term and the large CP violating phase. The most stringent bounds on the model come from the cosmological gravitino problem. We find a viable p…
In conventional models of gauge-mediated supersymmetry breaking, the lightest supersymmetric particle (LSP) is invariably the gravitino. However, if the supersymmetry breaking sector is strongly coupled, conformal sequestering may raise the mass of the gravitino relative to the remaining soft supersymmetry-breaking masses. In this letter, we demonstrate that such conformal dynamics in gauge-mediated theories may give rise to satisfactory neutralino dark matter while simultaneously solving the flavor and mu/ B mu problems.
Gauge mediation models have two drawbacks, that is, the so-called μ-problem and a lack of predictability of the gravitino dark matter abundance. We show that conformal sequestering in the supersymmetry breaking sector offers attractive solutions to both problems. The correct mass scale of the μand B_μterms is generated by taking the gravitino mass of O(100) GeV without causing the flavor-changing neutral-current problem. Moreover, a large anomalous dimension of the supersymmetry breaking field naturally realizes the small stau and neutralino mass difference required for the coannihilation to w…
We investigate the Q-ball decay in the gauge-mediated SUSY breaking. Q balls decay mainly into nucleons, and partially into gravitinos, while they are kinematically forbidden to decay into sparticles which would be cosmologically harmful. This is achieved by the Q-ball charge small enough to be unstable for the decay, and large enough to be protected kinematically from unwanted decay channel. We can then have right amounts of the baryon asymmetry and the dark matter of the universe, evading any astrophysical and cosmological observational constraints such as the big bang nucleosynthesis, which…
A keV-scale gravitino arsing from a minimal supersymmetric (SUSY) Standard Model (MSSM) is an interesting possibility since the small scale problems that $Λ$CDM model encounters in the modern cosmology could be alleviated with the keV-scale gravitino serving as the warm dark matter (WDM). Such a light gravitino asks for a low scale supersymmetry (SUSY) breaking for which the gauge mediation (GM) is required as a consistent SUSY-breaking mediation mechanism. In this paper, we show upperbounds of the masses of the second CP-even Higgs boson $H$ and the CP-odd Higgs boson $A$, assuming the keV-sc…
We explore the dark matter freeze-in mechanism within the gauge mediation framework, which involves a hidden Feebly Interacting Massive Particle (FIMP) coupling feebly with the messenger fields while the messengers are still in the thermal bath. The FIMP is the fermionic component of the pseudo-moduli in a generic metastable supersymmetry (SUSY) breaking model and resides in the hidden sector. The relic abundance and the mass of the FIMP are determined by the SUSY breaking scale and the feeble coupling. The gravitino, which is the canonical dark matter candidate in the gauge mediation framewor…
Many extensions of the Standard Model predict super-weakly interacting particles, which typically have to decay before Big Bang Nucleosynthesis (BBN). The entropy produced in the decays may help to reconcile thermal leptogenesis and BBN in scenarios with gravitino dark matter, which is usually difficult due to late decays of the next-to-lightest supersymmetric particle (NLSP) spoiling the predictions of BBN. We study this possibility for a general neutralino NLSP. We elaborate general properties of the scenario and strong constraints on the entropy-producing particle. As an example, we conside…
We investigate compatibility of the pure gravity mediation (or the minimal split supersymmetry) with chaotic inflation models in supergravity. We find that an approximate Z2 parity of the inflaton is useful to suppress gravitino production from thermal bath and to obtain consistent inflation dynamics. We discuss production of the lightest supersymmetric particle through the decay of the inflaton with the approximate Z2 symmetry and find that a large gravitino mass is favored to avoid the overproduction of the lightest supersymmetric particle, while a lower gravitino mass requires tuning of par…
Supersymmetric thermal leptogenesis with a hierarchical right-handed neutrino mass spectrum requires the mass of the lightest right-handed neutrino to be heavier than about 10^9 GeV. This is in conflict with the upper bound on the reheating temperature which is found by imposing that the gravitinos generated during the reheating stage after inflation do not jeopardize successful nucleosynthesis. In this paper we show that a solution to this tension is actually already incorporated in the framework, because of the presence of flat directions in the supersymmetric scalar potential. Massive right…
Simple SUSY GUT models based on the gauge group SO(10) require t-b-τYukawa coupling unification, in addition to gauge coupling and matter unification. The Yukawa coupling unification places strong constraints on the expected superparticle mass spectrum, with scalar masses \sim 10 TeV while gaugino masses are quite light. A problem generic to all supergravity models comes from overproduction of gravitinos in the early universe: if gravitinos are unstable, then their late decays may destroy the predictions of Big Bang nucleosynthesis. We present a Yukawa-unified SO(10) SUSY GUT scenario which av…
We argue that some of the difficulties in constructing realistic models of low-scale gauge mediation are artifacts of the narrow set of models that have been studied. In particular, much attention has been payed to the scenario in which the Goldstino superfield in an O'Raifeartaigh model is responsible for both supersymmetry breaking and R-symmetry breaking. In such models, the competing problems of generating sufficiently massive gauginos while preserving an acceptably light gravitino can be quite challenging. We show that by sharing the burdens of breaking supersymmetry and R-symmetry with a…
