Koichi Hamaguchi, Fuminobu Takahashi, T. T. Yanagida
We show that, if decaying gravitino dark matter is responsible for the PAMELA and ATIC/PPB-BETS anomalies in the cosmic-ray electron and positron fluxes, both a reheating temperature and a gluino mass are constrained from above. In particular, the gluino mass is likely within the reach of LHC, if the observed baryon asymmetry is explained by thermal leptogenesis scenario.
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We study the jets plus missing energy signature at the LHC in a scenario where the gravitino is very light and the gluino is the next-to-lightest supersymmetric particle and promptly decays into a gluon and a gravitino. We consider both associated gravitino production with a gluino and gluino pair production. By merging matrix elements with parton showers, we generate inclusive signal and background samples and show how information on the gluino and gravitino masses can be obtained by simple final state observables.
In split-supersymmetry (split-SUSY), gluino is a metastable particle and thus can freeze out in the early universe. The late decay of such a long-life gluino into the lightest supersymmetric particle (LSP) may provide much of the cosmic dark matter content. In this work, assuming the LSP is gravitino produced from the late decay of the metastable gluino, we examine the WMAP dark matter constraints on the gluino mass. We find that to provide the full abundance of dark matter, the gluino must be heavier than about 14 TeV and thus not accessible at the CERN Large Hadron Collider (LHC).
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.
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…
We derive Feynman rules for the interactions of a single gravitino with (s)quarks and gluons/gluinos from an effective supergravity Lagrangian in non-derivative form and use them to calculate the hadroproduction cross sections and decay widths of single gravitinos. We confirm the results obtained previously with a derivative Lagrangian as well as those obtained with the non-derivative Lagrangian in the high-energy limit and elaborate on the connection between gauge independence and the presence of quartic vertices. We perform extensive numerical studies of branching ratios, total cross section…
We report on constraints on the lifetime of decaying gravitino dark matter in models with bilinear R-parity violation derived from observations of cosmic-ray antiprotons with the PAMELA experiment. Performing a scan over a viable set of cosmic-ray propagation parameters we find lower limits ranging from $8\times 10^{28}$s to $6\times 10^{28}$s for gravitino masses from roughly 100 GeV to 10 TeV. Comparing these limits to constraints derived from gamma-ray and neutrino observations we conclude that the presented antiproton limits are currently the strongest and most robust limits on the graviti…
We analyze the cosmic-ray signatures of decaying gravitino dark matter in a model independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both, the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribu…
We derive 95% CL lower limits on the lifetime of decaying dark matter in the channels $Zν$, $W\ell$ and $hν$ using measurements of the cosmic-ray antiproton flux by the PAMELA experiment. Performing a scan over the allowed range of cosmic-ray propagation parameters we find lifetime limits in the range of $8 \times 10^{28}$s to $5 \times 10^{25}$s for dark matter masses from roughly 100 GeV to 10 TeV. We apply these limits to the well-motivated case of gravitino dark matter in scenarios with bilinear violation of R-parity and find a similar range of lifetime limits for the same range of graviti…
Very light gravitinos could be produced at a sizeable rate at colliders and have been searched for in the mono-photon or mono-jet plus missing momentum signature. Strategies for enhancing the signal over background and interpretations of the experimental results are typically obtained within an effective field theory approach where all SUSY particles except the gravitino are heavy and are not produced resonantly. We extend this approach to a simplified model that includes squarks and gluinos in the TeV range. In such a case, the jet(s)-plus-missing-momentum signature can be generated through t…
In this paper we study the experimental consequences of a theory which naturally has a heavy, stable (or almost stable) gluino. We define the boundary conditions at a messenger scale $M \sim 10^{14}$ GeV which lead to this alternative phenomenologically acceptable version of the minimal supersymmetric standard model. In this theory, either the gluino or the gravitino is the lightest supersymmetric particle [LSP]. If the gravitino is the LSP, then the gluino is the next-to-LSP with a lifetime on the order of 100 years. In either case, the gluino is (for all practical purposes) a stable particle…
Gravitinos are a fundamental prediction of supergravity, their mass ($m_{G}$) is informative of the value of the SUSY breaking scale, and, if produced during reheating, their number density is a function of the reheating temperature ($T_{\text{rh}}$). As a result, constraining their parameter space provides in turn significant constraints on particles physics and cosmology. We have previously shown that for gravitinos decaying into photons or charged particles during the ($μ$ and $y$) distortion eras, upcoming CMB spectral distortions bounds are highly effective in constraining the $T_{\text{r…
In higher-dimensional supersymmetric theories gauge couplings of the effective four-dimensional theory are determined by expectation values of scalar fields. We find that at temperatures above a critical temperature $T_*$, which depends on the supersymmetry breaking mass scales, gauge couplings decrease like $T^{-\a}$, $\a > 1$. This has important cosmological consequences. In particular it leads to a relic gravitino density which becomes independent of the reheating temperature for $T_R > T_*$. For small gravitino masses, $m_{3/2} \ll m_{\gl}$, the mass density of stable gravitinos is essenti…
In supersymmetric axion models, if the gravitino or axino is the lightest SUSY particle (LSP), the other is often the next-to-LSP (NLSP). We investigate the cosmology of such a scenario and point out that the lifetime of the NLSP naturally becomes comparable to the present age of the universe in a viable parameter region. This is a well-motivated example of the so-called decaying dark matter model, which is recently considered as an extension of the $Λ$CDM model to relax some cosmological tensions.
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 possibility of improving the constraints on the lifetime of gravitino dark matter in scenarios with bilinear R-parity violation by estimating the amount of cosmic-ray antideuterons that can be produced in gravitino decays. Taking into account all different sources of theoretical uncertainties, we find that the margin of improvement beyond the limits already set by cosmic-ray antiproton data are quite narrow and unachievable for the next generation of experiments. However, we also identify more promising energy ranges for future experiments.
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. Electron and positron fluxes from gravitino decays cannot explain both, the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. The observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying grav…
We propose a new class of R-parity violating extension of MSSM with type II seesaw mechanism for neutrino masses where an unstable gravitino is the dark matter of the Universe. It decays predominantly into three leptons final states, thereby providing a natural explanation of the positron excess but no antiproton excess in the PAMELA experiment. The model can explain neutrino masses without invoking any high scale physics while keeping the pre-existing baryon asymmetry of the universe in tact.
The `$μ$ from $ν$' supersymmetric standard model ($μν$SSM) solves the $μ$ problem of supersymmetric models and reproduces neutrino data, simply using couplings with the three families of right-handed neutrinos $ν$'s. Novel signatures of supersymmetry at the LHC are expected through these new states, and couplings breaking $R$ parity. All supersymmetric particles are potential candidates for the lightest one, which is not stable leading to prompt or displaced vertices and producing final states with multi-leptons/taus/jets/photons and missing energy. Besides, a decaying gravitino turns out to b…
In supergravity theories with a very light gravitino, the gluino decays dominantly to a gluon and a gravitino. This results in a much larger missing $E_T$ for the multijet final states in hadronic colliders. We use the latest Tevatron data for the multijet final states to set a new absolute lower bound of 3.0 x 10^{-13} GeV for the light gravitino mass.
We study the charged cosmic rays arising from the slow decay of gravitino dark matter within supersymmetric scenarios with trilinear R-parity violation. It is shown that operators of the LLE type can very well account for the recent anomalies in cosmic ray electron and positron data reported by PAMELA, ATIC and Fermi LAT, without violating any other bounds. This scenario will soon be tested by the Fermi LAT data on diffuse gamma ray emission.
Extremely weakly interacting particles like the gravitino may be stable enough on cosmological time scales to constitute a good dark matter candidate even in the presence of R-parity violation. We consider the possibility that the recently identified 3.5 keV x-ray line can be generated in light gravitino decays to neutrinos and photons. We find that this is indeed possible in loop processes induced by trilinear lepton-number-violating couplings. We show that in order to avoid overproduction of gravitinos, the reheating temperature has to be at most around 100 GeV to 1 TeV. Finally we briefly d…
Motivated by the recent results from the PAMELA and ATIC, we study the cosmic-ray electron and positron produced by the decay of gravitino dark matter. We calculate the cosmic-ray electron and positron fluxes and discuss implications to the PAMELA and ATIC data. In this paper, we will show that the observed anomalous fluxes by the PAMELA and ATIC can be explained in such a scenario. We will also discuss the synchrotron radiation flux from the Galactic center in such a scenario.
This letter describes how to perform searches over the complete kinematically-allowed parameter space for new pair-produced color octet particles that each subsequently decay into two jets plus missing energy at the Tevatron. This letter shows that current searches can miss otherwise discoverable spectra of particles due to CMSSM-motivated cuts. Optimizing the HT and MET cuts expands the sensitivity of these searches.
We consider models of Pure Gravity Mediation in which scalar mass universality is imposed at the grand unified scale and gaugino masses are generated through loops. The minimal model requires a very restricted range for $\tan β\approx 2-3$ and scalar masses (set by the gravitino mass) of order 300 TeV - 1.5 PeV in order to obtain a Higgs mass near 126 GeV. Here we augment the minimal model with one or more sets of vector multiplets (either a ${10}$ and $\bar {10}$ pair or one or more $5$ and $\bar 5$ pairs). If coupled to the MSSM Higgs, these allow for radiative electroweak symmetry breaking …
The discovery of a Higgs boson near 125 GeV, together with the absence of LHC signals for supersymmetry or direct detection signals of dark matter, motivate further study of a particular theory of split supersymmetry. In arguably the theoretically simplest implementation of split, the superpartner spectrum is spread over several decades. The squarks and sleptons are heavier than the gravitino and Higgsinos by a factor M_Pl/M_*, where M_* is the mediation scale of supersymmetry breaking and is high, between unified and Planck scales. On the other hand the gaugino masses are 1-loop smaller than …
In this paper we present a solution to the $μ$ problem in an SO(10) supersymmetric grand unified model with gauge mediated and D-term supersymmetry breaking. A Peccei-Quinn symmetry is broken at the messenger scale $M\sim 10^{12}$ GeV and enables the generation of the $μ$ term. The boundary conditions defined at $M$ lead to a phenomenologically acceptable version of the minimal supersymmetric standard model with novel particle phenomenology. Either the gluino or the gravitino is the lightest supersymmetric particle (LSP). If the gravitino is the LSP, then the gluino is the next-to-LSP (NLSP) w…
Supersymmetric theories with gravitino dark matter generally do not allow the high reheating temperature required by thermal leptogenesis without running afoul of relic abundance or big bang nucleosynthesis constraints. We report on a successful search for parameter space that does satisfy these requirements. The main implication is the near degeneracy of the gluino with the other neutralinos in the spectrum. The leading discovery channel at the LHC for this scenario is through monojet plus missing energy events.
In this paper, we discuss interesting scenarios resulting from the interplay between the gravitino and the lightest right-handed (s)neutrino. We consider two gravitino mass regimes vastly separated, that is, $m_{3/2}=\mathcal{O}(100){\rm eV}$ and $m_{3/2}\simeq100{\rm GeV}$. For the former case, a significant amount of the entropy production in the cosmological history to dilute the gravitino relic abundance is unavoidable for consistency with the number of satellite galaxies in the Milky way. We will show that the right-handed (s)neutrino can play the role of the heavy particle whose late tim…
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.…
The latest Lyman-$α$ forest data severely constrain the conventional warm dark matter solution to small-scale issues in the cold dark matter paradigm. It has been also reported that unconstrained astrophysical processes may address the issues. In response to this situation, we revisit the decaying dark matter solution to the issues, discussing possible signatures to discriminate decaying dark matter from astrophysical processes as a solution to small-scale issues. We consider an axinolike particle (ALPino) decaying into an axionlike particle (ALP) and gravitino with the lifetime around the age…
Gravitino Freeze-In Dark Matter with an Additional Scalar Field
本文研究在非标准宇宙学场景中，额外标量场如何通过改变状态方程影响引力微子暗物质的丰度，从而允许或限制再加热温度。
The possibility in supersymmetric scenarios that the dark matter candidate is a Higgsino-like neutralino means that its production can be associated with Higgs bosons. Taking advantage of this fact, we propose a LHC search strategy for gluinos with $τ$ leptons in the final state, coming from the decay of a Higgs boson. We consider the strong production of a pair of gluinos, one of which decays into the Higgsino plus jets while the other decays into the bino plus jets. In turn, this bino decays into the Higgsino plus a Higgs boson which finally decays into a $τ$-lepton pair. Therefore, the expe…
We investigate the production of antideuterons from decaying dark matter, using gravitinos in supersymmetric models with trilinear R-parity violating (RPV) operators as an example. The model used for antideuteron formation is shown to induce large uncertainties in the predicted flux, comparable to uncertainties from cosmic-ray propagation models. We improve on the formation model by tuning hadronization and coalesence parameters in Monte Carlo simulations to better reproduce the hadron spectra relevant for antideuteron production. In light of current bounds on fluxes and future prospects from …
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 …
Gravitino Dark Matter represents a compelling scenario in Supersymmetry, which brings together a variety of data from cosmology and collider physics. We discuss the constraints obtained from the LHC on supersymmetric models with gravitino dark matter and neutralino NLSP, which is the case most difficult to disentangle at colliders from a neutralino LSP forming DM. The phenomenological SUSY model with 19+1 free parameters is adopted. Results are obtained from broad scans of the phase space of these uncorrelated parameters. The relation between gravitino mass, gluino mass and reheating temperatu…
Supersymmetric extensions of the standard model of particle physics assuming the gravitino to be the lightest supersymmetric particle (LSP), and with the next-to-LSP decaying to the gravitino during Big Bang nucleosynthesis, are analyzed. Particular emphasis is laid on their potential to solve the "Li7 problem", an apparent factor 2-4 overproduction of Li7 in standard Big Bang nucleosynthesis (BBN), their production of cosmologically important amounts of Li6, as well as the resulting gravitino dark matter densities in these models. The study includes several improvements compared to prior stud…
The flux of electron and positron cosmic rays measured by the space-based experiments PAMELA, AMS-02, CALET, DAMPE and Fermi-LAT shows an unexpected behaviour at high energies, in comparison with expectations from standard astrophysical sources. In particular, AMS-02 observations provide compelling evidence for a new source of positrons and electrons whose origin is still unknown. Plausible scenarios include either the contribution of dark matter or unresolved astrophysical sources, such as nearby pulsars. It has been shown that explanations based mostly on dark matter, tend to overproduce gam…
The gravitino in models with a small violation of R-parity is a well-motivated decaying dark matter candidate that leads to a cosmological scenario that is consistent with big bang nucleosynthesis and thermal leptogenesis. The gravitino lifetime is cosmologically long-lived since its decays are suppressed by the Planck-scale as well as the small R-parity violating parameter. We discuss the signals in different cosmic-ray species coming from the decay of gravitino dark matter, namely gamma rays, positrons, antiprotons, antideuterons and neutrinos. Comparison to cosmic-ray data can be used to co…
We consider the phenomenological implications of gravitino dark matter in the context of the $μν$SSM. The latter is an R-parity breaking model which provides a solution to the $μ$-problem of the MSSM and explains the origin of neutrino masses by simply using right-handed neutrino superfields. In particular, we analyze the prospects for detecting gamma rays from decaying gravitinos. Gravitino masses larger than 20 GeV are disfavored by the isotropic diffuse photon background measurements, but a gravitino with a mass range between $0.1 - 20$ GeV gives rise to a signal that might easily be observ…
The gravitino is a promising supersymmetric dark matter candidate, even without strict R-parity conservation. In fact, with some small R-parity violation, gravitinos are sufficiently long-lived to constitute the dark matter of the universe, while the resulting cosmological scenario is consistent with primordial nucleosynthesis and the high reheating temperature needed for thermal leptogenesis. Furthermore, in this scenario the gravitino is unstable and might thus be accessible by indirect detection via its decay products. We compute in this thesis the partial decay widths for the gravitino in …
If dark matter particles are not perfectly stable, their decay products might be seen in the cosmic-ray fluxes. A natural candidate for decaying dark matter is the gravitino in R-parity violating scenarios. In the relevant GeV-TeV energy range, the Fermi Large Area Telescope (LAT) is now measuring cosmic gamma-ray fluxes with an unprecedented precision. We use the Fermi LAT gamma-ray data to search for signatures from gravitino dark matter particles, concentrating on gamma-ray lines and galaxy cluster observations. Implications of our results for the decay length of the next-to-lightest superp…
Gravitino Thermal Production, Dark Matter, and Reheating of the Universe
本文通过完整单圈计算引力子热产生率，在超引力框架下约束再加热温度，发现若引力子为全部暗物质，则再加热温度受严格上限，并给出不同参数下的具体数值关系。
We present a solution to the gravitino problem, which arises in the NMSSM, allowing for sparticle spectra from ordinary gravity-mediated supersymmetry breaking with weak-scale gravitino dark matter. The coupling, which links the singlet to the MSSM sector, enhances the tree-level Higgs mass, providing an attractive explanation why the observed Higgs boson is so heavy. The same coupling induces very efficient pair-annihilation processes of the neutralino NLSP. Its relic abundance can be sufficiently suppressed to satisfy the strong constraints on late decaying relics from primordial nucleosynth…
The $μν$SSM provides a solution to the $μ$-problem of the MSSM and explains the origin of neutrino masses by simply using right-handed neutrino superfields. Given that R-parity is broken in this model, the gravitino is a natural candidate for dark matter since its lifetime becomes much longer than the age of the Universe. We consider the implications of gravitino dark matter in the $μν$SSM, analyzing in particular the prospects for detecting gamma rays from decaying gravitinos. If the gravitino explains the whole dark matter component, a gravitino mass larger than 20 GeV is disfavored by the i…
We study the conditions for successful Affleck-Dine baryogenesis and the origin of gravitino dark matter in GMSB models. AD baryogenesis in GMSB models is ruled out by neutron star stability unless Q-balls are unstable and decay before nucleosynthesis. Unstable Q-balls can form if the messenger mass scale is larger than the flat-direction field Phi when the condensate fragments. We provide an example based on AD baryogenesis along a d = 6 flat direction for the case where m_{3/2} \approx 2 GeV, as predicted by gravitino dark matter from Q-ball decay. Using a phenomenological GMSB potential whi…
We calculate exotic cooling rates of stars due to photo-production of light particles (mostly scalars and pseudoscalars) which originate from the hidden sector of no scale supergravity theories. Using this we can restrict the gravitino mass $m_{3/2}$. The range of eliminated values of $m_{3/2}$ stretches over six orders of magnitude and is given by $\displaystyle{2 \times 10^8 < {m_{\tilde g} \over m_{3/2}} < 6 \times 10^{13}}$, $m_{\tilde g}$ being the gluino mass. Combining our result with the earlier analysis from colliders ($\displaystyle{ {m_{\tilde g} \over m_{3/2}} < 2.7 \times 10^{14}}…
We present models of decaying particles for increasing the effective number of neutrinos N_nu after big bang nucleosynthesis but before the structure formation begins. We point out that our scenario not only solves the discrepancy between the constraints on N_nu from these two epochs, but also provides a possible answer to deeper inconsistency in the estimation of the matter power spectrum amplitude at small scales, represented by sigma_8, between the WMAP and some small scale matter power measurements such as the Lyman-alpha forest and weak lensing. We consider (a) saxion decay into two axion…
Stable particle dark matter may well originate during the decay of long-lived relic particles, as recently extensively examined in the cases of the axino, gravitino, and higher-dimensional Kaluza-Klein (KK) graviton. It is shown that in much of the viable parameter space such dark matter emerges naturally warm/hot or mixed. In particular, decay produced gravitinos (KK-gravitons) may only be considered cold for the mass of the decaying particle in the several TeV range, unless the decaying particle and the dark matter particle are almost degenerate. Such dark matter candidates are thus subject …
The gravitino is a promising supersymmetric dark matter candidate which does not require exact R-parity conservation. In fact, even with some small R-parity breaking, gravitinos are sufficiently long-lived to constitute the dark matter of the Universe, while yielding a cosmological scenario consistent with primordial nucleosynthesis and the high reheating temperature required for thermal leptogenesis. In this paper, we compute the neutrino flux from direct gravitino decay and gauge boson fragmentation in a simple scenario with bilinear R-parity breaking. Our choice of parameters is motivated b…
Affleck-Dine (AD) baryogenesis along a d=6 flat direction in gauge-mediated supersymmetry-breaking (GMSB) models can produce unstable Q-balls which naturally have field strength similar to the messenger scale. In this case a new kind of Q-ball is formed, intermediate between gravity-mediated and gauge-mediated type. We study in detail these new Q-ball solutions, showing how their properties interpolate between standard gravity-mediated and gauge-mediated Q-balls as the AD field becomes larger than the messenger scale. It is shown that E/Q for the Q-balls can be greater than the nucleon mass bu…
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…
In supersymmetric theories without R-parity, the gravitino can play the role of a decaying Dark Matter candidate without the problem of late NLSP decays affecting Big Bang Nucleosynthesis. In this work, we elaborate on recently discussed limits on R-parity violating couplings from decays to antideuterons and discuss the implications for two classes of flavor symmetries: horizontal symmetries, and Minimal Flavor Violation. In most of the parameter space the antideuteron constraints on R-parity violating couplings are stronger than low-energy baryon-number-violating processes. Even in the absenc…
A successful implementation of thermal leptogenesis requires the re-heat temperature after inflation T_R to exceed ~2\times 10^9 GeV. Such a high T_R value typically leads to an overproduction of gravitinos in the early universe, which will cause conflicts, mainly with BBN constraints. Asaka and Yanagida (AY) have proposed that these two issues can be reconciled in the context of the Peccei-Quinn augmented MSSM (PQMSSM) if one adopts a mass hierarchy m(sparticle)>m(gravitino)>m(axino), with m(axino) keV. We calculate the relic abundance of mixed axion/axino dark matter in the AY scenario, and …
Recently the AMS-02 experiment reported an excess of cosmic ray antiprotons over the expected astrophysical background. We interpret the excess as a signal from annihilating or decaying dark matter and find that the observed spectrum is well fitted by adding contributions from the annihilation or decay of dark matter with mass of O(TeV) or larger. Interestingly, Wino dark matter with mass of around 3 TeV, whose thermal relic abundance is consistent with present dark matter abundance, can explain the antiproton excess. We also discuss the implications for the decaying gravitino dark matter with…
We investigate the LHC sensitivity to supersymmetric models with light higgsinos, small R-parity breaking and gravitino dark matter. The limits on decaying gravitino dark matter from gamma-ray searches with the Fermi-LAT put a lower bound on the higgsino-like neutralino NLSP decay length, giving rise to a displaced-vertex collider signature. Using publicly available tools for simulation of signal, background and detector response, we find that higgsinos with masses of 100-400 GeV and R-parity violation of approximately 10^-8 to 10^-9 can show up in the 8 TeV LHC data with 10-30 fb^-1 of integr…
The search for supersymmetry at Run 1 of LHC has resulted in gluino mass limits m(gluino)>~ 1.3 TeV for the case where m(gluino)<<m(squark) and in models with gaugino mass unification. The increased energy and ultimately luminosity of LHC13 will explore the range m(gluino)~ 1.3-2 TeV. We examine how the discovery of SUSY via gluino pair production would unfold via a comparative analysis of three LSP archetype scenarios: 1. mSUGRA/CMSSM model with a bino-like LSP, 2. charged SUSY breaking (CSB) with a wino-like LSP and 3. SUSY with radiatively-driven naturalness (RNS) and a higgsino-like LSP. I…
In all supersymmetric theories, gravitinos, with mass suppressed by the Planck scale, are an obvious candidate for dark matter; but if gravitinos ever reached thermal equilibrium, such dark matter is apparently either too abundant or too hot, and is excluded. However, in theories with an axion, a saxion condensate is generated during an early era of cosmological history and its late decay dilutes dark matter. We show that such dilution allows previously thermalized gravitinos to account for the observed dark matter over very wide ranges of gravitino mass, keV < $m_{3/2}$ < TeV, axion decay con…
Bilinear R-parity violation provides an attractive origin for neutrino masses and mixings. In such schemes the gravitino is a viable decaying dark matter particle whose R-parity violating decays lead to monochromatic photons with rates accessible to astrophysical observations. We determine the parameter region allowed by gamma-ray line searches, dark matter relic abundance and neutrino oscillation data, obtaining a limit on the gravitino mass $m_{\tilde G} \lsim$ 1-10 GeV corresponding to a relatively low reheat temperature $T_R \lsim$ few $\times 10^7-10^8$ GeV. Neutrino mass and mixing param…
Light gravitino productions in association with a neutralino (selectron) in e^+e^- (e^-γ) collisions are restudied in a scenario that the lightest supersymmetric particle is a gravitino and the produced neutralino (selectron) promptly decays into a photon (electron) and a gravitino. We explicitly give the helicity amplitudes for the production processes by using the effective goldstino interaction Lagrangian, and present the cross sections with different collision energies and mass spectra. We also examine selection efficiencies by kinematical cuts and beam polarizations for the signal and bac…
Affleck-Dine baryogenesis, accompanied by the formation and subsequent decay of Q-balls, can generate both the baryon asymmetry of the universe and dark matter in the form of gravitinos. The gravitinos from Q-ball decay dominate over the thermally produced population if the reheat temperature is less than 10^7 GeV. We show that a gravitino with mass around 1 GeV is consistent with all observational bounds and can explain the baryon-to-dark-matter ratio in the gauge-mediated models of supersymmetry breaking for a wide range of cosmological and Q-ball parameters. Moreover, decaying Q-balls can b…
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