1,441 research outputs found
Gravitino Freeze-In
We explore an alternative mechanism for the production of gravitino dark
matter whereby relic gravitinos originate from the decays of superpartners
which are still in thermal equilibrium, i.e. via freeze-in. Contributions to
the gravitino abundance from freeze-in can easily dominate over those from
thermal scattering over a broad range of parameter space, e.g. when the scalar
superpartners are heavy. Because the relic abundance from freeze-in is
independent of the reheating temperature after inflation, collider measurements
may be used to unambiguously reconstruct the freeze-in origin of gravitinos. In
particular, if gravitino freeze-in indeed accounts for the present day dark
matter abundance, then the lifetime of the next-to-lightest superpartner is
uniquely fixed by the superpartner spectrum.Comment: 5 pages, 3 figure
Seesaw Spectroscopy at Colliders
A low-scale neutrino seesaw may be probed or even reconstructed at colliders
provided that supersymmetry is at the weak scale and the LSP is a sterile
sneutrino. Because the neutrino Yukawa couplings are small, the NLSP is
typically long-lived and thus a significant fraction of colored or charged
NLSPs may stop in the detector material before decaying to the LSP and a
charged lepton, gauge boson, or Higgs. For two-body NLSP decays, the energy
spectrum of the visible decay product exhibits a monochromatic line for each
sterile sneutrino which can be used to extract the sterile sneutrino masses and
some or all entries of the neutrino Yukawa matrix modulo phases. Similar
methods can be used to extract these parameters from the Dalitz plot in the
case of three-body NLSP decays. Assuming that the sterile sneutrino and
neutrino are roughly degenerate, one can confirm the existence of a neutrino
seesaw by comparing these measured parameters to the observed active neutrino
masses and mixing angles. Seesaw spectroscopy can also provide genuinely new
information such as the value of , the nature of the neutrino mass
hierarchy, and the presence of CP conservation in the neutrino sector. We
introduce a weak-scale theory of leptogenesis that can be directly tested by
these techniques.Comment: 7 pages, 4 figure
Composition and Structure of Protein Bodies and Spherosomes Isolated from Ungerminated Seeds of Sorghum bicolor
Cosmological axino problem
We revisit the cosmology of the supersymmetric QCD axion, highlighting the existence of a serious cosmological axino problem that is fully analogous to the gravitino problem of overclosure via thermal production. A general analysis implies that the QCD axino has a mass greater than or equal to that of the gravitino in the absence of unnatural fine-tuning or sequestering. As a consequence, bounds from thermal gravitino and QCD axino production are complementary in parameter space, and together provide a quite stringent limit on the reheating temperature after inflation given by T_R < 10^3 − 10^6 GeV for an axion decay constant of f_a = 10^9 − 10^(12) GeV. Motivated by this result, we explore the cosmology of gravitino lightest supersymmetric particle and axino next to lightest supersymmetric particle at low T_R and present three realistic scenarios for dark matter
Aircraft anti-insect system
Insect debris is removed from or prevented from adhering to insect impingement areas of an aircraft, particularly on an inlet cowl of an engine, by heating the area to 180.degree.-500.degree. C. An apparatus comprising a means to bring hot air from the aircraft engine to a plenum contiguous to the insect impingement area provides for the heating of the insect impingement areas to the required temperatures. The plenum can include at least one tube with a plurality of holes contained in a cavity within the inlet cowl. It can also include an envelope with a plurality of holes on its surface contained in a cavity within the inlet cowl
Insect abatement system
An insect abatement system prevents adhesion of insect debris to surfaces which must be kept substantially free of insect debris. An article is coated with an insect abatement coating comprising polyorganosiloxane with a Shore A hardness of less than 50 and a tensile strength of less than 4 MPa. A method for preventing the adhesion of insect debris to surfaces includes the step of applying an insect abatement coating to a surface which must be kept substantially free of insect debris
Origins of hidden sector dark matter II: collider physics
We consider a broad class of supersymmetric theories in which dark matter (DM) is the lightest superpartner (LSP) of a hidden sector that couples very weakly to visible sector fields. Portal interactions connecting visible and hidden sectors mediate the decay of the lightest observable superpartner (LOSP) into the LSP, allowing the LHC to function as a spectacular probe of the origin of hidden sector DM. As shown in a companion paper, this general two-sector framework allows only for a handful of DM production mechanisms, each of which maps to a distinctive window in lifetimes and cross-sections for the LOSP. In the present work we perform a systematic collider study of LOSP candidates and portal interactions, and for each case evaluate the prospects for successfully reconstructing the origin of DM at the LHC. If, for instance, DM arises from Freeze-Out and Decay, this may be verified if the LOSP is a bino or right-handed slepton decaying to the LSP through a variety of portal interactions, and with an annihilation cross-section within a narrow range. On the other hand, the Freeze-In mechanism may be verified for a complimentary set of LOSP candidates, and within a narrow range of LOSP lifetimes. In all cases, the LOSP is relatively long-lived on collider time scales, leading to events with displaced vertices. Furthermore, scenarios with a charged or colored LOSP are particularly promising
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