1,876 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
Bisimple monogenic orthodox semigroups
We give a complete description of the structure of all bisimple orthodox
semigroups generated by two mutually inverse elements
From guidelines to local realities: evaluation of oral rehydration therapy and zinc supplementation in Guatemala
Objectives: Diarrhea remains a leading cause of morbidity and mortality for children in low- and middle-income countries throughout the Americas. WHO guidelines have been developed to incorporate zinc supplementation (ZS) with traditional oral rehydration therapy (ORT) to shorten duration and reduce poor health outcomes. Guatemala adopted these guidelines in 2011, but they have not yet been fully implemented at the community level. The objectives of this study were to co-design an ORT/ZS training program with community health promoters appropriate to the local context and to understand how training with the promoters changes attitudes and behaviors of community members.
Methods: In an observational study, community health promoters were trained in rural Guatemala according to WHO guidelines and collaboratively developed training curriculum to implement in their community. Community-based surveys, interviews, and focus group discussions were used to assess acceptability, accessibility, and availability of oral rehydration therapy and zinc supplementation
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
Variation in the Use of "Front" and "Back" by Bilingual Speakers
Proceedings of the First Annual Meeting of the Berkeley Linguistics Society (1975), pp. 196-20
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