187 research outputs found
Hadronic decay of the gravitino in the early universe and its implications to inflation
We discuss the effects of the gravitino on the big-bang nucleosynthesis
(BBN), paying particular attention to the hadronic decay mode of the gravitino.
We will see that the hadronic decay of the gravitino significantly affect the
BBN and, for the case where the hadronic branching ratio is sizable, very
stringent upper bound on the reheating temperature after inflation is obtained.Comment: 6 pages, 2 Postscript figures, Talk given at PASCOS'04 (Boston, MA,
August 16 -- 22 (2004
Revisiting Big-Bang Nucleosynthesis Constraints on Dark-Matter Annihilation
We study the effects of dark-matter annihilation during the epoch of big-bang
nucleosynthesis on the primordial abundances of light elements. We improve the
calculation of the light-element abundances by taking into account the effects
of anti-nucleons emitted by the annihilation of dark matter and the
interconversion reactions of neutron and proton at inelastic scatterings of
energetic nucleons. Comparing the theoretical prediction of the primordial
light-element abundances with the latest observational constraints, we derive
upper bounds on the dark-matter pair-annihilation cross section. Implication to
some of particle-physics models are also discussed.Comment: 10 pages, 2 figure
Cosmic Rays from Dark Matter Annihilation and Big-Bang Nucleosynthesis
Recent measurements of cosmic-ray electron and positron fluxes by PAMELA and
ATIC experiments may indicate the existence of annihilating dark matter with
large annihilation cross section. We show that the dark matter annihilation in
the big-bang nucleosynthesis epoch affects the light element abundances, and it
gives stringent constraints on such annihilating dark matter scenarios for the
case of hadronic annihilation. Constraints on leptonically annihilating dark
matter models are less severer.Comment: 21 pages, 5 figures; added references; corrected the
electromagnetic-emission part and got milder constraint from the
photodissociation processes by a factor of 50 (v3
Testing the Anomaly Mediation at the LHC
We consider a supersymmetric model in which gaugino masses are generated by
the anomaly-mediation mechanism while scalar masses are from tree-level
supergravity interaction. In such a model, scalar fermions as well as Higgsinos
become as heavy as O(10-100TeV) and hence only the gauginos are superparticles
kinematically accessible to the LHC. We study how and how well the properties
of gauginos can be studied. We also discuss the strategy to test the
anomaly-mediation model at the LHC.Comment: 12 pages, 6 figure
Cosmological Constraints on Neutrino Injection
We derive general constraints on the relic abundances of a long-lived
particle which mainly decays into a neutrino (and something else) at
cosmological time scales. Such an exotic particle may show up in various
particle-physics models based on physics beyond the standard model. The
constraints are obtained from big-bang nucleosynthesis, cosmic microwave
background and diffuse neutrino and photon fluxes, depending on the lifetime
and the electromagnetic and hadronic branching ratios.Comment: 33 pages, 23 figure
Cosmological constraints on dark matter models with velocity-dependent annihilation cross section
We derive cosmological constraints on the annihilation cross section of dark
matter with velocity-dependent structure, motivated by annihilating dark matter
models through Sommerfeld or Breit-Wigner enhancement mechanisms. In models
with annihilation cross section increasing with decreasing dark matter
velocity, big-bang nucleosynthesis and cosmic microwave background give
stringent constraints.Comment: 23 pages, 9 figures; Added reference
Right-handed sneutrino dark matter and big-bang nucleosynthesis
We study the light-element abundances in supersymmetric model where the
right-handed sneutrino is the lightest superparticle (LSP), assuming that the
neutrino masses are purely Dirac-type. In such a scenario, the lightest
superparticle in the minimal supersymmetric standard model sector (which we
call MSSM-LSP) becomes long-lived, and thermal relic MSSM-LSP may decay after
the big-bang nucleosynthesis starts. We calculate the light-element abundances
including non-standard nuclear reactions induced by the MSSM-LSP decay, and
derive constraints on the scenario of right-handed sneutrino LSP.Comment: 13 pages, 4 figure
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