28 research outputs found
Unparticle Self-Interactions and Their Collider Implications
In unparticle physics, operators of the conformal sector have
self-interactions, and these are unsuppressed for strong coupling. The 3-point
interactions are completely determined by conformal symmetry, up to a constant.
We do not know of any theoretical upper bounds on this constant. Imposing
current experimental constraints, we find that these interactions mediate
spectacular collider signals, such as , , , , , and
, with cross sections of picobarns or larger at the Large Hadron Collider.
Self-interactions may therefore provide the leading discovery prospects for
unparticle physics.Comment: 12 pages, 5 figures; v2: published versio
Hidden Charged Dark Matter
Can dark matter be stabilized by charge conservation, just as the electron is
in the standard model? We examine the possibility that dark matter is hidden,
that is, neutral under all standard model gauge interactions, but charged under
an exact U(1) gauge symmetry of the hidden sector. Such candidates are
predicted in WIMPless models, supersymmetric models in which hidden dark matter
has the desired thermal relic density for a wide range of masses. Hidden
charged dark matter has many novel properties not shared by neutral dark
matter: (1) bound state formation and Sommerfeld-enhanced annihilation after
chemical freeze out may reduce its relic density, (2) similar effects greatly
enhance dark matter annihilation in protohalos at redshifts of z ~ 30, (3)
Compton scattering off hidden photons delays kinetic decoupling, suppressing
small scale structure, and (4) Rutherford scattering makes such dark matter
self-interacting and collisional, potentially impacting properties of the
Bullet Cluster and the observed morphology of galactic halos. We analyze all of
these effects in a WIMPless model in which the hidden sector is a simplified
version of the minimal supersymmetric standard model and the dark matter is a
hidden sector stau. We find that charged hidden dark matter is viable and
consistent with the correct relic density for reasonable model parameters and
dark matter masses in the range 1 GeV < m_X < 10 TeV. At the same time, in the
preferred range of parameters, this model predicts cores in the dark matter
halos of small galaxies and other halo properties that may be within the reach
of future observations. These models therefore provide a viable and
well-motivated framework for collisional dark matter with Sommerfeld
enhancement, with novel implications for astrophysics and dark matter searches.Comment: 29 pages; v2: references added; v3: published versio
Supernova Bounds on Weinberg's Goldstone Bosons
Recently, Weinberg proposed a scenario where Goldstone bosons may be
masquerading as fractional cosmic neutrinos. We calculate the energy loss rates
through the emission of these Goldstone bosons in a post-collapse supernova
core. Invoking the well established emissivity bound from the Supernova 1987A
observations and simulations, we find that nuclear bremsstrahlung processes can
notably impose a bound on the Goldstone boson coupling to the Standard Model
Higgs, , dependent on the mass of the associated radial field, . For
large enough compared with the temperature in the post-collapse supernova
core, our bound is , very
competitive to that derived from collider experiments.Comment: 9 pages, 1 figur