2,134 research outputs found
Probing Gravitational Interactions of Elementary Particles
The gravitational interactions of elementary particles are suppressed by the
Planck scale M_P ~ 10^18 GeV and are typically expected to be far too weak to
be probed by experiments. We show that, contrary to conventional wisdom, such
interactions may be studied by particle physics experiments in the next few
years. As an example, we consider conventional supergravity with a stable
gravitino as the lightest supersymmetric particle. The next-lightest
supersymmetric particle (NLSP) decays to the gravitino through gravitational
interactions after about a year. This lifetime can be measured by stopping
NLSPs at colliders and observing their decays. Such studies will yield a
measurement of Newton's gravitational constant on unprecedentedly small scales,
shed light on dark matter, and provide a window on the early universe.Comment: 6 pages, second prize in the 2004 Gravity Research Foundation essay
competitio
Superweakly Interacting Massive Particles
We investigate a new class of dark matter: superweakly-interacting massive
particles (superWIMPs). As with conventional WIMPs, superWIMPs appear in
well-motivated particle theories with naturally the correct relic density. In
contrast to WIMPs, however, superWIMPs are impossible to detect in all
conventional dark matter searches. We consider the concrete examples of
gravitino and graviton cold dark matter in models with supersymmetry and
universal extra dimensions, respectively, and show that superWIMP dark matter
satisfies stringent constraints from Big Bang nucleosynthesis and the cosmic
microwave background.Comment: 4 pages, 4 figures, published versio
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
Unparticles: Scales and High Energy Probes
Unparticles from hidden conformal sectors provide qualitatively new
possibilities for physics beyond the standard model. In the theoretical
framework of minimal models, we clarify the relation between energy scales
entering various phenomenological analyses. We show that these relations always
counteract the effective field theory intuition that higher dimension operators
are more highly suppressed, and that the requirement of a significant conformal
window places strong constraints on possible unparticle signals. With these
considerations in mind, we examine some of the most robust and sensitive probes
and explore novel effects of unparticles on gauge coupling evolution and
fermion production at high energy colliders. These constraints are presented
both as bounds on four-fermion interaction scales and as constraints on the
fundamental parameter space of minimal models.Comment: 16 pages, 2 tables, 6 figures; reference added, published versio
Estimation of Standardized Effort in the Heterogeneous Gulf of Mexico Shrimp Fleet
In this paper we estimate nominal and standardized shrimping effort in the Gulf of Mexico for the years 1965 through 1993. We accomplish this by first developing a standardization method (model) and then an expansion method (model). The expansion model estimates nominal days fished for noninterview landings data. The standardization model converts nominal days fished to standard days fished. We then characterize the historical trends of the penaeid shrimp fishery byvessel configuration, relative fishing power, and nominal and standardized effort. Wherever possible, we provide comparison with previous estimates by the National Marine Fisheries Service, NOAA
SuperWIMP Solutions to Small Scale Structure Problems
Collisionless, cold dark matter in the form of weakly-interacting massive
particles (WIMPs) is well-motivated in particle physics, naturally yields the
observed relic density, and successfully explains structure formation on large
scales. On small scales, however, it predicts too much power, leading to cuspy
halos, dense cores, and large numbers of subhalos, in apparent conflict with
observations. We consider superWIMP dark matter, produced with large velocity
in late decays at times 10^5 s - 10^8 s. As analyzed by Kaplinghat in a more
general setting, we find that superWIMPs have sufficiently large free-streaming
lengths and low phase space densities to help resolve small scale structure
problems while preserving all of the above-mentioned WIMP virtues.Comment: 4 pages, 2 figures, published versio
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