3,729 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
Lower Limit on Dark Matter Production at the Large Hadron Collider
We evaluate the prospects for finding evidence of dark matter production at
the Large Hadron Collider. We consider WIMPs and superWIMPs, weakly- and
superweakly-interacting massive particles, and characterize their properties
through model-independent parameterizations. The observed relic density then
implies lower bounds on dark matter production rates as functions of a few
parameters. For WIMPs, the resulting signal is indistinguishable from
background. For superWIMPs, however, this analysis implies significant
production of metastable charged particles. For natural parameters, these rates
may far exceed Drell-Yan cross sections and yield spectacular signals.Comment: 4 pages, title changed, possibility of cross sections far above
Drell-Yan noted, published versio
Goldilocks Supersymmetry: Simultaneous Solution to the Dark Matter and Flavor Problems of Supersymmetry
Neutralino dark matter is well motivated, but also suffers from two
shortcomings: it requires gravity-mediated supersymmetry breaking, which
generically violates flavor constraints, and its thermal relic density \Omega
is typically too large. We propose a simple solution to both problems:
neutralinos freezeout with \Omega ~10-100, but then decay to ~1 GeV gravitinos,
which are simultaneously light enough to satisfy flavor constraints and heavy
enough to be all of dark matter. This scenario is naturally realized in
high-scale gauge-mediation models, ameliorates small scale structure problems,
and implies that ``cosmologically excluded'' models may, in fact, be
cosmologically preferred.Comment: 4 pages; v2: references added; v3: published versio
SuperWIMP Gravitino Dark Matter from Slepton and Sneutrino Decays
Dark matter may be composed of superWIMPs, superweakly-interacting massive
particles produced in the late decays of other particles. We focus on the case
of gravitinos produced in the late decays of sleptons or sneutrinos and assume
they are produced in sufficient numbers to constitute all of non-baryonic dark
matter. At leading order, these late decays are two-body and the accompanying
energy is electromagnetic. For natural weak-scale parameters, these decays have
been shown to satisfy bounds from Big Bang nucleosynthesis and the cosmic
microwave background. However, sleptons and sneutrinos may also decay to
three-body final states, producing hadronic energy, which is subject to even
more stringent nucleosynthesis bounds. We determine the three-body branching
fractions and the resulting hadronic energy release. We find that superWIMP
gravitino dark matter is viable and determine the gravitino and
slepton/sneutrino masses preferred by this solution to the dark matter problem.
In passing, we note that hadronic constraints disfavor the possibility of
superWIMPs produced by neutralino decays unless the neutralino is photino-like.Comment: 22 pages, updated figures and minor changes, version to appear in
Phys. Rev.
Gravitino and Axino SuperWIMPs
Gravitinos and axinos produced in the late decays of other supersymmetric
particles are well-motivated dark matter (DM) candidates, whose experimental
evidences are very distinctive and different from other standard candidates, as
thermal produced neutralinos in similar supersymmetric models. In particular,
charged sleptons could appear stable because of the length of its lifetime. The
direct production of such particles at both the Large Hadron Collider (LHC) and
a future International Linear Collider (ILC) can give not only a clear
signature of supersymmetry but also the first non-gravitational evidence of
dark matter.Comment: 4 pages, LaTeX, 1 figure, Updated references. To appear in
Proceedings of SUSY06, the 14th International Conference on Supersymmetry and
the Unification of Fundamental Interactions, UC Irvine, California, 12-17
June 200
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
SuperWIMP Cosmology and Collider Physics
Dark matter may be composed of superWIMPs, superweakly-interacting massive
particles produced in the late decays of other particles. We focus here on the
well-motivated supersymmetric example of gravitino LSPs. Gravitino superWIMPs
share several virtues with the well-known case of neutralino dark matter: they
are present in the same supersymmetric frameworks (supergravity with R-parity
conservation) and naturally have the desired relic density. In contrast to
neutralinos, however, gravitino superWIMPs are impossible to detect by
conventional dark matter searches, may explain an existing discrepancy in Big
Bang nucleosynthesis, predict observable distortions in the cosmic microwave
background, and imply spectacular signals at future particle colliders.Comment: 12 pages, to appear in the proceedings of SUSY2004, the 12th
International Conference on Supersymmetry and Unification of Fundamental
Interactions, Tsukuba, Japan, 17-23 June 200
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