3,994 research outputs found
Interpreting Dark Matter Direct Detection Independently of the Local Velocity and Density Distribution
We demonstrate precisely what particle physics information can be extracted
from a single direct detection observation of dark matter while making
absolutely no assumptions about the local velocity distribution and local
density of dark matter. Our central conclusions follow from a very simple
observation: the velocity distribution of dark matter is positive definite,
f(v) >= 0. We demonstrate the utility of this result in several ways. First, we
show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form
factor), such as from ordinary elastic scattering, can be "mocked up" by any
mass of dark matter above a kinematic minimum. As an example, we show that dark
matter much heavier than previously considered can explain the CoGeNT excess.
Specifically, m_chi < m_Ge} can be in just as good agreement as light dark
matter, while m_\chi > m_Ge depends on understanding the sensitivity of Xenon
to dark matter at very low recoil energies, E_R ~ 6 keVnr. Second, we show that
any rise in the deconvoluted recoil spectrum represents distinct particle
physics information that cannot be faked by an arbitrary f(v). As examples of
resulting non-trivial particle physics, we show that inelastic dark matter and
dark matter with a form factor can both yield such a rise
Direct Mass Limits for Chiral Fourth-Generation Quarks in All Mixing Scenarios
Present limits on chiral fourth-generation quark masses and
are broadly generalized and strengthened by combining both and decays
and considering the full range of and flavor-mixing scenarios (with
the lighter generations). Various characteristic mass-splitting choices are
considered. With we find that CDF limits on the mass
vary by no more than 10-20% with any choice of flavor-mixing, while for the
mass, we typically find stronger bounds, in some cases up to GeV. For we find GeV, depending on
the flavor-mixing and the size of the mass splitting
Erratum: Next-to-leading order supersymmetric QCD predictions for associated production of gauginos and gluinos [Phys. Rev. D 62, 095014 (2000)]
Errors in the published version of the paper are corrected, and new figures
are provided.Comment: 3 pages, latex, 4 figure
Z-prime Gauge Bosons at the Tevatron
We study the discovery potential of the Tevatron for a Z-prime gauge boson.
We introduce a parametrization of the Z-prime signal which provides a
convenient bridge between collider searches and specific Z-prime models. The
cross section for p pbar -> Z-prime X -> l^+ l^- X depends primarily on the
Z-prime mass and the Z-prime decay branching fraction into leptons times the
average square coupling to up and down quarks. If the quark and lepton masses
are generated as in the standard model, then the Z-prime bosons accessible at
the Tevatron must couple to fermions proportionally to a linear combination of
baryon and lepton numbers in order to avoid the limits on Z--Z-prime mixing.
More generally, we present several families of U(1) extensions of the standard
model that include as special cases many of the Z-prime models discussed in the
literature. Typically, the CDF and D0 experiments are expected to probe
Z-prime-fermion couplings down to 0.1 for Z-prime masses in the 500--800 GeV
range, which in various models would substantially improve the limits set by
the LEP experiments.Comment: 34 pages, 13 figure
The WIMP Forest: Indirect Detection of a Chiral Square
The spectrum of photons arising from WIMP annihilation carries a detailed
imprint of the structure of the dark sector. In particular, loop-level
annihilations into a photon and another boson can in principle lead to a series
of lines (a WIMP forest) at energies up to the WIMP mass. A specific model
which illustrates this feature nicely is a theory of two universal extra
dimensions compactified on a chiral square. Aside from the continuum emission,
which is a generic prediction of most dark matter candidates, we find a
"forest" of prominent annihilation lines that, after convolution with the
angular resolution of current experiments, leads to a distinctive (2-bump plus
continuum) spectrum, which may be visible in the near future with the Fermi
Gamma-Ray Space Telescope (formerly known as GLAST).Comment: 11 pages, 4 figure
Autocatalytic plume pinch-off
A localized source of buoyancy flux in a non-reactive fluid medium creates a
plume. The flux can be provided by either heat, a compositional difference
between the fluid comprising the plume and its surroundings, or a combination
of both. For autocatalytic plumes produced by the iodate-arsenous acid
reaction, however, buoyancy is produced along the entire reacting interface
between the plume and its surroundings. Buoyancy production at the moving
interface drives fluid motion, which in turn generates flow that advects the
reaction front. As a consequence of this interplay between fluid flow and
chemical reaction, autocatalytic plumes exhibit a rich dynamics during their
ascent through the reactant medium. One of the more interesting dynamical
features is the production of an accelerating vortical plume head that in
certain cases pinches-off and detaches from the upwelling conduit. After
pinch-off, a new plume head forms in the conduit below, and this can lead to
multiple generations of plume heads for a single plume initiation. We
investigated the pinch-off process using both experimentation and simulation.
Experiments were performed using various concentrations of glycerol, in which
it was found that repeated pinch-off occurs exclusively in a specific
concentration range. Autocatalytic plume simulations revealed that pinch-off is
triggered by the appearance of accelerating flow in the plume conduit.Comment: 10 figures. Accepted for publication in Phys Rev E. See also
http://www.physics.utoronto.ca/nonlinear/papers_chemwave.htm
Constraints on Dark Matter from Colliders
We show that colliders can impose strong constraints on models of dark
matter, in particular when the dark matter is light. We analyze models where
the dark matter is a fermion or scalar interacting with quarks and/or gluons
through an effective theory containing higher dimensional operators which
represent heavier states that have been integrated out of the effective field
theory. We determine bounds from existing Tevatron searches for monojets as
well as expected LHC reaches for a discovery. We find that colliders can
provide information which is complementary or in some cases even superior to
experiments searching for direct detection of dark matter through its
scattering with nuclei. In particular, both the Tevatron and the LHC can
outperform spin dependent searches by an order of magnitude or better over much
of parameter space, and if the dark matter couples mainly to gluons, the LHC
can place bounds superior to any spin independent search.Comment: 23 pages, 16 figure
Higgs Boson with Large Bottom Yukawa Coupling at Tevatron and LHC
We study the discovery reach of the Tevatron and the LHC for detecting a
Higgs boson (h), predicted in composite models of the electroweak symmetry
breaking or in supersymmetric theories, with an enhanced b-quark Yukawa
coupling via p \bar{p} / p p \to b \bbar h (\to b \bbar) + X. Our analysis
shows that studying this process at the Tevatron Run II or the LHC can provide
strong constraints on these models.Comment: Revtex, 4 pages, Corrected 1 reference and a few typographical error
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