1,209 research outputs found
Collisions of Jets of Particles from Active Galactic Nuclei with Neutralino Dark Matter
We examine the possibility that energetic Standard Model particles contained
in the jets produced by active galactic nuclei (AGN) may scatter off of the
dark matter halo which is expected to surround the AGN. In particular, if there
are nearby states in the dark sector which can appear resonantly in the
scattering, the cross section can be enhanced and a distinctive edge feature in
the energy spectrum may appear. We examine bounds on supersymmetric models
which may be obtained from the Fermi Gamma-ray Space Telescope observation of
the nearby AGN Centaurus A.Comment: 20 pages, 9 figures; v2: version published in JCA
Baryon Number as the Fourth Color
We propose an extension of the Standard Model in which baryon number is
promoted to be part of a non-Abelian gauge symmetry at high energies.
Specifically, we consider the gauge group SU(4) x SU(2)_L x U(1)_X, where the
SU(4) unifies baryon number and color. This symmetry is spontaneously broken
down to the Standard Model gauge group at a scale which can be as low as a few
TeV. The SU(4) structure implies that each SM quark comes along with an
uncolored quark partner, the lightest of which is stabilized by the generalized
baryon number symmetry and can play the role of dark matter. We explore
circumstances under which one can realize a model of asymmetric dark matter
whose relic abundance is connected to the observed baryon asymmetry, and
discuss unique signatures that can be searched for at the LHC.Comment: 6 pages, 3 figure
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
Effective Theories of Gamma-ray Lines from Dark Matter Annihilation
We explore theories of dark matter in which dark matter annihilations produce
mono-energetic gamma rays ("lines") in the context of effective field theory,
which captures the physics for cases in which the particles mediating the
interaction are somewhat heavier than the dark matter particle itself. Building
on earlier work, we explore the generic signature resulting from SU(2)xU(1)
gauge invariance that two (or more) lines are generically expected, and
determine the expected relative intensities, including the possibility of
interference between operators.Comment: 11 pages, 0 figure
Strange Couplings to the Higgs
We explored the coupling of strange quark to the state of mass close to 126
GeV recently observed by the ATLAS and CMS experiments at the LHC. An enhanced
coupling relative to the expectations for a SM Higgs has the effect of
increasing both the inclusive production cross section and the partial decay
width into jets. For very large modifications, the latter dominates and the net
rate into non-jet decay modes such as diphotons is suppressed, with the result
that one can use observations of the diphoton decay mode to place an upper
limit on the strange quark coupling. We find that the current observations of
the diphoton decay mode imply that the coupling of the new resonance to strange
quark can be at most ~ 50 times the SM expectation at the 95 % C.L., if one
assumes at most a O(1) modification of the coupling to gluons.Comment: 10 pages, 3 figure
Simplified Models for Dark Matter Interacting with Quarks
We investigate simplified models in which dark matter particles, taken to be
either Dirac or Majorana fermions, couple to quarks via colored mediators. We
determine bounds from colliders and direct detection experiments, and show how
the interplay of the two leads to a complementary view of this class of dark
matter models. Forecasts for future searches in light of the current
constraints are presented.Comment: 12 pages, 13 figures (39 images) Fixed erroneous calculation and
updated plot
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