799 research outputs found
Higgs Phenomenology of Minimal Universal Extra Dimensions
The minimal model of Universal Extra Dimensions (MUED) is briefly reviewed.
We explain how the cross-sections for Higgs production via gluon fusion and
decay into two photons are modified, relative the the Standard Model (SM)
values, by KK particles running in loops, leading to an enhancement of the gg
to h to two photons and gg to h to W+W- cross-sections. ATLAS and CMS searches
for the SM Higgs in these channels are reinterpreted in the context of MUED and
used to place new limits on the MUED parameter space. Only a small region of
between 1 and 3 GeV around mh = 125 GeV for 500 GeV < 1/R < 1600 GeV remains
open at the 95 % confidence level.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 4 figure
Light mixed sneutrinos as thermal dark matter
In supersymmetric models with Dirac neutrino masses, a left-right mixed
sneutrino can be a viable dark matter candidate. We examine the
MSSM+ parameter space where this is the case with particular
emphasis on light sneutrinos with masses below 10 GeV. We discuss implications
for direct and indirect dark matter searches, including the relevant
uncertainties, as well as consequences for collider phenomenology.Comment: 33 pages, 14 figures; one figure and references adde
The Thermal Abundance of Semi-Relativistic Relics
Approximate analytical solutions of the Boltzmann equation for particles that
are either extremely relativistic or non-relativistic when they decouple from
the thermal bath are well established. However, no analytical formula for the
relic density of particles that are semi-relativistic at decoupling is yet
known. We propose a new ansatz for the thermal average of the annihilation
cross sections for such particles, and find a semi-analytical treatment for
calculating their relic densities. As examples, we consider Majorana- and
Dirac-type neutrinos. We show that such semi-relativistic relics cannot be good
cold Dark Matter candidates. However, late decays of meta-stable
semi-relativistic relics might have released a large amount of entropy, thereby
diluting the density of other, unwanted relics.Comment: 22 pages, 5 figures. Comments and references adde
Electronic structure and magnetic anisotropy of Co/Au(111): A spin-resolved photoelectron spectroscopy study
Structure and magnetism of Fe thin films grown on Rh(001) studied by photoelectron spectroscopy
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