21 research outputs found
Minimum Length - Maximum Velocity
We study a framework where the hypothesis of a minimum length in space-time
is complemented with the notion of reference frame invariance. It turns out
natural to interpret the action of the obtained reference frame transformations
in the context of doubly special relativity. As a consequence of this formalism
we find interesting connections between the minimum length properties and the
modified velocity-energy relation for ultra-relativistic particles. For example
we can predict the ratio between the minimum lengths in space and time using
the results from OPERA about superluminal neutrinos.Comment: 12 pages + references, 1 eps figure. V2: one reference added, Eq.
(10) fixed, mild modification of introduction and some comments added in
sections 2 and 5. V3: one extra paragraph added at the end of section 2,
final version published in EPJ
A survey for low stau yields in the MSSM
We study the implications of LHC results for the abundance of long-lived
staus after freeze-out from thermal equilibrium in a super-WIMP dark matter
scenario. We classify regions in the MSSM parameter space according to the stau
yield, considering all possible co-annihilation effects as well as the effects
of resonances and large Higgs-sfermion couplings. Afterwards, we examine the
viability of these regions after imposing experimental and theoretical
constraints, in particular a Higgs mass around 125 GeV and null-searches for
heavy stable charged particles (HSCP) at the LHC. We work in a pMSSM framework
and perform a Monte Carlo scan over the parameter space. To interpret the HSCP
searches in our scenario, we consider all potentially important superparticle
production processes, developing a fast estimator for NLO cross sections for
electroweak and strong production at the LHC. After applying all constraints,
we find that stau yields below 10^-14 occur only for resonant annihilation via
a heavy Higgs in combination with either co-annihilation or large left-right
stau mixing. We encounter allowed points with yields as low as 2x10^-16, thus
satisfying limits from big bang nucleosynthesis even for large stau lifetimes.Comment: 60 pages + refereces, 60 eps figures, v2: references added,
presentation improved, figure 9 changed, results and conclusions unchanged,
matches journal versio
Gravity Effects on Neutrino Masses in Split Supersymmetry
The mass differences and mixing angles of neutrinos can neither be explained
by R-Parity violating split supersymmetry nor by flavor blind quantum gravity
alone. It is shown that combining both effects leads, within the allowed
parameter range, to good agreement with the experimental results. The
atmospheric mass is generated by supersymmetry through mixing between neutrinos
and neutralinos, while the solar mass is generated by gravity through flavor
blind dimension five operators. Maximal atmospheric mixing forces the tangent
squared of the solar angle to be equal to 1/2. The scale of the quantum gravity
operator is predicted within a 5% error, implying that the reduced Planck scale
should lie around the GUT scale. In this way, the model is very predictive and
can be tested at future experiments.Comment: 12 pages, 9 figures; In section 3 we extend our discussion about the
definition of flavor basis in order to clarify in which basis the Gravity
contributions are flavor blind. In the section 4 we add some words to explain
why the Gravity contributions will not affect the charged lepton mass matrix;
Finally we also fixed some minor typos regarding units or plot label
Gravitino Dark Matter in Split Supersymmetry with Bilinear R-Parity Violation
In Split-SUSY with BRpV we show that the Gravitino DM solution is consistent
with experimental evidence on its relic density and life time. We arrive at
this conclusion by performing a complete numerical and algebraic study of the
parameter space, including constraints from the recently determined Higgs mass,
updated neutrino physics, and BBN constraints on NLSP decays. The Higgs mass
requires a relatively low Split-SUSY mass scale, which is naturally smaller
than usual values for reheating temperature, allowing the use of the standard
expression for the relic density. We include restrictions from neutrino physics
with three generations, and notice that the gravitino decay width depends on
the atmospheric neutrino mass scale. We calculate the neutralino decay rate and
find it consistent with BBN. We mention some implications on indirect DM
searches.Comment: 35 pages, 7 figures. References added, typos corrected and
experimental constraints updated. Some clarifications added in Section 2.
Version to appear in EPJ
Possible Interpretations of IceCube High-Energy Neutrino Events
We discuss possible interpretations of the 37 high energy neutrino events
observed by the IceCube experiment in the South Pole. We examine the
possibility to explain the observed neutrino spectrum exclusively by the decays
of a heavy long-lived particle of mass in the PeV range. We compare this with
the standard scenario, namely, a single power-law spectrum related to neutrinos
produced by astrophysical sources and a viable hybrid situation where the
spectrum is a product of two components: a power-law and the long-lived
particle decays. We present a simple extension of the Standard Model that could
account for the heavy particle decays that are needed in order to explain the
data. We show that the current data equally supports all above scenarios and
try to evaluate the exposure needed in order to falsify them in the future.Comment: 29 pages, 9 figures; Re-analysis to include higher energy bins
resulting in slight changes in numerics and figures while the conclusions
remain unaffected. References updated and typos corrected to match the
published versio
Radiative Neutralino Decay in Split Supersymmetry
Radiative neutralino decay is studied in a Split
Supersymmetric scenario, and compared with mSUGRA and MSSM. This 1-loop process
has a transition amplitude which is often quite small, but has the advantage of
providing a very clear and distinct signature: electromagnetic radiation plus
missing energy. In Split Supersymmetry this radiative decay is in direct
competition with the tree-level three-body decay , and we obtain large values for the branching ratio which can be close to unity in the region .
Furthermore, the value for the radiative neutralino decay branching ratio has a
strong dependence on the split supersymmetric scale , which is
otherwise very difficult to infer from experimental observables.Comment: 15 pages and 10 figure