44 research outputs found
The Cosmic Neutrino Background on the Surface of the Earth
We argue that the reflection of relic neutrinos from the surface of the Earth
results in a significant local asymmetry, far exceeding the
expected primordial lepton asymmetry. The net fractional electron neutrino
number is up to
larger than that implied
by the baryon asymmetry. This enhancement is due to the weak 4-Fermi repulsion
of the from ordinary matter which slows down the near the
Earth's surface, and to the resulting evanescent neutrino wave that penetrates
below the surface. This repulsion thus creates a net overdensity in a
shell thick around
the Earth's surface. Similarly the repulsion between or
and ordinary matter creates an overdensity of of similar size. These local enhancements increase the size of
torques of the on spin-polarized matter by a factor
of order . In addition, they create a gradient of the net neutrino
density which naturally provides a way out of the forty-year-old ``no-go''
theorems on the vanishing of forces. The torque resulting
from such a gradient force can be times larger than that of earlier
proposals. Although the size of these effects is still far from current reach,
they may point to new directions for detection.Comment: 14 pages, 6 figures, references update
Mini-Split
The lack of evidence for new physics beyond the standard model at the LHC
points to a paucity of new particles near the weak scale. This suggests that
the weak scale is tuned and that supersymmetry, if present at all, is realized
at higher energies. The measured Higgs mass constrains the scalar sparticles to
be below 10^5 TeV, while gauge coupling unification favors Higgsinos below 100
TeV. Nevertheless, in many models gaugino masses are suppressed and remain
within reach of the LHC. Tuning the weak scale and the renormalization group
evolution of the scalar masses constrain Split model building. Due to the small
gaugino masses, either the squarks or the up-higgs often run tachyonic; in the
latter case, successful electroweak breaking requires heavy higgsinos near the
scalar sparticles. We discuss the consequences of tuning the weak scale and the
phenomenology of several models of Split supersymmetry including anomaly
mediation, U(1)_(B-L) mediation, and Split gauge mediation.Comment: 26 pages, 12 figures; v2:discussion and figure on the status of
fine-tuning in SUSY added, pheno section extende
Detecting high-frequency gravitational waves with optically-levitated sensors
We propose a tunable resonant sensor to detect gravitational waves in the
frequency range of 50-300 kHz using optically trapped and cooled dielectric
microspheres or micro-discs. The technique we describe can exceed the
sensitivity of laser-based gravitational wave observatories in this frequency
range, using an instrument of only a few percent of their size. Such a device
extends the search volume for gravitational wave sources above 100 kHz by 1 to
3 orders of magnitude, and could detect monochromatic gravitational radiation
from the annihilation of QCD axions in the cloud they form around stellar mass
black holes within our galaxy due to the superradiance effect.Comment: 5 pages, 2 figures, 2 tables, submitted to PRL -- v2: GR calculation
corrected, size of the signal and experimental geometry unaffected, cavity
response included in sensitivity plot and LIGO sensitivity curves update
Indirect Signals from Dark Matter in Split Supersymmetry
We study the possibilities for the indirect detection of dark matter in Split
Supersymmetry from gamma-rays, positrons, and antiprotons. The most promising
signal is the gamma-ray line, which may be observable at the next generation of
detectors. For certain halo profiles and a high mass neutralino, the line can
even be visible in current experiments. The continuous gamma-ray signal may be
observable, if there is a central spike in the galactic halo density. The
signals are found to be similar to those in MSSM models. These indirect signals
complement other experiments, being most easily observable for regions of
parameter space, such as heavy wino and higgsino dominated neutralinos, which
are least accessible for direct detection and accelerator searches.Comment: 10 pages, 5 figures; experimental sensitivities added to figure 2,
revised version to appear in Phys. Rev.