418 research outputs found
Halo-independent tests of dark matter annual modulation signals
I derive new halo-independent lower bounds on the product of the dark
matter-nucleon scattering cross section and the local dark matter density that
are valid for annual modulations of dark matter direct detection signals. They
are obtained by making use of halo-independent bounds based on an expansion of
the rate on the Earth's velocity that were derived in previous works. In
combination with astrophysical measurements of the local energy density, an
observed annual modulation implies a lower bound on the cross section that is
independent of the velocity distribution and that must be fulfilled by any
particle physics model. In order to illustrate the power of the bounds we apply
them to DAMA/LIBRA data and obtain quite strong results when compared to the
standard halo model predictions. We also extend the bounds to the case of
multi-target detectors.Comment: 23 pages, 5 figures, 1 table. Extended discussion on the phase, one
figure added, minor changes, results unchanged. Matches published version in
JCA
A halo-independent lower bound on the dark matter capture rate in the Sun from a direct detection signal
We show that a positive signal in a dark matter (DM) direct detection
experiment can be used to place a lower bound on the DM capture rate in the
Sun, independent of the DM halo. For a given particle physics model and DM mass
we obtain a lower bound on the capture rate independent of the local DM
density, velocity distribution, galactic escape velocity, as well as the
scattering cross section. We illustrate this lower bound on the capture rate by
assuming that upcoming direct detection experiments will soon obtain a
significant signal. When comparing the lower bound on the capture rate with
limits on the high-energy neutrino flux from the Sun from neutrino telescopes,
we can place upper limits on the branching fraction of DM annihilation channels
leading to neutrinos. With current data from IceCube and Super-Kamiokande
non-trivial limits can be obtained for spin-dependent interactions and direct
annihilations into neutrinos. In some cases also annihilations into
or start getting constrained. For spin-independent interactions
current constraints are weak, but they may become interesting for data from
future neutrino telescopes.Comment: 27 pages, 8 figures. Added discussion on equilibrium. Added section
5.4 on form factor uncertainties. Updated figures with SK new limits.
Published in JCA
Astrophysics independent bounds on the annual modulation of dark matter signals
We show how constraints on the time integrated event rate from a given dark
matter (DM) direct detection experiment can be used to set a stringent
constraint on the amplitude of the annual modulation signal in another
experiment. The method requires only very mild assumptions about the properties
of the local DM distribution: that it is temporally stable on the scale of
months and spatially homogeneous on the ecliptic. We apply the method to the
annual modulation signal in DAMA/LIBRA, which we compare to the bounds derived
from the constraints on the time-averaged rates from XENON10, XENON100, CDMS
and SIMPLE. Assuming a DM mass of 10 GeV, we show that a DM interpretation of
the DAMA/LIBRA signal is excluded at 6.3sigma (4.6sigma) for isospin conserving
(violating) spin-independent interactions, and at 4.9sigma for spin-dependent
interactions on protons.Comment: 4 pages, 4 figure
WHAT MAKES BALANCE SHEET EFFECTS DETRIMENTAL FOR THE COUNTRY RISK PREMIUM?
This paper builds upon the empirical literature on the macroeconomic impact of real exchange rate depreciations for a sample of 27 emerging economies. We find that real exchange rate depreciations tend to increase a countryâs risk premium. This effect is neither linear nor symmetric: large real exchange depreciations are much more detrimental and real appreciations do not seem to reduce the risk premium. We also show that the main channels for the real exchange rate to affect country risk are external and domestic balance sheet effects, stemming from the sudden increase in the stock of external or domestic dollar-denominated debt, respectively. This is particularly the case in the countries with the largest financial imperfections. Competitiveness is not an important enough factor to outweigh this negative effect. Finally, fixed exchange rate regimes tend to amplify balance sheet effects, beyond the extent of real depreciation. The data indicates that it could be due to a larger accumulation of external debt under fixed regimes.balance sheet effects, financial accelerator theories, exchange rate regime
Neutrino Masses, Grand Unification, and Baryon Number Violation
If grand unification is real, searches for baryon-number violation should be
included on the list of observables that may reveal information regarding the
origin of neutrino masses. Making use of an effective-operator approach and
assuming that nature is SU(5) invariant at very short distances, we estimate
the consequences of different scenarios that lead to light Majorana neutrinos
for low-energy phenomena that violate baryon number minus lepton number (B-L)
by two (or more) units, including neutron-antineutron oscillations and B-L
violating nucleon decays. We find that, among all possible effective theories
of lepton-number violation that lead to nonzero neutrino masses, only a subset
is, broadly speaking, consistent with grand unification.Comment: 12 pages, 1 figure. Improved discussion, references added, results
unchange
Phenomenology of SU(5) low-energy realizations: the diphoton excess and Higgs flavor violation
We discuss different low-energy realizations and illustrate their
use with the diphoton excess and Higgs flavor violation, which require new
physics at the TeV scale. In particular, we study two scenarios for a GeV
resonance: in the first one the resonance belongs to the adjoint of , being either an singlet or a triplet, while in the second
case the signal is due to the CP-even and CP-odd states of a new
Higgs doublet belonging to a or a representations,
giving rise to a two-Higgs doublet model at low energies. We study the
fine-tuning needed for the desired members of the multiplets to be light
enough, while having the rest at the GUT scale. In these scenarios, the
production and decay into photons of the new resonance are mediated by the
leptoquarks (LQ) present in these large representations. We analyse
the phenomenology of such scenarios, focusing on the most relevant predictions
that can help to disentangle the different models, like decays into gauge
bosons, Standard Model (SM) fermions and LQs pair production. In the case of
the (the Georgi-Jarlskog model), we also study the possibility to
have Higgs flavor violation. We find that mixing limits (in addition to
) always imply that .Comment: Minor clarifications and references added, typos corrected, matches
published version in NP
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