1,251 research outputs found
New constraints and discovery potential of sub-GeV dark matter with xenon detectors
Existing xenon dark matter (DM) direct detection experiments can probe the
DM-nucleon interaction of DM with a sub-GeV mass through a search for photon
emission from the recoiling xenon atom. We show that LUX's constraints on
sub-GeV DM, which utilise the scintillation (S1) and ionisation (S2) signals,
are approximately three orders of magnitude more stringent than previous xenon
constraints in this mass range, derived from the XENON10 and XENON100 S2-only
searches. The new LUX constraints provide the most stringent direct detection
constraints for DM particles with a mass below 0.5 GeV. In addition, the photon
emission signal in LUX and its successor LZ maintain the discrimination between
background and signal events so that an unambiguous discovery of sub-GeV DM is
possible. We show that LZ has the potential to reconstruct the DM mass with 20%
accuracy for particles lighter than 0.5 GeV.Comment: v2: Updated to match journal version. Additional technical
information provided in appendices. 11 pages, 7 figure
The Astrophysical Uncertainties Of Dark Matter Direct Detection Experiments
The effects of astrophysical uncertainties on the exclusion limits at dark
matter direct detection experiments are investigated for three scenarios:
elastic, momentum dependent and inelastically scattering dark matter. We find
that varying the dark matter galactic escape velocity and the Sun's circular
velocity can lead to significant variations in the exclusion limits for light
( GeV) elastic and inelastic scattering dark matter. We also
calculate the limits using one hundred velocity distributions extracted from
the Via Lactea II and GHALO N-body simulations and find that a
Maxwell-Boltzmann distribution with the same astrophysical parameters generally
sets less constraining limits. The elastic and momentum dependent limits remain
robust for masses GeV under variations of the astrophysical
parameters and the form of the velocity distribution.Comment: 14 pages, 7 figures; v2 final corrected version to appear in Physical
Review D; v3 corrected a typo in Eqn. (B4
Directly detecting sub-GeV dark matter with electrons from nuclear scattering
Dark matter (DM) particles with mass in the sub-GeV range are an attractive
alternative to heavier weakly-interacting massive particles, but direct
detection of such light particles is challenging. If however DM-nucleus
scattering leads to ionisation of the recoiling atom, the resulting electron
may be detected even if the nuclear recoil is unobservable. We demonstrate that
including this effect significantly enhances direct detection sensitivity to
sub-GeV DM. Existing experiments set world-leading limits, and future
experiments may probe the cross sections relevant for thermal freeze-out.Comment: 8 pages revtex4, 5 figures; v2: analysis updated to include
constraints from XENON1T; accepted for publication in PR
A weighty interpretation of the Galactic Centre excess
Previous attempts at explaining the gamma-ray excess near the Galactic Centre
have focussed on dark matter annihilation directly into Standard Model
particles. This results in a preferred dark matter mass of 30-40 GeV (if the
annihilation is into b quarks) or 10 GeV (if it is into leptons). Here we show
that the gamma-ray excess is also consistent with heavier dark matter
particles; in models of secluded dark matter, dark matter with mass up to 76
GeV provides a good fit to the data. This occurs if the dark matter first
annihilates to an on-shell particle that subsequently decays to Standard Model
particles through a portal interaction. This is a generic process that works in
models with annihilation, semi-annihilation or both. We explicitly demonstrate
this in a model of hidden vector dark matter with an SU(2) gauge group in the
hidden sector.Comment: 5 pages, 4 figures. v2: Matches PRD version. Note: title of PRD
version is "Interpretation of the Galactic Center excess of gamma rays with
heavier dark matter particles
Therapeutic potential of the renin angiotensin system in ischaemic stroke
The renin angiotensin system (RAS) consists of the systemic hormone system, critically involved in regulation and homeostasis of normal physiological functions [i.e. blood pressure (BP), blood volume regulation], and an independent brain RAS, which is involved in the regulation of many functions such as memory, central control of BP and metabolic functions. In general terms, the RAS consists of two opposing axes; the ‘classical axis’ mediated primarily by Angiotensin II (Ang II), and the ‘alternative axis’ mediated mainly by Angiotensin-(1–7) (Ang-(1–7)). An imbalance of these two opposing axes is thought to exist between genders and is thought to contribute to the pathology of cardiovascular conditions such as hypertension, a stroke co-morbidity. Ischaemic stroke pathophysiology has been shown to be influenced by components of the RAS with specific RAS receptor antagonists and agonists improving outcome in experimental models of stroke. Manipulation of the two opposing axes following acute ischaemic stroke may provide an opportunity for protection of the neurovascular unit, particularly in the presence of pre-existing co-morbidities where the balance may be shifted. In the present review we will give an overview of the experimental stroke studies that have investigated pharmacological interventions of the RAS
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