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

Does Online Availability Increase Citations? Theory And Evidence From A Panel Of Economics And Business Journals

Does online availability boost citations? Using a panel of citations to economics and business journals, we show that the enormous effects found in previous studies were an artifact of their failure to control for article quality, disappearing once fixed effects are added as controls. The absence of aggregate effects masks heterogeneity across platforms: JSTOR has a uniquely large effect, boosting citations around 10%. We examine other sources of heterogeneity, including whether JSTOR disproportionately increases cites from developing countries or to ‘‘long-tail’’ articles. Our theoretical analysis informs the econometric specification and allows citation increases to be translated into welfare terms

Identifying the Effect of Open Access on Citations Using a Panel of Science Journals

An open‐access journal allows free online access to its articles, obtaining revenue from fees charged to submitting authors or from institutional support. Using panel data on science journals, we are able to circumvent problems plaguing previous studies of the impact of open access on citations. In contrast to the huge effects found in these previous studies, we find a more modest effect: moving from paid to open access increases cites by 8% on average in our sample. The benefit is concentrated among top‐ranked journals. In fact, open access causes a statistically significant reduction in cites to the bottom‐ranked journals in our sample, leading us to conjecture that open access may intensify competition among articles for readers\u27 attention, generating losers as well as winners

A Dark Matter Hurricane: Measuring the S1 Stream with Dark Matter Detectors

The recently discovered S1 stream passes through the Solar neighbourhood on a low inclination, counter-rotating orbit. The progenitor of S1 is a dwarf galaxy with a total mass comparable to the present-day Fornax dwarf spheroidal, so the stream is expected to have a significant DM component. We compute the effects of the S1 stream on WIMP and axion detectors as a function of the density of its unmeasured dark component. In WIMP detectors the S1 stream supplies more high energy nuclear recoils so will marginally improve DM detection prospects. We find that even if S1 comprises less than 10% of the local density, multi-ton xenon WIMP detectors can distinguish the S1 stream from the bulk halo in the relatively narrow mass range between 5 and 25 GeV. In directional WIMP detectors such as CYGNUS, S1 increases DM detection prospects more substantially since it enhances the anisotropy of the WIMP signal. Finally, we show that axion haloscopes possess by far the greatest potential sensitivity to the S1 stream. Once the axion mass has been discovered, the distinctive velocity distribution of S1 can easily be extracted from the axion power spectrum.Comment: 21 pages, 11 figure

A Lower Bound on the Mass of Cold Thermal Dark Matter from Planck

We show that the new measurement of the effective number of neutrinos Neff by the Planck satellite can be used to set a robust lower bound on the mass of cold thermal dark matter of O(MeV). Our limit applies if the dark matter remains in thermal equilibrium by coupling to electrons and photons or through interactions with neutrinos, and applies regardless of whether the dark matter annihilation cross-section is s-wave or p-wave. To illustrate our bounds we apply them to a model of a supersymmetric neutralino annihilating to neutrinos, via a light mixed left-right handed sneutrino mediator. While this scenario was not constrained by previous data, the Planck limits on Neff allow us to set a lower bound on the neutralino dark matter mass of 3.5 MeV.Comment: 16 pages, 7 figures. v2: Added a comparison with BBN and new plots, updated references, typos corrected. v3: Matches version in jCA

Precise predictions and new insights for atomic ionization from the Migdal effect

Probabilities for atomic ionisation via the Migdal effect using Dirac-Hartee-Fock wavefunctions. Dataset accompanies the publication P. Cox, M. J. Dolan, C. McCabe, H. M. Quiney, Precise predictions and new insights for atomic ionization from the Migdal effect, Phys. Rev. D (2023)

Combined antiapoptotic and antioxidant approach to acute neuroprotection for stroke in hypertensive rats

We hypothesized that targeting key points in the ischemic cascade with combined neuroglobin (Ngb) overexpression and c-jun N-terminal kinase (JNK) inhibition (SP600125) would offer greater neuroprotection than single treatment after in vitro hypoxia/reoxygenation and in a randomized, blinded in vivo experimental stroke study using a clinically relevant rat strain. Male spontaneously hypertensive stroke-prone rats underwent transient middle cerebral artery occlusion (tMCAO) and were divided into the following groups: tMCAO; tMCAO+control GFP-expressing canine adenovirus-2, CAVGFP; tMCAO+Ngb-expressing CAV-2, CAVNgb; tMCAO+SP600125; tMCAO+CAVNgb+SP600125; or sham procedure. Rats were assessed till day 14 for neurologic outcome before infarct determination. In vitro, combined lentivirus-mediated Ngb overexpression+SP600125 significantly reduced oxidative stress and apoptosis compared with single treatment(s) after hypoxia/reoxygenation in B50 cells. In vivo, infarct volume was significantly reduced by CAVNgb, SP600125, and further by CAVNgb+SP600125. The number of Ngb-positive cells in the peri-infarct cortex and striatum was significantly increased 14 days after tMCAO in animals receiving CAVNgb. Neurologic outcome, measured using a 32-point neurologic score, significantly improved with CAVNgb+SP600125 compared with single treatments at 14 days after tMCAO. Combined Ngb overexpression with JNK inhibition reduced hypoxia/reoxygenation-induced oxidative stress and apoptosis in cultured neurons and reduced infarct and improved neurologic outcome more than single therapy after in vivo experimental stroke in hypertensive rats