Abstract
We present a method for the in-flight relative flux self-calibration of a spectro-photometer instrument, general enough to be applied to any upcoming galaxy survey on satellite. The ...instrument response function, that accounts for a smooth continuous variation due to telescope optics, on top of a discontinuous effect due to the segmentation of the detector, is inferred with a
χ
2
statistics. The method provides unbiased inference of the sources count rates and of the reconstructed relative response function, in the limit of high count rates. We simulate a simplified sequence of observations following a spatial random pattern and realistic distributions of sources and count rates, with the purpose of quantifying the relative importance of the number of sources and exposures for correctly reconstructing the instrument response. We present a validation of the method, with the definition of figures of merit to quantify the expected performance, in plausible scenarios.
Abstract
Directional sensitivity to nuclear recoils would provide a smoking gun for a possible discovery of dark matter in the form of WIMPs (Weakly Interacting Massive Particles). A hint of ...directional dependence of the response of a dual-phase argon Time Projection Chamber (TPC) was found in the SCENE experiment. Given the potential importance of such a capability in the framework of dark matter searches, a new dedicated experiment, ReD (Recoil Directionality), was designed by the Global Argon Dark Matter Collaboration, in order to scrutinise this hint. A small dual-phase argon TPC was irradiated with neutrons produced by the p(
7
Li,
7
Be)n reaction using the 15 MV TANDEM accelerator of the INFN - Laboratori Nazionali del Sud, Catania, Italy, so as to produce argon nuclear recoils in the range (20 - 100) keV of interest for dark matter searches. Energy and direction of nuclear recoils are inferred by the detection of the elastically-scattered neutron by a set of scintillation detectors. Events were selected by gating of the associated
7
Be, which is detected by a telescope of Si detectors.
The human pathogen xenotropic murine leukaemia virus-related virus (XMRV) has been tentatively associated with prostate cancer and chronic fatigue syndrome. Unfortunately, subsequent studies failed ...to identify the virus in various clinical settings. To determine whether XMRV circulates in humans and the relationship with its host, we searched for the virus in 124 human immunodeficiency virus-infected patients who might have been exposed to XMRV, might be prone to infection as a result of progressive immunodeficiency, and had not yet been treated with antiretroviral drugs. Using nested PCR and single-step TaqMan real-time PCR, both designed on the XMRV gag gene, we could not find any positive samples. These findings add to the growing amount of scepticism regarding XMRV.
Borexino is a low background liquid scintillation detector acquiring solar neutrino data at the LNGS underground laboratory in Italy. Borexino is capable to perform spectral-resolved measurements of ...the low-energy 7Be and pep solar neutrinos. Borexino has performed the first direct measurement of the 7Be solar neutrino rate with accuracy better than 5%. The absence of day–night asymmetry of the 7Be solar neutrino rate was measured with a total uncertainty of 1%. Borexino results alone reject the LOW region of solar neutrino oscillation parameters at more than 8.5 σ CL. Combined with the other solar neutrino data, Borexino measurements isolate the MSW-LMA solution of neutrino oscillations without assuming CPT invariance in the neutrino sector. Borexino has also directly observed, for the first time, solar neutrinos in the 1.0–1.5 MeV energy range, leading to the first direct evidence of the pep solar neutrino signal and the strongest constraint of the CNO solar neutrino flux up to date.
We present new constraints on sub-GeV dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This ...analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and 100 MeV/c^{2}.
We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly ...induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4±0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (1422±67) kgd exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1×10−44 cm2 for a WIMP mass of 100 Gev/c2.
Liquid argon is a bright scintillator with potent particle identification properties, making it an attractive target for direct-detection dark matter searches. The DarkSide-50 dark matter search here ...reports the first WIMP search results obtained using a target of low-radioactivity argon. DarkSide-50 is a dark matter detector, using a two-phase liquid argon time projection chamber, located at the Laboratori Nazionali del Gran Sasso. The underground argon is shown to contain super(39) Ar at a level reduced by a factor (1.4+ or -0.2)x10 super(3) relative to atmospheric argon. We report a background-free null result from (2616+ or -43)kgd of data, accumulated over 70.9 live days. When combined with our previous search using an atmospheric argon, the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section, based on zero events found in the WIMP search regions, is 2.0x10 super(-44)cm super(2)(8.6x10-44cm super(2), 8.0x10 super(-43)cm super(2)) for a WIMP mass of 100GeV/c super(2)(1TeV/c super(2), 10TeV/c super(2)).
The rate of neutrino-electron elastic scattering interactions from 862 keV Be7 solar neutrinos in Borexino is determined to be 46.0±1.5(stat)-1.6+1.5(syst)counts/(day*100ton). This corresponds to a ...νe-equivalent Be7 solar neutrino flux of (3.10±0.15)×109cm-2s-1 and, under the assumption of νe transition to other active neutrino flavours, yields an electron neutrino survival probability of 0.51±0.07 at 862 keV. The no flavor change hypothesis is ruled out at 5.0σ. A global solar neutrino analysis with free fluxes determines Φpp=6.06-0.06+0.02×1010cm-2s-1 and ΦCNO<1.3×109cm-2s-1 (95% C.L.). These results significantly improve the precision with which the Mikheyev-Smirnov-Wolfenstein large mixing angle neutrino oscillation model is experimentally tested at low energy.
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