349 research outputs found
Black hole masses and starbursts in X-shaped radio sources
It has been suggested that the X-shaped morphology observed in some radio
sources can reflect either a recent merger of two supermassive black holes
(SMBHs) or the presence of a second active black hole in the galactic nucleus.
These scenarios are tested by studying the relationship between the black hole
mass, radio and optical luminosity, starburst history, and dynamic age of radio
lobes in a sample of 29 X-shaped radio galaxies drawn from a list of 100
X-shaped radio source candidates identified from the FIRST survey. The same
relationships are also studied in a control sample consisting of 36 radio-loud
active nuclei with similar redshifts and optical and radio luminosities. The
X-shaped objects are found to have statistically higher black hole masses and
older starburst activity compared to the objects from the control sample.
Implications of these findings are discussed for the black hole merger scenario
and for the potential presence of active secondary black holes in post-merger
galaxies.Comment: 11 pages, 8 figure
Limits on Dark Matter Effective Field Theory Parameters with CRESST-II
CRESST is a direct dark matter search experiment, aiming for an observation
of nuclear recoils induced by the interaction of dark matter particles with
cryogenic scintillating calcium tungstate crystals. Instead of confining
ourselves to standard spin-independent and spin-dependent searches, we
re-analyze data from CRESST-II using a more general effective field theory
(EFT) framework. On many of the EFT coupling constants, improved exclusion
limits in the low-mass region (< 3-4 GeV) are presented.Comment: 7 pages, 9 figure
Exploring CEvNS with NUCLEUS at the Chooz Nuclear Power Plant
Coherent elastic neutrino-nucleus scattering (CENS) offers a unique way
to study neutrino properties and to search for new physics beyond the Standard
Model. Nuclear reactors are promising sources to explore this process at low
energies since they deliver large fluxes of (anti-)neutrinos with typical
energies of a few MeV. In this paper, a new-generation experiment to study
CENS is described. The NUCLEUS experiment will use cryogenic detectors
which feature an unprecedentedly low energy threshold and a time response fast
enough to be operated in above-ground conditions. Both sensitivity to
low-energy nuclear recoils and a high event rate tolerance are stringent
requirements to measure CENS of reactor antineutrinos. A new experimental
site, denoted the Very-Near-Site (VNS) at the Chooz nuclear power plant in
France is described. The VNS is located between the two 4.25 GW
reactor cores and matches the requirements of NUCLEUS. First results of on-site
measurements of neutron and muon backgrounds, the expected dominant background
contributions, are given. In this paper a preliminary experimental setup with
dedicated active and passive background reduction techniques is presented.
Furthermore, the feasibility to operate the NUCLEUS detectors in coincidence
with an active muon-veto at shallow overburden is studied. The paper concludes
with a sensitivity study pointing out the promising physics potential of
NUCLEUS at the Chooz nuclear power plant
First results from the CRESST-III low-mass dark matter program
The CRESST experiment is a direct dark matter search which aims to measure
interactions of potential dark matter particles in an earth-bound detector.
With the current stage, CRESST-III, we focus on a low energy threshold for
increased sensitivity towards light dark matter particles. In this manuscript
we describe the analysis of one detector operated in the first run of
CRESST-III (05/2016-02/2018) achieving a nuclear recoil threshold of 30.1eV.
This result was obtained with a 23.6g CaWO crystal operated as a cryogenic
scintillating calorimeter in the CRESST setup at the Laboratori Nazionali del
Gran Sasso (LNGS). Both the primary phonon/heat signal and the simultaneously
emitted scintillation light, which is absorbed in a separate
silicon-on-sapphire light absorber, are measured with highly sensitive
transition edge sensors operated at ~15mK. The unique combination of these
sensors with the light element oxygen present in our target yields sensitivity
to dark matter particle masses as low as 160MeV/c.Comment: 9 pages, 9 figure
Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes
The EDELWEISS-II collaboration has completed a direct search for WIMP dark
matter with an array of ten 400-g cryogenic germanium detectors in operation at
the Laboratoire Souterrain de Modane. The combined use of thermal phonon
sensors and charge collection electrodes with an interleaved geometry enables
the efficient rejection of gamma-induced radioactivity as well as near-surface
interactions. A total effective exposure of 384 kg.d has been achieved, mostly
coming from fourteen months of continuous operation. Five nuclear recoil
candidates are observed above 20 keV, while the estimated background is 3.0
events. The result is interpreted in terms of limits on the cross-section of
spin-independent interactions of WIMPs and nucleons. A cross-section of
4.4x10^-8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints
are also set on models where the WIMP-nucleon scattering is inelastic.Comment: 23 pages, 5 figures; matches published versio
A detector module with highly efficient surface-alpha event rejection operated in CRESST-II Phase 2
The cryogenic dark matter experiment CRESST-II aims at the direct detection
of WIMPs via elastic scattering off nuclei in scintillating CaWO crystals.
We present a new, highly improved, detector design installed in the current run
of CRESST-II Phase 2 with an efficient active rejection of surface-alpha
backgrounds. Using CaWO sticks instead of metal clamps to hold the target
crystal, a detector housing with fully-scintillating inner surface could be
realized. The presented detector (TUM40) provides an excellent threshold of
keV and a resolution of keV (at
2.60keV). With significantly reduced background levels, TUM40 sets
stringent limits on the spin-independent WIMP-nucleon scattering cross section
and probes a new region of parameter space for WIMP masses below
3GeV/c. In this paper, we discuss the novel detector design and the
surface-alpha event rejection in detail.Comment: 9 pages, 6 figure
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