54 research outputs found
Metastatic melanoma: An unusual presentation
In this report we describe a case of a malignant cutaneous melanoma metastasizing to the pleural surface and peritoneal cavity 5 years after surgical resection of the primary lesion. Malignant cutaneous melanoma is a very aggressive cancer able to metastasize anywhere in the body. Pleural secondary lesions represent a rare event described only in a small number of patients and the association with peritoneal localizations may suggest an uncommon pattern of spread that we discuss. Free full text available at www.tumorionline.it
Results from the Super Cryogenic Dark Matter Search (SuperCDMS) experiment at Soudan
We report the result of a blinded search for Weakly Interacting Massive
Particles (WIMPs) using the majority of the SuperCDMS Soudan dataset. With an
exposure of 1690 kg days, a single candidate event is observed, consistent with
expected backgrounds. This analysis (combined with previous Ge results) sets an
upper limit on the spin-independent WIMP--nucleon cross section of () cm at 46 GeV/. These results set the
strongest limits for WIMP--germanium-nucleus interactions for masses 12
GeV/
Ionization yield measurement in a germanium CDMSlite detector using photo-neutron sources
Two photo-neutron sources, YBe and SbBe, have been
used to investigate the ionization yield of nuclear recoils in the CDMSlite
germanium detectors by the SuperCDMS collaboration. This work evaluates the
yield for nuclear recoil energies between 1 keV and 7 keV at a temperature of
50 mK. We use a Geant4 simulation to model the neutron spectrum assuming
a charge yield model that is a generalization of the standard Lindhard model
and consists of two energy dependent parameters. We perform a likelihood
analysis using the simulated neutron spectrum, modeled background, and
experimental data to obtain the best fit values of the yield model. The
ionization yield between recoil energies of 1 keV and 7 keV is shown to be
significantly lower than predicted by the standard Lindhard model for
germanium. There is a general lack of agreement among different experiments
using a variety of techniques studying the low-energy range of the nuclear
recoil yield, which is most critical for interpretation of direct dark matter
searches. This suggests complexity in the physical process that many direct
detection experiments use to model their primary signal detection mechanism and
highlights the need for further studies to clarify underlying systematic
effects that have not been well understood up to this point
Energy loss due to defect formation from \u3csup\u3e206\u3c/sup\u3ePb recoils in SuperCDMS germanium detectors
The Super Cryogenic Dark Matter Search experiment (SuperCDMS) at the Soudan Underground Laboratory studied energy loss associated with Frenkel defect formation in germanium crystals at mK temperatures using in situ 210Pb sources. We examine the spectrum of 206Pb nuclear recoils near its expected 103 keV endpoint energy and determine an energy loss of (6.08±0.18) %, which we attribute to defect formation. From this result and using TRIM simulations, we extract the first experimentally determined average displacement threshold energy of (19.7+0.6−0.5) eV for germanium. This has implications for the analysis thresholds of future germanium-based dark matter searches
Search for low-mass dark matter via bremsstrahlung radiation and the Migdal effect in SuperCDMS
We present a new analysis of previously published SuperCDMS data using a profile likelihood framework to search for sub-GeV dark matter (DM) particles through two inelastic scattering channels: bremsstrahlung radiation and the Migdal effect. By considering these possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that are undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to 220  MeV/c2 at 2.7×10−30  cm2 via the bremsstrahlung channel. The Migdal channel search provides overall considerably more stringent limits and excludes DM masses down to 30  MeV/c2 at 5.0×10−30  cm2
A Search for Low-mass Dark Matter via Bremsstrahlung Radiation and the Migdal Effect in SuperCDMS
We present a new analysis of previously published of SuperCDMS data using a
profile likelihood framework to search for sub-GeV dark matter (DM) particles
through two inelastic scattering channels: bremsstrahlung radiation and the
Migdal effect. By considering these possible inelastic scattering channels,
experimental sensitivity can be extended to DM masses that are undetectable
through the DM-nucleon elastic scattering channel, given the energy threshold
of current experiments. We exclude DM masses down to at
via the bremsstrahlung channel. The Migdal
channel search provides overall considerably more stringent limits and excludes
DM masses down to at .Comment: Submitted to PR
First measurement of the nuclear-recoil ionization yield in silicon at 100 eV
We measured the nuclear--recoil ionization yield in silicon with a cryogenic
phonon-sensitive gram-scale detector. Neutrons from a mono-energetic beam
scatter off of the silicon nuclei at angles corresponding to energy depositions
from 4\,keV down to 100\,eV, the lowest energy probed so far. The results show
no sign of an ionization production threshold above 100\,eV. These results call
for further investigation of the ionization yield theory and a comprehensive
determination of the detector response function at energies below the keV
scale
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