27 research outputs found
On some notions of good reduction for endomorphisms of the projective line
Let be an endomorphism of \SR(\bar{\Q}), the projective line over
the algebraic closure of \Q, of degree defined over a number field
. Let be a non-archimedean valuation of . We say that has
critically good reduction at if any pair of distinct ramification points of
do not collide under reduction modulo and the same holds for any
pair of branch points. We say that has simple good reduction at if
the map , the reduction of modulo , has the same degree of
. We prove that if has critically good reduction at and the
reduction map is separable, then has simple good reduction at
.Comment: 15 page
Search for anomalies in the neutrino sector with muon spectrometers and large LArTPC imaging detectors at CERN
A new experiment with an intense ~2 GeV neutrino beam at CERN SPS is proposed
in order to definitely clarify the possible existence of additional neutrino
states, as pointed out by neutrino calibration source experiments, reactor and
accelerator experiments and measure the corresponding oscillation parameters.
The experiment is based on two identical LAr-TPCs complemented by magnetized
spectrometers detecting electron and muon neutrino events at Far and Near
positions, 1600 m and 300 m from the proton target, respectively. The ICARUS
T600 detector, the largest LAr-TPC ever built with a size of about 600 ton of
imaging mass, now running in the LNGS underground laboratory, will be moved at
the CERN Far position. An additional 1/4 of the T600 detector (T150) will be
constructed and located in the Near position. Two large area spectrometers will
be placed downstream of the two LAr-TPC detectors to perform charge
identification and muon momentum measurements from sub-GeV to several GeV
energy range, greatly complementing the physics capabilities. This experiment
will offer remarkable discovery potentialities, collecting a very large number
of unbiased events both in the neutrino and antineutrino channels, largely
adequate to definitely settle the origin of the observed neutrino-related
anomalies.Comment: Contribution to the European Strategy for Particle Physics - Open
Symposium Preparatory Group, Kracow 10-12 September 201
Search for "anomalies" from neutrino and anti-neutrino oscillations at Delta_m^2 ~ 1eV^2 with muon spectrometers and large LAr-TPC imaging detectors
This proposal describes an experimental search for sterile neutrinos beyond
the Standard Model with a new CERN-SPS neutrino beam. The experiment is based
on two identical LAr-TPC's followed by magnetized spectrometers, observing the
electron and muon neutrino events at 1600 and 300 m from the proton target.
This project will exploit the ICARUS T600, moved from LNGS to the CERN "Far"
position. An additional 1/4 of the T600 detector will be constructed and
located in the "Near" position. Two spectrometers will be placed downstream of
the two LAr-TPC detectors to greatly complement the physics capabilities.
Spectrometers will exploit a classical dipole magnetic field with iron slabs,
and a new concept air-magnet, to perform charge identification and muon
momentum measurements in a wide energy range over a large transverse area. In
the two positions, the radial and energy spectra of the nu_e beam are
practically identical. Comparing the two detectors, in absence of oscillations,
all cross sections and experimental biases cancel out, and the two
experimentally observed event distributions must be identical. Any difference
of the event distributions at the locations of the two detectors might be
attributed to the possible existence of {\nu}-oscillations, presumably due to
additional neutrinos with a mixing angle sin^2(2theta_new) and a larger mass
difference Delta_m^2_new. The superior quality of the LAr imaging TPC, in
particular its unique electron-pi_zero discrimination allows full rejection of
backgrounds and offers a lossless nu_e detection capability. The determination
of the muon charge with the spectrometers allows the full separation of nu_mu
from anti-nu_mu and therefore controlling systematics from muon
mis-identification largely at high momenta.Comment: Experiment proposa
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Cryogenic Characterization of FBK RGB-HD SiPMs
We report on the cryogenic characterization of Red Green Blue - High Density
(RGB-HD) SiPMs developed at Fondazione Bruno Kessler (FBK) as part of the
DarkSide program of dark matter searches with liquid argon time projection
chambers. A dedicated setup was used to measure the primary dark noise, the
correlated noise, and the gain of the SiPMs at varying temperatures. A
custom-made data acquisition system and analysis software were used to
precisely characterize these parameters. We demonstrate that FBK RGB-HD SiPMs
with low quenching resistance (RGB-HD-LR) can be operated from 40 K to 300
K with gains in the range to and noise rates on the order of a
few Hz/mm
SiPM-matrix readout of two-phase argon detectors using electroluminescence in the visible and near infrared range
Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The “standard” EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (“neutral bremsstrahlung”, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science
Design and construction of a new detector to measure ultra-low radioactive-isotope contamination of argon
Large liquid argon detectors offer one of the best avenues for the detection of galactic weakly interacting massive particles (WIMPs) via their scattering on atomic nuclei. The liquid argon target allows exquisite discrimination between nuclear and electron recoil signals via pulse-shape discrimination of the scintillation signals. Atmospheric argon (AAr), however, has a naturally occurring radioactive isotope, 39Ar, a β emitter of cosmogenic origin. For large detectors, the atmospheric 39Ar activity poses pile-up concerns. The use of argon extracted from underground wells, deprived of 39Ar, is key to the physics potential of these experiments. The DarkSide-20k dark matter search experiment will operate a dual-phase time projection chamber with 50 tonnes of radio-pure underground argon (UAr), that was shown to be depleted of 39Ar with respect to AAr by a factor larger than 1400. Assessing the 39Ar content of the UAr during extraction is crucial for the success of DarkSide-20k, as well as for future experiments of the Global Argon Dark Matter Collaboration (GADMC). This will be carried out by the DArT in ArDM experiment, a small chamber made with extremely radio-pure materials that will be placed at the centre of the ArDM detector, in the Canfranc Underground Laboratory (LSC) in Spain. The ArDM LAr volume acts as an active veto for background radioactivity, mostly γ-rays from the ArDM detector materials and the surrounding rock. This article describes the DArT in ArDM project, including the chamber design and construction, and reviews the background required to achieve the expected performance of the detector