arXiv subjects

F. Sanchez

Publications and source records attributed to F. Sanchez.

At least 37 records · Page 2Linked to original sources

arXiv2014

Digital Electronics for the Pierre Auger Observatory AMIGA Muon Counters

The "Auger Muons and Infill for the Ground Array" (AMIGA) project provides direct muon counting capacity to the Pierre Auger Observatory and extends its energy detection range down to 0.3 EeV. It currently consists of 61 detector pairs (a Cherenkov surface detector and a buried muon counter) distributed over a 23.5 km2 area on a 750 m triangular grid. Each counter relies on segmented scintillator modules storing a logical train of '0's and '1's on each scintillator segment at a given time slot. Muon counter data is sampled and stored at 320 MHz allowing both the detection of single photoelectrons and the implementation of an offline trigger designed to mitigate multi-pixel PMT crosstalk and dark rate undesired effects. Acquisition is carried out by the digital electronics built around a low power Cyclone III FPGA. This paper presents the digital electronics design, internal and external synchronization schemes, hardware tests, and first results from the Observatory.

astro-ph.IM↗

arXiv2013

Orientational tuning of the 2D-superconductivity in LaAlO3/SrTiO3 interfaces

The discovery of a two-dimensional (2D) electron gas at the (110)-oriented LaAlO3/SrTiO3 in- terface provided us with the opportunity to probe the effect of crystallographic orientation and the ensuing electronic reconstructions on interface properties beyond the conventional (001)-orientation. At temperatures below 200 mK, we have measured 2D superconductivity with a spatial extension significantly larger (d approx. 24 - 30 nm) than previously reported for (001)-oriented LaAlO3/SrTiO3 interfaces (d approx. 10 nm). The more extended superconductivity brings about the absence of violation of the Pauli paramagnetic limit for the upper critical fields, signaling the distinctive nature of the electronic structure of the (110)-oriented interface with respect to their (001)-counterparts

cond-mat.str-el↗

arXiv2012

Dual baseline search for muon antineutrino disappearance at 0.1 eV^2 < Δm^2 < 100 eV^2

The MiniBooNE and SciBooNE collaborations report the results of a joint search for short baseline disappearance of \bar{ν_μ} at Fermilab's Booster Neutrino Beamline. The MiniBooNE Cherenkov detector and the SciBooNE tracking detector observe antineutrinos from the same beam, therefore the combined analysis of their datasets serves to partially constrain some of the flux and cross section uncertainties. Uncertainties in the ν_μ background were constrained by neutrino flux and cross section measurements performed in both detectors. A likelihood ratio method was used to set a 90% confidence level upper limit on \bar{ν_μ} disappearance that dramatically improves upon prior limits in the Δm^2=0.1-100 eV^2 region.

hep-ex↗

arXiv2012

Neutrino Energy Reconstruction and the Shape of the CCQE-like Total Cross Section

We show that because of the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events, and a distortion of the total flux unfolded cross section shape is produced. This amounts to a redistribution of strength from high to low energies, which gives rise to a sizable excess (deficit) of low (high) energy neutrinos. This distortion of the shape leads to a good description of the MiniBooNE unfolded CCQE-like cross sections published in Phys.Rev. D81 (2010) 092005. However, these changes in the shape are artifacts of the unfolding process that ignores multinucleon mechanisms.

hep-ph↗

arXiv2012

Characterization of the Hamamatsu S8664 Avalanche Photodiode for X-Ray and VUV-light detection

We present the first operation of the Avalanche Photodiode (APD) from Hamamatsu to xenon scintillation light and to direct X-rays of 22.1 keV and 5.9 keV. A large non-linear response was observed for the direct X-ray detection. At 415 V APD bias voltage it was of about 30 % for 22.1 keV and about 45 % for 5.9 keV. The quantum efficiency for 172 nm photons has been measured to be 69 +/- 15 %.

physics.ins-det↗

arXiv2011

Dual baseline search for muon neutrino disappearance at 0.5 eV^2 < Δm^2 < 40 eV^2

The SciBooNE and MiniBooNE collaborations report the results of a ν_μdisappearance search in the Δm^2 region of 0.5-40 eV^2. The neutrino rate as measured by the SciBooNE tracking detectors is used to constrain the rate at the MiniBooNE Cherenkov detector in the first joint analysis of data from both collaborations. Two separate analyses of the combined data samples set 90% confidence level (CL) limits on ν_μdisappearance in the 0.5-40 eV^2 Δm^2 region, with an improvement over previous experimental constraints between 10 and 30 eV^2.

hep-ex↗

arXiv2011

Measurement of K+ production cross section by 8 GeV protons using high energy neutrino interactions in the SciBooNE detector

The SciBooNE Collaboration reports K+ production cross section and rate measurements using high energy daughter muon neutrino scattering data off the SciBar polystyrene (C8H8) target in the SciBooNE detector. The K+ mesons are produced by 8 GeV protons striking a beryllium target in Fermilab Booster Neutrino Beam line (BNB). Using observed neutrino and antineutrino events in SciBooNE, we measure d2σ/dpdΩ = (5.34 \times 0.76) mb/(GeV/c \times sr) for p + Be -> K+ + X at mean K+ energy of 3.9 GeV and angle (with respect to the proton beam direction) of 3.7 degrees, corresponding to the selected K+ sample. Compared to Monte Carlo predictions using previous higher energy K+ production measurements, this measurement, which uses the NUANCE neutrino interaction generator, is consistent with a normalization factor of 0.85\times0.12. This agreement is evidence that the extrapolation of the higher energy K+ measurements to an 8 GeV beam energy using Feynman scaling is valid. This measurement reduces the error on the K+ production cross section from 40% to 14%.

hep-ex↗

arXiv2011

Phase transition close to room temperature in BiFeO3 thin films

BiFeO3 (BFO) multiferroic oxide has a complex phase diagram that can be mapped by appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, displays a reversible temperature-induced phase transition at about 100\circ, thus close to room temperature.

cond-mat.mtrl-sci↗

arXiv2011

Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

We report a Raman scattering investigation of columnar BiFeO3-CoFe2O4 (BFO-CFO) epitaxial thin film nanostructures, where BFO pillars are embedded in a CFO matrix. The feasibility of a strain analysis is illustrated through an investigation of two nanostructures with different BFO-CFO ratios. We show that the CFO matrix presents the same strain state in both nanostructures, while the strain state of the BFO pillars depends on the BFO/CFO ratio with an increasing tensile strain along the out-of-plane direction with decreasing BFO content. Our results demonstrate that Raman scattering allows monitoring strain states in complex 3D multiferroic pillar/matrix composites.

cond-mat.mtrl-sci↗

arXiv2011

A Multi-APD readout for EL detectors

Detectors with an electroluminesence readout show an excellence performance in respect of energy resolution making them interesting for various applications as X-ray detection, double beta and dark matter experiments, Compton and gamma cameras, etc. In the following the study of a readout based on avalanche photo diodes to detect directly the VUV photons is presented. Results of measurements with 5 APDs in xenon at pressures between 1 and 1.65 bar are shown indicating that such a readout can provide excellent energy and a moderate position resolution.

physics.ins-det↗

arXiv2011

Measurement of inclusive charged current interactions on carbon in a few-GeV neutrino beam

The SciBooNE Collaboration reports a measurement of inclusive charged current interactions of muon neutrinos on carbon with an average energy of 0.8 GeV using the Fermilab Booster Neutrino Beam. We compare our measurement with two neutrino interaction simulations: NEUT and NUANCE. The charged current interaction rates (product of flux and cross section) are extracted by fitting the muon kinematics, with a precision of 6-15% for the energy dependent and 3% for the energy integrated analyses. We also extract CC inclusive interaction cross sections from the observed rates, with a precision of 10-30% for the energy dependent and 8% for the energy integrated analyses. This is the first measurement of the CC inclusive cross section on carbon around 1 GeV. These results can be used to convert previous SciBooNE cross section ratio measurements to absolute cross section values.

hep-ex↗

arXiv2010

Measurement of neutral current coherent neutral pion production on carbon in a few-GeV neutrino beam

The SciBooNE Collaboration reports a measurement of neutral current coherent neutral pion production on carbon by a muon neutrino beam with average energy 0.8 GeV. The separation of coherent from inclusive neutral pion production has been improved by detecting recoil protons from resonant neutral pion production. We measure the ratio of the neutral current coherent neutral pion production to total charged current cross sections to be (1.16 +/- 0.24) x 10-2. The ratio of charged current coherent pion to neutral current coherent pion production is calculated to be 0.14+0.30 -0.28, using our published charged current coherent pion measurement.

hep-ex↗

arXiv2010

Measurement of Inclusive Neutral Current Neutral Pion Production on Carbon in a Few-GeV Neutrino Beam

The SciBooNE Collaboration reports inclusive neutral current neutral pion production by a muon neutrino beam on a polystyrene target (C8H8). We obtain (7.7 \pm 0.5(stat.) \pm 0.5 (sys.)) x 10^(-2) as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein-Sehgal model implemented in our neutrino interaction simulation program with nuclear effects. The spectrum shape of the neutral pion momentum and angle agree with the model. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be (0.7 \pm 0.4) x 10^(-2).

hep-ex↗

arXiv2009

NEXT, a HPGXe TPC for neutrinoless double beta decay searches

We propose a novel detection concept for neutrinoless double-beta decay searches. This concept is based on a Time Projection Chamber (TPC) filled with high-pressure gaseous xenon, and with separated-function capabilities for calorimetry and tracking. Thanks to its excellent energy resolution, together with its powerful background rejection provided by the distinct double-beta decay topological signature, the design discussed in this Letter Of Intent promises to be competitive and possibly out-perform existing proposals for next-generation neutrinoless double-beta decay experiments. We discuss the detection principles, design specifications, physics potential and R&D plans to construct a detector with 100 kg fiducial mass in the double-beta decay emitting isotope Xe(136), to be installed in the Canfranc Underground Laboratory.

hep-ex↗

arXiv2007

Detectors and flux instrumentation for future neutrino facilities

This report summarises the conclusions from the detector group of the International Scoping Study of a future Neutrino Factory and Super-Beam neutrino facility. The baseline detector options for each possible neutrino beam are defined as follows: 1. A very massive (Megaton) water Cherenkov detector is the baseline option for a sub-GeV Beta Beam and Super Beam facility. 2. There are a number of possibilities for either a Beta Beam or Super Beam (SB) medium energy facility between 1-5 GeV. These include a totally active scintillating detector (TASD), a liquid argon TPC or a water Cherenkov detector. 3. A 100 kton magnetized iron neutrino detector (MIND) is the baseline to detect the wrong sign muon final states (golden channel) at a high energy (20-50 GeV) neutrino factory from muon decay. A 10 kton hybrid neutrino magnetic emulsion cloud chamber detector for wrong sign tau detection (silver channel) is a possible complement to MIND, if one needs to resolve degeneracies that appear in the $δ$-$θ_{13}$ parameter space.

physics.ins-det↗

arXiv2007

Magnetoelectric coupling in epitaxial orthorhombic YMnO3 thin films

We have grown epitaxial thin-films of the orthorhombic phase of YMnO3 oxide on Nb:SrTiO3(001) substrates and their structure, magnetic and dielectric response have been measured. We have found that a substrate-induced strain produces an in-plane compression of the YMnO3 unit cell. The temperature-dependent magnetization curves display a significant ZFC-FC hysteresis at temperatures below the Neel temperature (TN around 40K). The dielectric constant increases gradually (up to 26%) below TN and mimics the ZFC magnetization curve. We argue that these effects are a manifestation of magnetoelectric coupling in thin films and that the magnetic structure of YMnO3 can be controlled by substrate selection.

cond-mat.str-el↗

arXiv2007

Electric field effects on magnetotransport properties of multiferroic Py/YMnO3/Pt heterostructures

We report on the exchange bias between antiferromagnetic and ferroelectric hexagonal YMnO3 epitaxial thin films sandwiched between a metallic electrode (Pt) and a soft ferromagnetic layer (Py). Anisotropic magnetoresistance measurements are performed to monitor the presence of an exchange bias field. When the heteroestructure is biased by an electric field, it turns out that the exchange bias field is suppressed. We discuss the dependence of the observed effect on the amplitude and polarity of the electric field. Particular attention is devoted to the role of current leakage across the ferroelectric layer.

cond-mat.str-el↗

arXiv2006

Exchange biasing and electric polarization with YMnO3

We report on the growth and functional characterization of epitaxial thin films of the multiferroic YMnO3. We show that using Pt as a seed layer on SrTiO3(111) substrates, epitaxial YMnO3 films (0001) textured are obtained. An atomic force microscope has been used to polarize electric domains revealing the ferroelectric nature of the film. When a Permalloy layer is grown on top of the YMnO3(0001) film, clear indications of exchange bias and enhanced coercivity are observed at low temperature. The observation of coexisting antiferromagnetism and electrical polarization suggests that the biferroic character of YMnO3 can be exploited in novel devices.

cond-mat.str-el↗