arXiv subjects

E. A. Garcés

Publications and source records attributed to E. A. Garcés.

14 recordsLinked to original sources

arXiv2022

Volume reduction of water samples to increase sensitivity for radioassay of lead contamination

The World Health Organisation (WHO) presents an upper limit for lead in drinking water of 10 parts per billion ppb. Typically, to reach this level of sensitivity, expensive metrology is required. To increase the sensitivity of low cost devices, this paper explores the prospects of using a volume reduction technique of a boiled water sample doped with Lead-210 ($^{210}Pb$), as a means to increase the solute's concentration. $^{210}$Pb is a radioactive lead isotope and its concentration in a water sample can be measured with e.g. High Purity Germanium (HPGe) detectors at the Boulby Underground Germanium Suite. Concentrations close to the WHO limit have not been examined. This paper presents a measurement of the volume reduction technique retaining $99\pm(9)\%$ of $^{210}$Pb starting from a concentration of $1.9\times10^{-6}$ ppb before reduction and resulting in $2.63\times10^{-4}$ ppb after reduction. This work also applies the volume reduction technique to London tap water and reports the radioassay results from gamma counting in HPGe detectors. Among other radio-isotopes, $^{40}$K, $^{210}$Pb, $^{131}$I and $^{177}$Lu were identified at measured concentrations of $2.83\times10^{3}$ ppb, $2.55\times10^{-7}$ ppb, $5.06\times10^{-10}$ ppb and $5.84\times10^{-10}$ ppb in the London tap water sample. This technique retained $90\pm50\%$ of $^{40}$K. Stable lead was inferred from the same water sample at a measured concentration of 0.012 ppb, prior to reduction.

physics.ins-det↗

arXiv2022

PlomBOX -- development of a low-cost CMOS device for environmental monitoring

This paper reports on the development of a novel CMOS device employing lead-sensing bacteria to assay lead in drinking water. The objective of the PlomBOX project is to develop a low-cost sensor (£10) which can expedite access to on-demand assay methods and thus help mitigate lead intake through contaminated drinking water. The project follows three development paths: a) Certain bacteria can fluoresce or change colour when in the presence of lead. A genetically modified strain of Escherichia coli sensitive to lead concentrations up to 10 ppb is being developed. This constitutes the biosensor that fluoresces in proportion to the presence of lead. b) Bacteria response is imaged using a microprocessor (ESP32) with a camera module. This constitutes the optical metrology component of the PlomBOX. c) Data acquisition and control of the PlomBOX is achieved through a Bluetooth connection with the PlomApp, a custom-developed mobile phone application. Data are sent from the PlomApp to a database where a bespoke automated analysis software provides a result of the lead concentration in a sample of water. This paper reports on the instrumentation challenges of developing the electronics for the PlomBOX and on the first prototype.

physics.ins-det↗

arXiv2022

Constraints on dark matter-nucleon effective couplings in the presence of kinematically distinct halo substructures using the DEAP-3600 detector

DEAP-3600 is a single-phase liquid argon detector aiming to directly detect Weakly Interacting Massive Particles (WIMPs), located at SNOLAB (Sudbury, Canada). After analyzing data taken during the first year of operation, a null result was used to place an upper bound on the WIMP-nucleon spin-independent, isoscalar cross section. This study reinterprets this result within a Non-Relativistic Effective Field Theory framework, and further examines how various possible substructures in the local dark matter halo may affect these constraints. Such substructures are hinted at by kinematic structures in the local stellar distribution observed by the Gaia satellite and other recent astronomical surveys. These include the Gaia Sausage (or Enceladus), as well as a number of distinct streams identified in recent studies. Limits are presented for the coupling strength of the effective contact interaction operators $\mathcal{O}_1$, $\mathcal{O}_3$, $\mathcal{O}_5$, $\mathcal{O}_8$, and $\mathcal{O}_{11}$, considering isoscalar, isovector, and xenonphobic scenarios, as well as the specific operators corresponding to millicharge, magnetic dipole, electric dipole, and anapole interactions. The effects of halo substructures on each of these operators are explored as well, showing that the $\mathcal{O}_5$ and $\mathcal{O}_8$ operators are particularly sensitive to the velocity distribution, even at dark matter masses above 100 GeV/$c^2$.

astro-ph.CO↗

arXiv2020

Characterization of Germanium Detectors for the First Underground Laboratory in Mexico

This article reports the characterization of two High Purity Germanium detectors performed by extracting and comparing their efficiencies using experimental data and Monte Carlo simulations. The efficiencies were calculated for pointlike $γ$-ray sources as well as for extended calibration sources. Characteristics of the detectors such as energy linearity, energy resolution, and full energy peak efficiencies are reported from measurements performed on surface laboratories. The detectors will be deployed in a $γ$-ray assay facility that will be located in the first underground laboratory in Mexico, Laboratorio Subterráneo de Mineral del Chico (LABChico), in the Comarca Minera UNESCO Global Geopark

physics.ins-det↗

arXiv2020

The liquid-argon scintillation pulseshape in DEAP-3600

DEAP-3600 is a liquid-argon scintillation detector looking for dark matter. Scintillation events in the liquid argon (LAr) are registered by 255 photomultiplier tubes (PMTs), and pulseshape discrimination (PSD) is used to suppress electromagnetic background events. The excellent PSD performance of LAr makes it a viable target for dark matter searches, and the LAr scintillation pulseshape discussed here is the basis of PSD. The observed pulseshape is a combination of LAr scintillation physics with detector effects. We present a model for the pulseshape of electromagnetic background events in the energy region of interest for dark matter searches. The model is composed of a) LAr scintillation physics, including the so-called intermediate component, b) the time response of the TPB wavelength shifter, including delayed TPB emission at $\mathcal O$(ms) time-scales, and c) PMT response. TPB is the wavelength shifter of choice in most LAr detectors. We find that approximately 10\% of the intensity of the wavelength-shifted light is in a long-lived state of TPB. This causes light from an event to spill into subsequent events to an extent not usually accounted for in the design and data analysis of LAr-based detectors.

physics.ins-det↗

arXiv2019

The reactor antineutrino anomaly and low energy threshold neutrino experiments

Short distance reactor antineutrino experiments measure an antineutrino spectrum a few percent lower than expected from theoretical predictions. In this work we study the potential of low energy threshold reactor experiments in the context of a light sterile neutrino signal. We discuss the perspectives of the recently detected coherent elastic neutrino-nucleus scattering in future reactor antineutrino experiments. We find that the expectations to improve the current constraints on the mixing with sterile neutrinos are promising. We also analyse the measurements of antineutrino scattering off electrons from short distance reactor experiments. In this case, the statistics is not competitive with inverse beta decay experiments, although future experiments might play a role when compare it with the Gallium anomaly.

hep-ph↗

arXiv2019

Search for dark matter with a 231-day exposure of liquid argon using DEAP-3600 at SNOLAB

DEAP-3600 is a single-phase liquid argon (LAr) direct-detection dark matter experiment, operating 2 km underground at SNOLAB (Sudbury, Canada). The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel. This paper reports on the analysis of a 758 tonne\cdot day exposure taken over a period of 231 live-days during the first year of operation. No candidate signal events are observed in the WIMP-search region of interest, which results in the leading limit on the WIMP-nucleon spin-independent cross section on a LAr target of $3.9\times10^{-45}$ cm$^{2}$ ($1.5\times10^{-44}$ cm$^{2}$) for a 100 GeV/c$^{2}$ (1 TeV/c$^{2}$) WIMP mass at 90\% C. L. In addition to a detailed background model, this analysis demonstrates the best pulse-shape discrimination in LAr at threshold, employs a Bayesian photoelectron-counting technique to improve the energy resolution and discrimination efficiency, and utilizes two position reconstruction algorithms based on PMT charge and photon arrival times.

astro-ph.CO↗

arXiv2018

The $S3$ Symmetric Model with a Dark Scalar

We study the $S3$ symmetric extension of the Standard Model in which all the irreducible representations of the permutation group are occupied by $SU(2)$ scalar doublets, one of which is taken as inert and can lead to dark matter candidates. We perform a scan over parameter space probing points against physical constraints ranging from unitarity tests to experimental Higgs searches limits. We find that the latter constraints severely restrict the parameter space of the model. For acceptable points we compute the value of the relic density of the dark scalar candidates and find that it has a region for low dark matter masses which complies with the Higgs searches bounds and lies within the experimental Planck limit. For masses $\gtrsim 80$ GeV the value of the relic density is below the Planck bound, and it reaches values close to it for very heavy masses $\sim 5$ TeV. In this heavy mass region, this opens the interesting possibility of extending the dark sector of the model with additional particles.

hep-ph↗

arXiv2018

Flavored Non-Minimal Left-Right Symmetric Model Fermion Masses and Mixings

A complete study on the fermion masses and flavor mixing is presented in a non-minimal left-right symmetric model (NMLRMS) where the ${\bf S}_{3}\otimes {\bf Z}_{2}\otimes {\bf Z}^{e}_{2}$ flavor symmetry drives the Yukawa couplings. In the quark sector, the mass matrices possess a kind of the generalized Fritzsch textures that allow us to fit the CKM mixing matrix in good agreement to the last experimental data. In the lepton sector, on the other hand, a soft breaking of the $μ\leftrightarrow τ$ symmetry provides a non zero and non maximal reactor and atmospheric angles, respectively. The inverted and degenerate hierarchy are favored in the model where a set of free parameters is found to be consistent with the current neutrino data.

hep-ph↗

arXiv2018

Exploring NSI degeneracies in long-baseline experiments

One of the main purposes of long-baseline neutrino experiments is to unambiguously measure the CP violating phase in the neutrino sector within the three neutrino oscillation picture. In the presence of physics beyond the Standard Model, the determination of the CP phase will be more difficult, due to the already known degeneracy problem. Working in the framework of non-standard interactions (NSI), we compute the appearance probabilities in an exact analytical formulation and analyze the region of parameters where the confusion problem is present. We also discuss some cases where the falsification of the NSI parameters can be done in long-baseline experiments.

hep-ph↗

arXiv2018

Future perspectives for a weak mixing angle measurement in coherent elastic neutrino nucleus scattering experiments

After the first measurement of the coherent elastic neutrino nucleus scattering (CENNS) by the COHERENT Collaboration, it is expected that new experiments will confirm the observation. Such measurements will allow to put stronger constraints or discover new physics as well as to probe the Standard Model by measuring its parameters. This is the case of the weak mixing angle at low energies, which could be measured with an increased precision in future results of CENNS experiments using, for example, reactor antineutrinos. In this work we analyze the physics potential of different proposals for the improvement of our current knowledge of this observable and show that they are very promising.

hep-ph↗

arXiv2017

Effective-field theory analysis of the $τ^- \to η^{(\prime)} π^- ν_τ$ decays

The rare $τ^- \to η^{(\prime)} π^- ν_τ$ decays, which are suppressed by $G$-parity in the Standard Model (SM), can be sensitive to the effects of new interactions. We study the sensitivity of different observables of these decays in the framework of an effective field theory that includes the most general interactions between SM fields up to dimension six, assuming massless neutrinos. Owing to the strong suppression of the SM isospin breaking amplitudes, we find that the different observables would allow to set constraints on scalar interactions that are stronger than those coming from other low-energy observables.

hep-ph↗

arXiv2015

Top quark Chromoelectric and Chromomagnetic Dipole Moments in a Two Higgs Doublet Model with CP violation

In this work we study the anomalous top quark-gluon couplings Chromoelectric Dipole Moment (CEDM) and Chromomagnetic Dipole Moment (CMDM) in a general THDM with CP violation. We find that this model provides an important contribution from the $Y_{tt}$ Yukawa coupling that needs to be taken into account. The CMDM and CEDM obtained are $-0.03<Δ\tilde{k} < 0.005}$ and $|Δ\tilde{d}| < 0.005$, respectively.

hep-ph↗

arXiv2013

Scalar-pseudoscalar interactions in neutrino-electron scattering

Many extensions to the Standard Model imply the existence of new charged scalar Higgs bosons. We study the contribution of a general scalar or pseudoscalar coupling for the neutrino-electron scattering. We take a phenomenological approach in order to obtain model independent limits to the couplings that arise in this picture. We illustrate the reach of the constraints by studying the particular case of the type III two Higgs doublet model, where we have found new constraints to some elements of the Yukawa couplings mixing matrix ($|Y_{ee}| \leq 1 \times 10^{-1}$ and $|Y_{eμ}| \leq 7\times10^{-2}$ at 90% CL).

hep-ph↗