Improvement of the signal-to-background discrimination in search for Dark Matter produced in association with a pair of topantitop quarks

RESUMEN: Este trabajo se basa en una búsqueda de materia oscura en asociación con un par de quarks top-antitop en el detector CMS del CERN. El trabajo se centra en el estudio de la reconstrucción cinemática de los neutrinos producidos en los casos en los que los quark top decaen leptónicamente, para mejorar y optimizar las técnicas de discriminación que se usan actualmente. Como resultado se ha conseguido obtener un nuevo método que mejora al precedente de las siguientes formas: reducción de su complejidad computacional, ya que se trata de un método analítico; entendimiento del problema en términos físicos, lo que ha permitido definir de forma rigurosa las variables de discriminación y posibilidad de aplicar el método a colisiones de partículas para las que previamente no era posible hacerlo.ABSTRACT: This project is based on the search of dark matter in association with quark top pair in the CMS detector of CERN. The work studies the kinematic reconstruction of the neutrinos produced in the cases where the quark tops decay into leptons, trying to improve and optimize the techniques currently in use. As a result, a new method has been developed improving the previous in the following ways: reduction of the computational complexity, as it is an analytical method; understanding of the problem in physical terms which allows to define the discrimination variables in a rigorous manner and the possibility to apply the method to collisions of particles for which it was impossible with the previous approach.Grado en Físic

Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection

Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of O ( 10     eV ) . In this regime, ionization signals from small-angle Compton scatters of environmental γ rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23 eV. A skipper charge-coupled device with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a 241 Am γ -ray source over several months. Features associated with the silicon K-, L 1 -, and L 2 , 3 -shells are clearly identified, and scattering on valence electrons is detected for the first time below 100 eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5 keV. The data are in better agreement with ab initio calculations originally developed for x-ray absorption spectroscopy.The DAMIC-M project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme Grant Agreement No. 788137, and from NSF through Grant No. NSF PHY-1812654. The work at University of Chicago and University of Washington was supported through Grant No. NSF PHY-2110585. This work was supported by the Kavli Institute for Cosmological Physics at the University of Chicago through an endowment from the Kavli Foundation. We also thank the College of Arts and Sciences at UW for contributing the first CCDs to the DAMIC-M project. I. F. C. A. was supported by project PID2019–109829 GB-I00 funded by MCIN/ AEI /10.13039/501100011033. The Centro Atómico Bariloche group is supported by ANPCyT Grant No. PICT-2018-03069. The University of Zürich was supported by the Swiss National Science Foundation. The CCD development work at Lawrence Berkeley National Laboratory Microsystems Lab was supported in part by the Director, Office of Science, of the U.S. Department of Energy under Award No. DE-AC02-05CH11231. We thank Gerald T. Seidler for introducing us to the feff code, and thank Joshua J. Kas, Micah P. Prange, and John J. Rehr for their support with feff. We also thank Christian Sternemann for sharing his NRIXS silicon spectra

Skipper-CCD Sensors for the Oscura Experiment: Requirements and Preliminary Tests

Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark matter (DM) direct detection search that will reach unprecedented sensitivity to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is planning to operate at SNOLAB with 2070 m overburden, and aims to reach a background goal of less than one event in each electron bin in the 2-10 electron ionization-signal region for the full 30 kg-year exposure, with a radiation background rate of 0.01 dru. In order to achieve this goal, Oscura must address each potential source of background events, including instrumental backgrounds. In this work, we discuss the main instrumental background sources and the strategy to control them, establishing a set of constraints on the sensors' performance parameters. We present results from the tests of the first fabricated Oscura prototype sensors, evaluate their performance in the context of the established constraints and estimate the Oscura instrumental background based on these results

Certificación y validación de un sistema de Monitorización de la calidad de la toma de Datos del experimento DAMIC-M

ABSTRACT: This project is the base for the elaboration of a Data Quality Monitoring System (DQM) for the direct search Dark Matter experiment: DAMIC (Dark Matter in CCDs). In this project, different variables are going to be studied to see to identify which ones characterised the data and perform a simple statistic test that allows to distinguish good and bad images. To be able to find possible elements that can be used to classify the images taken by the CCD, the data reading process has been studied along with the different variables taken from it.RESUMEN: Este trabajo se basa en la búsqueda de una serie de parámetros que puedan ser usados en un sistema de monitorización de la toma de datos, para el experimento de detección directa de Materia Oscura DAMIC (en inglés, Dark Matter in CCDs). Para ello, se va a diseñar un prototipo de DQM (en inglés, Data Quality Monitoring), donde se estudiarán diferentes variables que caracterizan los datos y con las que implementar un test estadístico sencillo, que pueda separar las imágenes buenas de las malas. Para ver los posibles elementos con las que poder clasificar las imágenes tomadas por las CCD, se ha estudiado la cadena de procesado de datos y las distintas variables que se extraen de la lectura de las imágenes.Máster en Física de Partículas y del Cosmo

Skipper-CCD sensors for the Oscura experiment: Requirements and preliminary tests

Oscura collaboration: et al.Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark matter (DM) direct detection search that will reach unprecedented sensitivity to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is planning to operate at SNOLAB with 2070 m overburden, and aims to reach a background goal of less than one event in each electron bin in the 2–10 electron ionization-signal region for the full 30 kg-year exposure, with a radiation background rate of 0.01 dru.[1 dru (differential rate unit) corresponds to 1 event/kg/day/keV.] In order to achieve this goal, Oscura must address each potential source of background events, including instrumental backgrounds. In this work, we discuss the main instrumental background sources and the strategy to control them, establishing a set of constraints on the sensors' performance parameters. We present results from the tests of the first fabricated Oscura prototype sensors, evaluate their performance in the context of the established constraints and estimate the Oscura instrumental background based on these results.This document was prepared by members of the Oscura collaboration using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. Also, part of this work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, and was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.Peer reviewe

The Oscura Experiment

This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.The Oscura experiment will lead the search for low-mass dark matter particles using a very large array of novel silicon Charge Coupled Devices (CCDs) with a threshold of two electrons and with a total exposure of 30 kg-yr. The R&D effort, which began in FY20, is currently entering the design phase with the goal of being ready to start construction in late 2024. Oscura will have unprecedented sensitivity to sub-GeV dark matter particles that interact with electrons, probing dark matter-electron scattering for masses down to ∼500 keV and dark matter being absorbed by electrons for masses down to ∼1 eV. The Oscura R&D effort has made some significant progress on the main technical challenges of the experiment, of which the most significant are engaging new foundries for the fabrication of the CCD sensors, developing a cold readout solution, and understanding the experimental backgrounds.Peer reviewe

Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection

DAMIC-M Collaboration: et al.Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of O(10 eV). In this regime, ionization signals from small-angle Compton scatters of environmental γ rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23 eV. A skipper charge-coupled device with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a 241Am γ-ray source over several months. Features associated with the silicon K-, L1-, and L2,3-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100 eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5 keV. The data are in better agreement with ab initio calculations originally developed for x-ray absorption spectroscopy.The DAMIC-M project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme Grant Agreement No. 788137, and from NSF through Grant No. NSF PHY-1812654. The work at University of Chicago and University of Washington was supported through Grant No. NSF PHY-2110585. This work was supported by the Kavli Institute for Cosmological Physics at the University of Chicago through an endowment from the Kavli Foundation. We also thank the College of Arts and Sciences at UW for contributing the first CCDs to the DAMIC-M project. I.F.C.A. was supported by project PID2019–109829 GB-I00 funded by MCIN/ AEI /10.13039/501100011033. The Centro Atómico Bariloche group is supported by ANPCyT Grant No. PICT-201803069. The University of Zürich was supported by the Swiss National Science Foundation. The CCD development work at Lawrence Berkeley National Laboratory Microsystems Lab was supported in part by the Director, Office of Science, of the U.S. Department of Energy under Award No. DE-AC02-05CH11231.Peer reviewe

Searching for millicharged particles with 1 kg of Skipper-CCDs using the NuMI beam at Fermilab

Abstract Oscura is a planned light-dark matter search experiment using Skipper-CCDs with a total active mass of 10 kg. As part of the detector development, the collaboration plans to build the Oscura Integration Test (OIT), an engineering test with 10% of the total mass. Here we discuss the early science opportunities with the OIT to search for millicharged particles (mCPs) using the NuMI beam at Fermilab. mCPs would be produced at low energies through photon-mediated processes from decays of scalar, pseudoscalar, and vector mesons, or direct Drell-Yan productions. Estimates show that the OIT would be a world-leading probe for mCPs in the ∼MeV mass range