Canada

The major ongoing upgrade of the ATLAS detector at the Large Hadron Collider at CERN consists in the replacement of parts of its muon spectrometer. The so-called New Small Wheels (NSWs) will be covered with two detector types that must trigger on and track outgoing particles - one type is small-strip thin gap chambers (sTGCs) assembled into modules of four layers. Canadian-built sTGC modules are characterized at McGill University using cosmic rays before being shipped to CERN for integration into the wheels. To achieve the design tracking performance, misalignments between sTGC layers must be corrected for. The charge profile left by an x-ray gun and coordinate measuring machine (CMM) measurements of quadruplet layers are being used to define these parameters. Work on using cosmic ray data to validate misalignment parameters derived using the above-mentioned methods will be presented.

CAP Virtual Congress 2021

Validating misalignment measurements between particle detectors for the ATLAS New Small Wheels

particle detector physics

experimental particle physics

data analysis

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Molecular dynamics simulations are, in principle, numerically exact, but severely restricted with respect to the accessible time- and length-scale of the system studied. Stochastic simulations offer an alternative modeling method that overcomes these limitations. Unfortunately, the relation between the properties of the original system and the parameters used in stochastic modeling is not always clear. We address this problem by studying the diffusion of a Brownian particle along a chain of coupled stochastic oscillators. We show that stochastic simulations of the Brownian particle alone may be in quantitative as well as in qualitative disagreement with the result of the full-scale molecular dynamics simulations. As a remedy, we propose to simulate a small part of the chain together with the Brownian particle, which now becomes ``dressed''. We introduce a recipe to perform the stochastic simulations of the part of the chain. We show that the diffusion coefficient of the Brownian particle in this type of stochastic modeling is practically the same as in the molecular dynamics simulations in a broad parameter range.

Brownian motion on a stochastic oscillator chain

The detected spectrum in the Unruh effect is Planckian for massless fields. The reason is that the latter display a linear dispersion relation. It is also well known that for massive fields, the detected spectrum in the Unruh effect would lose its Planckian profile. Remarkably, the relativistic Doppler shift approach to the Unruh effect shows that, just like with massive fields, fields with nonlinear dispersion relations also lead to a departure from a Planckian spectrum. The approach even applies to the case of modified Lorentz transformations. The big advantage of the approach, however, lies in the fact that it offers a very intuitive explanation for the reasons behind such results, and applies even to analogs of the Unruh effect. Detecting such a departure from thermality using water surface waves is very promising.

Revisiting the Unruh effect with modified dispersion relations

An orbital free related density functional theory based on the principles of polymer self-consistent field theory is used to calculate the electron densities, bond energy, bond length and fundamental vibrational frequency of homonuclear diatomic molecules. A simple exchange-correlation functional that neglects correlations is used, and the Pauli potential is based on Edwards–Flory-Huggins interaction taken from polymer physics. Other approximations include a Fermi-Amaldi correction for electron-electron self-interactions and cylindrical averaging to reduce the dimensionality of the problem. Expected bonding characteristics are observed for the first 7 elements in the periodic table. Specifically, quantitatively accurate bond lengths and qualitatively accurate bond energy structure for hydrogen and nitrogen molecules. Bond energy and fundamental vibrational frequency are discrepant up to a factor of two when compared with accepted values. Other elements do not exhibit bonding as expected.

Homonuclear diatomic molecule properties from an orbital-free-related density functional theory

MATHUSLA (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles) is a long-lived particle (LLP) detector which would be constructed on the surface above CMS and is currently in its planning stages. This large-area detector would be composed of several layers of solid plastic scintillator, with wavelength-shifting fibers connected to silicon photomultipliers (SiPMs), allowing us to monitor an empty air-filled decay volume. The purpose of this research is to examine the behavior of a candidate SiPM and signal amplifier for this detection array. The SiPM in question is the SensL MicroFB-30035 and the amplifier is the Broadcom AFBR-S4E001. This goal was accomplished by simulating these components in Ngspice, an electronic circuit simulator. Using this simulation method, we were able to measure the amplified signal output and produce voltage-time plots for it. We will next build this setup in the lab and compare our results to other candidate SiPMs. This research will be useful in developing other aspects of the detection array, the triggering system, and the readout system.

Analyzing the behavior of a Candidate SiPM and Signal Amplifier for MATHUSLA

The NEWS-G experiment uses a spherical proportional counter filled with gas in order to detect potential dark matter particles that can ionize the gas after a nuclear recoil. The detector works by attracting the free electrons towards the center of the sphere where there is a high voltage anode inducing a radial electric field. Near the anode, the accelerated electrons then cause a Townsend avalanche that produces many drifting ions, which creates an identifiable electrical signal. Since this method has been most efficient at energies below 1 GeV, that is where keeping the background contamination at minimum is of upmost importance. However, there is approximately 20 mBq of alpha particles coming from impurities in the copper surface of the sphere that create a sudden influx of events close to the region of interest for up to five seconds. These alphas also lead to fluctuations in the electric field, which in turn alters the time taken for electrons to reach the anode at the center. This presentation aims to show how the consequences of alpha particles in the detector can be characterized, as well as how those consequences can be used to better identify alpha events in order to remove the correlated influx of low energy events.
*On behalf of the NEWS-G collaboration

Analysis and identification of alpha events for NEWS-G

To allow for precision measurements of neutrino interactions in water Cherenkov neutrino detectors, reducing the position uncertainty on the photomultiplier tubes (PMTs) and calibration sources is necessary. This can be achieved with the photogrammetry technique. Detected PMTs in images of the detectors can be used to reconstruct a 3D model of their positions. This photogrammetry technique is being applied in the current Super-Kamiokande (Super-K) detector, and there are plans for its application in the next generation of water Cherenkov detectors, Hyper-K and its intermediate water Cherenkov detector (IWCD).
This talk discusses detection and identification of PMT features from a drone photographic survey of the Super-K detector, and camera calibration and R&D for a built-in photogrammetry camera system in the upcoming IWCD and Hyper-K detectors.

Automated Feature Detection and Camera R&D for Photogrammetry in Super-K and Future Water Cherenkov Neutrino Detectors

The possible existence the magnetic monopole is strongly motivated by theories and extensively tested in experiments. Searches at the LHC have been exclusively conducted with proton-proton collisions. However, the LHC not only collides protons but also heavy ions. Highly relativistic ultraperipheral collisions (UPC), where the ion-ion impact parameter exceeds the ion’s diameter, act as a strong source of electromagnetic radiation. Characterized by minimal hadronic activities, the UPC creates a clean environment to study magnetic monopoles produced via photon-fusion processes. I will present a generator-level study of this production mode, including the modelling of the photon energy spectrum and the monopole interaction required to compute the production cross section at the maximal collision energy of the LHC.

Model of magnetic monopole production in heavy-ion ultraperipheral collisions at the LHC

SNO+ is a neutrino detector located 2 km underground at the deep clean lab facility - SNOLAB, in Vale’s Creighton Mine, in Sudbury ON. The primary goal of the SNO+ experiment is to search for an extremely rare, hypothesized phenomenon, neutrino-less double beta decay (0vbb) - the discovery of which will have a multitude of major implications in fundamental physics. Given the rarity of this phenomenon, it is paramount that all backgrounds in the detector be carefully measured and understood. In this poster, I will show the importance of background analysis and detail the method used to find a rate for K40 backgrounds – a signal that is especially difficult to measure. The techniques used in this analysis allowed for the first-ever estimate of the K40 background made directly from data taken with a detector partially filled with liquid organic scintillator.

K40 Backgrounds in the SNO+ Neutrino Detector

ABSTRACT: 
SNO+ is large multipurpose detector located at SNOLAB, Canada, Sudbury filled with liquid scintillator. The scintillator will eventually be loaded with a tellurium isotope, allowing to look for neutrino-less double beta decay which is extremely rare. This will determine if the neutrino is its own antiparticle. One of the main concerns for these rare event experiments is the presence of backgrounds, which could mask the signals of interest. This presentation will focus on Rn222, one of the most common backgrounds due to its excessive prevalence in the mine environment. Radon decays into daughters where the energies lie within the region of interest for neutrino-less double beta decay. The detector is housed in a large cavity that is filled with ultrapure water and has a nitrogen cover-gas in order to avoid contamination. This presentation will focus on radon assays, a technique that was developed for the SNO experiment. Assays are performed frequently at different positions to monitor the radon levels. During a radon assay, radon is trapped with a ZnS coated lucas cell for a period of time and known amount of flow. This lucas cell can then be connected to a PMT, which detects the decayed alphas that are used to calculate the number of radon atoms in the cavity. This external technique is a crucial part of measuring and monitoring the low background for the experiment.

SN0+ U-238 External Background Measurements using Radon Assay Technique

Cherenkov radiation plays a crucial role in particle physics experiments. 
This is of particular importance in water-filled neutrino detectors, where electron neutrinos are observed through the Cherenkov radiation of ultra-relativistic secondary particles created in the detector's volume. Modern simulation methods of the process that describe Cherenkov emission assume coherence of the radiation throughout the particle’s path without accounting for the impact of scattering of the electrons in matter. Here we consider a more physically accurate calculation of Cherenkov radiation as a phenomenon of wave interference. We then apply this calculation to a simulation that accounts for single Coulomb scattering of the electron with the material. 
The obtained angular distributions of the photons as they would be observed in a detector are compared to the ones predicted by standard simulation tools.

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Validating misalignment measurements between particle detectors for the ATLAS New Small Wheels

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