DOCSLIB.ORG

A Statistical Framework for the Characterisation of WIMP Dark Matter with the LUX-ZEPLIN Experiment

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Statistical Framework for the Characterisation of WIMP Dark Matter with the LUX-ZEPLIN Experiment A statistical framework for the characterisation of WIMP dark matter with the LUX-ZEPLIN experiment Ibles Olcina Samblas Department of Physics A thesis submitted for the degree of Doctor of Philosophy November 2019 Abstract Several pieces of astrophysical evidence, from galactic to cosmological scales, indicate that most of the mass in the universe is composed of an invisible and essentially collisionless substance known as dark matter. A leading particle candidate that could provide the role of dark matter is the Weakly Interacting Massive Particle (WIMP), which can be searched for directly on Earth via its scattering off atomic nuclei. The LUX-ZEPLIN (LZ) experiment, currently under construction, employs a multi-tonne dual-phase xenon time projection chamber to search for WIMPs in the low background environment of the Davis Campus at the Sanford Underground Research Facility (South Dakota, USA). LZ will probe WIMP interactions with unprecedented sensitivity, starting to explore regions of the WIMP parameter space where new backgrounds are expected to arise from the elastic scattering of neutrinos off xenon nuclei. In this work the theoretical and computational framework underlying the calculation of the sensitivity of the LZ experiment to WIMP-nucleus scattering interactions is presented. After its planned 1000 live days of exposure, LZ will be able to achieve a 3σ discovery for spin independent cross sections above 3.0 10 48 cm2 at 40 GeV/c2 WIMP mass or exclude at × − 90% CL a cross section of 1.3 10 48 cm2 in the absence of signal. The sensitivity of LZ × − to spin-dependent WIMP-neutron and WIMP-proton interactions is also presented. All the sensitivity projections are calculated using the LZStats software package, which is discussed in detail in this thesis. In addition, this work classifies key systematic uncertainties by their impact on the WIMP sensitivity and motivates the inclusion of the highest-ranked into the analysis likelihood function. The effect of some of these systematics on the reconstruction of the WIMP cross section is also studied and it is found to be sub-dominant. Declaration I hereby declare that the contents in this thesis are my own work, except where explicit reference is made to the work of others. My specific contributions in each chapter are listed below. Chapter 2 reviews the main pieces of evidence favouring the dark matter hypothesis and the different types of WIMP searches are discussed. All the figures in this chapter are borrowed from the references indicated in the caption, except for Figure 2.5, which is my own. Chapter 3 describes direct detection WIMP searches with a liquid xenon time projection chamber and presents the main characteristics of the LZ experiment. In this chapter I compared the prediction of the liquid xenon yields between the two most used (until recently) versions of the NEST software package: libNEST 5.0.0 and NEST v2.0.0. I used NEST in combination with a parametrisation of the LZ detector system, which is based on the extensive body of simulations described in the LZ Technical Design Report [1] that were done by LZ collaborators, to generate probability density functions as a function of S1 and S2 observables. This allowed me to give an estimation of the electron recoil discrimination in LZ. Also, I presented the main background contributions to the WIMP search in Table 3.3, which are based on a similar table developed by the LZ collaboration in Ref. [2], but it contains the most up-to-date estimates. In Chapter 4 I presented the LZStats package, which I developed and has become a key analysis tool used by the LZ collaboration. Although I have been the main developer of the code for most of my PhD, I got valuable input from other members of the collaboration and the original design was partly based on previous work developed by Alastair Currie and Attila Dobi. I was responsible for implementing the spin-independent and spin-dependent calculations, described in Chapter 3, into LZStats. Then, and in collaboration with other LZ members, we calculated the sensitivity projections shown in Ref. [2] (submitted for publication). This chapter describes that calculation in detail and provides the most up-to-date sensitivity projections. 6 Chapter 5 describes an analysis of the systematic uncertainties that are expected to be most relevant for the projected performance of the LZ experiment. I presented the relative impact of each systematic uncertainty ranked by the combined impact when the nominal value is shifted by 1σ in either direction. This is my own work, but it was inspired by similar studies conducted by the ATLAS and CMS collaborations, amongst others. The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Re- searchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. Ibles Olcina Samblas November 2019 Acknowledgements There are so many people that have accompanied me in this journey and whose support was vital to make the writing of this thesis possible. I would like to thank first my colleagues at Imperial: Brais, Nellie and Rob (and our beloved plant Lidia too!). You became my second family, and you made the PhD experience a great deal more exciting. Also, I would like to extend my gratitude to those who I shared the corridor with at some point, and who made me grow both professionally and personally: Alfredo, Francis and Alastair. I also would like to thank my supervisor Henrique, who has been my physics (plus grammar, math and politics) educator during the entire duration of the PhD. You have been a source of constant inspiration and I feel fortunate of having had the opportunity to work closely with you. Special thanks go to all the members of the LZ collaboration, whose dedication and hard work have been inspiring since the very beginning. With an almost certain 100% probability that I will forget to mention someone, I would like to acknowledge those people who I have interacted with more closely over the past years and who I have enjoyed dearly working with: Asher, Jim, Hugh, Maria Elena, Aaron, Carmen, Theresa, Cees, Umit, Sally, Nicolas, Amy, Maria Francesa, Elizabeth, Athoy, Curt, Ben K. , Björn, Greg, Jordan, Luke, Quentin, Andrew S. , Andew N. , Scott H. and Billy. Also, I would like to extend my thanks to Glen Cowan, who put everything in order in my very disorganised mental section on statistics. I would like to thank the President’s PhD Scholarship for kindly funding my studies at Imperial College London. I am grateful of the friends I have made because of this incredible opportunity and of the warm community of fellow scholars that I found right from the beginning of my PhD. I would also like to thank, hoping not to appear too pedantic, those great composers who have brought so much enjoyment to my life. Vivaldi, Beethoven and Sarasate always gave me the strength back when I most needed it, while Brahms, Schubert and Bach made me levitate from my seat in those long hours sitting in front of the computer. Also, thank you Liam for teaching me how to enjoy playing music. 8 Thanks Pedro for always bringing that aura of knowledge around you, from which I somehow still managed to learn one thing or two. For starters, I would not be writing this thesis in Vim (and secretly enjoying it), if it wasn’t for you. Thanks also to all my former flatmates for all the great moments that we shared: Andy, Dani and Chris (plus the regular visitors to the Fort Comfort: Alan, Ignacio, Mada, Dylan, Irene, Erica and Zhiyu). I learned something valuable from each of you. This would not have been possible without that amazing group of friends that I feel so fortunate to have around me. Thanks for all the support you have given me and for holding on there waiting during my (embarrassingly frequent) long silences during the writing period. Thanks Guillem, Arianna, Alex C. , Alex B. , Ruben, Elias, Irene, Bea and Sarah. I don’t have words to describe my gratitude towards Julie and Duncan. You have done so much for me and I will always carry your affection wherever I go. Also, my special thanks to Alan, Katie and Polly for turning the big and scary city of London into a cosy and friendly environment. Thanks also to my family for the immeasurable love you have given me. I always felt your proximity despite the distance, and your support and undertanding has been my refuge for years. Gràcies Freix, Violeta i Joansa de tot cor. And of course you, senyoreta meua. You deserve half the credit for this thesis (maybe more). Tú encengueres la flama. “Tot està per fer, tot és possible avui.” Miquel Martí i Pol Contents List of figures 11 List of tables 13 Symbols and Acronyms 15 1 Introduction 19 2 Dark matter 23 2.1 A jigsaw puzzle . 23 2.2 Particle landscape . 32 2.2.1 WIMPs . 33 2.2.2 Axions . 36 2.2.3 Sterile neutrinos . 38 2.3 WIMP detection . 38 2.3.1 Direct searches . 39 2.3.2 Indirect searches . 44 2.3.3 Collider searches . 47 3 Direct detection of WIMPs with dual-phase xenon 49 3.1 WIMP-induced nuclear recoil rate . 49 3.1.1 WIMP astrophysics .
Load more

Recommended publications
  • Galaxy Formation Simulations: "Sub-Grid" Vs. Physics
    GalaxyGalaxy formationformation simulations:simulations: "sub-grid""sub-grid" vs.vs. physicsphysics DeboraDebora SijackiSijacki IoAIoA && KICCKICC CambridgeCambridge Cosmic Mergers Workshop Birmingham Sept 22th 2017 Cosmological simulations of galaxy and structure formation 2 Provide ab initio physical understanding on all scales Standard (and less standard) ingredients: ► “simple” ΛCDM assumption (WDM, SIDM,…, evolving w,…, coupled DM+DE models,…) ► Newtonian gravity (dark matter and baryons) (relativistic corrections, modified gravity models,...) ► Ideal gas hydrodynamics + collisionless dynamics of stars (conduction, viscosity, MHD,…, stellar collisions, stellar hydro) ► Gas radiative cooling/heating, star & BH formation and feedback (non equlibrium low T cooling, dust, turbulence, GMCs,…) ► Reionization in form of an uniform UV background (simple accounting for the local sources,…, full RT on the fly) Pure dark matter simulations in ΛCDM cosmology 3 Millennium XXL 40 yrs! See also: Horizon Run 3 (Kim 2011) MultiDark (Prada 2012) DEUS (Alimi et al. 2012) Watson et al. 2013 The importance of baryons 4 Baryons are directly observable and they affect the underlying dark matter distribution (contraction/expansion/shape/bias, WL,...) => profound implications for cosmology SDSS, BOSS, eBOSS Hubble UDF composite DES WL The importance of baryons 5 Vast range of spatial scales involved and very complex, non-linear physics → SUB-GRID models (“free parameters” constrained by obs) Cosmic web Galaxies 109 pc 103 pc GMCs 10-100 pc Massive stars SNae SMBHs -8 -6 0.1 pc 10 - 10 pc < 10-6 pc Current state-of-the-art in cosmological hydro simulations 6 The Eagle Project (Schaye et al. 2015) The Horizon AGN project (Dubois et al. 14) Magneticum (Dolag et al.
    [Show full text]
  • The Illustris Simulation: the Evolving Population of Black Holes Across Cosmic Time
    MNRAS 452, 575–596 (2015) doi:10.1093/mnras/stv1340 The Illustris simulation: the evolving population of black holes across cosmic time Debora Sijacki,1‹ Mark Vogelsberger,2 Shy Genel,3,4† Volker Springel,5,6 Paul Torrey,2,3,7 Gregory F. Snyder,8 Dylan Nelson3 and Lars Hernquist3 1Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 2Department of Physics, Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 3Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 4Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA 5Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg, Germany 6Zentrum fur¨ Astronomie der Universitat¨ Heidelberg, ARI, Monchhofstr.¨ 12-14, D-69120 Heidelberg, Germany Downloaded from 7Caltech, TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA 8Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218, USA Accepted 2015 June 12. Received 2015 June 12; in original form 2014 August 28 http://mnras.oxfordjournals.org/ ABSTRACT We study the properties of black holes and their host galaxies across cosmic time in the Illustris simulation. Illustris is a large-scale cosmological hydrodynamical simulation which resolves a (106.5 Mpc)3 volume with more than 12 billion resolution elements and includes state-of-the-art physical models relevant for galaxy formation. We find that the black hole mass density for redshifts z = 0–5 and the black hole mass function at z = 0 predicted by Illustris are in very good agreement with the most recent observational constraints.
    [Show full text]
  • Astrophysical Uncertainties of Direct Dark Matter Searches
    Technische Universit¨atM¨unchen Astrophysical uncertainties of direct dark matter searches Dissertation by Andreas G¨unter Rappelt Physik Department, T30d & Collaborative Research Center SFB 1258 “Neutrinos and Dark Matter in Astro- and Particlephysics” Technische Universit¨atM¨unchen Physik Department T30d Astrophysical uncertainties of direct dark matter searches Andreas G¨unter Rappelt Vollst¨andigerAbdruck der von der Fakult¨atf¨urPhysik der Technischen Universit¨at M¨unchen zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigten Dissertation. Vorsitzender: Prof. Dr. Lothar Oberauer Pr¨uferder Dissertation: 1. Prof. Dr. Alejandro Ibarra 2. Prof. Dr. Bj¨ornGarbrecht Die Dissertation wurde am 12.11.2019 bei der Technischen Universit¨at M¨unchen eingereicht und durch die Fakult¨atf¨urPhysik am 24.01.2020 angenommen. Abstract Although the first hints towards dark matter were discovered almost 100 years ago, little is known today about its properties. Also, dark matter has so far only been inferred through astronomical and cosmological observations. In this work, we therefore investi- gate the influence of astrophysical assumptions on the interpretation of direct searches for dark matter. For this, we assume that dark matter is a weakly interacting massive particle. First, we discuss the development of a new analysis method for direct dark matter searches. Starting from the decomposition of the dark matter velocity distribu- tion into streams, we present a method that is completely independent of astrophysical assumptions. We extend this by using an effective theory for the interaction of dark matter with nucleons. This allows to analyze experiments with minimal assumptions on the particle physics of dark matter. Finally, we improve our method so that arbitrarily strong deviations from a reference velocity distribution can be considered.
    [Show full text]
  • Book of Abstracts Ii Contents
    DMSS: A Dark Matter Summer School Monday, 16 July 2018 - Friday, 20 July 2018 Other Institute Book of Abstracts ii Contents Introduction to Dark Matter .................................. 1 Supersymmetry ......................................... 1 Large Scale Structure Formation ................................ 1 Roundtable Discussions ..................................... 1 Dark Matter in the Milky Way ................................. 1 Neutrinos ............................................ 1 Direct Detection of Dark Matter ................................ 1 Roundtable Discussions ..................................... 1 Indirect Dark Matter Searches ................................. 2 Statistical Methods used in Dark Matter ............................ 2 Axions .............................................. 2 Cosmic Microwave Background ................................ 2 Non-SUSY Dark Matter ..................................... 2 Roundtable Discussions ..................................... 2 Dark Matter at the LHC ..................................... 2 Dark Energy ........................................... 2 Roundtable Discussions ..................................... 3 Roundtable Discussions ..................................... 3 Dark Matter search activity at the University of Montreal .................. 3 Extra Dimensions in High-Mass Diphoton Spectrum at 13 TeV ............... 3 The XENONnT Time Projection Chamber .......................... 4 Calibration of the XENON1T experiment at low energies using a Kr83m source . 4 Gravitational-wave
    [Show full text]
  • LUX Detector
    LUX results and LZ sensitivity to dark matter WIMPs Vitaly A. Kudryavtsev University of Sheffield for the LUX and LZ Collaborations Outline n Dark matter direct detection with two-phase noble element instruments. n LUX detector. n LUX results: o WIMPs – spin-independent interactions; o WIMPs – spin-dependent interactions; o Axions and axion-like particles (ALPs). o Modulation search. n LZ detector. n Backgrounds n Sensitivity to WIMPs. n Conclusions. ICNFP2018, 6 July 2018 Vitaly Kudryavtsev 2 Principle of WIMP detection in LXe TPC n Liquid xenon time projection chamber – LXe TPC. n S1 – primary scintillation. n S2 –secondary scintillation, proportional to ionisation. n Position reconstruction based on the light pattern in the PMTs and delay between S2 and S1. ICNFP2018, 6 July 2018 Vitaly Kudryavtsev 3 Advantages of LXe n Good scintillator. n Two-phase -> TPC with good position resolution. n Self-shielding. n Good discrimination between electron recoils (ERs) and nuclear recoils (NRs). n High atomic mass: spin-independent cross- section ∝ A2 n Presence of even-odd isotopes (odd number of neutrons) for spin-dependent studies. n Other physics: o Axion search, o Neutrinoless double-beta decay. LZ Collaboration, LZ TDR, 1703.09144v1 [physics.ins-det] ICNFP2018, 6 July 2018 Vitaly Kudryavtsev 4 LUX Collaboration ² Brown University ² University at Albany, SUNY ² Imperial College London ² University College London ² LIP Coimbra, Portugal ² University of California, Berkeley ² Lawrence Berkley National Laboratory ² University of California, Davis
    [Show full text]
  • Jhep07(2020)081
    Published for SISSA by Springer Received: February 10, 2020 Revised: May 28, 2020 Accepted: June 9, 2020 Published: July 13, 2020 Impact of uncertainties in the halo velocity profile on JHEP07(2020)081 direct detection of sub-GeV dark matter Andrzej Hryczuk,a Ekaterina Karukes,b Leszek Roszkowskib;a and Matthew Taliab aNational Centre for Nuclear Research, Pasteura 7, Warsaw 02-093, Poland bAstroCeNT, Nicolaus Copernicus Astronomical Center Polish Academy of Sciences, ul. Rektorska 4, Warsaw 00-614, Poland E-mail: [email protected], [email protected], [email protected], [email protected] Abstract: We use the state-of-the-art high-resolution cosmological simulations by Illus- trisTNG to derive the velocity distribution and local density of dark matter in galaxies like our Milky Way and find a substantial spread in both quantities. Next we use our find- ings to examine the sensitivity to the dark matter velocity profile of underground searches using electron scattering in germanium and silicon targets. We find that sub-GeV dark matter search is strongly affected by these uncertainties, unlike nuclear recoil searches for heavier dark matter, especially in multiple electron-hole modes, for which the sensitivity to the scattering cross-section is also weaker. Therefore, by improving the sensitivity to lower ionization thresholds not only projected sensitivities will be boosted but also the dependence on the astrophysical uncertainties will become significantly reduced. Keywords: Cosmology of Theories beyond the SM, Beyond Standard Model ArXiv ePrint: 2001.09156 Open Access, c The Authors. https://doi.org/10.1007/JHEP07(2020)081 Article funded by SCOAP3.
    [Show full text]
  • Dark Matter Vienna University of Technology V2.1
    Dark Matter Vienna University of Technology V2.1 Jochen Schieck and Holger Kluck Institut f¨urHochenergiephysik Nikolsdorfer Gasse 18 1050 Wien Atominstitut derTechnischen Universit¨atWien Stadionallee 2 1020 Wien Wintersemester 2017/18 18.12.2017 2 Contents 1 Introduction 7 1.1 What is "Dark Matter" . .7 1.1.1 Dark . .7 1.1.2 Matter . .7 1.1.3 Cosmology . .7 1.1.4 Massive particles as origin of "Dark Matter" . .7 1.1.5 "Dark Matter" as contribution to the energy density of the universe in Cosmology . .7 1.2 First Indication of observing "Dark Matter" . 13 1.3 Brief Introduction to Cosmology . 15 1.3.1 Special Relativity . 16 1.3.2 Differential geometry . 16 1.3.3 General Relativity . 16 1.3.4 Cosmology . 17 1.3.5 Decoupling of matter and radiation . 18 1.4 The Standard Model of Particle Physics . 19 1.4.1 The matter content of the Standard Model . 19 1.4.2 Forces within the Standard Model . 19 1.4.3 Shortcoming of the Standard Model . 20 1.4.4 Microscopic Behaviour of Gravity . 21 2 Evidence 23 2.1 Dynamics of Galaxies . 23 2.2 Gravitational Lensing . 24 2.2.1 Bullet Cluster . 31 2.3 Cosmic Microwave Background . 33 2.4 Primordial Nucleosynthesis (Big Bang Nucleosynthesis - BBN) . 35 3 Structure Evolution 39 3.1 Structure Formation . 39 3.1.1 The Classic Picture . 39 3.1.2 Structure Formation and Cosmology . 41 3.2 Model of the Dark Matter Halo in our Galaxy . 45 3 4 Unsolved Questions and Open Issues 49 4.1 Core-Cusp Problem .
    [Show full text]
  • Dark Energy Survey Year 3 Results: Multi-Probe Modeling Strategy and Validation
    DES-2020-0554 FERMILAB-PUB-21-240-AE Dark Energy Survey Year 3 Results: Multi-Probe Modeling Strategy and Validation E. Krause,1, ∗ X. Fang,1 S. Pandey,2 L. F. Secco,2, 3 O. Alves,4, 5, 6 H. Huang,7 J. Blazek,8, 9 J. Prat,10, 3 J. Zuntz,11 T. F. Eifler,1 N. MacCrann,12 J. DeRose,13 M. Crocce,14, 15 A. Porredon,16, 17 B. Jain,2 M. A. Troxel,18 S. Dodelson,19, 20 D. Huterer,4 A. R. Liddle,11, 21, 22 C. D. Leonard,23 A. Amon,24 A. Chen,4 J. Elvin-Poole,16, 17 A. Fert´e,25 J. Muir,24 Y. Park,26 S. Samuroff,19 A. Brandao-Souza,27, 6 N. Weaverdyck,4 G. Zacharegkas,3 R. Rosenfeld,28, 6 A. Campos,19 P. Chintalapati,29 A. Choi,16 E. Di Valentino,30 C. Doux,2 K. Herner,29 P. Lemos,31, 32 J. Mena-Fern´andez,33 Y. Omori,10, 3, 24 M. Paterno,29 M. Rodriguez-Monroy,33 P. Rogozenski,7 R. P. Rollins,30 A. Troja,28, 6 I. Tutusaus,14, 15 R. H. Wechsler,34, 24, 35 T. M. C. Abbott,36 M. Aguena,6 S. Allam,29 F. Andrade-Oliveira,5, 6 J. Annis,29 D. Bacon,37 E. Baxter,38 K. Bechtol,39 G. M. Bernstein,2 D. Brooks,31 E. Buckley-Geer,10, 29 D. L. Burke,24, 35 A. Carnero Rosell,40, 6, 41 M. Carrasco Kind,42, 43 J. Carretero,44 F. J. Castander,14, 15 R.
    [Show full text]
  • TECHNICAL ASPECTS of ILLUSTRIS- a COSMOLOGICAL SIMULATION Dr Sheshappa SN1, Megha S Kencha Reddy2 , N Chandana3
    International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 05 | May 2020 www.irjet.net p-ISSN: 2395-0072 TECHNICAL ASPECTS OF ILLUSTRIS- A COSMOLOGICAL SIMULATION Dr Sheshappa SN1, Megha S Kencha Reddy2 , N Chandana3, Ranjitha N4, Sushma Fouzdar5 1Faculty, Dept. of ISE, Sir MVIT, Karnataka, India, [email protected], 2VIII semester, Dept. of ISE, Sir MVIT ---------------------------------------------------------------------------***--------------------------------------------------------------------------- Abstract - THE BIG QUESTION - Where did we come galaxy formation. Recent simulations follow the from and where are we going?Humans have been trying formation of individual galaxies and galaxy populations to figure out the origin of the known universe since the from well-defined initial conditions and yield realistic beginning of time and Since the early part of the 1900s, galaxy properties. At the core of these simulations are the Big Bang theory is the most accepted explanation and detailed galaxy formation models. Of the many aspects has dominated the discussion of the origin and fate of the these models are capable of, they describe the cooling of universe. And the future of the universe can only be gas, the formation of stars, and the energy and hypothesized based on our knowledge but the question momentum injection caused by supermassive black does not seem to get irrelevant anytime in the near holes and massive stars. Nowadays, simulations also future. With the advancement technology and the model the impact of radiation fields, relativistic particles available research, data and techniques like data mining and magnetic fields, leading to an increasingly complex and machine learning the problems can be visualised description of the galactic ecosystem and the detailed through accurate digital representations and simulations evolution of galaxies in the cosmological context.
    [Show full text]
  • The Next Generation of Hydrodynamical Simulations of Galaxy Formation
    HLRS Golden Spike Award 2016 The Next Generation of Hydrodynamical Simulations of Galaxy Formation Scientific background galaxies in clusters and the characteristics of Galaxies are comprised of up to several hundred hydrogen on large scales, and at the same time billion stars and display a variety of shapes and matched the metal and hydrogen content of sizes. Their formation involves a complicated galaxies on small scales. Indeed, the virtual uni- blend of astrophysics, including gravitational, verse created by Illustris resembles the real one hydrodynamical and radiative processes, as well so closely that it can be adopted as a powerful as dynamics in the enigmatic „dark sector“ of laboratory to further explore and characterize the Universe, which is composed of dark mat- galaxy formation physics. This is underscored ter and dark energy. Dark matter is thought to by the nearly 100 publications that have been consist of a yet unidentified elementary parti- written using the simulation thus far. cle, making up about 85% of all matter, whereas dark energy opposes gravity and has induced However, the Illustris simulation also showed an accelerated expansion of the Universe in the some tensions between its predictions and recent past. Because the governing equations observations of the real Universe, calling for both, are too complicated to be solved analytically, improvements in the physical model as well as numerical simulations have become a primary in the numerical accuracy and size of the simu- tool in theoretical astrophysics to study cosmic lations used to represent the cosmos. For exam- structure formation. Such calculations connect ple, one important physical ingredient that was the comparatively simple initial state left behind missing are magnetic fields.
    [Show full text]
  • Evaluating the Viability of Low-Energy Multi-Scattered Neutron
    Evaluation of Low-Energy Multi-scattered Neutron Calibrations for LUX-ZEPLIN A thesis presented for the degree of Bachelor of Science Anna Zuckerman Advisor: Dr. Richard Gaitskell Department of Physics Brown University April 18, 2021 Abstract Over the past several decades, evidence for the existence of dark matter in the uni- verse has become irrefutable. However, the nature of dark matter remains elusive. A prevailing theory is that dark matter takes the form of a Weakly Interacting Mas- sive Particle (WIMP), which could theoretically be detected through various types of experiments. LUX-ZEPLIN (LZ) is one such experiment which seeks to detect WIMPS through the light and charge produced in their collisions with Xenon nuclei in a large underground detector. In order to understand and interpret the results of the LZ experiment, it is important to calibrate the expected light and charge signals for events which deposited known energies into the detector. Thus, various types of calibrations have been developed in the past. However, calibrating for low energies is made difficult by low photon yields, and past calibration techniques have not fully exploited the additional statistics provided by neutrons which scatter multiple times within the detector. This work develops and compares two methods for calibration of the LZ detector at low energies using multi-scattered neutrons. 2 Acknowledgements I would like to thank my advisor Dr. Richard Gaitskell for his guidance and insight over the course of this project. I will take the skills I have learned in this project with me as I continue my academic career. I am also grateful for the help of Casey Rhyne, whose expertise and patience was invaluable to me in starting this project with no prior experience in the field.
    [Show full text]
  • Determining Properties of LEGA-C Galaxies Through Spectral Star-Formation History Reconstruction
    Determining Properties of LEGA-C Galaxies through Spectral Star-formation History Reconstruction Priscilla Chauke Dissertation submitted to the Combined Faculties for the Natural Sciences and for Mathematics of the Ruperto-Carola University of Heidelberg, Germany for the degree of Doctor of Natural Sciences Put forward by Priscilla Chauke Born in Giyani, South Africa Oral Examination: 24 July 2019 Determining Properties of LEGA-C Galaxies through Spectral Star-formation History Reconstruction Referees: Prof. Dr. Arjen van der Wel Prof. Dr. Jochen Heidt Va ka hina “My work amounts to a drop in a limitless ocean. Yet what is any ocean, but a multitude of drops?” -Adapted from David Mitchell, Cloud Atlas Acknowledgements I thank Arjen van der Wel for giving me the opportunity to pursue a PhD at the Max Planck Institut für Astronomy and for being my advisor throughout the years. I thank IMPRS and the DAAD for supporting me financially for the last four years. Lastly, I thank my family and friends for their love, support and encouragement. Abstract Over the past decade, photometric and spectroscopic surveys have enabled us to obtain an integrated view of galaxy evolution. We have measured the cosmic star formation history, and we know that about half of the stars we observe formed before the Universe was half of its current age. However, crucial knowledge of individual galaxy evolution has been limited because the detailed stellar population proper- ties that we know about galaxies, such as ages, metallicities and kinematics, have mostly been obtained from nearby galaxies, which contain mostly old stellar popu- lations.
    [Show full text]