Supernova Model Discrimination with Hyper-Kamiokande Jost Migenda University of Sheffield Department of Physics & Astronomy arXiv:2002.01649v1 [astro-ph.IM] 5 Feb 2020 A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy November 2019 However big you think supernovae are, they’re bigger than that. — Donald Spector [1] Supervisors: Dr. Susan L. Cartwright Dr. Matthew S. Malek Declaration I, the author, confirm that the Thesis is my own work. I am aware of the University’s Guidance on the Use of Unfair Means1. This work has not been previously been presented for an award at this, or any other, university. ∗ ∗ ∗ Due to the nature of a large experiment like Hyper-Kamiokande, this research is built on the contributions of hundreds of scientists. In the following, I will describe the extent of my personal contributions. Chapter 1 provides an overview over previous research on supernovae and neu- trinos, summarising the work of many generations of scientists. The detector design described in chapter 2 is the result of the combined work of the whole Hyper- Kamiokande proto-collaboration. Both chapters do not constitute original research of this thesis. Chapter 3 describes a software toolchain for generating, simulating and recon- structing supernova neutrino interactions in Hyper-Kamiokande. While I have contributed to all parts of this toolchain, my main contributions are the event gen- erator sntools and the energy reconstruction. Both were largely developed by me, with some contributions by Liz Kneale and Owen Stone as part of undergraduate research projects under my co-supervision. The data analysis performed in chapter 4 constitutes original research performed solely by me. Finally, chapter 5 summarizes the results of this work and gives an outlook on future research. 1https://www.sheffield.ac.uk/ssid/unfair-means iii If I have seen further it is by standing on the shoulders of giants. Isaac Newton Acknowledgements First and foremost, I would like to thank my supervisors, Susan Cartwright and Matthew Malek. The story of this PhD started in the spring of 2015, when I discovered the thesis topic “Supernova Neutrinos in TITUS and Hyper-K” being advertised on the Univer- sity of Sheffield’s website. The official application deadline had already passed, but since the topic matched my interests so perfectly, I wrote an email to Susan anyway. Without hesitation, she invited me to start a PhD in Sheffield. In the following years, missing that application deadline has led to an unusual funding situation. However, Susan always went above and beyond to find the resources to allow me to attend numerous conferences, workshops, collaboration meetings and summer schools across three continents. Time and again, her incredibly sharp mind and attention to detail have also helped me with issues ranging from physics to data analysis to proofreading this thesis. Matthew is that legendary supervisor any PhD student can barely dare dream of—a brilliant physicist and an equally wonderful human being, all in one person. He has been my North Star during this research, always being available to provide guidance and direction while, at the same time, giving me the freedom to find my own way. His intimate knowledge of the science involved in this research and familiarity with the scientists working on it have been invaluable resources for me. At the same time, Matthew has fostered my outreach efforts, hobbled next to me on the Big Walk, called me a gentleman2, invited me to a late-night cup of tea in the Austin Room and has always been available when I wanted to chat about important or not-so-important topics. His encouragement has been genuine and his criticism fair and constructive (and more accurate than I wanted to admit at the time). During the past four years, Marcus O’Flaherty has been almost like a brother to me. He helped me find my feet when I first arrived, shared in the joys and tribulations of being a PhD student, accompanied me to my first conference and summer school and, during my stay at Fermilab in August 2017, even let me stay in his living room for over two weeks. If Marcus is like an older brother, Liz Kneale is probably most akin to a younger sister. When we first met in 2016, I was equal parts nervous and honoured to co-supervise her project work contributing to an early version of sntools. In the 2and apologized afterwards v years since, I have seen her grow into an experienced neutrino physicist and spent many lunch breaks with her discussing physics and life in general, which has been incredibly enjoyable. Completing the list of my academic siblings is Owen Stone. I started co- supervising him during a summer project in 2017 and was happy to see him return to work with Matthew and me for several other projects since. I’m really excited that he has now started a PhD in our group and can’t wait to learn what he will discover! While I cannot list them all by name here, there are so many other members of the neutrino group, the HEP group and the whole department who have created a wonderful atmosphere that has truly allowed me to feel comfortable and do fantastic work here. I’m also grateful to the staff in F10 (and elsewhere) without whom the group and the whole department couldn’t function. Finally, writing the early parts of this thesis would have been much slower and more frustrating if it hadn’t been for Connor Heapy’s help as part of the thesis mentoring programme. ∗ ∗ ∗ Beyond Sheffield, I am grateful to the hundreds of members of the Hyper- Kamiokande proto-collaboration around the world, without whom none of this work could exist. I particularly want to thank the leaders and fellow members of the astrophysics and software working groups for many interesting discussions and frequent feedback; Yano-san for patiently answering countless questions about low-energy physics and the software tools; Francesca Di Lodovico for giving me opportunities to contribute more than just my own research to the collaboration; and the group at Kobe University for their hospitality during my visit in February/March 2017. Starting in mid-2017, I also spent a few months working as part of the DUNE collaboration. While this did not produce any tangible results, I am grateful to the collaboration—particularly Kate Scholberg and the whole SNB/LE group—for welcoming me with open arms and teaching me so much about LAr TPCs. For giving me access to the supernova models used in this thesis and patiently answering all my related questions, I am grateful to MacKenzie Warren, Nakazato- san, Totani-san, Adam Burrows, David Vartanyan and Irene Tamborra. I would like to thank the organizers and participants of the various conferences, workshops and summer schools I have had the pleasure to attend. Georg Raffelt introduced me to supernova neutrinos during my Master’s thesis, which led me to where I am today—even though neither of us could have seen this coming at the start. Thank you, Georg. ∗ ∗ ∗ vi All of this work has been made so much easier by powerful tools that were often a joy to use: online resources like InspireHEP, arXiv and NASA’s Astrophysics Data System; software like Python, the MacTeX distribution, Keynote and BBEdit; and, of course, the operating system and trusty laptop on which all this software runs. Thanks to the people who created all these tools. ∗ ∗ ∗ The past four years contained not only the work reflected in this thesis. They also contained copious amounts of joy and sorrow, infinite jest and depths of despair, love and heartbreak and beauty and wonder and one thousand green-tinted photos of a rapper. One day, all these moments will be lost in time, like tears of a unicorn lost in the rain. But today is not that day. Today, as I am writing these lines, all these moments mean the world to me. Thank you to my family: Angela. Thomas. Jakob. Uwe. To Alex and to Lisa: We’ve known each other for over a decade now and I love you both dearly—in different ways yet equally much. To Mel, for making me feel at home. To my “cuddly friends”, both current and former. To the CdE and all the wonderful people who make its events so special. To Ashley, Izzy & Jess, Ida, Abbie and Jenna for being incredibly generous with your time and advice and everything else. To the whole LGBTSTEM community, particularly Beth and Alfredo and the many others who work tirelessly to build something wonderful. To Héloïse, Catherine, Matt, Katherine, Morri, Burkhard & John and all the many, many others who brightened up my days with open ears, deep conversations over a cup of tea, heartfelt messages and—literal or figurative—rainbows. To everyone who supported my outreach efforts—whether as organizers, as speakers or simply by attending and getting excited about the universe. To all those people I only know from afar, yet who make my life and work beautiful with their writing or podcasts or music or videos. Finally, to the many giants upon whose shoulders I stand. vii Abstract Supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants—neutron stars and black holes—are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to ob- serve the neutrino flux from the next galactic supernova in unprecedented detail.