NATIONAL CENTRE FOR NUCLEAR RESEARCH DOCTORAL THESIS Indirect Search for Dark Matter with the Super-Kamiokande Detector Author: Supervisors: Katarzyna FRANKIEWICZ Prof. dr hab. Ewa RONDIO Dr Piotr MIJAKOWSKI A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy April 2018 iii NATIONAL CENTRE FOR NUCLEAR RESEARCH Abstract Doctor of Philosophy Indirect Search for Dark Matter with the Super-Kamiokande Detector by Katarzyna FRANKIEWICZ One of the strategies for dark matter detection is to search for the products of its self-annihilation or decay, such as antimatter, photons, or neutrinos. The later are particularly interesting since they can travel unaffected through the galactic scales. Therefore, neutrinos can provide valuable information on their source location and initial energy spectra related to dark matter annihilation/decay processes. In this dissertation, an indirect search for dark matter induced neutrinos is described. Two types of analyses are performed: the search for neutrinos originating from dark matter annihilation or decay in the Milky Way, and a search for neutrinos from dark matter annihilation inside the Earth’s core. In both presented analyses, atmospheric neutrino data set collected with the Super-Kamiokande detector from 1996 to 2016 is used. The expected dark matter induced signal would manifest itself as an excess in the number of neutrinos originating from the direction corresponding to position of the Galactic Center or the Earth’s core, when compared to the background level of atmospheric neutrinos. The selection criteria which allows us to effectively distin- guish the signal from background are developed in order to estimate the potential contribution of dark matter induced neutrinos to all detected neutrino interactions. No statistically significant excess of neutrinos coming from the direction of the con- sidered sources has been found in the performed analyses. The allowed number of dark matter induced neutrinos which can be contained in the Super-Kamiokande data so far is estimated. In case of the Galactic Center analysis, obtained limits on dark matter induced neutrino flux are related to the upper limits on the velocity- averaged dark matter self-annihilation cross-section, < sAv >, and lower limits on dark matter particle lifetime, t. Limits are set for wide range of masses from 1 GeV up to 10 TeV, and different possible annihilation/decay channels including: nn¯, bb¯, m+m− and W+W−. The influence of the dark matter halo model choice on the ob- tained results is also estimated for the annihilation scenario. For the Earth’s core analysis, the spin-independent WIMP-nucleon scattering cross- section is constrained for dark matter particle masses ranging from 10 to 1000 GeV, and for bb¯, t+t− and W+W− annihilation channels. The limits from performed analysis are compared against the results of other direct and indirect detection ex- periments. High sensitivity of the Super-Kamiokande detector, allows to set the strongest limits among all neutrino experiments up to date. For the dark matter particle mass ∼ 50 GeV, limit for t+t− annihilation channel reaches 10−44 cm2. NATIONAL CENTRE FOR NUCLEAR RESEARCH Streszczenie Jednym ze sposobów na poszukiwanie ciemnej materii jest próba detekcji produk- tów jej anihilacji lub rozpadów, takich jak antymateria, fotony lub neutrina. Te os- tatnie s ˛aszczególnie interesuj ˛ace,poniewaz˙ podczas propagacji w przestrzeni kos- micznej ich kierunek oraz energia pozostaj ˛aniezmienione i mog ˛aone dostarczy´c niezwykle istotnych informacji na temat ´zródłaz którego pochodz ˛a. W ponizszej˙ rozprawie opisane s ˛aposzukiwania neutrin pochodz ˛acychz anihi- lacji lub rozpadów ciemnej materii. Przeprowadzone zostały dwie analizy, poszuki- wanie neutrin pochodz ˛acychz centrum Drogi Mlecznej oraz neutrin pochodz ˛acych z wn˛etrzaZiemi. Do obydwu analiz uzyto˙ przypadków oddziaływa´nneutrin zareje- strowanych w japo´nskimdetektorze Super-Kamiokande, w latach 1996-2016. W´sród wszystkich zarejestrowanych przypadków poszukiwane s ˛ate posiadaj ˛acecharak- terystyki zgodne z potencjalnym wkładem od neutrin produkowanych w wyniku anihilacji lub rozpadów ciemnej materii. Poszukiwanym sygnałem jest nadwyzka˙ neutrin pochodz ˛acaz centrum Galaktyki lub wn˛etrzaZiemi, w stosunku do tła, które stanowi ˛aneutrina produkowane w atmosferze ziemskiej przez promienio- wanie kosmiczne. W przeprowadzonych analizach nie stwierdzono nadmiaru przypadków zwi ˛azane- go z rozpatrywanymi ´zródłami,co pozwoliło na górne ograniczenie liczby przypad- ków mog ˛acychpochodzi´cod ciemnej materii, rejestrowanych w detektorze Super- Kamiokande. Na tej podstawie dla analizy z centrum Galaktyki obliczono górne limity na wazony˙ pr˛edko´sci˛aprzekrój czynny na samo-anihilacj˛eciemnej materii, < sAv >, i dolne limity na czas zycia˙ cz ˛astekciemnej materii, t. Limity te wyz- naczono w szerokim zakresie mas od 1 GeV do 10 TeV i dla czterech rozwazanych˙ kanałów anihilacji/rozpadów ciemnej materii: nn¯, bb¯, m+m− oraz W+W−. W przy- padku anihilacji ciemnej materii dodatkowo rozwazono˙ wpływ wybranego modelu galaktycznego halo na otrzymywane wyniki. W przypadku analizy z centrum Ziemi, wyznaczono górne limity na niezalezny˙ od spinu przekrój czynny na rozpraszanie WIMP-nukleon, sc−N, dla mas cz ˛astek ciemnej materii w zakresie od 10 GeV do 1 TeV,dla trzech rozwazanych˙ kanałów ani- hilacji: bb¯, t+t− oraz W+W−. Dzi˛ekiduzej˙ czuło´scidetektora Super-Kamiokande uzyskano najsilniejsze limity pochodz ˛acez eksperymentów neutrinowych na ´swiecie, si˛egaj˛ace10−44 cm2 dla cz ˛astekciemnej materii o masie ∼ 50 GeV, przy załozeniu˙ anihilacji w pary leptonów t+t−. vii Acknowledgements First of all, I would like to express my deep gratitude to Prof. Ewa Rondio. She guided me through my PhD and was an excellent supervisor. I gained a lot from her vast experience in neutrino physics and I am very happy that I decided to join her group. She would always find time to discuss physics problems and answer any of my questions. Thank you for your support, patience, and encouragement. I am very thankful to Dr Piotr Mijakowski, who helped supervise my work, es- pecially through the last and most difficult part – preparing this dissertation. He also introduced me to the Super-Kamiokande experiment, during the last year of my Masters, what convinced me to pursue a PhD in neutrino physics. In addition to all his help, he always was a good friend. Super-Kamiokande is an exceptional experiment, which provides the opportunity to study a wide range of physics topics. The experiment was built and has been operated with funding from the Japanese Ministry of Education, Culture, Sports, Science and Technology and the U.S. National Science Foundation. Special thanks goes to Kamioka Mining and Smelting Company for helping to host the experiment. I would like to thank all my collaborators for their dedication and engagement in the Super-K experiment. In particular, I want to mention the ATMPD working group conveners: Prof. Ed Kearns and Prof. Masato Shiozawa. They provided excellent leadership and guidance in my analysis group. Moreover, a special thanks to Ed for giving me the opportunity to visit Boston and Fermilab. I had a great time working with his neutrino group at Boston University. Thanks to his help I had a chance to broaden my outlook. I really appreciate his time, support and advice. My greatest debt is to Roger Wendell, who prepared the framework which we all use in the ATMPD working group. He was a tremendous help when dealing with nearly any kind of problems: software, statistics, physics, and much more. My anal- ysis would not have been possible without his support. Thank you for the time you spent with us during the WIMP meetings, and for the hundreds of emails with my questions that you have answered. Lluis Marti is a great friend and colleague, and I really appreciated his company during the long days spent in Mozumi. I enjoyed our conversations very much and I am in debt to you for the delicious coffee and cookies. I would like to thank my family and friends. Thanks to my parents support I was able to take up my studies in Warsaw. My sister and brother were always ready to help me with every problem I have encountered. Krzysztof was not only the best flatmate, but above all, the best friend. I don’t know what I would do without his support and great advice. I would like to thank you for all this good times we had during our PhDs. A special thanks goes to Elzbieta˙ Gaca, my first physics teacher, who aroused my interest in science. I am very grateful for her time and commitment, and having the viii faith in me. If it was not for her I would probably never have thought that I could be a physicist. Last but not the least, I would like to say thank you to Spencer. For everything. For his love and understanding, and always being there for me. My work has been supported by the funds from the National Science Centre, Poland (2015/17/N/ST2/04064) and the European Union (H2020 RISE-GA641540-SKPLUS). ix Contents Abstract iii Streszczeniev Acknowledgements vii 1 Introduction1 2 Dark Matter5 2.1 Observational Evidence...........................5 2.1.1 Galaxy Clusters............................5 2.1.2 Galaxy Rotation Curves.......................5 2.1.3 Gravitational Lensing........................6 2.1.4 Cosmic Microwave Background..................7 2.1.5 Big Bang Nucleosynthesis......................7 2.1.6 Structure Formation.........................8 2.2 Dark Matter Candidates...........................8