DOCSLIB.ORG

DMSAG Report on the Direct Detection of Dark Matter

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
DMSAG Report on the Direct Detection of Dark Matter The Dark Matter Scientific Assessment Group (DMSAG) A Joint Sub-panel of HEPAP and AAAC Report on the Direct Detection and Study of Dark Matter July 5, 2007 Table of Contents Table of Contents................................................................................................................ 2 I. Executive Summary......................................................................................................... 4 Scientific Introduction .................................................................................................... 7 Findings & Recommendations...................................................................................... 11 1. Findings................................................................................................................. 11 2. Recommendations................................................................................................. 15 II. Discussions................................................................................................................... 18 1. Theoretical Motivation.............................................................................................. 18 2. Current State of Technology and Issues to be Resolved........................................... 21 2.1 Axion searches.................................................................................................... 22 2.2 WIMP Searches .................................................................................................. 24 2.2.1 Solid State Detectors........................................................................................ 24 2.2.2 Noble Liquids................................................................................................... 29 Xenon........................................................................................................................ 30 Argon and Neon........................................................................................................ 33 2.2.3 Warm Bubble Detectors................................................................................... 38 2.2.4 Direction-Sensitive Detectors .......................................................................... 40 2.2.5 New Techniques............................................................................................... 41 III. Maintaining U. S. Leadership ..................................................................................... 45 IV. Facilities and Space for the Direct Detection Program .............................................. 47 V. Standards of Proof for Dark Matter ............................................................................. 51 VI. Theory......................................................................................................................... 53 1. Overview................................................................................................................... 53 2. Evidence for the Existence of Dark Matter............................................................... 54 2.1 Clusters of galaxies............................................................................................. 54 2.2 Rotation Curves .................................................................................................. 54 2.3 Lensing................................................................................................................ 55 2.4 Hot Gas in Clusters ............................................................................................. 56 2.5 The Cosmic Microwave Background and other Cosmological Measurements.. 57 2.6 Alternatives to Dark Matter ................................................................................ 58 3. Dark Matter Candidates ........................................................................................... 59 3.1 Axion................................................................................................................... 59 3.2 WIMPs ................................................................................................................ 60 3.3 SuperWIMPs....................................................................................................... 61 3.4 Exotic Candidates ............................................................................................... 61 4. Dark Matter Relic Density........................................................................................ 62 4.1 The WIMP miracle ............................................................................................. 62 4.2 Relic density of a thermal WIMP ....................................................................... 62 4.3 Relic density of neutralinos in supersymmetric models ..................................... 64 4.4 Relic density of a superWIMP............................................................................ 66 4.5 Relic density of axions........................................................................................ 66 5. Direct detection of WIMPs and axions..................................................................... 67 5.1 WIMP-nucleon scattering cross sections............................................................ 67 2 5.2 Target detection rates for various supersymmetric models ................................ 68 5.3 Results from DAMA and spin-dependent direct detection................................. 70 5.4 WIMP mass determination ................................................................................. 71 5.5 Direct detection of axion dark matter ................................................................. 73 6. Distribution of dark matter in the galaxy.................................................................. 73 7. Indirect detection of WIMP dark matter................................................................... 77 7.1 Neutrino Telescopes............................................................................................ 77 7.2 Gamma-ray and Cosmic-ray Telescopes ............................................................ 78 7.3 Relation between direct and indirect dark matter detection................................ 79 8. Dark Matter at Colliders ........................................................................................... 81 8.1 WIMPs at colliders ............................................................................................. 81 8.2 SUSY at colliders................................................................................................ 81 8.3 Extracting astrophysical results from collider measurements. ........................... 82 8.4 SuperWIMPs at Colliders ................................................................................... 85 APPENDIX A – Review of Neutron Backgrounds .......................................................... 86 APPENDIX B – Glossary of Experiments ....................................................................... 91 APPENDIX C – DMSAG Panel Charge .......................................................................... 92 APPENDIX D – DMSAG Panel Members ...................................................................... 94 APPENDIX E – Schedule of Panel Meetings................................................................... 95 3 I. Executive Summary DMSAG has been charged to make a detailed examination of the field of direct detection of dark matter and to consider it in the broader context of particle physics and astrophysics. Some specific guidance was provided in the Charge to DMSAG and includes questions such as these abstracted from the Charge Letter (see Appendix C) and listed immediately below. The progress in experimental techniques in the field is in a state of rapid flux and new levels of sensitivity have been reached; many advances have been made during the course of the work of this sub-panel. From present evidence, further advances can be confidently expected in both the near and long term. The funding for the US direct detection program is currently severely limited and constraining relative to the new opportunities and importance of the field. Consequently, answers to many of the questions posed are often conditional on present and soon to be expected progress in funding and technology. The DMSAG response to the Charge questions are contained in a set of Findings and Recommendations summarized at the end of this Section and repeated in distribution through-out the relevant portions of the text. To aid the reader, we cite in the questions below those Findings, Recommendations and Sections most directly related to a particular question; each may appear more than once. For analyses leading to the Findings and Recommendations the reader is directed to the topical Sections indicated in the Table of Contents. • What are the most promising experimental approaches for the direct detection of dark matter using particle detectors in underground laboratories? Cryogenic techniques based on solid state (phonons and ionization in Ge and Si) and noble liquids (in two-phase systems of both liquid Xe and liquid Ar) are presently leading the field and showing the greatest promise for coherent scattering of WIMPs. Methods with single phase liquid argon and warm liquids or gases are showing significant promise for the future. (The leading axion search, ADMX, does not require underground siting.) See Findings #3, 4, and 5 and Recommendations #3, 4, 5 and 8 and Sec. II-2. • What are: the relative advantages, disadvantages,
Load more

Recommended publications
  • The Planck Satellite and the Cosmic Microwave Background
    The Cosmic Microwave Background, Dark Matter and Dark Energy Anthony Lasenby, Astrophysics Group, Cavendish Laboratory and Kavli Institute for Cosmology, Cambridge Overview The Cosmic Microwave Background — exciting new results from the Planck Satellite Context of the CMB =) addressing key questions about the Big Bang and the Universe, including Dark Matter and Dark Energy Planck Satellite and planning for its observations have been a long time in preparation — first meetings in 1993! UK has been intimately involved Two instruments — the LFI (Low — e.g. Cambridge is the Frequency Instrument) and the HFI scientific data processing (High Frequency Instrument) centre for the HFI — RAL provided the 4K Cooler The Cosmic Microwave Background (CMB) So what is the CMB? Anywhere in empty space at the moment there is radiation present corresponding to what a blackbody would emit at a temperature of ∼ 2:74 K (‘Blackbody’ being a perfect emitter/absorber — furnace with a small opening is a good example - needs perfect thermodynamic equilibrium) CMB spectrum is incredibly accurately black body — best known in nature! COBE result on this showed CMB better than its own reference b.b. within about 9 minutes of data! Universe History Radiation was emitted in the early universe (hot, dense conditions) Hot means matter was ionised Therefore photons scattered frequently off the free electrons As universe expands it cools — eventually not enough energy to keep the protons and electrons apart — they History of the Universe: superluminal inflation, particle plasma,
    [Show full text]
  • Overview of Dark Matter Searches with Liquid Nobles
    Overview of Dark Matter searches with liquid nobles Marcin Kuźniak [email protected] 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 1 Outline ● Dark matter detection ● Noble liquid technology ● Physics landscape – High mass WIMPs ● Spin-independent ● Spin-dependent – Low mass WIMPs ● Status of experimental Ar and Xe programs ● Target complementarity ● Main challenges moving forward ● (Biased) selection of new ideas ● Summary 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 2 DM direct detection signature Direct detection ● Only through rare interactions with ordinary matter ● After the interaction, recoiling nucleus deposits energy (heat, 100 GeV WIMP light, electric charge, ...) in the detector Nuclear recoil spectrum ● featureless, ~exponential ● lower threshold =>more sensitivity ● natural radioactivity is a background astrophysics detector response particle/nuclear physics 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 3 Backgrounds 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 4 Liquid noble detectors Excitation Heat Nuclear recoils (NR) Ar and Xe are used for WIMP detection. ● Ar inexpensive and advantageous for purification and background rejection Why noble elements? ● High light yield, transparent to their own scintillation ● Easy to purify and scalable to very high masses ● (At least) two available detection channels: scintillation and ionization 29-08-2019 Marcin Kuźniak – LIDINE2019, Manchester 5 Single or dual phase DEAP gas DarkSide approach approach Detect primary scintillation light (S1) from the original
    [Show full text]
  • Gammev: Fermilab Axion-Like Particle Photon Regeneration Results
    GammeV: Fermilab Axion-like Particle Photon Regeneration Results William Wester Fermilab, MS222, Batavia IL, USA presented on behalf of the GammeV Collaboration DOI: http://dx.doi.org/10.3204/DESY-PROC-2008-02/wester william GammeV is an axion-like particle photon regeneration experiment conducted at Fermilab that employs the light shining through a wall technique. We obtain limits on the cou- pling of a photon to an axion-like particle that extend previous limits for both scalar and pseudoscalar axion-like particles in the milli-eV mass range. We are able to exclude the axion-like particle interpretation of the anomalous PVLAS 2006 result by more than 5 standard deviations. 1 Introduction The question, What are the particles that make up the dark matter of the universe?, is one of the most fundamental scientific questions today. Besides weakly interacting massive particles (WIMPs) such as neutralinos, axion-like particles or other weakly interacting sub-eV particles (WISPs) are highly motivated dark matter particle candidates since they have properties that might explain the cosmic abundance of dark matter. The milli-eV mass scale is of particular interest in modern particle physics since that mass scale may be constructed with a see-saw between the Planck and TeV mass scales, and may be related to neutrino mass differences, the dark energy density expressed in (milli-eV)4, and known dark matter candidates such as gravitinos and axion-like particles. In 2006, the PVLAS experiment reported [1] anomalous polarization effects in the presence of a magnetic field including polarization rotation and el- lipticity generation that could be interpreted as being mediated by an axion-like particle in the milli-eV mass range with a unexpectedly strong coupling to photons.
    [Show full text]
  • Parallel Sessions
    Identification of Dark Matter July 23-27, 2012 9th International Conference Chicago, IL http://kicp-workshops.uchicago.edu/IDM2012/ PARALLEL SESSIONS http://kicp.uchicago.edu/ http://www.nsf.gov/ http://www.uchicago.edu/ http://www.fnal.gov/ International Advisory Committee Daniel Akerib Elena Aprile Rita Bernabei Case Western Reserve University, Columbia University, USA Universita degli Studi di Roma, Italy Cleveland, USA Gianfranco Bertone Joakim Edsjo Katherine Freese University of Amsterdam Oskar Klein Centre / Stockholm University of Michigan, USA University Richard Gaitskell Gilles Gerbier Anne Green Brown University, USA IRFU/ CEA Saclay, France University of Nottingham, UK Karsten Jedamzik Xiangdong Ji Lawrence Krauss Universite de Montpellier, France University of Maryland, USA Arizona State University, USA Vitaly Kudryavtsev Reina Maruyama Leszek Roszkowski University of Sheffield University of Wisconsin-Madison University of Sheffield, UK Bernard Sadoulet Pierre Salati Daniel Santos University of California, Berkeley, USA University of California, Berkeley, USA LPSC/UJF/CNRS Pierre Sikivie Daniel Snowden-Ifft Neil Spooner University of Florida, USA Occidental College University of Sheffield, UK Max Tegmark Karl van Bibber Kavli Institute for Astrophysics & Space Naval Postgraduate School Monterey, Research at MIT, USA USA Local Organizing Committee Daniel Bauer Matthew Buckley Juan Collar Fermi National Accelerator Laboratory Fermi National Accelerator Laboratory Kavli Institute for Cosmological Physics Scott Dodelson Aimee
    [Show full text]
  • Circular and Linear Magnetic Birefringences in Xenon at =1064 Nm
    Downloaded from orbit.dtu.dk on: Oct 06, 2021 Circular and linear magnetic birefringences in xenon at =1064 nm Cadene, Agathe; Fouche, Mathilde; Rivere, Alice; Battesti, Remy; Coriani, Sonia; Rizzo, Antonio; Rizzo, Carlo Published in: Journal of Chemical Physics Link to article, DOI: 10.1063/1.4916049 Publication date: 2015 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Cadene, A., Fouche, M., Rivere, A., Battesti, R., Coriani, S., Rizzo, A., & Rizzo, C. (2015). Circular and linear magnetic birefringences in xenon at =1064 nm. Journal of Chemical Physics, 142(12), [124313]. https://doi.org/10.1063/1.4916049 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Circular and linear magnetic birefringences in xenon at λ = 1064 nm Agathe Cadène, Mathilde Fouché, Alice Rivère,
    [Show full text]
  • The PICASSO Dark Matter Physics Program at SNOLAB
    33RD INTERNATIONAL COSMIC RAY CONFERENCE,RIO DE JANEIRO 2013 THE ASTROPARTICLE PHYSICS CONFERENCE The PICASSO Dark Matter Physics Program at SNOLAB A.J. NOBLE1 FOR THE PICASSO COLLABORATION: S. ARCHAMBAULT2, E. BEHNKE3, P. BHATTACHARJEE4, S. BHATTACHARYA4, X. DAI1, M. DAS4, A. DAVOUR1, F. DEBRIS2, N. DHUNGANA5, J. FARINE5, S. GAGNEBIN6, G. GIROUX2, E. GRACE3, C. M. JACKSON2, A. KAMAHA1, C. KRAUSS6, S. KUMARATUNGA2, M. LAFRENIRE2, M. LAURIN2, I. LAWSON7, L. LESSARD2, I. LEVINE3, C. LEVY1, R. P. MACDONALD6, D. MARLISOV6, J.-P. MARTIN2, P. MITRA6, A. J. NOBLE1, M.-C. PIRO2, R. PODVIYANUK5, S. POSPISIL8, S. SAHA4, O. SCALLON2, S. SETH4, N. STARINSKI2, I. STEKL8, U. WICHOSKI5, T. XIE1, V. ZACEK2 1 Department of Physics, Queens University, Kingston, K7L 3N6, Canada 2 Departement´ de Physique, Universite´ de Montreal,´ Montreal,´ H3C 3J7, Canada 3 Department of Physics & Astronomy, Indiana University South Bend, South Bend, IN 46634, USA 4 Saha Institute of Nuclear Physics, Centre for AstroParticle Physics (CAPP), Kolkata, 700064, India 5 Department of Physics, Laurentian University, Sudbury, P3E 2C6, Canada 6 Department of Physics, University of Alberta, Edmonton, T6G 2G7, Canada 7 SNOLAB, 1039 Regional Road 24, Lively ON, P3Y 1N2, Canada 8 Institute of Experimental and Applied Physics, Czech Technical University in Prague, Prague, Cz-12800, Czech Republic [email protected] Abstract: PICASSO is a dark matter search experiment currently operational at the SNOLAB International Facility for Astroparticle Physics, located 2 km underground in Sudbury, Canada. PICASSO is based on the superheated bubble technique. With good control of radiological backgrounds and a detector design that stabilizes the superheated liquid even when very close to the critical temperature, PICASSO has achieved very low nuclear recoil thresholds.
    [Show full text]
  • European Astroparticle Physics Strategy 2017-2026 Astroparticle Physics European Consortium
    European Astroparticle Physics Strategy 2017-2026 Astroparticle Physics European Consortium August 2017 European Astroparticle Physics Strategy 2017-2026 www.appec.org Executive Summary Astroparticle physics is the fascinating field of research long-standing mysteries such as the true nature of Dark at the intersection of astronomy, particle physics and Matter and Dark Energy, the intricacies of neutrinos cosmology. It simultaneously addresses challenging and the occurrence (or non-occurrence) of proton questions relating to the micro-cosmos (the world decay. of elementary particles and their fundamental interactions) and the macro-cosmos (the world of The field of astroparticle physics has quickly celestial objects and their evolution) and, as a result, established itself as an extremely successful endeavour. is well-placed to advance our understanding of the Since 2001 four Nobel Prizes (2002, 2006, 2011 and Universe beyond the Standard Model of particle physics 2015) have been awarded to astroparticle physics and and the Big Bang Model of cosmology. the recent – revolutionary – first direct detections of gravitational waves is literally opening an entirely new One of its paths is targeted at a better understanding and exhilarating window onto our Universe. We look of cataclysmic events such as: supernovas – the titanic forward to an equally exciting and productive future. explosions marking the final evolutionary stage of massive stars; mergers of multi-solar-mass black-hole Many of the next generation of astroparticle physics or neutron-star binaries; and, most compelling of all, research infrastructures require substantial capital the violent birth and subsequent evolution of our infant investment and, for Europe to remain competitive Universe.
    [Show full text]
  • Dark Matter the Invisible Material
    Dark matter The invisible material Our universe holds everything we know and everything we are still figuring out. For years, physicists around the world have studied our universe to better understand its nature and its future. They have found that we only understand about 4% of the matter and energy in our universe (including stars, planets, and hot gas). The other 96% is invisible to us and 23% of this invisible material is named dark matter. If dark matter is invisible, how do we know it exists? To answer this, we go back to the 1930s when physicist Fritz Zwicky Galaxy cluster* coined the term dark matter while studying galaxy clusters. Galaxy clusters have up to thousands of galaxies (like our Milky Way for example) held together by gravity. When Dr. Zwicky calculated the total visible mass of galaxies in the Coma cluster, he found that it was not enough to create the gravity needed to hold the cluster together (mass causes gravity). He concluded that there must be an invisible material causing the extra gravity: dark matter. Now fast forward to the 1970s when Vera Rubin studied galaxy rotation curves. According to Newton’s laws, when objects rotate around a common centre, the ones furthest from the centre move more slowly Gravitational lens – than those near it. Otherwise, the furthest objects would fly off. Dr. Rubin galaxies look long found that stars in galaxies do not follow this rule. In fact, stars at the and distorted* outer edges of galaxies move at about the same rate as those near the centre.
    [Show full text]
  • A Propensity for Genius: That Something Special About Fritz Zwicky (1898 - 1974)
    Swiss American Historical Society Review Volume 42 Number 1 Article 2 2-2006 A Propensity for Genius: That Something Special About Fritz Zwicky (1898 - 1974) John Charles Mannone Follow this and additional works at: https://scholarsarchive.byu.edu/sahs_review Part of the European History Commons, and the European Languages and Societies Commons Recommended Citation Mannone, John Charles (2006) "A Propensity for Genius: That Something Special About Fritz Zwicky (1898 - 1974)," Swiss American Historical Society Review: Vol. 42 : No. 1 , Article 2. Available at: https://scholarsarchive.byu.edu/sahs_review/vol42/iss1/2 This Article is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Swiss American Historical Society Review by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Mannone: A Propensity for Genius A Propensity for Genius: That Something Special About Fritz Zwicky (1898 - 1974) by John Charles Mannone Preface It is difficult to write just a few words about a man who was so great. It is even more difficult to try to capture the nuances of his character, including his propensity for genius as well as his eccentric behavior edging the abrasive as much as the funny, the scope of his contributions, the size of his heart, and the impact on society that the distinguished physicist, Fritz Zwicky (1898- 1974), has made. So I am not going to try to serve that injustice, rather I will construct a collage, which are cameos of his life and accomplishments. In this way, you, the reader, will hopefully be left with a sense of his greatness and a desire to learn more about him.
    [Show full text]
  • Light Dark Matter in a Minimal Extension with Two Additional Real Singlets
    PHYSICAL REVIEW D 103, 015010 (2021) Light dark matter in a minimal extension with two additional real singlets Markos Maniatis * Centro de Ciencias Exactas and Departamento de Ciencias Básicas, UBB, Avenida Andres Bello 720, 3780000 Chillán, Chile (Received 24 August 2020; accepted 12 December 2020; published 8 January 2021) The direct searches for heavy scalar dark matter with a mass of order 100 GeV are much more sensitive than for light dark matter of order 1 GeV. The question arises whether dark matter could be light and has escaped detection so far. We study a simple extension of the Standard Model with two additional real singlets. We show that this simple extension may provide the observed relic dark matter density, does neither disturb big bang nucleosynthesis nor the cosmic microwave background radiation observations, and fulfills the conditions of clumping behavior for different sizes of Galaxies. The potential of one Standard Model–like Higgs-boson doublet and the two singlets gives rise to a changed Higgs phenomenology, in particular, an enhanced invisible Higgs-boson decay rate is expected, detectable by missing transversal momentum searches at the ATLAS and CMS experiments at CERN. DOI: 10.1103/PhysRevD.103.015010 I. INTRODUCTION collisions. In particular, in this way a DM candidate may enhance the invisible decay rate of a SM-like Higgs boson. Recently it has been reported [1] that the NGC1052–DF2 Note that in the SM the only invisible decay channel of galaxy with a stellar mass of approximately 2 × 108 solar the Higgs boson (h) is via two electroweak Z bosons masses has a rotational movement in accordance with its which subsequently decay into pairs of neutrinos (ν), that observed mass.
    [Show full text]
  • Direct Dark Matter Searches: the Experimental Context
    Conseil Scientifique de l’IN2P3, 25-26 octobre 2018 Direct Dark Matter searches: the experimental context Alessandra Tonazzo (APC, Université Paris-Diderot) Direct search for WIMPs : current status ���������� ��������� -�� -� �� ����-� �� - ] ��� ] � ����� -�� -� �� �� �� [ �� [ ������ ������ �� �� σ σ -�� -��� -� �� ����� �� - -�� �� �������� � �� -���� ��� ���� -�� - �������� ������� -�� � -� ������� �� �� - - ��� ��-�� ������� ��-�� ���� ������ ���� ������ ��-�� ��-�� ���� ����� ������� ������� �� ����� ����� ���������� �� ������� ��� �������� ��������� ������������ ���������� ������� ��������� �� ��������� coherent ν scattering on Xe ��-�� � �� ��� ���� A personal selection ���� ������ ���� [���/��] CS IN2P3, 25/10/2018 A. Tonazzo - World context for direct dark matter searches 2 Direct detection of WIMPs WIMP <v>˜220 km/s Nuclear Recoil detectable signal ER < 100 keV Rate: ~1 evt/(ton*year) for σ~10-47cm2 in noble liquids CS IN2P3, 25/10/2018 A. Tonazzo - World context for direct dark matter searches 3 Backgrounds WIMP • Cosmic rays and cosmogenic neutron neutrons/isotopes neutrino • Radioactivity, natural (238U,232Th,235U,222Rn,...) or anthropogenic Nuclear Recoil (85Kr,137Cs,...), from detector elements e, γ • Neutrinos (solar, atmospheric, diffuse SN) scattering coherently off nuclei (”neutrino floor”) Electron Recoil Possibility for background discrimination CS IN2P3, 25/10/2018 A. Tonazzo - World context for direct dark matter searches 4 Direct detection of WIMPs : signatures • Anomalous rate of low-energy nuclear recoils •
    [Show full text]
  • Letter of Interest Cosmic Probes of Ultra-Light Axion Dark Matter
    Snowmass2021 - Letter of Interest Cosmic probes of ultra-light axion dark matter Thematic Areas: (check all that apply /) (CF1) Dark Matter: Particle Like (CF2) Dark Matter: Wavelike (CF3) Dark Matter: Cosmic Probes (CF4) Dark Energy and Cosmic Acceleration: The Modern Universe (CF5) Dark Energy and Cosmic Acceleration: Cosmic Dawn and Before (CF6) Dark Energy and Cosmic Acceleration: Complementarity of Probes and New Facilities (CF7) Cosmic Probes of Fundamental Physics (TF09) Astro-particle physics and cosmology Contact Information: Name (Institution) [email]: Keir K. Rogers (Oskar Klein Centre for Cosmoparticle Physics, Stockholm University; Dunlap Institute, University of Toronto) [ [email protected]] Authors: Simeon Bird (UC Riverside), Simon Birrer (Stanford University), Djuna Croon (TRIUMF), Alex Drlica-Wagner (Fermilab, University of Chicago), Jeff A. Dror (UC Berkeley, Lawrence Berkeley National Laboratory), Daniel Grin (Haverford College), David J. E. Marsh (Georg-August University Goettingen), Philip Mocz (Princeton), Ethan Nadler (Stanford), Chanda Prescod-Weinstein (University of New Hamp- shire), Keir K. Rogers (Oskar Klein Centre for Cosmoparticle Physics, Stockholm University; Dunlap Insti- tute, University of Toronto), Katelin Schutz (MIT), Neelima Sehgal (Stony Brook University), Yu-Dai Tsai (Fermilab), Tien-Tien Yu (University of Oregon), Yimin Zhong (University of Chicago). Abstract: Ultra-light axions are a compelling dark matter candidate, motivated by the string axiverse, the strong CP problem in QCD, and possible tensions in the CDM model. They are hard to probe experimentally, and so cosmological/astrophysical observations are very sensitive to the distinctive gravitational phenomena of ULA dark matter. There is the prospect of probing fifteen orders of magnitude in mass, often down to sub-percent contributions to the DM in the next ten to twenty years.
    [Show full text]