The Dark Matter Landscape

Rocky Kolb

Radiation: Chemical Elements: 0.005% (other than H & He) 0.025% Neutrinos: ne 0.17% nµ nt Stars: 0.8%

H & He: gas 4%

? Dark Matter: 25%

? Dark Energy: 70% Precision (but not accurate) cosmology

Epicycle Mars

Deferent Eccentric A precision (but not accurate) cosmological ´ model that agreed with observations for Earth Equant 1300 years!

We have to discover how dark matter, dark energy, inflation, the baryon asymmetry, t =0, is grounded in physical law. 95% of mass-energy in the universe is dark! 25% Dark Matter 70% Dark Energy

Dark matter usually assumed to be • Non-baryonic (not quark nuggets, 30 M⊙ Black Holes, planets, little stars, etc.) • Cold (slowly moving) • Dissipationless Is • Not self-interacting this • Associated with all galaxies and other structures true? • A particle • Stable • No strong or electromagnetic interactions

Two philosophies: Simplicio Salviati

I don’t care about the nature of dark I care about the nature of dark matter matter, as long as it is dark, cold, & because it must exist for a reason other dissipationless (CDM) I can calculate than to be a part of Simplicio’s code. (simulate) its role in the evolution of Feynman: “Nature weaves its tapestry structure and understand necessary from the longest threads.” What is the astrophysics. dark matter thread? Physics crucial for cosmology

"Until cosmology and particle physics can be brought together in the same context there is not much hope for real progress in cosmology."

Bohr’s 1939 reply to question after a Berkeley colloquium (Philip Morrison, private communication) Astronomy crucial for physics

"How helpful to us is astronomy's pedantic accuracy, which I used to secretly ridicule!"

Einstein’s statement to Arnold Sommerfeld on December 9, 1915 (regarding measurements of the advance of the perihelion of Mercury) Dark Matter particle mass range

Mass Range for Particle Dark Matter m 10-22 eV: de Broglie wavelength smaller than dark-matter dominated objects m 1019 GeV: mass less than Planck mass m few eV: if fermion (exclusion principle)

If thermal freeze-out m me : annihilation to SM particles m 100 TeV: annihilation cross section too small for larger masses

Is Dark Matter a Particle Or a Wave? m 1 eV: occupation number in de Broglie-wavelength volume 1 ® WAVE m 1 eV: occupation number in de Broglie-wavelength volume 1 ® PARTICLE Dark Matter particle mass range

19 Plancktons: m ~ mPlanck = 10 GeV

10 13 WIMPzillas: m ~ minflaton = 10 – 10 GeV

Supermassive: m > 100 TeV

WIMP range: mproton < m < 1 TeV

Light dark matter: melectron < m < mproton

Ultralight dark matter: m < 1 eV

Fuzzy dark matter: m ~ 10-22 eV Particle dark-matter debate: need > two nights for debate

• (sub-) eV mass neutrinos (WIMPs exist!) (hot) • sterile neutrinos, gravitinos (warm) thermal relics, or decay of or oscillation from • lightest supersymmetric particle (cold) thermal relics • lightest Kaluza-Klein particle (cold) • Bose-Einstein condensates from phase • axions, axion miniclusters transitions • solitons (Q-balls, B-balls, …) nonthermal relics • supermassive WIMPZILLAs from inflation

Mass Interaction Strength 10-22 eV (10-56 g) Bose-Einstein only gravitational: WIMPzillas -8 +25 10 Mʘ (10 g) axion miniclusters strongly interacting: B balls Most popular paradigm: cold thermal relic* • DM abundance set by creation/annihilation with standard-model particles • Equilibrium abundance of DM determined by M / T (no asymmetry) • DM species final abundance determined by “freeze-out” of equilibrium, or “freeze-in” to final abundance Freeze-out

nncg Freeze-in Equilibrium

• Freeze-out/in: interplay between mTc particle physics (DM—SM interactions) and expansion rate (gravity)

* An object of particular veneration. Dark Matter talks to Standard Model through a PORTAL

DM (c) SM

gc g PORTAL

DM (c) SM

Usually assume PORTAL is some mediator more massive than dark matter

Evolution of DM abundance set by Boltzmann equation:

22 nHn+=3v--s A ( nnEQ )

NR annihilation cross m2 � v = s v = 22 c Tm � section × Møller flux A ggc 4 c á …thermal average…ñ M Final freeze-out abundance:

sAv Wh2 » 0.12 ´ 10-36 cm2

2 22mc ��v = gg assume gc » g » e ; M » few ´ mc c M 4 2 -36 2 a ��v = 10 cm = Lawyer voiceover: (150 GeV) 2 • velocity dependence • resonances weak scale! • co-annihilation Weakly Interacting Massive Particle (WIMP) • log dependence on M • decay production • spin-dependence • asymmetries • … s = 10 -36 cm2: the WIMP “Miracle”

mir·a·cle \ˈmir-i-kəl \ S. Harris noun

1 : an extraordinary event manifestingI think you should be more divine intervention in humanexplicit affairs here in step two

WIMP hypothesis predicts WIMP hypothesis relates DM mass range, and DM mass and DM—SM interaction strength DM interactions (But not 6:1) to a “known” scale Direct detection—spin independent picobarn

femtobarn Completed Mqq-2 cgµµ c× g

attobarn

Projected zeptobarn neutrino floor

yoctobarn

http://cdms.berkeley.edu/limitplots/mm/WIMP_limit_plotter.htmlgc

Completed Projected Direct detection—spin dependent

Completed nanobarn

picobarn Mqq-25cgµµ c× g 5 Projected femtobarn neutrino floor

attobarn

http://cdms.berkeley.edu/limitplots/mm/WIMP_limit_plotter.html zeptobarn Direct, Indirect, Accelerator

Where is the WIMP?

No signal in direct (DAMA?), indirect (g – ray excess?), or accelerator searches.

Even more troubling, no sign of BSM physics at LHC.

This doesn’t seem to be the decade of the WIMP!!!

(Perhaps) DM is NOT a WIMP (cold thermal relic), time to focus elsewhere

go lighter go ultralight go ultraheavy boldly go where no dark sector axion, dark photon WIMPzilla one has gone before Top down: discover “Theory of Everything” (ToE)*

Supersymmetry, supergravity, grand unification, string theory, M theory, multiverse, landscape, etc.

*ToE — Theory omitting Evidence Solves YUGE problems by pure thought (à la ancient Greeks) without making boring testable predictions. Who needs observational verification? Sad. EXPERIMENTS ARE FOR LOSERS!

MAGA Program in Physics MAGA: #MakeAstrophysicsGreekAgain. Let 103 flowers bloom? We need a disruption

Will it come from a. a mile underground? b. 300 feet underground? c. 7200 feet above ground? d. space? Disruptive particle discoveries

1. Dark matter at LHC.

2. Something/anything new at LHC.

3. Axion discovered.

4. Dark sector in fixed-target experiments.

5. Dark photon.

6. Dark matter underground.

7. (g - 2)µ not in line with SM prediction.

8. Unexpected neutrino mass. Dark matter "Nothing more can be done by the theorists. In this matter it is only you, the astronomers, who can perform a simply invaluable service to theoretical physics."

Einstein in August 1913 to Berlin astronomer Erwin Freundlich encouraging him to mount an expedition to measure the deflection of light by the sun. Disruptive astro observations

1. LIGO/VIRGO discovers black hole less than Chandrasekhar mass (say, less than 1 M).

2. Observations from high- z (z 10) universe ® assembly of galaxies not as expected in CDM.

3. A g – ray excess in many systems (dSphs, galactic center, LMC, M-31, ) proportional to J factor.

4. There really is an unexplained universal 3.5 keV line.

5. Anything that can’t be explained by CDM simulations. 1. Self-interactions 2. Warm component 3. Small-scale structure LSST well-positioned 4. Miniclusters (esp. LSST + JWST + ELTs ) 5. Lensing 6. Minimum halo mass 7. Core/cusp

6. Failure of LCDM 1. Tension/Hypertension in H0 2. Tension in s8 Basic Research Needs (BRN) Study for Dark-Matter Small Projects

NGC 4414 (HST) Dark Matter CPAC, ANL

Summary of the High Energy Physics Workshop on Basic Research Needs for Dark-Matter Small Projects New Initiatives October 15 – 18, 2018 DMBRN Charge

• Identify science opportunities for new directions and areas of parameter space that will provide high impact science return and advancement for DM particle detection.

• Determine the high impact science opportunities which could be pursued by small projects (approximately $5M to $15M in Total Project Cost) that could be ready to start within the next few years, and in which DOE’s laboratory infrastructure and/or technology capabilities are required to be realized.

• Suggest opportunities that could be pursued by future small projects, which also require DOE capabilities, but need further technology development before project initiation.

Note that the priority opportunities should not include significant upgrades of current large projects or development of new large projects in the HEP program, nor small contributions to large projects supported by other sources.

The BRN did not: • Recommend anything • Advise DOE • Prioritize projects • Rank PRD opportunities

The BRN did: • Describe SCIENCE OPPORTUNITIES Basic Research Needs (BRN) Study for Dark-Matter Small Projects

Two co-chairs, 10 panel leads (conveners), 27 panel members

Co-chairs: Accelerator Panel Members: Ultralight Panel Members: Rocky Kolb (Chicago) Marco Battaglieri (INFN) Karl van Bibber (Berkeley) Harry Weerts (Argonne) Brian Batell (Pitt) Kent Irwin (SLAC) Stefania Gori (Santa Cruz) Tim Kovachy (Northwestern) Accelerator Panel Leads: Gordon Krnjaic (FNAL) Surjeet Rajendran (Berkeley) Natalia Toro (SLAC) Tim Nelson (SLAC) Gray Rybka (U Washington) Richard Van de Water (LANL) Adam Ritz (Victoria) Alex Sushkov (Boston U) Philip Schuster (SLAC) Lindley Winslow (MIT) Direct Detection Panel Leads: Rex Tayloe (Indiana) Rouven Essig (Stony Brook) Nhan Tran (FNAL) Dan McKinsey (Berkeley) Kathryn Zurek (LBNL) Direct Detection Panel Members: Cross Cut Panel Members: Adam Bernstein (LLNL) Roni Harnik (FNAL) Ultralight Panel Leads: Jodi Cooley (SMU) Yoni Kahn (Chicago) Aaron Chou (FNAL) Eric Dahl (Northwestern) Mariangela Lisanti (Princeton) Peter Graham (Stanford) Sunil Golwala (Caltech) Cross Cut Panel Leads: Scott Hertel (U Mass) Reina Marayama (Yale) Juan Estrada (FNAL) Joe Incandela (Santa Barbara) Matt Pyle (Berkeley) Javier Tiffenberg (FNAL) Tim Tait (Irvine) Three Priority Research Directions Low-Mass DM

DM (c) SM

gc g

DM (c) SM 222 2 2mggcc - 36 2 s A vggc 42 10 cm Mmc

• mc smaller ® gc × g must be smaller

SM SM • g must be small to avoid undetected g g

new SM force. Can take gc ~ e SM SM

• Example: dark photon mediator kinetically mixed with SM photon. Create and detect dark-matter particles and associated forces below the proton mass, leveraging DOE accelerators. Create and detect dark-matter particles and associated forces below the proton mass, leveraging DOE accelerators.

Green areas are high-priority parameter space identified at BRN, singled out by thermal models for the origin of dark matter – many are uniquely explored at accelerators Detect individual galactic dark-matter particles below the proton mass through interactions with advanced, ultra-sensitive detectors Detect individual galactic dark-matter particles below the proton mass through interactions with advanced, ultra-sensitive detectors

Galactic dark matter scattering off nuclei Galactic dark matter scattering off electrons Galactic dark-photons absorbed by electrons The Dark Matter Landscape

Rocky Kolb https://voices.uchicago.edu/cosmiccontroversies/

1: What is the resolution of the current H0 discrepancy? 2: Theory beyond Cold Dark Matter needed to describe structure formation? 3: The explanation of Cosmic Acceleration? Cosmic Convergence 4: Can Inflation be transformed into a fundamental theory? 5: Do we need a Multiverse; can it made turned into a scientific theory? or 6: Dark Matter Particle or another explanation for dark matter? Cosmic Disruption? 7: What more can we learn from particle physics about cosmology? 9: What tools are critical for making progress in the coming decades?