Dark Matter

Rocky Kolb, KICP

Dark Matter: 25%

Dark Energy: 70%

Stars:0.8%

H & He:gas 4%

Chemical Elements: (other than H & He) 0.025%

Neutrinos:0.17%

Radiation: 0.005%

e

WIMP?

?

…it’s most of the mass in the Universe (kind of important)Why You Should Care About Dark Matter

… the dinosaurs didn’t care, and look what happened to them!Why You Should Care About Dark Matter

Far Future of Dark Matter• Particle Physics:

Understand the nature of dark matter (DM) and how it is embedded into a deeper theoretical framework:

• If DM is a particle, want to know more than just mass, spin, and couplings, want to know how it fits into a model or theory

• Want to know why DM exists

• Want to understand its contribution to the mass budget

• Astrophysics:

Understand the role of DM in the evolution of the universe and structure formation:

• Is the DM completely cold?

• Is there only one DM component?

• Does DM have interactions that affect structure formation?

Eight Decades of Dark MatterOort 1932 Local Neighborhood a Little Dim (/) ~

Zwicky 1937 Galaxy Clusters Really Dark (/) ~

Rubin & Ford 1970s Individual Galaxy Halos Also Dark (/) ~

Dwarf Observers 1990s Dwarfs Really, Really Dark (/) ~

While at ETH Zwicky lived in Spiegelgasse 17Zurich, Switzerland

Vladimir Lenin 1916

Varna, Bulgaria

Fritz Zwicky

Coma Cluster

Image: Jim Misti

cluster dynamics

cluster gas in x-raysgravitational lensing

structure formation cluster collisionsbackground radiation

dwarf galaxies

observed

luminous disk

galactic rotation curves

nucleosynthesis

Astronomy Contributions to Dark Matter1. It exists!!! Thank you astronomy!

2. What is the local DM phase-space velocity distribution?

3. What is the local value of DM ?

4. Are there nearby DM subclumps?

5. What is the background for -ray emission from the galactic center?

6. What is DM (r)

7. Is DM multi-component like visible matter?

8. Does DM have self-interactions?

9. Does DM have normal gravitational interactions?

(a complete theory containing dark matter could answer the last three)

very near the galactic center?in dwarf spheroidals?in DM subclumps?

• Einstein or Newton didn’t have the last wordModified GravityModified Newtonian Dynamics, i.e., F ≠ m a

• Mass Challenged Stars

• Black Holes

• Rocky Rogue Planets

Massive Compact Halo Objects(MACHOs)

Dark MatterDark Matter

• Unknown Particle Species

Known Particle Species

AntiquarksQuarks

AntileptonsLeptons

Image: CERN

and now the HIGGS!top bottom

strange charm

electron electron neutrino

muon muon neutrino

up down

tau tau neutrino

Force Carriers

photon gluon W Z graviton

Dark particle must be stable and massive and interact weakly

Dark particle must be “Beyond the Standard Model” (BSM)

Some Possible Origins of Dark MatterCosmological Phase Transitions (axions, mass ca. GeV)Asymmetric Relics (name needed, mass ca. GeV)Cold Thermal Relics (WIMPs, mass ca. GeV)Gravitational (Inflation) Production (WIMPZILLAs, mass ca. GeV)

WIMPZILLA vs. KING WIMP KONG

Interaction Strengthonly gravitational: WIMPZILLAsstrongly interacting: B balls

Particle Dark Matter Bestiary

MasseV (g) Bose-Einstein Mʘ (g) axion miniclusters

• (sub-) eV mass neutrinos (WIMPs exist!) (hot)

• sterile neutrinos, gravitini (warm)

• lightest supersymmetric particle (cold)

• lightest Kaluza-Klein particle (cold)

• Bose-Einstein condensates

• axions, axion miniclusters

• solitons (Q-balls, B-balls, …)

• supermassive WIMPZILLAs from inflation

thermal relics, or decay of or oscillation from thermal relics

nonthermal relics

from phase transitions

Rel

ativ

e ab

unda

nce

M / T

equilibrium eM / Tequilibrium eM / Tequilibrium eM / Tequilibrium eM / T

increasing A

decreasing abundance

Cold Thermal Relics*

* An object of particular veneration.

Ben Lee (1935 — June 1977)

Steve Weinberg

Model− effective field theory − excluded by

direct detectionLEP counting

Motivated by an incorrectexperimental result (high-yanomaly)

Model:G Heavy Neutrino

(GeV mass) with annihilation cross-section

á vñ

NR annihilationcross sectionMøller flux

thermal average

h cm

ávñ

cm

GeV)

weak scale!

• velocity dependence• resonances• co-annihilation• log dependence on M• decay production• spin-dependence• asymmetries• …

Not quite so clean:

DM Has “Weak-Scale” InteractionsWeakly-Interacting Massive Particle:

Michael Turner(actual size)

If I have seen further, it is by sitting on the shoulders….

A WIMP!

… often used to give an impression of great and unusual value in a trivial context …

The WIMP “Miracle”

mir·a·cle\ˈmir-i-kəl \

noun

1 : an extraordinary event manifestingdivine intervention in human affairs

Indirect Detection

WIMP STANDARD-MODELPARTICLE

Relic Abundance

Collider Production

DirectDetectionh

WIMPs Interact with SM Particles

WIMP STANDARD-MODELPARTICLE

WIMPs: Social or Maverick Species?

Not friended by any new particlesAny un-WIMPy pals beyond reachTheory framework: Don’t ask/Don’t tellBottom upNot UV complete: Effective Field TheoryFind the WIMP through what is not seenExample: Neutrinos before late 1960s

Friended by many like-mass particlesPals around with new un-WIMPy particlesPart of a larger theoretical frameworkTop downGenerally UV completeFind the WIMP by finding its friendsExample: SUSY

Social WIMP Maverick WIMP

upersymmetry & Socialist WIMPs

Developed in the early 70’s

Every known particle has an undiscovered superpartner.

Superpartners are massive.

Lightest superpartner should be stable!

In many realizations, lightest superpartner is weakly interacting.

Superpartners

squarkssleptons

u d s

e m t

h H A H + Higgsinos

g

photino g

Ggravitinogluonino

W Zwino, zino

Particles

Higgs h H A H +

quarksleptons

u d s e m t

photon g

Ggravitongluon

W ZW, Zg

Lightest Supersymmetric Particle is a candidate WIMP

gravitinos, sneutrinos, axinos, … neutralinos

SWIMPs

Lightest neutralino: linear combination of SUSY partners of , Z, and Higgs bosons

• Mass and gaugino/Higgsino fractions depend on about SUSY parameters• Reduce to a manageable number of parameters (pMSSM, CMSSM, mSUGRA, …)• Many processes/diagrams contribute to annihilation into many channels

− WW , ZZ, Zh, ZH, ZA, WH , HH, Hh, AA, hh, Ah, AH, f f− annihilation into f f proportional to fermion mass− no two-body final state with a photon (at lowest order)

• LHC & other experiments have pushed SUSY scale high, usually too large h,unless some chicanery increases A :

~

A

SM

SM

“Focus Point” SUSY Resonant Annihilation Coannihilation

mA ≅ m m mt c e= +

neutralino haslarge Higgsinocomponent

gravitinos, sneutrinos, axinos, … neutralinos

SUSY DM phenomenology very interesting and very rich.

SWIMPs

SUSY/DM Relationship:

Lightest neutralino: linear combination of SUSY partners of , Z, and Higgs bosons

• Choose a model framework to reduce from about SUSY parameters• Require consistent low-energy model

− with neutralino DM candidate− that satisfies all experimental constraints

• Low-energy annihilation cross section depends on neutralino composition, mass, and coupling and possibly other masses; all of these depend on about SUSY parameters

• Generally Av a b v ( velocity-independent part plus velocity-suppressed part)

Maverick Effective Field Theory (EFT)

• WIMP is the only state accessible to experiments: other states too massive (Maverick)

• Many theories have common low-energy behavior when mediating particles are heavy compared to energies involved

• EFT not as desirable as a UV-complete theory:– can miss relations between quantities– can’t describe high-energy behavior

(possibly like LHC)

• One example (DM fermionic & couples to quarks)

q q

mq q q Minimal Flavor Violation

g g

q

q

q

q

M EcY

22

2

gM

-

Y

L =

Maverick WIMPs

q q vsuppressed q q vsuppressed

q q unsuppressed q q unsuppressed q q unsuppressed q q unsuppressed q q vsuppressed* q q vsuppressed* q q unsuppressed q q unsuppressed

Av a b v

DM: v2 EFT

operator

h (M)

DM

DM SM

SM

Direct Detection

Direct DetectionVogelsberger et al.

• f (v) local WIMP phase-space density

− Assume: DM GeV cm

(subclumps, streams,…?)− Assume: Maxwellian velocity distribution ávñ km s

( )( )

( )2 2

22

8axial 1NN

N

m mJ J

m mc

c

c

sp

= L ++

• Spin dependent or independent?

( )( )

( )2 2

2

21scalar N

N n p

N

m mA Z f Z f

m mc

c

c

sp

é ù= - +ê úë û+

• Same coupling to p and n?

Kopp et al.

(f n

fp

)

(f n

f p)

NUCLEUS

Direct Detection

( )( )( )

MIN

3WIMP

Nucleus WIMP v

v1 v v vvR R

ddR d fdE M M dE

sr= ò

Recoil energies few to few dozen keV

WIMP

nuclear

recoil

WIMP

Experiment:

Detector Mass

Nuclear Target(s) (MNucleus and JNucleus)

EThreshold N vMIN /MNucleus

/

Particle physics: MWIMP/Astrophysics:

WIMPf (v)

IONIZATION

DAMA/LIBRA, KIMS,ANAIAS, SABRECUORE

PHONONS

CDMS,Edelweiss

CRESST

CoGeNT, CDMSlite,MALBEK TEXANO, CDEX

LIGHT

XENON, LUX,DarkSide, ZEPLIN

SUPERHEATEDBUBBLES

COUPP, PICASSO,PICO

After Jodi Cooley

Nuclear Recoil SignalDirect Detection

Direct Detection

COUPP CDMS

XenonCoGeNT( EDELWEISS, DAMA, EURECA, ZEPLIN, DEAP, ArDM, WARP, LUX, SIMPLE, PICASSO, DMTPC, DRIFT, KIMS, LUX, ARDM, ANAIS, CDEX PandaX, DarkSide, DAMA/LIBRA …)

Direct Detection PICO

Maverick WIMPs

q q spin independent q q v2, Q suppressed

q q v2, Q suppressed q q (v2, Q) suppressed q q spin independent q q v2, Q suppressed q q v2, Q suppressed q q spin dependent q q spin dependent q q v2, Q suppressed

S c d ( v + Q ) spin-independent/-dependent

EFToperator

h (M)

S (M)

DM

DM SM

SM

Direct Detection

M. Fedderke

Spin-Independent Scattering

cm zeptobarn!

cm attobarn

cm yoctobarn

cm femtobarn

cm picobarn

Direct Detection

M. Fedderke

Spin-Dependent Scattering

Direct Detection

M. Fedderke

3fm f fcc-LEFT:

Minimal Flavor Violation

Spin-Independent Scattering

Direct Detection

M. Fedderke

2 55f fm

mc g c g-LEFT:

Spin-Dependent Scattering

SWIMPs/Direct-Detection Relationship

• Spin-independent/dependent ratio depends on model parameters

• Cross section depends on model parameters, can vary many, many orders of magnitude

q q

Z

qq

q

qq

H, h

qq

q

Spin-dependent (axial vector) Spin-independent (scalar)

Direct Detectionde Vries

et al. 2015One analysis of one of many possible SUSY frameworks

Direct Detection: The PresentMaverick WIMPs (for given M, choose relic abundance):

Vector couplings excluded in range GeV to GeVScalar couplings excluded in range GeV to GeVAxial & Tensor couplings spin-dependent, weak or no limitsPseudoscalar couplings velocity suppressed no limits

SWIMPs (choose or so SUSY parameters):

Any limits very model dependentDirect detection limits constraining LHC+ pushing SUSY scale high pushing to higher-mass SWIMPs

mass

N

Direct Detection: The Future

New Techniques

Supersize

ExcludedRegion

Also:DirectionalityDifferent mass targetsSpin-dependent

Direct Detection: The Future

• Push spin-independent limits down to neutrino background – no more than orders-of-magnitude below proposed experiments

• Lot of white space for spin-dependent limits

• Push sensitivity to lower WIMP mass (new techniques?)

• If see a signal:− Seasonal variations− Different targets− Directional sensitivity

• If don’t see a signal:− Think beyond nuclear recoil− Work on cm astrophysics

The path is clear (at least to me)(Goal is to discover WIMP or kill a 39-year old idea.)

v cm cm s

Indirect Detection

Wimps

Indirect DetectionGalactic CenterDwarf spheroidalsDM clumps, Sun

Indirect Detection( ) ( )2

,2WIMPline of region of

sight interest

, ,vcos

4 2A r s l bdNd E

ds b db dldE dE M

g n rsp

é ùF ë û= ò

• Galactic Centerknow where to looklargest signallargest backgrounds

• Nearby subclumpsclean: no baryonsdon’t know where to looksignal down

• Dwarf spheroidals (/) > know where to look (about 20)clean: very few baryonssignal down another

Where to look for it

• Charged particles: p, high-energy eeeasy to detectastronomical backgroundsbent by magnetic field

• Continuum photons, neutrinos easy to detectastronomical backgrounds hard to detect/often not dominant

• Monoenergetic photon line ( )low background(probably) low signal“golden” detection channel

What to look for

ATIC Fermi/GLAST

IceCube

AMS-02

Veritas

H.E.S.S.

MAGIC

PAMELA

Indirect Detection

q q suppressed independent q q suppressed suppressed

q q unsuppressed suppressed q q unsuppressed suppressed q q unsuppressed independent q q unsuppressed suppressed q q suppressed* suppressed q q suppressed* dependent q q unsuppressed dependent q q unsuppressed suppressed

Av a b v S c d ( v + Q ) DM: v2 spin-independent/-dependent

indirect detection: v direct detection: v2, Q

Indirect Detection: Maverick WIMPs

EFToperator

DM

DM SM

SM DM

DM SM

SM

h (M)

Maverick WIMPs

DIRECT (SI) INDIRECT V VDIRECT (SD) INDIRECT T T

DIRECT (SI) INDIRECT S SDIRECT (SD) INDIRECT A A

DIRECT INDIRECT P P, P S, V A

DIRECT INDIRECT S P, A V

Signal or lack thereof WIMP FERMIONoperator(s)

SWIMPs/Indirect-Detection Relationship• Low-energy annihilation cross section depends on neutralino composition, mass, and

coupling and possibly other masses; all of these depend on about SUSY parameters

• Generally both velocity-independent & velocity-suppressed parts

• Relative size depends on model parameters

• Many possible final states depending on model parameters

• Many possible diagrams depending on model parameters

• Branching fractions depending on model parameters

• Annihilation to fermions

• No two-body final state with a photon (at lowest order)—no - ray “lines”

2fmµ

Diffuse -Rays from the Galactic CenterGoodenough, Hooper, Dalyan, Portillo, Rood, Boyarsky, Malyshev, Ruchayskiy, Linden, Abazajian, Kaplinghat, Gordon, Macias, Canac, Horiuchi, Slayter, Berlin, Cholis, McDermott, Lin, Finkbeiner, Calore, Cholis, Weniger, …

• Start with FERMI public data and tools• Pick search region of interest (around galactic center)• Remove point sources and model and remove every non-DM astrophysical source• Fit excess (if any) to cross section & annihilation channel(s)

Dalyan, et al. 1402.6703

M GeVannihilation to bb v cm/s

Calore, Cholis, Weniger JCAP 2015

2

0.22 0.13 0.231 0.31 1 0.095 0.17

Model Parameters dof -valueBPL 1.42 2.63 2.06 GeV 1.06 0.39

B

pE

bb

c

a a+ + +- - -= = =

6.4 0.28 26 25.4 0.27

4.6 0.2 26 23.9 0.18

3.9

49 GeV v 1.76 10 cm 1.08 0.36

38.2 GeV v 1.25 10 cm 1.07 0.37

0.337

M

cc M

M

s

s

tt

+ + -- -

+ + -- -

+-

= = ´

= = ´

= 0.047 0.2 26 20.18GeV v 1.25 10 cm 1.52 0.06s + -

-= ´

• Have an overwhelmingly statistically significant -ray excess from GC

• Why aren’t we all as excited as Dan Hooper?

• Possible background contamination (thousands of millisecond pulsars, …)

• Better astrophysical understanding of galactic center

• Better understanding of dark-matter density profile

• Better observations

− Better angular resolution

(resolve background sources, remove emission correlated with gas, …)

− Better spectral resolution

− More collecting area—look for signals elsewhere, stacked dwarfs, etc.

− Ground observations, e.g., CTA will teach us about backgrounds

Indirect Detection: The Future

IceCube

The path is clear (at least to me)(Goal is to discover WIMP or kill a 39-year old idea.)

WIMPs at the LHCWIMPs at the LHC

Looking for aninvisible

needle in a haystack

q q spin independent q q v2, Q suppressed

q q v2, Q suppressed q q v2, Q suppressed q q spin independent q q v2, Q uppressed q q v2, Q suppressed q q spin dependent q q spin dependent q q v2, Q suppressed

P In relativistic limit c d ( v + Q )

spin-independent/-dependent

EFToperator

h (M)

P (M)

same for all operators

DM

DM SM

SM

Maverick WIMPs at the LHC

Maverick WIMPs at the LHC

Beltran, Hooper, Kolb, Krusberg, Tait 2009; Goodman, Ibe, Rajaraman, Shepard, Tait, Yu; Rajaraman, Shepherd, Tait, Wijangco; Bai, Fox, Harnik; Fox, Harnik, Kopp, Tsai; CDF, CMS, ATLAS, …

• Look for “monojets”• Monojets are Nature’s garbage can• Also mono-’s & mono-Z’s, inclusive b jets• SM background extremely well modeled and understood• Neutrino background can be removed• Couplings irrelevant in relativistic limit• Validity of EFT?

q

q

Final state: nothing!

q

q

jet

Final state: an energetic jet of particlesunbalanced in momentum

• Gluinos, squarks, charginos will be discovered first

• Analysis model dependent

• LHC chewing away allowed region

• Can swiggle out … but it is getting harder

• Don’t throw in towelino just yet

• Stay tuned for results from TeV run

• Eventually will see WIMP in missing energy signals

Most popular cold thermal relic: the neutralinoSWIMPs at the LHC

Trickle Down SUSYnomics

Complicated decay chain—very model dependent

g

g

l

l

l

lD

D

g

g

g

U

U

U

U

W

W

l

l

SWIMPs

g g u u d d m m n n cc+ +

Collider Searches: The Future

• LHC has just started running at TeV

• LHC will eventually accumulate a tremendous amount of data

• If DM is a SUSY relic, some indication of SUSY will be discovered at LHC− gluinos, squarks, charginos, will be seen first− search strategies well developed

• If DM is a Maverick particle − only hope is missing-energy searches− most effective for low masses− no guarantee EFT valid at LHC

Dark Matter: If Not a WIMP

• If DM not a WIMP, many other possibilities:− Axions− Asymmetric DM− Sterile neutrino DM (e.g., keV sterile neutrino producing keV X-ray

line which may, or may not, be observed)− Axino ( keV axino) DM− Self-interacting DM− Inelastic DM− Q-balls or other solitonic DM− Quark nuggets− Hidden-sector DM− WIMPZILLA

Dark Matter: The Future

• We are in the eighth decade of Dark Matter!

• 2010s is the Decade of the WIMP− LHC− Direct detection− Indirect detection

Have to run to ground the WIMP (cold thermal relic) hypothesis.

• Indirect/Direct/LHC confusion not an issue

• WIMPs may be more complicated than discussed: Leptophilic, Leptophobic, Flavorful, Self-Interacting, Dynamical, Inelastic, …

• My predictions:− We will know the answer before a century of dark matter− Dark matter discovery will be unanticipated− Dark matter will be “none of the above”− Dark matter will be multicomponent− Dark matter will be part of a dark sector

Dark MatterRocky Kolb, KICP