Dark Matter Rocky Kolb, KICP
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
q
H, h
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