The SIMP Miracle

J a y W a c k e r S L A C

D e c e m b e r

With: Tomer Volansky Eric Kuflik Yonit Hochberg

The Universe is Dark

The biggest unexplained mystery of the Universe is

Dark Matter

It is physics strictly beyond the Standard Model

It requires at least one new degree of freedom to exist

At least one incredibly long lived particle that exists in our galaxy today

DM Lifetime > 107 Age of Universe

The Long List of Dark Matter Properties

It is a massive particleof unknown mass

It has suppressed interactions with QED & QCDcould have milli-charge

or interact through higher dim operators

It doesn’t strongly self-interactLimits on σ/mdm < 1 barn/GeV

neutron scattering is 0.1 barn/GeV

Dark Matter has 5 times the mass density of Baryons�dm

�b� � � 5

1.)

2.)

3.)

4.)

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Outline

Early Universe Cosmology and Dark Matter

Lee & Weinberg in 1977 elegantly linked Dark Matter genesis

and Early Universe Cosmology

If a new stable particle has 2-to-2 interactions with SM, and Universe has hotter than its mass, there will be a relic density left over

DM

DM

SM

SM

Dark Matter Freeze Out

1 3 10 30 100 300 1000−20

−15

−10

−5

0

log

Y(x

)/Y

(x=

0)

x ≡ m/T

⟨σAnnv⟩

Increasing

t →

DM

DM

SM

SMt →

DM SM

DM SM

�pro = nsm��v� �ann = ndm��v�

Ydm = ndm/s

neq � e�m/T s

s ~ number of photons per volume

number of DM per photon

n ~ number of DM per volume

n + 3Hn = (n2eq � n2)��annv�

WIMPsIf the interactions are through the weak interactions,

mdm should be between 100 GeV and 3 TeV

WIMPs have been the dominant model for 35+years

Coincidence if the interactions are weak, dark matter should be at the weak scale

Back of the Envelope Solution

�ann � H���f.o.

�mp�b�2

x3F

� m2dm

x2F MPl

mdm � ����bmpMPl/xF

� 12

nb = �bs

s � T 3

mdmndm = �mpnb ��annv� � �2

m2dm

�ann � ndm��annv� H =T 2

MPl

T���f.o.

=mdm

xF

Examination of Lee-Weinbergmdm � �

���bmpMPl/xF

� 12

Teq � 1 eV

mdm � ��TeqMPl/xF

� 12

Particle Physics

20 <� xF<� 30

α unknown strength of 2-to-2 annihilation

of DM to SM

Details of solving Boltzmann Equation

mdm � � � 30 TeV

Matter-Radiation Equality Temperature

TeV Scale EmergedNo Particle Physics went into

mdm � � � 30 TeVαweak= 1/30

WIMPs at 1 TeV emerged without input of scale

If interactions are suppressed, then DM could be lightere.g. if DM is admixture of singlet & EW-charged state

Truly a coincidence of scales

�e� = �weak sin2 �mix

The Search for WIMPS3 Pillars in the Search for DM

Direct Production

t →

DM

DM

SM

SM

Direct Detection

t →DM DM

SM SM

Indirect Detection

t →

DM

DM

SM

SM

WIMPs Being Challenged

Xe100 greatly constrained h0-mediated interactions

h0

N

N

DM

DM

Spin independent Z0-mediated interactions long ruled out

WIMPs Being Challenged

) [GeV]20χ∼ (=m

1±χ∼ m

100 200 300 400 500 600

[GeV

]0 1χ∼

m

0

50

100

150

200

250

300

350

400

450

500Expected limitsObserved limits

ATLAS-CONF-2013-035, µ, 3e/ν∼/ Ll~, via 0

2χ∼±

1χ∼→pp

ATLAS-CONF-2013-049, µ, 2e/ν∼/ Ll~, via -

1 χ∼

+1χ∼→pp

ATLAS-CONF-2013-028, τ, 2τν∼/ Lτ

∼, via 02χ∼±

1χ∼→pp

ATLAS-CONF-2013-028, τ, 2τν∼/ Lτ

∼, via -1 χ∼

+1χ∼→pp

ATLAS-CONF-2013-035, µ, via WZ, 3e/02χ∼±

1χ∼→pp

ATLAS-CONF-2013-093bb, µ, via Wh, e/02χ∼±

1χ∼→pp

=8 TeV Status: SUSY 2013s, -1 = 20.3-20.7 fbint

Preliminary LATLAS

)20χ∼ + m

10χ∼ = 0.5(m ν∼/ Lτ

∼/ Ll~m

10χ∼

< m2

0χ∼m

Z + m

10χ∼

= m2

0χ∼m

h + m

10χ∼

= m2

0χ∼m

10χ∼ = 2m

20χ∼m

LHC extending searches for EW DM

W/Z

qbarq

DMDMW/Z/h W/Z/h

DM’ DM’

WIMPs Being Challenged

HESS ruled out thermal Wino

Cohen, Lisanti Slayter 1307.4082

DM DM

γγ

WIMPs in 2013

Dominant paradigm in DM is being challenged

Lots of non-thermal/quasi-thermal mechanisms

Asymmetric DM

Freeze-In DM

Axion DM

Gravitino DM

Is there another simple thermal mechanism that gives qualitatively different signatures?

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Outline

An Alternate Paradigm

Lee-Weinberg assumed unsuppressed interactions with the SM

DM is really part of enlarged SM sector

What if DM was completely sequestered from SM?

SM DM

SM & DM charged under same interactions

A Hot Hidden SectorDark Matter is the lightest state in a hot Hidden Sector

After Inflation, both SM & Dark Sector reheated to comparable temperatures

During Radiation Domination, both sectors cool together

Time

Tem

pera

ture

Reheating

A Hot Hidden Sector

When Tdark≃ mdm , dark matter needs to annihilate

Time

Tem

pera

ture

Reheating

mdm

DM

DMDM

DM

doesn’t change the number density

but

Life without 2-2 Annihilation

With no 2-to-2 annihilation possible, is the story is over?

No…2-to-2 is the leading interaction that can change number density

Always absent in a closed system

The first process that can change number density in a closed system is a 3-to-2 interaction

t →

4-to-2 4-to-3 etc.

(only 3-to-2 will be viable)

ndm

s� 1

5-point Interactions

For single-scale models

5-point interactions are a little unfamiliar

Consider a Z3 -symmetric model

DM is stable (proof-in-principle)

� � gm � � g2

M � �3

m4M � ��

m2

M � g3

m

L � m2|�|2 + ��3 + �|�|4

�� e2�i3 �

Redoing Lee-Weinberg

�ann � H���f.o.

�ann � n2dm��3�2v

2�

��3�2v2� � �3

m5dm

H =T 2

MPl

The GeV Scale emerges for Strongly Interacting DM

mdm � �� 100 MeV

� � g2

4�

mdm � ��Teq

2MPl/x4F

� 13

The SIMP MiracleThe Lee-Weinberg mechanism leads to the WIMP Miracle

This leads to the SIMP Miracle

No particle physics went into the derivation of this scale

“The second thing you should think of in Big Bang Cosmology leads to Dark Matter”

Strongly Interacting Massive ParticleSelf Interacting Massive Particle

Boltzmann Equation (Part 1)

��3�2v� =�3

m5dm

0.1 1 10 100 100010-3

10-2

0.1

1

10

m @MeVD

a3 Æ 2 Freezeout

0.1 1 10 100 1000

14

16

18

20

22

24

m @MeVDx F

Freeze Out

n + 3Hn = (n2neq � n3)��3�2v�

CaveatEverything about the SIMP Miracle is a not quite right...

Tacitly assumed that the DM temperature was following SM temperature

Cold Hot

Temperature is approximately constant while freezing out

ndm(t) � exp(�mdm/Tdm) �= exp(�mdm/Tsm)

Carlson-Hall-Machacek

Predicts Light Hot Dark Matter

Disaster! Thoroughly ruled out

Tsm

Tdm

Keeping DM & SM in Thermal Equilibrium

Want to cool dark sector

t →

DM

SM

DM

SM

However, don’t want Lee-Weinberg Mechanism

Is this possible?t →

DM SM

DM SM

Cooling but not annihilating

t →

�cool = nsm��annv�

t →

�ann = ndm��annv�

Need to scatter off light SM species: e, γ, ν

ndm

nsm� e�mdm/T

Model of SIMP Interactions

Simple model for the interaction

�SM int =�2

m2dm

Assume DM dominantly interacts with electrons

(note: does not have to lead to DM decay)

Lint ��

mdm|�|2 ee

Boltzmann Equation (Part 2)

E�tf �Hp2�Ef = �self kin + �3�2 + �SM kin + �ann SM

DM

SM

DM

SM

DM SM

DM SM

DM

DM

DM

DM

DM

DM

DMDM

DM

Needed Size of ε

0.1 1 10 100 100010-11

10-10

10-9

10-8

10-7

10-6

10-5

m @MeVD

e

e

WIMPs

Hot DM

SIMPs

Points to new physics in the 10 GeV to 10 TeV

Lint ��

mdm|�|2 ee

�NP ��

mdmme/�

Could be Higgs portal interactionL � µ s |h|2 + ye h ee + � s |�|2

The SIMP Miracle Requires SM Interactions

Dark Matter cannot be completely sequestered from the SM

Some residual interactions, smaller than WIMPs, but not arbitrarily small

SIMPs are visible through cadre of standard experiments, but a lower interaction rates than standard WIMPs

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Outline

Limits on SIMP Interactions5 Classes of Limits

Direct

Detecti

on

Direct Production

Indirect Detection

Cos

mol

ogic

al

Self Interaction

Direct Detection

Essig, Manalaysay, Mardon, Soerensen, Volansky1206.2644

Nucleon scattering kinematically suppressed for mdm < 5 GeV, better to scatter off electrons

Indirect Detection

Essig, Kuflik, McDermott, Volansky, Zurek 1309.4091

Cosmic Ray Flux Provides LimitsEGRET & COMPTEL provide best limits

Cosmological Searches

Slatyer, Padmanabhan, Finkbeiner 0906.1197

Nν eff ModificationCMB Distortion

Boehm, Dolan, McCabe 1303.6270

If in equilibrium with QED sector beneath ν-freeze out

Nν eff will be modified

Late DM annihilations add energy into CMB

Combined Limits

Self InteractionLong standing structure formation problem

Cored DM Profiles & Missing Satellite (or now TBTF)

Recent analyses showed DM self-interaction of

can solve problem

and allowed by Galactic Shape analysis and Bullet Cluster bounds

Strong-Scale Cross Sections!

�

m� 0.2

barnGeV

� 500 GeV�3

Just Perfect!

�int

mdm� �2

mdm� 500

1 GeVmdm

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Outline

Higher Point Interactions

4-to-2 4-to-3 etc.

(only 3-to-2 will be viable)

What about higher point interactions?

6 point interactions automatically conserve Z2 symmetry

��n�2v� =�n

m2+3n

n=4 corresponds to 10 keV

mdm � ��Teq

n�1MPl

� 1n

dead by Nν eff

Hidden Glueball DMHidden pure SU(N) sector that confines

Ldark � G2µ� + (�a)2 + m2

aa2

+a

fGG +

a

f � FF

Confines at �dark

Ga

aγ

γγ

γ

Axion heavier than glueball � � �4dark

ff �m2a

Scalar Glueball decays through 4 body

O(10) states stable to strong decays

Juknevich, Melnikov, Strassler 0903.0883

~ε4 borderline 1025 seconds

electrons safer

OutlookSIMPs offer a new window to DM

Points to different physical scales

Lighter DM that self-interacts

New model building challengesSimplest models still need to be discovered

Truly a miracle that it isn’t ruled out

Discovery of the particle physics of DM could be through long standing structure formation problems