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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.)
• L e e - W e i n b e r g & W I M P s
!
• T h e S I M P M i r a c l e
!
• T h e S e a r c h F o r S I M P s
!
• O u t l o o k
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?
• L e e - W e i n b e r g & W I M P s
!
• T h e S I M P M i r a c l e
!
• T h e S e a r c h F o r S I M P s
!
• O u t l o o k
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
• L e e - W e i n b e r g & W I M P s
!
• T h e S I M P M i r a c l e
!
• T h e S e a r c h F o r S I M P s
!
• O u t l o o k
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
• L e e - W e i n b e r g & W I M P s
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• O u t l o o k
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