UCLA Dark Matter, 18 Feb 2016

Models of Self-Interacting Dark Matter

Kimberly BoddyUniversity of HawaiiDepartment of Physics & Astronomy

Motivation for SIDM

SIDM helps alleviate small-scale structure issues from dwarf to cluster scales

(see earlier talks by J. Bullock and H.B. Yu)

Think beyond WIMPs

�

m⇠ cm2

g⇠ 2

barn

GeV

Simple Hidden Sectors1. SU(N)

❖ Pure gauge SU(N)

❖ With adjoint fermion

2. U(1) — massless mediator

❖ Atomic dark matter

3. U(1) — massive mediator

❖ Attractive/Repulsive Yukawa potential

This list is not exhaustive!

Aim is to cover a few models and some phenomenology.

Case 1: SU(N)

Minimal Model

❖ Hidden SU(N) gauge

❖ Confinement scale 𝚲

❖ Particle content:❖ Massless gluons❖ Composite glueballs

with mass ~𝚲

❖ Massless gluon sets relic density❖ Geometric scattering cross section

(velocity-independent)

� ⇠ 4⇡

⇤2N2

target SIDM (at small N)

0.1 cm2êg1 cm2êg

N=2

N=10

N=100

10-5 10-4 0.001 0.010.01

0.1

1

10

100

xL

L@Ge

VD

Glueball-only dark matter

KB, Feng, Kaplinghat, Tait, PRD 89, 115017 (2014).

fixed N

Include Adjoint Fermion

Excluded by LEP2

Wgbino = 0.1 WDMWgb = 0.9 WDM

N=2

N=10

N=100

x f=4.5¥10-3

x f=1.4¥10-3

x f=3.0¥10-4

0.01 0.1 1 10 1000.01

0.1

1

10

100

mX @TeVD

L@Ge

VD

Mostly-Glueball Dark Matter HNo ConnectorsL

❖ Include SU(N) adjoint fermion with mass mX — “gluino”

❖ At confinement, form both glueballs (gluon+gluon) and glueballinos (gluino+gluon)

fixed N

fixed ξf

KB, Feng, Kaplinghat, Tait, PRD 89, 115017 (2014).

Scattering via Yukawa

Tulin, et al., PRD 87, 115007 (2013).

Wide range of velocitiesfor which the

cross section ~ constant

Scattering via Yukawa

Excluded by LEP2

Wgbino = 0.9 WDMWgb = 0.1 WDM

N=2

N=10N=100

x f=2.0¥10-2

x f=5.0¥10-3

x f=7.0¥10-4

0.01 0.1 1 10 1000.01

0.1

1

10

100

1000

mX @TeVD

L@Me

VD

Mostly-Glueballino Dark Matter HNo ConnectorsL

fixed N

fixed ξf

dwarfs

LSBs

mX = 14 TeV𝚲 = 0.35 MeV

KB, Feng, Kaplinghat, Tait, PRD 89, 115017 (2014).

3.5 keV LineChromomagnetic interactions give hyperfine splittings:

∆E ~ Λ2/mX

KB, Feng, Kaplinghat, Shadmi, Tait, PRD 90, 095016 (2014).

sêm=0.1 cm 2êg10 cm2êg

35.6 keV

DE=0.356 keV

x=1

N=30 10 3

N=3

10

Flux

DwarfLSB

0.01 0.1 1 10 1000.01

0.1

1

10

100

1000

mX @TeVD

L@Me

VD

Case 2: Unbroken U(1)

Atomic Dark Matter❖ Particle content and model

parameters:

❖ Dark proton (mp)

❖ Dark electron (me)

❖ Dark photon

❖ Dark fine structure constant αD

❖ Temperature ratio ξ=TD/T

❖ Consider scattering of dark hydrogen with mass mD

KB, Kaplinghat, Kwa, Peter (in prep).

(All quantities in atomic units)

Preliminary

Wide range of energies (velocities)for which the cross section ~ constant

R =

mp / m

e

Dark Recombination

Cyr-Racine and Sigurdson, PRD 87, 103515 (2013).

BD = mD H8êaD 2-1L -1BD = 10 keVx = 0.37

Ionized DM

Neutral DM

10 102 103 104 105

10-4

10-3

10-2

10-1

10 102 103 104 105

10-4

10-3

10-2

10-1

mD @GeVD

a D

10-12

10-10

10-8

10-6

10-4

10-2

1

xDionization fraction

↵6D

⇠

✓⌦DMh2

0.11

◆⇣ mD

GeV

⌘�1✓BD

keV

◆�1

& 1.5⇥ 10�16

Binding energy

Matching to SIDM

Cline et al., PRD 89, 043514 (2014).

f i = 1 →

= 0.01α

= 0.02α

= 0.03α f i = 1 →

allowed →

excluded

→

0.01

0.03

0.1

0.3

1

1e−5

1e−4

0.001

Lines of constant α for which

σV/mH = 0.5 cm2/g

R=mp/me

Lines of constant α for which

ionization fraction = 1

Effects on Cosmology

⌃DAO ⌘ ↵D

✓BD

eV

◆�1 ⇣ mD

GeV

⌘�1/6

Cyr-Racine et al., PRD 89, 063517 (2014).

Case 3: Broken U(1)

Yukawa Scattering

Vogelsberger and Zavala, MNRAS 430, 1722 (2013).

V (r) = ��

rexp(��r)

Matching to SIDM

dw0.1

dw1

dw10

MW 0.1

MW 1cl 0.1

cl 1

10-4 0.001 0.01 0.1 10.1

1

10

100

1000

104

mf HGeVL

mXHGe

VL

Dark matter with relic density Hs-waveLdw0.1

dw1

dw10

MW 0.1MW 1

cl 0.1

cl 1

0.001 0.01 0.1 10.1

1

10

100

1000

104

mf HGeVL

mXHGe

VL

Dark matter with relic density Hp-waveLscalar mediator

α fixed to obtain correctrelic density

Tulin, et al., PRD 87, 115007 (2013).

vector mediator

mediator mass DM mass

Include U(1) Kinetic Mixing

Kaplinghat, et al., PRD 89, 035009 (2013).

Summary❖ SIDM helps solve small-scale problems, while preserving large-scale structure

❖ Rich phenomenology from very simple models

❖ SU(N) dark matter:

❖ confinement separates early- and late-universe physics

❖ keV line from connectors to SM

❖ U(1) atomic dark matter:

❖ dark recombination forms neutral dark hydrogen

❖ dissipative dark matter can affect cosmology

❖ U(1) Yukawa interactions:

❖ light mediator gives velocity-dependent cross sections

❖ kinetic mixing with SM photon can produce direct detection signal