Exploring Dark Matter From Colliders To The Cosmos

Hai-Bo YuUniversity of Michigan, Ann Arbor

HET Seminar, TAMU10/29/2012

Outline• A brief introduction

• WIMP dark matter An effective field theory approach

Searches at colliders

• Beyond the WIMP paradigm Asymmetric dark matter

Hidden sector dark matter

We Need Dark Matter

• Not luminous• Not short-lived• Not hot• Dissipation-less X ‣Mass

‣Spin‣Quantum Number

The WIMP “Miracle”X

X

SM (q,l...)

SM (q,l...)_ _

ΩX ∼ 0.23

3× 10−26 cm3/s

σAv

Weak-scale cross section

A remarkable coincidence!

Dark matter indicates weak-scale new physics!

Hunt For WIMPsLHC

NeutronStars

X SM

SMX

Indirect detection (now)Relic density (early Universe)

Dir

ect

dete

ctio

n

Collider Search

AMS PAMELA

IceCube

LHC

Direct Detection Status

• Three experiments saw something • The preferred regions do not overlap (simple WIMP models) • They conflict with results from CDMS and XENON

We need a better understanding

Challenges

Colliders can provide complementary searches

No A dependence

∼ SX · SN

Spin-dependent WIMP

Nucleus

Coherent scattering Cross section ~A2 Enhanced by a large A

Spin-independent

Low m

ass

Collider Search

X SM

SMX

Indirect detection

Dir

ect

dete

ctio

nCollider Search

WIMPs at Colliders

X

X

q

q_

Time

q_

q X

XTime

gluon(jet)/photon/Zq X

X

⟿q_

Time

⟿X

X

p p_

Visible

Invisible pp→Monojet+Missing Energy _

Goodman, Ibe, Rajaraman, Shepherd, Tait, HBY (2010) PRD, PLB, NPB

WIMPs at Colliders

How sensitive to the details?

q X

X

⟿

q_

?

Effective Theory Approachq X

Xq_

Q∼ gqgX

Q2 −m2φ

q X

Xq_

∼ gqgXm2

φ

=1

M2∗

If mφ Q

The Power of Effective Theoryq

X

q

X

σDD ∼ µ2

M4∗

µ ∼ 1 GeV σj ∼ αsp2TM4

∗pT ∼ 100 GeV

σj

σDD∼ αs

p2Tµ2

∼ O(1000)

Direct detection and collider production are correlated directly• If there is an excess, σDD~σj/1000• Otherwise σj<σmax, σDD<σmax/1000

q

q

X

X

⟿gluon (jet)

M* M*

Back of the Envelope

Events: monojet+missing energy

Predicted from the SM: 8663±332

Observed at the Tevatron: 8449

Allowed contributions from WIMPs: 332⨉2=664

σj⨉1 fb-1⩽664 ⇒ σj⩽664 fb

σDD~σj/1000 ⩽ 0.664 fb~6.6⨉10-40 cm2

Tevatron CDF luminosity 1 fb-1

http://www-cdf.fnal.gov/physics/exotic/r2a/20070322.monojet/public/ykk.html

Back of the Envelope

Colliders can provide complementary searches for light WIMPs and WIMPs with SD scattering

below 5-10 GeV

An Effective Theory of Dark Matter

Goodman, Ibe, Rajaraman, Shepherd, Tait, HBY (2010)

X

X

q

q

Invariant under Lorentz symmetry and U(1)em

The cut-off scale controls everything

M*

see also: Bai, Fox, Harnik (2010)

CDF, ATLAS and CMS have done the analysis

Recent ATLAS Results

D1 : χχqq D5 : χγµχqγµq D11 : χχGµνGµν

D8 : χγµγ5χqγµγ5q D9 : χσµνχqσµνq

arXiv:1210.4491

The LHC provides complementary searches

Beyond the Effective Theory

Fox, Harnik, Kopp, Tsi (2011)

• If the mediator is light, the EFT approach breaks down• The monojet+MET search is still valid • The bound depends on details of the WIMP theory

σj ∼ αsp2TM4

∗

σj ∼ αs1

p2T

heavy mediator

light mediator

Limits from the Fermi-LAT

Goodman, Ibe, Rajaraman, Shepherd, Tait, HBY (2010)

Spin-dependent WIMP-nucleon scattering

M∗

X

X

qɣ/Z

ɣ

Fermi-LAT (2010)

D8 : χγµγ5χqγµγ5q

The 130 GeV Line signal?

Weniger (2012) see also Su, Finkbeiner (2012)

mχ 130 GeV

σvγγ ∼ 10−27 cm3/s

See for example: Sean, HBY, Zurek (2012)

Not the usual WIMP

Beyond the WIMP Paradigm• WIMPs satisfy all cosmological requirements to be dark

matter candidates

• Moreover, the WIMP paradigm is very predictive

• The effective field theory is a powerful tool

• Colliers provide complementary searches for WIMPs

• Beyond the WIMP paradigm: asymmetric dark matter and hidden sector dark matter

Asymmetric Dark Matter• Baryon asymmetry in the universe

Nussinov (1985); Kaplan (1992); Kaplan, Luty, Zurek (2009); Dutta, Kumar (2010); Tulin, HBY, Zurek (2012)...

ηB =nB − nB

s∼ 10−10 ηX =

nX − nX

s= 0

ΩX =ηXsmX

ρc

ηX ∼ ηB ,mX ∼ mBΩX/ΩB ∼ 5 GeV

XX

_X

XX

_X

X_

• The usual WIMP is in the symmetric limit

Stars as Natural Labs

• Stars capture dark matter particles gravitationally

• They scatter with baryons and lose energy

• They are trapped in stars

Gould (1987)

An Interesting Application

Mack, Beacom, Bertone (2007)

• Earth captures WIMPs• WIMP annihilation produces heat • Inside the heavily-shaded region, WIMP annihilation would overheat Earth

Underground

detecto

rs

Capture rate ∝σ

ADM VS. Symmetric WIMP

A speculated event: Captured ADM particles collapse to a mini black hole at the center of neutron stars

Capture rate∝σ

• Symmetric DM: NX~constant

• Asymmetric DM: NX∝t

Example: Scalar asymmetric dark matter

• Neutron stars as natural labs for ADM

Neutron star

ADM

ADM in Neutron Stars

Thermal states

⟿⟿⟿⟿BEC

Neutron star

ADM

Thermal

BEC

Thermal

ADM in Neutron Stars

Step 1: Capture

Step 2: Dark Matter Cooling

after 30 minutes

An example: ADM mass 10 GeV

Step 3: Bose-Einstein Condensation

ADM number in the BEC state

σn = 2× 10−45 cm2

N totalX ∼ 1042

tth ∼ 30 minutes

vhalo ∼ 10−3c vesc ∼ 0.6c

vth ∼ 3× 10−5c

N critX ∼ 1036

NBECX = N total

X −N critX ∼ 1042

Neutron star

ADM

Thermal

BEC

Thermal

ADM in Neutron StarsStep 4: Self-gravitating

Step 5: Gravitational Collapse

ADM is heated up, but will be cooled down again by neutrons

When the ADM density is higher than the neutron density, ADM becomes self-gravitating

rBEC ∼ 3× 10−5 cm

rth ∼ 76 cm

Rns 10.6 km

Thermal

BEC

Thermal

BEC

Form a Mini Black HoleStep 6: Overcome zero point energy

A mini black hole forms !

Recall

Chandrasekhar limit for bosons

Only if ADM can collapse to a black hole

Note

E ∼ −GNm2

R+

1

R< 0 N boson

Cha ∼ 1.5× 1036

NfermionCha ∼ 1.8× 1054

NBECX > N boson

Cha

NBECX = N total

X −N critX ∼ 1042

Hawking Radiation

Eating baryons Hawking radiation

The black hole will destroy the host star if its initial mass is larger than

dMBH

dt= 4πλs

GMBH

v2s

2

ρBvs −1

15360πG2M2BH

M crit

BH 1.2× 1037 GeV

⟿⟿

⟿⟿

Limits from Neutron Stars• Observed old neutron stars set an upper bound

on DM-neutron scattering cross section

McDermott, HBY, Zurek (2011)

Capture rate∝σn

The black hole evaporates due to Hawking radiation

In the shaded regions, bounds are lifted

Beyond the WIMP Paradigm• Hidden sector dark matter

• An example: hidden charged dark matter

nightmare scenario?

e

e

e

ePhoton

Visible

XX

X XPhoton

HiddenαX =?αem =

1

137

YES NOCan we still understand dark matter?

Feng, Tu, HBY (2008); Feng, Kaplinghat, Tu, HBY (2009)

Self-interacting Dark Matter• Self-interactions can affect dark matter dynamics

Morphology:randomize the dark matter velocity dispersion; lead to spherical halos and clusters

Self-interacting dark matter may behave as hot gas

Markevitch et al. (2003);Clowe et al. (2006)

gasDM

DM

Bullet Cluster

Spergel, Steinhardt(1999); Miralda-Escude (2000)Dave et al. (2001); Yoshida et al. (2001); Feng, Kaplinghat, Tu, HBY (2009); Feng, Kaplinghat, HBY (2009)

Star

gas

star

Limits on the Hidden Charge

XX

X X

Photon

Hidden

αX =?

Feng, Kaplinghat, Tu, HBY (2009)

Excludedαem

Small Scale Structure and SIDM

• Self-interacting DM is actually motivated to solve the small scale structure problem of collisionless cold DMSpergel, Steinhardt (1999)...

X

X

X

X

Vogelsberger, Zavala, Loeb (2012) Rocha, Peter, Bullock, Kaplinghat, et al. (2012)Peter, Rocha, Bullock,Kaplinghat (2012)

σT /mχ ∼ 0.1− 10 cm2/g

σT ∼ 10−36 cm2 WIMP

1 cm2/g ∼ 2× 10−24 cm2/GeV

Recent simulations suggest

r/rs

SIDM with a Yukawa Potential

Tulin, HBY, Zurek (2012)

XX

X X

ɸ

Feng, Kaplinghat, HBY (2009)Loeb, Weiner (2010)

σT ≈ 5× 10−23 cm2 αX

0.01

2 mX

10GeV

210MeV

mφ

4

A light mediator is required

• The scattering cross section has a rich structure• In general, σT has a velocity-dependence• It helps avoid constraints from large scales

mx, mɸ,αX

A Unified Model

XX

X X

ɸ

ɸ

ɸX

X

• For a given dark matter mass, we fix the coupling constant by the correct relic density• We map out the parameter space (mx, mɸ) required to solve the small scale structure problem

DM self-scattering and the relic density are usually considered separately

Fix αX

σT ∼ 0.1− 10 cm2/gTulin, HBY, Zurek (2012)

Self-interacting Dark Matter

Tulin, HBY, Zurek (2012)contours (cm2/g)

The blue regions are preferred by the simulations to solve the small scale structure problem

X-X, X-X_

X-X

σAv 6× 10−26 cm3/s

σT /mX

Summary

• Cosmological/Astrophysical observations cry out for new physics beyond the Standard Model

• WIMPs are well-motivated dark matter candidates and the WIMP paradigm is very predictive

• Both the Tevatron and the LHC are probing the dark sector

• Different search strategies are available for dark matter beyond the WIMP paradigm

• We are in an exciting data-driven era

Self-interacting Dark Matter• In usual WIMP models, self-scattering cross

sections are too small to play a role in galactic dynamics

• Self-interacting DM is motivated to solve the small scale structure problem of collisionless cold DM

Vogelsberger, Zavala, Loeb (2012)

Spergel, Steinhardt (1999)...15 most massive subhalos

X

X

X

X

X

X

SM

SM

“Too Big to Fail”Boylan-Kolchin, Bullock, Kaplinghat (2011)

Vogelsberger, Zavala, Loeb (2012) Rocha, Peter, Bullock, Kaplinghat, et al. (2012)Peter, Rocha, Bullock,Kaplinghat (2012)

The problem can be solved by SIDM

σT ∼ 10−36 cm2WIMP1 cm2/g ∼ 2× 10−24 cm2/GeV

σT /mχ ∼ 0.1− 10 cm2/g