Search for Dark Matter

S. Park (SKKU) Lecture at 2014 KIAS-SNU winter camp Feb 9 - 16

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enormously active field in physics!

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plan

1. Introduction to DM

2. Evidences for DM

3. Search strategies

4. Heavier DM

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1. Introduction to Dark Matter

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Higgs discovered 2013

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…seems quite consistent with the `standard model’

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What’s the next goal?

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DE DM SM Matter

The standard model explains !4% of the Energy budget!

Dark Matter =??!

“Cosmic pie”

Message from CosmologyCMB+BAO+SN1a+…

Dark Energy =cc ??"8

After a long, painful works more than 45years, we end up with bigger

mystery..

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What’s the DM and how to find it?

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deep connection between cosmology and particle

physicsBig-bang cosmology is supported by MANY, INDEPENDENT observations..

..including Hubble expansion, BBN, CMBR (+fluctuation ~10^-5), large structure formation etc

Universe was hot and dense in the early time … p~h/d, E~p~T thus study of High energy physics = study of early universe

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A standard history of DM in BB theoryDM was produced with other particles (quarks, leptons, gauge bosons)

stayed in thermal equilibrium (i.e. production rate = annihilation rate)

Universe cools down T<Mdm, no more production only annihilation

high-T

T~Mdm

BB

T>Mdm

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T~Mdm

BBT>Mdm

T<Monly annihilation

production & thermal equilibrium

T=Tfno more annihilation

due to expansion

nowFreeze-out

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Lee-Weinberg (1977)

T>M

T<M

T~Tf

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Typical weak interaction

WIMP miracle

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Neutrino(Heavy) Neutrino is the only possible WIMP candidate in the

SM but way too small..

Planck

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Upper bound for thermal WIMP

unitarity

Bullet cluster

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Properties of WIMP- Stable (or very long lived >>age of Univ.)

- Non-luminous (not seen by light)

- Cold (warm) to explain Galaxy formation!

- the right density!

- M<80 TeV typically GeV-TeV (can be heavier if non-thermal)

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model realizationStable : symmetry (Z2, new gauge symmetry ︙), kinematically stable)!

Non-luminous : electrically neutral or milli-charged (QFT?), weakly interacting!

Massive ~ GeV-TeV by certain mechanism other than the Higgs mechanism (??)!

WIMP miracle almost always guarantees the right relic abundance

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(EX) A model: Real singlet scalar DM

~100 GeV

~weak

“Higgs portal”

Silveira, Zee (1985)

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Cline et. al [2013]

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WIMP candidates in BSM

Stability :R-parity, KK-parity, T-parity (all Z2)!

- In MSSM, LSP~neutralino = (bino, wino, higgsinos) !

- In UED (or RS), LKP~KK-photon (KK-B or Z)!

many others!! (# of candidate > # of theorists)

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SUSY Dark Matter

Mass =SUSY breaking scale!

Stability = R-parity!

Neutralino = (wino, bino, higgsinoX2)

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KK Dark Matter

!Mass = Quantized momentum to compact extra dimension Stable due to Kaluza-Klein parity KK-photon~TeV fits the right relic density

Planck brane TeV brane

e

gu

y=0 y=pR

WDark matter

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2. Evidences for DM ~invisible mass

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Mass of the earth

Mass of the sun

Mass of our Galaxy

Mass of Universe

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Freely falling bodies !near the surface

Gravitational field is due to the earth mass

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Q. Mass of the sun?

S

Ev

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How heavy is the Galaxy?How heavy is the Galaxy?

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=3.26 Ly

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Huge number of stars in our Galaxy!

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Galaxy is not a single object but a collection of many:

one wants to see the rotation curve!

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Dark Halo

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Galactic Rotation Curve

Expectation:

!

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Observed: v~const

Invisible component exist!

Evidence#1

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Many thousands of Galaxies have been checked! !The behavior quite universal.

dmvisible

Salucci,Burkert [2000]

Rubin etal [1980]

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Some remarksThe size of Galaxy is not known (finite?) ︙ no indication of ‘end’ up to 40kpc!

The shape (not amplitude!) of Rotational curve of different galaxies quite similar

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Galactic Rotation curve

Conservation of the mass (+spherical symmetry)

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mass density

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r-2 dependence strong contrast to the visible number of stars.. Dominant part of Galaxy =Dark!

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A naïve model for Density profile

To include Rigid rotation

!

!

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Better modeling based on Simulations of DM halo

• To go beyond the smooth spherical isotropic model for the galactic halo, numerical studies of the

formation of dark matter halos are used • N-body simulations of the gravitational collapse of a collisionless system of particles have yielded global

properties of halos that are tested against observational data ranging from the scale of dwarf galaxies to galaxy

clusters • There is quite some uncertainly regarding the inner (< few 100 pc) density profiles, however: these central regions in galaxies, groups and clusters are dominated

by baryons

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[ex]GHALO by Moore

GHALO: A billion particle simulation of the dark matter distribution surrounding a galaxy. 3 million cpu hours with the parallel gravity code pkdgrav (Stadel et al 2008)

50 parsec, 1000Mo

resolution, 100,000 substructures

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[ex] Milky way Halo

High resolution (109

particles, each particles has 1000 Mo) cosmological CDM simulation of a Milky Way type halo

<20kpc

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Results: !numerical simulation

NFW-profile !(Navaro-Frenk-White 1996)

General profile

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Profiles

NFW

Isothermal

Large uncertainty in the inner part

of galaxies

(this is important for direct and indirect detection)

Density if low but significant in galactic dynamics! -first noticed by Zwicky 1933

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Gravitational lensingHubble deep field

Can you see Dark Matter ?Evidence#2

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Gravitational lensingstretched shape

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Galaxy Cluster MACS 1206

M/Mvis~6�48

Bullet cluster

http://chandra.harvard.edu/photo/2007/a520/

Two colliding galaxies

S. Randall etal 0704.026!

Evidence#3

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Blue: gravitational potential

seen by lensing

!

Red: visible matter seen by X-ray

Direct evidence for DM!

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http://chandra.harvard.edu/photo/2006/1e0657/1e0657_bullett_anim_lg.mpg

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slide from [K.Choi’s talk at SI2014]�52

Evidence #4 : CMBR

Theory Planck 2013Gravitational potential by the DM at the time of CMBR can be seen in (T-T’)/T

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Evidence #5 : Cosmological acceleration

Theory Perlmutter 1998

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Evidence summaryGalactic rotation curve + Galaxy formation (CDM)

Gravitational lensing

Bullet cluster

CMBR

Cosmological acceleration

SM DM DE

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3. Search strategies

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Search strategies for WIMP

Direct detection of DM+SM scattering (~underground experiments)

Indirect detection of WIMP signals from pair annihilation in Galaxy or in the Sun

Collider search for `missing energy’

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dm+dm -> q +q

dm+ q -> dm+q

q+q -> dm +dm

They are all the same physics!

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Direct detectionWIMP are all around us! (rotation curve, density~0.3 GeV/cm3)!

velocity~240 km/sec (depending on season, why?)!

WIMP can interact with the SM particles (weakly though)!

WIMP-Nucleon recoil energy~1-100keV

a review see e.g. [arXiv:1402.1507]

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n

DM DM

nSignal

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better using heavy nucleon..�62

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R.F.Lang Physics 6, 136 (2013)�65

annual modulation

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Indirect detectionDM in Galaxy would pair annihilate into visible particle

DM+DM -> e+e-, photon, quarks …

propagation model : GALPROP

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several different type of

detectors are required!

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