cosmo 2013 dark matter overview - centre for theoretical ... · cosmo 2013 dark matter overview ....

Malcolm Fairbairn

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COSMO 2013 Dark Matter Overview

Dec. 1-8, 2010

• Reminder – Why we think Dark Matter exists

• Indirect Detection of WIMPs

• Direct Detection of WIMPs

• Some Particle Models of WIMPs which are

still healthy in September 2013

Program

Evidence for Dark Matter

What’s all the rest???

10-29 4 x 10-31

2

“I have a good idea every two years. Give me a topic, I will give you the idea!”

Fritz Zwicky Coma Cluster 1933

velocity of galaxies in the cluster is too large for the visible mass of the cluster

Bullet Cluster

SDSS

HI velocity field of NGC 5055

Lensing Also Suggests Presence of Dark Matter

+

Wimps Work !

(at least for the dark matter bit)

Right amount of dark matter if dark matter mass 100 MeV < M < 100 TeV

We know that WIMP self annihilation

cross section has to be 3x10-26cm3s-1

WIMP indirect detection

Dark Matter Self-Annihilation

Rate of self-annihilation of Dark Matter

We think we might know this

But how well do we know this

at the Galactic Centre?

And we have some ideas about this

Navarro et al 0810.1522

Simulations show halos denser in middle.

http://www.mpa-garching.mpg.de/aquarius/

Aquarius Simulations

Springel et al.

Comparison of

actual flux

with DM ann.

flux

Same Vertical

scale

g=1.2

g=1.6-1.7 The Galactic Centre

Coincidence

g = - d ln r / d ln r

Fermi Signal

Boyarsky et al. 1012.5839

Has Fermi detected

dark matter

annihilation at the

galactic centre?

Hooper and Goodenough.

arXiv:1010.2752

Bulge

Disc

Total

?

Boyarsky et al 1012.5839 Chernyakova et al. 1009.2630

Hooper+Goodenough purported DM spectrum

Alternative explanation for spectrum

Boyarsky et al 1012.5839 Chernyakova et al. 1009.2630

Chernyakova et al. purported proton induced spectrum

Alternative explanation for spectrum

Difference between scenarios may be

apparent using radio synchrotron,

situation unclear as yet

Fermi Analysis

Looking specifically

for Lines (Weniger 1204.2797)

Choose only those

pixels that will

together maximise

the overall signal to

noise ratio.

This choice is

based upon known

sources and differs

for each assumed

halo model.

Possible Evidence

for 130 GeV Dark

Matter

Annihilation Line?

4.6s or 3.3s when

taking into account

“look elsewhere” effect

Test statistic TS follows nice Poisson distribution

when applied to random data where you don’t

expect signal.

Bump in Energy Response of Fermi at 133 GeV?

Observations of the Earth Limb arXiv:1305.5597

!!!

Repeated baryonic

contraction and

shocking reduces

central density of

dark matter.

If correct, bad for

indirect detection

signals.

arXiv:1202.0554

GENERAL NEW

PROBLEM FOR

INDIRECT

SEARCHES?

dSphs - Dwarf Spheroidal Galaxies

What can Inner Density Profile

of dSph galaxies tell us?

• Expected WIMP annihilation signal

• Is dark matter self interacting?

• Is dark matter warm/hot-cold/mixed/decaying

BORING HEALTH WARNING:- Gastrophysical effects can affect inner densities as

well as sexy new physics

Fermi constraints on gamma ray emission from Dwarf Spheroidals

However, this makes assumptions about the density

distribution that many people question. arXiv:1108.3546

Again, Baryonic Effects on the Cusps May Be Important

Governato et al.

arXiv:1202.0554

Tangential

Velocity

Dispersion

Radial

Velocity

Dispersion

Can obtain this by fitting data

Cannot observe this directly for stars so free parameter

How do you work out how much

DM in Dwarf Spheroidals?

Use the Jeans equation and the line of sight stellar dispersion

Scenes from

Spherical/triaxial

Working Group at the

Gaia Challenge

University of Surrrey,

two weeks ago

New Method to Constraint Density of Dwarf Spheroidals

MF with Tom Richardson

Recovering test data

Red lines are

actual values

With and Without 4th

order information (Kurtosis)

G = d ln M / d ln r

Richardson and Fairbairn 2013

DOESN’T ALWAYS WORK SO WELL… YET

(see Tom’s Talk)

Positrons!

Pamela and AMS both see positrons

If you accept certain prerequisites,

Fermi and PAMELA data can be fit by dark matter.

Branching ratio into e+e-

Thermally averaged self annihilation cross section at freeze-out

Thermally averaged self annihilation cross section today

Expected local density (0.3 GeV cm-3)

Actual local density

Possible origins of the Boost Factor

This enhancement not thought to be

large enough, see e.g. Pieiri, Lavalle,

Bertone and Branchini 0908.0195

Sommerfeld Enhancement

S-channel annihilations

P-channel annihilations

Need something else to enhance the cross section. If

Then dark matter particles are pulled together by exchange of W,Z bosons, enhancing annihilation by


In general, we can consider a much lighter GeV boson, weakly coupled (Arkani-Hamed & Weiner 0810.0713)

Also DM annihilates through boson – muon final states! (no helicity supression)

However, since cross section goes like 1/v, forms problems for first structures formed (Kamionkowski and Profumo)


In general, we can consider a much lighter GeV boson, weakly coupled (Arkani-Hamed & Weiner 0810.0713)

Also DM annihilates through boson – muon final states! (no helicity supression)

However, since cross section goes like 1/v, forms problems for first structures formed (Kamionkowski and Profumo)

i.e. the poor guy

who’s flight got

cancelled

Possible astrophysical origin of electrons/positrons 10 GeV – 10 TeV

SNR - Secondary Pulsars - Primary

Where are we now?

HOWEVER, 3% anisotropy still larger than that expected

from single pulsar, Linden and Profumo 1304.1791

SLIDE

STOLEN

FROM

AMS

WEBSITE

INDIRECT DETECTION:-

CONCLUSIONS

• Hints from galactic centre of low mass WIMPs.

• Other astrophysical explanations exist.

•Hints from galactic centre of gamma ray delta function.

• Understanding the density profile of Dwarf Spheroidals is important.

• Anomalous Positron and Electron flux might be a signal, might not.

An Aside – Self Interacting Dark Matter

1. Theories with Sommerfeld Enhancement contain

exchange boson leading to inter-DM force

2. Missing Satellites Problem (not enough dSph)

3. Core vs. Cusp Problem (dSph “cored not cuspy”)

4. Too Big to Fail Problem (Biggest dSph not as big as

CDM predictions)

MOTIVATIONS

2. and 3. can potentially be solved with baryons, 4. with baryons and

bad estimate for Milky Way Mass and 1. could just be plain wrong.

NEED TO TEST IT


For a potential

You expect the perturbative cross section (easy to work with)

However for real astrophysical systems, things can get non-perturbative, need to use

classical expressions from fitting numerical modelling of individual classical scattering in

potentials

Also many resonant effects (see e.g. Zurek 1302.3898)


Besides these difficulties, people are trying to constrain such

models using objects such as the Bullet Cluster and

Elliptical Galaxy NGC-720

Typical constraints are currently ~ cm2/g

which is around 1012 times weak interaction

Direct detection of dark matter

Solar Orbit signal

The State of the ART: XENON100+ Others

CDMS-II Recent Data 1304.4279

“5.4%” prob!!!

CDMS-II signal at 8.6 GeV?

XENON100

Spherical Sources of

Astrophysical Uncertainty

• Uncertain Density profile

• Uncertain mass of galaxy

• Spherical Baryonic contraction

• Non Maxwellian Velocities

• Lack of knowledge of velocity Anisotropy b(r)

• Uncertain solutions to Jeans Equation

Non-Spherical Sources of

Astrophysical Uncertainty

• Tidal Streams

• Substructure

• Dark Discs (density and/or velocity)

• Effect of Baryonic Disk

• Effect of Spiral Arms

• Lack of axial symmetry of Galaxy

Let’s just look at Uncertainties in Spherical Profile

Tangential

Velocity

Dispersion

Radial

Velocity

Dispersion

Solutions of Jeans Equations

Can obtain this by fitting data

Cannot observe this so cannot be fitted

Fitting Galactic Parameters

Use Observed Baryonic Profile and Einasto Profile for Dark matter

Fit:-

• rotation of galactic disk

• local rotation and derivative

• Motion of distant blue stars

• Motion of Milky Way Satellites

Fairbairn, Douce and Swift 2012 (following Catena and Ullio)

Prediction for Local Density

Fairbairn, Douce and Swift 2012

Prediction for Escape Velocity


Prediction for Velocity Dispersion

Fairbairn,

Douce and

Swift 2012

Then have to solve Jeans equation in this potential

Also include non-Gaussianity


Variation due to all these effects

Doesn’t include streams from Local Group…

Left Hand Wall particularly Sensitive to Escape Velocity….

…. However this doesn’t necessarily help reconcile, for

example, CDMS and XENON100

450 km/s

• These Astrophysical issues affect different

experiments in different ways.

• Spherical Uncertainties much worse at low mass.

• Need a significant detection at multiple detectors

to 1) get a signal and 2) measure the mass

LUX- ZEPLIN 9 Tons

The UK forum for direct dark matter searches

“The DMUK Institute Board has decided to choose LUX-ZEPLIN as the UK direct dark matter project for a capital funding proposal to STFC in 2013/14. The current UK groups (Imperial, Edinburgh, UCL, RAL) already on LZ will be strengthened by Kraus and his group from Oxford and Kudryavtsev from Sheffield joining LZ. This is a decisive step in the implementation of the STFC Science Board Dark Matter Sub-Group Strategy for Dark Matter.”

SNOWMASS Cosmic Frontiers 2013 (preprint)

Some Particle Models of WIMPs

which are still healthy in

September 2013

Constrained Minimal Supersymmetric

Standard Model

All sfermion masses equal at GUT scale

All gaugino masses equal at GUT scale

Reduced to 5 free parameters

Superpartners of neutral gauge and higgs bosons mix into four

majorana neutralinos which make good WIMP candidate

Is Neutralino Dark Matter Still OK?

Higgs too

light

Stau lighter than neutralino

No EW breaking min. tan b=51

Stolen from Oliver Buchmuller

talk at Dark Attack

Stolen from Oliver Buchmuller talk at Dark Attack

Changing Direct Detection Predictions

Stolen from Oliver Buchmuller talk at Dark Attack

(SUSY no-show, 125/6

GeV Higgs & XENON100)

Changing Direct Detection Predictions

So, CMSSM under pressure.

Is that because it is too C, M and not enough SSM?

Phenomenological Minimal Supersymmetric Standard Model PMSSM

See e.g.

Boehm, Dev,

Mazumdar &

Pukartas 2013

Fine tuning is sensitivity of

(observed) Z-mass to small

changes in parameters

Fits in PMSSM

Low mass DM Boehm, Dev,

Mazumdar &

Pukartas 2013

Higher mass DM Grothaus, Lindner and

Yakanishi 2012

Higgs Portal Dark Matter

Simply another particle which couples to the Standard model

through the Higgs

Scalar dark matter Standard model Higgs Field

V. Silveira, A. Zee, Phys. Lett. B161, 136 (1985);

J. McDonald, Phys. Rev. D50 (1994) 3637-3649;

C. P. Burgess, M. Pospelov, T. ter Veldhuis, Nucl. Phys. B619 (2001) 709-728 [hep-ph/0011335]

Higgs Portal Dark Matter

In fact you can look at scalar, vectorial and fermionic partners also.

One Example of a working Higgs Portal model

Fairbairn and Hogan 2013

Scalars help with Higgs Stablity

Degrassi et a;

Particle Candidates:- Conclusion

• As the LHC probes the electroweak scale, all WIMP

models are facing tighter constraints as one would

expect

• The simplest models of SUSY are under severe

pressure, but it will be some time before SUSY itself can

be ruled out as the origin of dark matter.

• Many more much simpler models are being studied in

the light of the new data which will also face (welcome)

pressure in the next few years.

CONCLUSIONS

Indirect, Direct and Collider experiments are severely

constraining the parameter space of WIMP models.

THIS IS GOOD!!!

With more running of the LHC and the next generation of

direct detection experiments, SEVERE constraints will be

placed on MOST WIMP scenarios.

Astrophysicists and Particle Physicists are working

together in new ways to constrain the nature of dark

matter, be it WIMPs or otherwise

Next few years will be a VERY exciting time for

dark matter physics.

Additional Material



Additional scalar field s coupled only through the Higgs:-

S is coupled to a singlet Dirac Fermion which is dark matter

Leads to two mass eigenstates and a mixing angle

Constrained by experiment


(Ellis and You ’13,

Falkowski, Riva and Urbino, ‘13)

Similar analogous constraints for the decay of h2.

Still plenty of room though…

Earth goes round Sun, Sun goes round Galaxy Annual Modulation Signal

Annual modulation signal

DAMA/LIBRA results

Is Dark Matter explanation of PAMELA ruled out by Synchrotron?

Bertone et al arXiv:0811.3744.

Monojets at the LHC

Imagine some purely phenomenological contact interactions for

coupling between dark matter and standard model particles

Bai, Fox and Harnik arXiv:10053797

Slide stolen from Steve Worm Oxford Presentation

Monojet/Monophoton

Constraints from CMS

CMS collaboration CMS-PAS-EXO-12-048

Precise constraints vary hugely depending upon

assumed nature of interaction, Majorana vs Dirac etc…

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