Dark Matter Alejandro Ibarra Technische Universitt Mnchen Summer - - PowerPoint PPT Presentation

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Dark Matter Alejandro Ibarra Technische Universitt Mnchen Summer - - PowerPoint PPT Presentation

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Dark Matter Alejandro Ibarra Technische Universitt Mnchen Summer School on Cosmology ICTP, Trieste August 2014 Main results from the previous lecture WIMP dark matter production DM SM g n i r e t DM t a SM c s

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Dark Matter

Alejandro Ibarra Technische Universität München

Summer School

  • n Cosmology

ICTP, Trieste August 2014

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Main results from the previous lecture

SM SM DM DM

annihilation production s c a t t e r i n g

WIMP dark matter

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WIMP dark matter

SM SM DM DM

annihilation s c a t t e r i n g

Relic abundance of DM particles

production

Main results from the previous lecture

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WIMP dark matter

SM SM DM DM

annihilation s c a t t e r i n g

Relic abundance of DM particles Correct relic density if

production

Main results from the previous lecture

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WIMP dark matter

SM SM DM DM

annihilation s c a t t e r i n g

Relic abundance of DM particles Correct relic density if

production

~ weak interaction

Main results from the previous lecture

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SM SM DM DM

annihilation s c a t t e r i n g

Relic abundance of DM particles Correct relic density if (provided )

WIMP dark matter

production

~ weak interaction

DM DM SM SM

Main results from the previous lecture

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Collider searches

DM nucleus  DM nucleus DM DM  g X, e+e-... (annihilation) pp  DM X

Indirect detection Direct detection

DM  g X, e+X... (decay)

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Collider searches

DM nucleus  DM nucleus DM DM  g X, e+e-... (annihilation) pp  DM X

Indirect detection Direct detection

DM  g X, e+X... (decay) DM DM  g X, e+e-... (annihilation)

Indirect detection

DM  g X, e+X... (decay)

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Collider searches

DM nucleus  DM nucleus DM DM  g X, e+e-... (annihilation) pp  DM X

Indirect detection Direct detection

DM  g X, e+X... (decay) DM nucleus  DM nucleus

Direct detection

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Collider searches

DM nucleus  DM nucleus DM DM  g X, e+e-... (annihilation) pp  DM X

Indirect detection Direct detection

DM  g X, e+X... (decay)

Collider searches

pp  DM X

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Ind ndirect Da Dark Ma k Matter Searche hes

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General idea:

1) Dark matter particles annihilate or decay producing a flux of stable particles: photons, electrons, protons, positrons, antiprotons or (anti-)neutrinos. 3) The products of the dark matter annihilations or decays are detected together with other particles produced in astrophysical processes (for example, cosmic ray collisions with nuclei in the interstellar medium). The existence of dark matter can then be inferred if there is a significant excess in the fluxes compared to the expected astrophysical backgrounds.

Indirect dark matter searches

2) These particles propagate through the galaxy and through the Solar System. Some of them will reach the Earth.

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Indirect dark matter searches

Antimatter Gamma-rays Neutrinos Production Propagation Detection

  • f
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Antimatter Antimatter

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The production is described by the source function: number of particles produced at a given position per unit volume, unit time and unit energy.

Production Production

DM DM DM

Annihilation rate  r2 Decay rate  r

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Propagation Propagation

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Propagation

x y z

R = 20 kpc L=1-15 kpc

f : number density of antiparticles per unit kinetic energy interstellar antimatter flux:

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PAMELA collaboration arXiv:1007.0821

Experimental results: antiprotons

Fairly good agreement between the measurements and the theoretical predictions from collisions of cosmic rays on the interstellar medium p p → p X

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Expectation

  • ns from
  • m theor
  • ry

A concrete example in the minimal supersymmetric standard model.

TeV 10-26 cm3s-1

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A concrete example in the minimal supersymmetric standard model.

TeV 10-26 cm3s-1

sv = 3  10-26 cm3s-1

Expectation

  • ns from
  • m theor
  • ry
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A concrete example in the minimal supersymmetric standard model.

TeV 10-26 cm3s-1

Expectation

  • ns from
  • m theor
  • ry
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A concrete example in the minimal supersymmetric standard model.

TeV 10-26 cm3s-1

Annihilation rate “boosted”!

Expectation

  • ns from
  • m theor
  • ry
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Experimental results: positrons

Expected from “secondary production”, namely collisions of cosmic rays on the interstellar medium (p p → e+ X).

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Experimental results: positrons

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Experimental results: positrons

PAMELA coll. arXiv:0810.4995

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Experimental results: positrons

AMS-02 coll. Phys.Rev.Lett. 110 (2013) 14, 141102

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More puzzles: the electron+positron flux

Abdo et al. ArXiv:0905.0025

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Present situation: Evidence for a primary component of positrons

(possibly accompanied by electrons)

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Cholis et al. arXiv:0811.3641

An electron/positron excess could arise from dark matter annihilations ...

Dark matter inter erpretation

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… or dark matter decays

“Democratic” decay n

Ibarra, Tran, Weniger mDM=2500 GeV mDM=600 GeV AI, Tran, Weniger arXiv:0906.1571

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sv = 3  10-26 cm3s-1

Is this the first non-gravitational evidence of dark matter?

“Extraordinary claims require extraordinary evidence” Carl Sagan

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Beware of backgrounds!

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Pulsars Pulsars are are sources sources

  • f high energy
  • f high energy

electrons electrons & & positrons positrons

Atoyan, Aharonian, Völk '95 Chi, Cheng, Young '95 Grimani '04

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Pulsar expl xplana nati tion

  • n I: Ge

Gemi ming nga + Mo Monog

  • gem

Monogem (B0656+14) Geminga

T=370 000 years D=157 pc T=110 000 years D=290 pc

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Nice agreement. However, it is not a prediction!

  • dNe/dEe

 Ee

  • 1.7 exp(-Ee/1100 GeV)
  • Energy output in e+e- pairs: 40% of the spin-down rate

Pulsar expl xplana nati tion

  • n I: Ge

Gemi ming nga + Mo Monog

  • gem

Grasso et al.

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  • dNe/dEe

 Ee

  • a exp(-Ee/E0), 1.5 < a < 1.9, 800 GeV < E0 < 1400 GeV
  • Energy output in e+e- pairs: between 10-30% of the spin-down rate

Pulsar exp xplanati tion

  • n II:

: Mul ulti tipl ple pul pulsars

Grasso et al.

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The origin of the positron excess is still unclear:

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The origin of the positron excess is still unclear:

 Dark matter? Probably not.

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The origin of the positron excess is still unclear:

 Dark matter? Probably not.  Pulsars? Perhaps yes.

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The origin of the positron excess is still unclear:

 Dark matter? Probably not.  Pulsars? Perhaps yes.  Something else? Perhaps yes.

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The origin of the positron excess is still unclear:

 Dark matter? Probably not.  Pulsars? Perhaps yes.  Something else? Perhaps yes.  Regardless of the origin of the positron excess, the positron data can be used to set limits on the dark matter parameters.

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Latest limits from the positron fraction:  Use AMS-02 data  Make a fit of a model with secondary positrons + source + dark matter

AI, Lamperstorfer, Silk '13 See also Bergström et al. '13

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Gamma-rays Gamma-rays

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The gamma ray flux from dark matter annihilations/decays has two components:  Prompt radiation of gamma rays produced in the annihilation/decay (final state radiation, pion decay...)  May contain spectral features.  Inverse Compton Scattering radiation of electrons/positrons produced in the annihilation/decay.  Always smooth spectrum.

Production of gamma-rays Production of gamma-rays

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Inverse Compton Scattering radiation

The inverse Compton scattering of electrons/positrons from dark matter annihilation/decay with the interstellar and extragalactic radiation fields produces gamma rays.

e from dark matter annihilation/decay Ee  1 TeV Interstellar radiation field (starlight, thermal radiation of dust, CMB) Upscattered photon

This produces

Eg*  100 GeV

Porter et al.

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Prompt radiation

Annihilation Decay Source term (particle physics) Line-of-sight integral (astrophysics)

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Annihilation Decay Source term (particle physics) Line-of-sight integral (astrophysics)

Prompt radiation

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Propagation Propagation

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Where to look for annihilating dark matter

Kuhlen, Diemand, Madau Baltz et al. arXiv:0806.2911

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Kuhlen, Diemand, Madau

Where to look for annihilating dark matter

Baltz et al. arXiv:0806.2911

Galactic center

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Kuhlen, Diemand, Madau

Where to look for annihilating dark matter

Baltz et al. arXiv:0806.2911

Satellites

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Kuhlen, Diemand, Madau

Where to look for annihilating dark matter

Baltz et al. arXiv:0806.2911

Galactic halo

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Kuhlen, Diemand, Madau

Where to look for annihilating dark matter

Baltz et al. arXiv:0806.2911

Extragalactic background

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Kuhlen, Diemand, Madau

Where to look for annihilating dark matter

Baltz et al. arXiv:0806.2911

Galaxy clusters

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Kuhlen, Diemand, Madau

Where to look for annihilating dark matter

Baltz et al. arXiv:0806.2911

Features in the energy spectrum

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Divide the sky in different regions: 3°  3°

Diffuse Galactic emission

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5°  30° Divide the sky in different regions:

Diffuse Galactic emission

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10° - 20° galactic latitude Divide the sky in different regions:

Diffuse Galactic emission

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Galactic poles Divide the sky in different regions:

Diffuse Galactic emission

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Background I: sources But beware of backgrounds when searching for dark matter...

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Inverse Compton Bremmstrahlung

p0-decay

Background II: modelling of the diffuse emission

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Cirelli, Panci, Serpico

Conservative approach: demand that the flux from dark matter annihilation does not exceed the measured flux

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Cirelli, Panci, Serpico

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Dwarf spheroidal galaxies

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High mass-to-light ratio: dwarf galaxies contain large amounts of dark matter Relatively close

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Assume a Navarro-Frenk-White dark matter halo profile inside the tidal radius:

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Constraints on WIMP dark matter models

Fermi coll. arXiv:1001.4531

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Closing in on light WIMP scenarios from dwarf galaxy observations

Geringer-Sameth, Koushiappas '11

MDM> 40 GeV for DM DM → b b MDM> 19 GeV for DM DM → t+ t-

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“Smoking gun” for dark matter: no (known) astrophysical process can produce a sharp feature in the gamma-ray energy spectrum

Gamma ray line Gamma ray box Internal bremsstrahlung

Three gamma-ray spectral features have been identified:

Gamma-ray features

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Gamma-ray lines

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Fermi-LAT col. arXiv:1305.5597

Gamma-ray lines

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Fermi-LAT col. arXiv:1305.5597

Gamma-ray lines

“Canonical value of sv”

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Fermi-LAT col. arXiv:1305.5597

Expected cross section

Gamma-ray lines

DM DM SM SM DM DM

“Canonical value of sv”

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Internal Bremsstrahlung

DM DM SM SM med g

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Internal Bremsstrahlung

DM DM SM SM med g

Bringmann, Huang, AI, Vogl, Weniger arXiv:1203.1312

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Internal Bremsstrahlung

DM DM SM SM med g

“Canonical value of sv”

Bringmann, Huang, AI, Vogl, Weniger arXiv:1203.1312

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Internal Bremsstrahlung

DM DM SM SM med g

“Canonical value of sv”

Bringmann, Huang, AI, Vogl, Weniger arXiv:1203.1312

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H.E.S.S. II – in operation GAMMA 400 – Launch in 2018 DAMPE – Launch in 2015 CTA – Construction starting in 2017 Bright future for dark matter searches using gamma-rays!

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Di Direct Da Dark Ma k Matter Searche hes

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Direct dark matter searches

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General idea:

1) The Sun (and the Earth) is moving through a “gas” of dark matter

  • particles. Or, from our point of view, there is a flux of dark matter particles

going through the Earth.

Direct dark matter searches

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General idea:

1) The Sun (and the Earth) is moving through a “gas” of dark matter

  • particles. Or, from our point of view, there is a flux of dark matter particles

going through the Earth.

Direct dark matter searches

2) Once in a while a dark matter particle will interact with a nucleus.

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General idea:

1) The Sun (and the Earth) is moving through a “gas” of dark matter

  • particles. Or, from our point of view, there is a flux of dark matter particles

going through the Earth.

Direct dark matter searches

2) Once in a while a dark matter particle will interact with a nucleus. 3) The nucleus gains momentum and recoils. The existence of dark matter can then be inferred if there is a significant excess in the number of recoils compared to the expected recoils induced by natural radiactivity in your lab

  • r in your detector.
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… bu but ve very ch challenging in practice! Simp mple idea ...

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Annual modulation

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June 2nd December 2nd

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June 2nd December 2nd

DM M in interpretation very controversial! l! Mo More later...

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Kuhlen et al.'09

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Billard, Figueroa-Feliciano, Strigari '14

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arXiv:1304.4279

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Billard, Figueroa-Feliciano, Strigari '14

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