Dark Matter and Dark Energy components chapter 7 Lecture 4

The early universe chapters 5 to 8 Particle Astrophysics, D. Perkins, 2 nd edition, Oxford 5.The expanding universe 6.Nucleosynthesis and baryogenesis 7.Dark matter and dark energy components 8.Development of structure in early universe Slides + book

Overview Part 1: Observation of dark matter as gravitational effects – Rotation curves galaxies, mass/light ratios in galaxies – Velocities of galaxies in clusters – Gravitational lensing – Bullet cluster Part 2: Nature of the dark matter : – Baryons and MACHO’s – Standard neutrinos – Axions Part 3: Weakly Interacting Massive Particles (WIMPs) Part 4: Experimental WIMP searches: direct & indirect detection Part 5: Dark energy Dark Matter - Dark Energy lect 43

Energy budget of universe today Dark Matter - Dark Energy lect 44 Today only 5% of the matter- energy consists of known particles 25% is Cold Dark Matter = new type of particles 70% is completely unknown Planck, 2013

Where should we look? Search for WIMPs in the Milky Way halo  Indirect detection: expect WIMPs from the halo to annihilate with each other to known particles  Direct detection: expect WIMPs from the halo to interact in a detector on Earth Dark Matter - Dark Energy lect 45 Dark matter halo Luminous disk Solar system © ESO Weakly Interacting Massive Particles

three complementary roads 6 Indirect search experiments direct search experiments Production at the LHC collider Model Dark Matter - Dark Energy lect 4

PART 4: WIMP DETECTION Identify the nature of dark matter with experiment Dark Matter - Dark Energy lect 47

DIRECT DETECTION EXPERIMENTS Dark Matter - Dark Energy lect 48 See Lecture 3

INDIRECT DETECTION EXPERIMENTS Dark Matter - Dark Energy lect 49

Indirect detection of WIMPs Search for signals of annihilation of WIMPs in the Milky Way halo accumulation near galactic centre or in heavy objects like the Sun or Earth due to gravitational attraction Detect the produced antiparticles, gamma rays, neutrinos Dark Matter - Dark Energy lect 410 WIMP e +, γ, υ, p

neutrinos from WIMP annihilations : IceCube Neutrinos from WIMP annihilations in the Sun Neutrinos from WIMP annihilations in galactic halo, galactic centre, dwarf spheroidal galaxies Neutrinos from WIMP annihilations in the centre of the Earth Dark Matter - Dark Energy lect 4

WIMPs accumulated in the Sun Dark Matter - Dark Energy lect 412  Detector μ  ν interaction 1. WIMPs are captured 2. WIMPs annihilate Capture rate Annihilation rate

13 Search for GeV-TeV neutrinos from Sun A few 100’000 atmospheric neutrinos per year from northern hemisphere Max. a few 100 neutrinos per year from WIMPs in the Sun signal ~10 11 atmospheric muons per year from southern hemisphere BG Dark Matter - Dark Energy lect 4

No excess above known background Dark Matter - Dark Energy lect 414 Data Background No significant signal found Rate is compatible with atmospheric background Set upper limit on possible neutrino flux and annihilation rate ψ(deg) Number of events Signal?  νμνμ νμνμ

Combining direct and IceCube searches Dark Matter - Dark Energy lect 415 A selection of SuperSymmetry models Physical review letters 2013

Overview Part 1: Observation of dark matter as gravitational effects – Rotation curves galaxies, mass/light ratios in galaxies – Velocities of galaxies in clusters – Gravitational lensing – Bullet cluster Part 2: Nature of the dark matter : – Baryons and MACHO’s – Standard neutrinos – Axions Part 3: Weakly Interacting Massive Particles (WIMPs) Part 4: Experimental WIMP searches Part 5: Dark energy Dark Matter - Dark Energy lect 416

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Part 5: Dark Energy Observations The nature of Dark Energy ΩΛΩΛ

Energy budget of universe today Dark Matter - Dark Energy lect 419 Today only 5% of the matter- energy consists of known particles 25% is Cold Dark Matter = new type of particles 70% is completely unknown

OBSERVATIONS SNIa surveys Link to cosmological parameters Dark Matter - Dark Energy lect 420

Dark Matter - Dark Energy lect 421 Nobel Prize in Physics 2011

SNIa as standard candles ( see lecture 1 ) Supernovae Ia are very bright - very distant SN can be observed All have roughly the same luminosity curve which allows to extract the absolute magnitude M → effective magnitudes yield luminosity distance Network of telescopes united in – Supernova Cosmology Project SCP, (Perlmutter) up to z=1.4 – have now data from 500 SN ( – High-z SN search HZSNS (Schmidt & Riess, in 1990’s) Dark Matter - Dark Energy lect 422

Luminosity distance vs redshift - 1 SN at redshift z emits light at time t E – is observed at time t 0 Light observed today travelled during time (t 0 - t E ) distance travelled depends on history of expansion Proper distance D H from SN to Earth ( lecture 1, part 2 ) For flat universe (k=0) with negligible radiation content Dark Matter - Dark Energy lect 423

Luminosity distance vs redshift - 2 Luminosity distance Dark Matter - Dark Energy lect 424

Luminosity distance D L vs redshift z Neglect radiation at low z – different examples Dark Matter - Dark Energy lect 425

normalise to empty universe normalise measurements to empty universe Deceleration parameter is zero – universe is ‘coasting’ Dark Matter - Dark Energy lect 426

Hubble plot with high z SNIa Dark Matter - Dark Energy lect 427 Empty universe: Ω m = Ω r =0 Ω k =1 No acceleration no deceleration Vacuum dominated & flat Matter dominated & flat Log D L (Mpc) Redshift Z past Far away & dimmer now

Influence of cosmological parameters best fit Empty universe Dark Matter - Dark Energy lect 428 Difference between measured logD L vs z and expected logD L vs z for empty universe best fit Empty universe measurements

Measurements up to z=1.7 Best fit Dark Matter - Dark Energy lect 429 …. empty --- Best fit Δ (m-M)= ΔD L z q(t)<0 accelerationq(t)>0 deceleration pastpresent

SN observations show acceleration Earlier universe : universe dominated by matter decelerates due to gravitational collapse : Recently : universe dominated by vacuum energy accelerates Acceleration = zero around z=0.5 when → Switch from deceleration (matter dominated) to acceleration (dark energy dominated) Dark Matter - Dark Energy lect 430

Fit ΛCDM model to observations Dark Matter - Dark Energy lect 431 pdg.lbl.gov SN Ia distance-redshift surveys CMB anisitropies survey by WMAP Anisotropies in galaxy surveys

THE NATURE OF DARK ENERGY Related to cosmological constant ? problems Dark Matter - Dark Energy lect 432

Dark vacuum Energy Observed present-day acceleration means that something = Dark Energy generates a negative pressure Yields gravitational repulsion like vacuum energy Equation of state ( see lecture 1 ) Fits to SNIa data yield that w is compatible with vacuum energy Dark Matter - Dark Energy lect 433

Related to cosmological constant Λ? In ΛCDM – Ω Λ is constant and related to Einsteins cosmological constant If Universe contains constant vacuum energy density related to Λ then we set A natural value would be the energy density at the Planck energy scale - energy and length scales And expected energy density Quantum field theory yields same value Dark Matter - Dark Energy lect 434

Cosmological constant problem Today vacuum energy density is of order of critical density Discrepancy of 100 orders of magnitude !!! Did vacuum energy evolve with time? There is no explanation yet need high statistics data : – Dark Energy Survey – start 2011 ( /) / – WFIRST mission of NASA – launch 2020 ( ) – ESA EUCLID mission – launch ( ) Dark Matter - Dark Energy lect 435

Dark Matter - Dark Energy lect 436 © J. Frieman Is w DE constant with time?

Alternatives Quintessence – 5th force : new type of scalar field Mechanism analogue to inflation in early universe Vacuum energy density would vary with time Maybe general relativity works differently at short distances Dark Matter - Dark Energy lect 437

Summary Observations of SNIa emission show that the universe presently accelerates This can be explained by a constant dark vacuum energy contribution which dominates today In the Λ CDM model the dark energy is related to the cosmological constant introduced by Einstein There is yet no satisfactory explanation for the observed magnitude of the dark energy Dark Matter - Dark Energy lect 438

Overview Part 1: Observation of dark matter as gravitational effects – Rotation curves galaxies, mass/light ratios in galaxies – Velocities of galaxies in clusters – Gravitational lensing – Bullet cluster Part 2: Nature of the dark matter : – Baryons and MACHO’s – Standard neutrinos – Axions Part 3: Weakly Interacting Massive Particles (WIMPs) Part 4: Experimental WIMP searches Part 5: Dark energy Dark Matter - Dark Energy lect 439

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