Dark Matter. Axel Lindner, DESY. with contributions by Bridget Sheeran and Augustinas Malinauskas. DESY Summer Student Lecture, August 17 th, 2015

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1 Dark Matter Axel Lindner, DESY with contributions by Bridget Sheeran and Augustinas Malinauskas DESY Summer Student Lecture, August 17 th, 2015

2 Our dark matter menu > Starters Historical annotations: how to discover new stuff? Our anchor: the Standard Model of particle physics > Main course 1 The necessity of Dark Matter Alternatives and hidden assumptions > Main course 2 Dark matter candidates Searching for Dark Matter candidate particles Direct searches for Dark Matter particles > Dessert Astrophysical puzzles > Doggy bag Summary and outlook Axel Lindner DESY Summer Students 2015 Dark Stuff Page 2

3 Our dark matter menu > Starters Historical annotations: how to discover new stuff? Our anchor: the Standard Model of particle physics > Main course 1 The necessity of Dark Matter Alternatives and hidden assumptions > Main course 2 Dark matter candidates Searching for Dark Matter candidate particles Direct searches for Dark Matter particles > Dessert Astrophysical puzzles > Doggy bag Summary and outlook Dark Matter Coffee 738 North Western Ave Chicago, IL Axel Lindner DESY Summer Students 2015 Dark Stuff Page 3

4 Is there additional stuff around? Some reminders from history: > Discovery of Neptune by irregularities of the Uranus orbit: Sept. 24th 1846 by Johann Gottfried Galle at the Berlin Observatory. > An application of the known laws of nature (gravitation) led to the discovery of previously invisible mass.. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 4

Is there additional stuff around? Some reminders from history: > Motion of the perihelion of Mercury: http://www.schoolphysics.co.uk/age16-19/relativity/text/ Perihelion_of_mercury/index.

5 Is there additional stuff around? Some reminders from history: > Motion of the perihelion of Mercury: Perihelion_of_mercury/index.html Attempts to describe this by the gravitational pull of a new planet Vulcan failed (in spite of numerous observations ). Finally the explanation was given by General Relativity. > A failed search for an invisible mass strongly supported an improved theory of gravitation. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 5

6 A recipe for discoveries Apply known laws of nature in regions where they have not been tested before. > New regions of space Quantum mechanics > New regions of time Cosmology > More energetic particle collisions LHC > More precise experiments ALPS DESY You might find deviations from expectations hinting at > New stuff Neptune discovery > More fundamental laws of nature General relativity Axel Lindner DESY Summer Students 2015 Dark Stuff Page 6

7 Our starting point: what we know > Microcosm: down to m > Macrocosm: up to m > And we even know about how connecting quarks and the cosmos. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 7

8 Cornerstone I: the Standard Model of particle physics With these few constituents and forces all phenomena observed on earth can be described (in principle). Since more than 30 years there is not a single particle physics experiment really questioning the Standard Model. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 8

However (see later): Evidence for gravitational waves at

9 Cornerstone II: understanding gravity > General relativity paved the way to understand the universe. However (see later): Evidence for gravitational waves at PSR (Nobel prize 1993 to Hulse and Taylor) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 9

http://www.physicsoftheuniverse.com/topics_bigbang_expanding.html Cornerstone III: the history of the universe > The universe started as a tiny point (a quantum fluctuation?

10 Cornerstone III: the history of the universe > The universe started as a tiny point (a quantum fluctuation?), has expanded to its present size and keeps on expanding. > It cools down during this expansion. Cosmology lectures by A. Westphal on 2 September! > Thus high energy particle physics gives an insight to the early universe. > Thus the universe might teach us about particle physics. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 10

Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. http://thebricklife.

11 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 11

12 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 12

13 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 13

14 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 14

15 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 15

16 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Two important consequences: The binding of electrons to nuclei releases radiation. The universe becomes transparent for the first time (because the matter inside becomes neutral for the first time), so that this radiation propagates freely. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 16

http://map.gsfc.nasa.gov/media/990053/990053sb.jpg Cornerstone IV: the quark-cosmos connection > We understand how everything evolved.

17 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 17

18 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 18

19 Cornerstone IV: the quark-cosmos connection > We understand how everything evolved. We know this precisely and not only in a qualitative way! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 19

20 Frontiers In spite of the successes mentioned, physicists are nor satisfied with the present picture. Some very fundamental questions still escape any explanation: > How does particle physics work in strong gravitational fields? The standard model does not include gravitation. > Why aren t there equal amounts of matter and antimatter in the universe? The standard model can not describe the early universe. > Why is the geometry of the universe flat? The standard model overestimates the energy content of space by a factor We do not understand the vacuum. > How can we understand the (value of the) masses and numbers of the SM particles? > Axel Lindner DESY Summer Students 2015 Dark Stuff Page 20

21 A brief review of the Standard Model There exist numerous theories for beyond standard model (BSM) physics. Experimental guidance is required to figure out which of these theories is realized in nature. However, at present there is not a single experiment at earth hinting (convincingly) at BSM physics. But indications for BSM physics become obvious in the sky. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 21

22 Our dark matter menu > Starters Historical annotations: how to discover new stuff? Our anchor: the Standard Model of particle physics > Main course 1 The necessity of Dark Matter Alternatives and hidden assumptions > Main course 2 Dark matter candidates Searching for Dark Matter candidate particles Direct searches for Dark Matter particles > Dessert Astrophysical puzzles > Doggy bag Summary and outlook Axel Lindner DESY Summer Students 2015 Dark Stuff Page 22

23 Discussion time > What is meant by dark matter? > Which evidences do we have today for dark unknowns in the universe? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 23

24 A closer look to the universe From the laboratory to the edge of the visible universe. > Laboratory: Many very different experimental tests do not show any hint for BSM physics! LHC Bouncing neutrons in the earth s gravitation Axel Lindner DESY Summer Students 2015 Dark Stuff Page 24

25 A closer look to the universe From the laboratory to the edge of the visible universe. > Solar system: Gravitation works perfectly! Parameterized-Post-Newtonian formalisms (general relativity =β=1). (from Slava G. Turyshev, JPL 2012) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 25

26 A closer look to the universe From the laboratory to the edge of the visible universe. > Galaxies: things get weird. Jan H. Oort 1932: The visible mass cannot provide a sufficient gravitational pull to bind the stars to the milky way. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 26

27 A closer look to the universe From the laboratory to the edge of the visible universe. > Galaxies: things get weird. Vera Rubin: n6960/full/425773a.html Axel Lindner DESY Summer Students 2015 Dark Stuff Page 27

28 A closer look to the universe From the laboratory to the edge of the visible universe. > Galaxies: things get weird. Galaxies don t rotated as they should according to the visible mass distribution. Far away from the center: GmM r 2 = m v2 r v = MG r Axel Lindner DESY Summer Students 2015 Dark Stuff Page 28

29 How to measure a Rotation Curve Results from data collected using the 7-m radio telescope at Jodrell Bank Observatory (University of Manchester, UK) Bridget Sheeran

31 The 21-cm HI line

32 HI Profiles of the Milky Way

33 Differential Rotation l V R = V max + V 0 sin l [Diagram taken from arxiv: v1]

34 The Rotation Curve of the Milky Way F = GMm a 2 F = mv2 a v~ 1 a

35 The Rotation Curve of the Milky Way [Figure from Clemens, Ap. J., 295, 422, 1985]

36 Mass Distribution of the Milky Way M = v2 a G

37 Extragalactic Astronomy: M31 Total visible mass Dynamical 7.1 ± M 4.35 ± M Visible to Dynamical Mass Ratio: 0.16 ± 5%

38 A closer look to the universe From the laboratory to the edge of the visible universe. > Galaxies: things get weird. Galaxies don t rotated as they should according to the visible mass distribution. NGC 3198 Far away from the center: GmM a 2 = m v2 a v = const. M = M 0 a Axel Lindner DESY Summer Students 2015 Dark Stuff Page 38

39 A closer look to the universe From the laboratory to the edge of the visible universe. > Galaxies: things get weird. Galaxies don t rotated as they should according to the visible mass distribution. expected observed Axel Lindner DESY Summer Students 2015 Dark Stuff Page 39

40 A closer look to the universe From the laboratory to the edge of the visible universe. > Galaxies: things get weird. The visible matter of galaxies is embedded in a large halo of dark matter. v = MG r = const M r = Mo r Dark matter 10 visible matter! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 40

41 A closer look to the universe From the laboratory to the edge of the visible universe. > Cluster of galaxies: Axel Lindner DESY Summer Students 2015 Dark Stuff Page 41

http://ircamera.as.arizona.edu/natsci102/natsci102/lectures/galaxydist.

> Cluster of galaxies: Galaxies within clusters move much too fast to be bound by the gravitation of the visible mass.

42 A closer look to the universe From the laboratory to the edge of the visible universe. > Cluster of galaxies: Galaxies within clusters move much too fast to be bound by the gravitation of the visible mass. Clusters do not diffuse in spite of the high speed of the galaxies. > Some dark matter has to provide the necessary gravitational potential. This dark component was first proposed 1933 by F. Zwicky after analysis of the Coma cluster. Dark matter 30 visible matter Axel Lindner DESY Summer Students 2015 Dark Stuff Page 42

A closer look to the universe From the laboratory to the edge of the visible universe. > Gravitational lensing: http://www.lsst.org/files/img/xxnyt.

43 A closer look to the universe From the laboratory to the edge of the visible universe. > Gravitational lensing: Light is bent by mass and hence can trace also invisible mass. If one knows how the undistorted image looks like, one can determine the properties (mass) of the gravitational lens. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 43

A closer look to the universe From the laboratory to the edge of the visible universe. > Gravitational lensing: Light is bent by mass and hence can trace also invisible mass. http://astronomyonline.

44 A closer look to the universe From the laboratory to the edge of the visible universe. > Gravitational lensing: Light is bent by mass and hence can trace also invisible mass. If one knows how the undistorted image looks like, one can determine the properties (mass) of the gravitational lens. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 44

45 A closer look to the universe From the laboratory to the edge of the visible universe. > Gravitational lensing: it s out there! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 45

46 A closer look to the universe From the laboratory to the edge of the visible universe. > Gravitational lensing: tomography of the universe. Dark matter 30 visible matter Axel Lindner DESY Summer Students 2015 Dark Stuff Page 46

Observe light originating from the recombination of electrons and nuclei in the early

47 A closer look to the universe From the laboratory to the edge of the visible universe. > Cosmic Microwave Background Radiation: the edge of the visible universe. Observe light originating from the recombination of electrons and nuclei in the early universe well before any structures have emerged. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 47

48 A closer look to the universe From the laboratory to the edge of the visible universe. > Cosmic Microwave Background Radiation: the edge of the visible universe. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 48

> Cosmic Microwave Background Radiation: Axel Lindner

49 A closer look to the universe From the laboratory to the edge of the visible universe. > Cosmic Microwave Background Radiation: the edge of the visible universe. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 49

http://sci.esa.int/planck/ A closer look to the universe From the laboratory to the edge of the visible universe.

50 A closer look to the universe From the laboratory to the edge of the visible universe. > Cosmic Microwave Background Radiation: the edge of the visible universe. Dark matter / ordinary matter = 5.5! In addition: 68% dark energy! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 50

$dark energy (Einstein s Λ) > Dark energy is an attribute of space. Dark energy per volume is constant. The larger the universe, the larger the fraction of dark energy!$

51 More dark stuff: dark energy drives the universe apart Measurements of Supernovae Ia by the Hubble Space Telescope (and others): > There is a repulsive force ("anti-gravitation") best explained by dark energy (Einstein s Λ) > Dark energy is an attribute of space. Dark energy per volume is constant. The larger the universe, the larger the fraction of dark energy! > The universe expands currently with increasing speed! > This scenario is strongly confirmed by analyses of the Cosmic Microwave Background Radiation and many other data! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 51

52 Precision cosmology! > Geometry of the Universe: flat > Age of the Universe: ± Gyr > Hubble Constant: 67.9 ± 1.5 km s -1 Mpc -1 > Fluctuations compatible with inflation > Ω b (baryons): > Ω c (dark matter): > Ω Λ (dark energy): ± > Early star light (re-ionisation): Ω ν << Ω dm Very good agreement among very different data (CMBR, supernova search with HST, galaxy counting, Big Bang Nucleonsynthesis,...) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 52

built a universe by NASA: http://map.gsfc.nasa.

53 built a universe by NASA: Axel Lindner DESY Summer Students 2015 Dark Stuff Page 53

The smoking gun observation for dark matter? Bullet cluster 1E 0657-56: merging of two galaxy clusters (Clowe et al.

54 The smoking gun observation for dark matter? Bullet cluster 1E : merging of two galaxy clusters (Clowe et al., astro-ph/ v1) Contours from gravitational lensing hot gas from X-rays Gases in the clusters have interacted (heated up) during the collision and have been left behind the not visible (non-interacting) dark matter. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 54

55 In-between-summary > Beyond the scale of the solar system evidences for the existence of dark matter are overwhelming. > There is strong evidence also for a dark energy component. > Our models to describe the present universe as well as its development since the big bang work nicely provide that 95% of the present matter-energy budget of the universe is made out of yet unknown components. > There is no real promising alternative to this interpretation. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 55

56 In-between-summary > Beyond the scale of the solar system evidences for the existence of dark matter are overwhelming. > There is strong evidence also for a dark energy component. > Our models the to describe only the fundamental present universe as well as its development since the big bang work nicely provide that However: It is all about gravity, interaction not included in the Standard Model 95% of the present matter-energy budget of the universe is made out of yet unknown components. of particle physics! > There is no real promising alternative to this interpretation. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 56

57 .. let s have a short 15 minutes break! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 57

58 Discussion time > Why don t we notice dark matter and dark energy at earth? > Are they real? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 58

59 Dark matter and dark energy in this room Why did physics overlook Dark Matter and Dark Energy so long? Densities in this room: Matter (earth s crust): 3 g/cm 3 Dark Matter (DM): g/cm 3 Dark Energy (DE): g/cm 3 Why dominates matter here and DM und DE in the Universe? Matter is clumpy, interacts strongly: planets are formed. Dark matter interacts only gravitationally: halos around galaxies. Dark energy is distributed uniformly all over the universe. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 59

60 Hitchhiker s guide to the galaxy There is a theory which states that if ever anybody discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened. Douglas Adams English humorist & science fiction novelist ( ) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 60

61 Some caveats on our picture of a strange universe > The Copernican principle is used to interpret the data. The Universe in our neighborhood is not special. Homogeneity (similarity in all regions of space) Isotropy (similarity in all directions). This principle is compatible with observations (if you accept Dark Energy!), but fundamentally untested! > Which is the relevant scale for homogeneity of the Universe? Does one have to take into account in-homogeneities when calculating cosmological parameters? > Do we really understand gravity in the weak acceleration regime on cosmological scales? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 61

62 An alternative to dark matter? > MoND: Modified-Newtonian-Dynamics (Mordehai Milgrom, 1983) > TeVeS: Tensor Vector Scalar gravity, a relativistic generalization of MoND (Jacob Bekenstein, 2004) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 62

63 Modified Newtonian Dynamics and TeVeS > Let s revisit to the rotation curve of galaxies! Curve A: Expected Newtonian dynamics curve with visible matter only. Curve B: Experimentally measured. To fix Curve A, either: a) Introduce dark matter halo surrounding the galaxy b) Modify dynamical laws Axel Lindner DESY Summer Students 2015 Dark Stuff Page 63

Modified Newtonian Dynamics and TeVeS http://www.astro.umd.

a a 0 For a a 0 F = μ ma = m a2 a 0 Then, for the outer region: GmM r 2 Assuming = m a2 a =

64 Modified Newtonian Dynamics and TeVeS Idea of MOND to redefine 2 nd Newton s law: F = μ ma μ = 1 if a a 0 a a 0 if a a 0 For a a 0 F = μ ma = m a2 a 0 Then, for the outer region: GmM r 2 Assuming = m a2 a = v2 4 v = GM a 0 circular a 0 motion: r This could also reproduce B!?!? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 64

65 Modified Newtonian Dynamics and TeVeS 4 v = GM a 0 a 0 can be extracted from astronomical data and is m s 2 MOND / TeVeS: > could explain galaxy rotation curves, > could explain the (strong) gravitational lensing, > but have difficulties with the CMBR: Let us stick to the dark matter paradigm for the time being! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 65

66 Our dark matter menu > Starters Historical annotations: how to discover new stuff? Our anchor: the Standard Model of particle physics > Main course 1 The necessity of Dark Matter Alternatives and hidden assumptions > Main course 2 Dark matter candidates Searching for Dark Matter candidate particles Direct searches for Dark Matter particles > Dessert Astrophysical puzzles > Doggy bag Summary and outlook Axel Lindner DESY Summer Students 2015 Dark Stuff Page 66

67 What is dark matter? Dark matter > Shows no electromagnetic interaction > Shows no strong interaction > Is stable Could it be neutrinos? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 67

68 Excurse: structures in the universe > Galaxies in the universe are arranged in a cosmic web! Over 1.6 million galaxies Blue: bright and near Red: faint and far away (up to z=0.1) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 68

69 Excurse: structures in the universe > These structures as well as details of galaxy distributions can be simulated quite well with these assumptions: 1 Cubes: (10 Mpc) 3 2: Dark matter is cold, moving non-relativistic. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 69

70 What is dark matter? Dark matter > shows no strong or electromagnetic interaction (some weak interaction could have escaped detection by now). > has not decayed during the evolution of the universe. > should be cold to form the structures in the universe. Neutrinos are very lightweight so that cosmic neutrinos move at relativistic speeds. Hence neutrinos can not explain the structure formation. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 70

http://www.gridpp.ac.uk/cubes/ What is dark matter?

71 What is dark matter? Dark matter constituents are not the particles of the Standard Model! At least the dominant fraction of dark matter Axel Lindner DESY Summer Students 2015 Dark Stuff Page 71

The couplings is weakly at maximum. > It is cold, moving at non-relativistic speeds only. > It is non-baryonic.

72 Dark matter properties > The dark matter density around us is of about 0.3 GeV/cm 3 = g/cm 3 > It has negligible interactions with our visible world and negligible self-interaction. The couplings is weakly at maximum. > It is cold, moving at non-relativistic speeds only. > It is non-baryonic. > The dark matter constituents must have a lifetime much longer than the age of the universe. None of the known particles within the Standard Model fulfills all these requirements! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 72

73 60 orders of magnitude Prog.Part.Nucl.Phys. 71 (2013) arxiv: [hep-ph] Theory: dark matter candidates > There is a plentitude of theories predicting dark matter candidates covering more than 50 orders of magnitude in mass range and predicting interaction strength with normal matter orders of magnitude below neutrino cross sections. 52 orders of magnitude Axel Lindner DESY Summer Students 2015 Dark Stuff Page 73

74 Dark matter candidates: where to focus experimentally? Selection criteria: > Are experimental options in reach to either identify dark matter candidates in laboratory experiments, find directly of indirectly the particles composing the dark matter halo we are living in? > Does the theory explain just dark matter or is it embedded in a more general extension of the standard model of particle physics? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 74

75 Prog.Part.Nucl.Phys. 71 (2013) arxiv: [hep-ph] Dark matter candidates: where to focus experimentally? Selection criteria: > Are experimental options in reach to either identify dark matter candidates in laboratory experiments, find directly of indirectly the particles composing the dark matter halo we are living in? > Does the theory explain just dark matter or is it embedded in a more general extension of the standard model of particle physics? + a word on sterile neutrinos Axel Lindner DESY Summer Students 2015 Dark Stuff Page 75

76 Our prime DM Candidates 1. Weakly Interacting Massive Particles: WIMPs Most promising candidate: lightest supersymmetric particle (neutralino, a linear combination of photino, zino and higgsinos, to be found at LHC?), very heavy (around ev). 2. Sterile neutrinos Naturally relax a hierarchy in the fermion sector, could show up indirectly in neutrino oscillations, could constitute DM if Dark Matter: medium weight (around 10 3 ev) 3. Axion or Axion Like Particles: ALPs Invented to explain CP conservation in QCD ( why is the electric dipole moment of the neutron zero or extremely small? ). Non-thermal production in the early universe, very light (around 10-5 ev). Axel Lindner DESY Summer Students 2015 Dark Stuff Page 76

77 Dark matter (DM) search strategies > Direct: an experiment detects particles of the DM halo all around us. > Indirect: an experiment finds astrophysical signatures (next to gravitation) of the DM halo particles. > Candidates: an experiment identifies new particles which are candidates for the constituents of the DM halo. Don t mix this up with finding DM! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 77

78 Dark matter candidates: WIMPs > Many particle physicists would subscribe: Lectures by F. Brümmer this week! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 78

Dark matter candidates: WIMPs > Weakly Interacting Massive Particles (WIMPs) Theory: a SUperSYmmetry between fermions and bosons might exist. The lightest SUSY particle could make up the dark matter.

79 Dark matter candidates: WIMPs > Weakly Interacting Massive Particles (WIMPs) Theory: a SUperSYmmetry between fermions and bosons might exist. The lightest SUSY particle could make up the dark matter. Dark matter: the lightest stable SUSY particle with an self interaction strengths of the order of the weak interaction would naturally be produced as dark matter in the early universe. Additional benefit: if SUSY masses are at the TeV scale one could understand details of the standard model (e.g. Higgs mass) and SUSY could show up at the LHC. > Prediction: Dark matter is composed out of elementary particles with masses O(10 to 100 GeV). Its number density is about /cm 3. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 79

80 Dark matter (DM) search strategies: WIMPs > Direct: an experiment detects particles of the DM halo all around us. DM scatters of a nucleus > Indirect: an experiment finds astrophysical signatures (next to gravitation) of the DM halo particles. Gamma-rays from DM-DM annihilation > Candidates: an experiment identifies new particles which are candidates for the constituents of the DM halo. Missing ET events at particle colliders Axel Lindner DESY Summer Students 2015 Dark Stuff Page 80

http://lpsc.in2p3.fr/mayet/dm.php Dark matter (DM) search strategies: WIMPs > Direct: an experiment detects particles of the DM halo all around us.

81 Dark matter (DM) search strategies: WIMPs > Direct: an experiment detects particles of the DM halo all around us. About 24 experiments world-wide > Indirect: an experiment finds astrophysical signatures (next to gravitation) of the DM halo particles. About 18 experiments world-wide > Candidates: an experiment identifies new particles which are candidates for the constituents of the DM halo. A huge world-wide effort of many large experiments! LHC, BELLE, Axel Lindner DESY Summer Students 2015 Dark Stuff Page 81

82 Direct detection of dark matter WIMPs Basic Idea: > The earth moves through the WIMP halo. > WIMPs scatter elastically on nuclei. > Measure nuclear recoils. Experimental challenge: > WIMP mass: 10 GeV to TeV ( mass of nuclei) > Relative speed (earth - WIMP in galactic halo): 250 km/s kinetic energy kev > Very low cross sections: σ χ < cm 2 = 10-4 pb σ pp > Local density 0.3 GeV / cm 3 Event rate < 0.1 / day / kg (10-6 Hz / kg) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 82

83 The "smoking gun" of WIMP detection 30 km/s Speed relative to WIMP halo: (230 ± 15) km/s (10 4 to 10 6 WIMPs/cm 2 /s) 230 km/s Due to varying speed of earth relative to galactic halo: 7% annual modulation of WIMP detection rate Axel Lindner DESY Summer Students 2015 Dark Stuff Page 83

84 Basic detector considerations > Radioactivity from the surrounding: 1 Hz/kg > Muons from cosmic rays: 0.01 Hz/kg Shield and / or identify radioactivity induced events Shield cosmic rays underground laboratory (1.5 km rock) Expected Rate: 10-6 Hz / kg Axel Lindner DESY Summer Students 2015 Dark Stuff Page 84

radioactivity and cosmic muons > No event-by-event background /

85 DAMA/LIBRA Detection of scintillating light from recoiled nuclei > Large mass (240 kg NaI(Tl) detectors), careful shielding of radioactivity and cosmic muons > No event-by-event background / signal identification Axel Lindner DESY Summer Students 2015 Dark Stuff Page 85

86 DAMA/LIBRA: evidence for WIMPs? arxiv: v1 Annual modulation! Results (model dependent): M χ GeV, σ χ 10-5 pb Axel Lindner DESY Summer Students 2015 Dark Stuff Page 86

87 DAMA/LIBRA: WIMPs or background? The muon rate at LNGS shows a similar annual modulation! Is the background rellay under control? Need new experimental approaches to reduce backgrounds. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 87

88 New Experiments with background rejection If ionisation could be measured (charge, scintillating light): Distinguish em. radiation and nuclear recoils by the ratio E(phonon)/E(ion.) Axel Lindner DESY Summer Students 2015 Dark Stuff Page 88

89 New Experiments with background rejection Presentation by L. Baudis, Patras 2007, Axel Lindner DESY Summer Students 2015 Dark Stuff Page 89 A. Lindner Summerstudents 2009

90 The XENON experiment T. Marrodán Undagoitia, PATRAS 2013, Mainz Axel Lindner DESY Summer Students 2015 Dark Stuff Page 90

91 The XENON experiment T. Marrodán Undagoitia, PATRAS 2013, Mainz Axel Lindner DESY Summer Students 2015 Dark Stuff Page 91

The XENON experiment > Systematics are well under control. > Two events are found in the WIMP parameter region! > However, one expects 1.0 0.

92 The XENON experiment > Systematics are well under control. > Two events are found in the WIMP parameter region! > However, one expects background events (from neutron scattering for example). > Other experiments show similar results. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 92

93 Status of direct dark matter WIMP searches > Dark matter WIMP searches have seen fantastic technological improvements in the past decade. > However, no convincing indication for the existence of dark matter WIMPs have been found. > The next generation of experiments will come close to the irreducible background of neutrino interactions. > At LHC no hint for the existence of WIMPy dark matter candidates has been seen. > Are we approaching the final stage of dark matter WIMP searches? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 93

94 Sterile neutrinos Axel Lindner DESY Summer Students 2015 Dark Stuff Page 94

95 Sterile neutrinos > Massive sterile neutrinos are predicted by extensions of the Standard Model to explain dark matter for example. Sterile neutrinos would be right-handed in contrast to the left-handed known neutrinos. They would interact only gravitationally with known particles and hence be extremely difficult to detect. However, sterile neutrinos might be unstable with a lifetime larger than the age of the universe. They would decay: One could search for the photons originating in such decays. > Important: sterile neutrinos of kev masses would compose warm dark matter and alter a little structure formation in the universe. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 95

> Candidates: an experiment identifies new particles which are candidates for the constituents of the DM halo.

96 Dark matter (DM) search strategies: sterile neutrinos > Direct: an experiment detects particles of the DM halo all around us. No ideas > Indirect: an experiment finds astrophysical signatures (next to gravitation) of the DM halo particles. > Candidates: an experiment identifies new particles which are candidates for the constituents of the DM halo. X-rays from DM ν decays in the galactic centre? Neutrino oscillation measurements could hint at a sterile neutrino. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 96

http://www.sciencedirect.com/science/article/pii/s2212686412000131 Dark matter (DM) search strategies: sterile neutrinos Status of searches for sterile neutrinos: > There is no experimental evidence!

97 Dark matter (DM) search strategies: sterile neutrinos Status of searches for sterile neutrinos: > There is no experimental evidence! > We do not know how to probe the whole parameter region as predicted by theory. White: allowed region Blue: ruled out by measurements Red: expected by combination of all archival data Axel Lindner DESY Summer Students 2015 Dark Stuff Page 97

98 Axions Axel Lindner DESY Summer Students 2015 Dark Stuff Page 98

99 roups/admx/axion.html Axions Why an axion? > The axion was invented to overcome an often ignored riddle of the Standard Model: why does QCD conserve the CP-symmetry? > Surprisingly, the axion could also solve the dark matter problem! See ALPS lecture this Thursday! > However, for a long time the axion has been ignored by many particle physicists, because it seemed close to impossible to detect it. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 99

100 Our dark matter menu > Starters Historical annotations: how to discover new stuff? Our anchor: the Standard Model of particle physics > Main course 1 The necessity of Dark Matter Alternatives and hidden assumptions > Main course 2 Dark matter candidates Searching for Dark Matter candidate particles Direct searches for Dark Matter particles > Dessert Astrophysical puzzles > Doggy bag Summary and outlook Axel Lindner DESY Summer Students 2015 Dark Stuff Page 100

101 /1/tumblr_lapf0aD7811qaityk Are there hints from astrophysics on the nature of DM? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 101

102 Indications for unexplained effects? Probe the transparency of the universe! > GeV photons have a mean free path-length comparable to the size of the universe. > 100 GeV to TeV photons travel just about 100 Mpc, because they interact with extragalactic background light. Center of mass energy about 1 MeV ( LHC)! M. Meyer, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011 Axel Lindner DESY Summer Students 2015 Dark Stuff Page 102

103 Indications for unexplained effects? Probe the transparency of the universe! > GeV photons have a mean free pathlength comparable to the size of the universe. > 100 GeV to TeV photons should travel just about 100 Mpc, because they should interact with extragalactic background light. Center of mass energy about 1 MeV ( LHC)! M. Meyer, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011 Axel Lindner DESY Summer Students 2015 Dark Stuff Page 103

104 Indications for unexplained effects? However: > The expected propagation of TeV photons seems to be in conflict with observations: D. Horns, M. Meyer, JCAP 1202 (2012) 033 > If physics beyond the SM is involved, it shows up around the MeV scale! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 104

105 Indications for unexplained effects? > Axion-like particles might explain the apparent transparency of the universe for TeV photons: M. Meyer, 7th Patras Workshop on Axions, WIMPs and WISPs, 2011 TeV photons may hide as axions: compare the ALPS II experiment at DESY! More on Thursday! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 105

Do we understand the evolution of stars? > Cooling of white dwarfs: White dwarfs are the final stage of sun-like stars once energy production by fusion has come to an end.

106 Do we understand the evolution of stars? > Cooling of white dwarfs: White dwarfs are the final stage of sun-like stars once energy production by fusion has come to an end. Sirius White dwarfs just radiate their energy away to cool down on rather long time scales. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 106

107 Do we understand the evolution of stars? > Cooling of white dwarfs: White dwarfs are the final stage of sun-like stars once energy production by fusion has come to an end. Sirius White dwarfs just radiate their energy away to cool down on rather long time scales. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 107

108 Do we understand the evolution of stars? > Cooling of white dwarfs: Measurements indicate a cooling rate, which is about a factor of four larger than expected. Sirius > Do we have to refine the stellar models? > Do stars radiate off an unknown species of particles in addition? This could be axions! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 108

(Vague) hints for unexpected phenomena? > TeV transparency of the universe? > Cooling of stars? > Indications for a Cosmic ALP background (CAB)? Phenomenon ALP mass [ev] ALP- coupl.

109 (Vague) hints for unexpected phenomena? > TeV transparency of the universe? > Cooling of stars? > Indications for a Cosmic ALP background (CAB)? Phenomenon ALP mass [ev] ALP- coupl. [GeV -1 ] Reference TeV transparency < 10-7 > arxiv: [astro-ph.he] Globular cluster stars (HB) < arxiv: [astro-ph.sr] CAB (Coma Cluster) < to arxiv: [hep-ph] White dwarfs < 10-2 (g ae ) arxiv: [astro-ph.sr] > There are allowed regions in parameter space where an ALP can simultaneously explain the gamma ray transparency, the cooling of HB stars, and the soft X-ray excess from Coma and be a subdominant contribution to CDM. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 109

110 Our dark matter menu > Starters Historical annotations: how to discover new stuff? Our anchor: the Standard Model of particle physics > Main course 1 The necessity of Dark Matter Alternatives and hidden assumptions > Main course 2 Dark matter candidates Searching for Dark Matter candidate particles Direct searches for Dark Matter particles > Dessert Astrophysical puzzles > Doggy bag Summary and outlook Axel Lindner DESY Summer Students 2015 Dark Stuff Page 110

Summary I: Reminder > We claim to understand the deepest structure, the fundamental forces and the early universe. > However, our knowledge just makes up 5% of the present universe.

111 Summary I: Reminder > We claim to understand the deepest structure, the fundamental forces and the early universe. > However, our knowledge just makes up 5% of the present universe. > From laboratory experiments we do not have the slightest indication for the constituents of the 95% stuff. Despite the huge technical progress in the last 30+ years! > Is there something fundamentally wrong with our approaches to understand nature?? Axel Lindner DESY Summer Students 2015 Dark Stuff Page 111

112 Summary II (a more conventional one): to take home > It is almost certain that Dark Matter of unknown constituents exist. > It is well possible that in addition Dark Energy exists. We might know just 5% of the universe. > Constituents making up the Dark Matter in the universe could be essentially anything from ultra-light to extremely heavy. A lot of experiments search for WIMPs at the high energy frontier, also at LHC. Astrophysical observations can point direct detection onto interesting parameter region A new experimental frontier is developing: seachers for axions and similar particles (see Thursday lecture). Axel Lindner DESY Summer Students 2015 Dark Stuff Page 112

Outlook > Next generations of experiments will come and search for dark matter candidates as well as directly and indirectly for dark matter. > Perhaps we (you!

113 Outlook > Next generations of experiments will come and search for dark matter candidates as well as directly and indirectly for dark matter. > Perhaps we (you!) are lucky like the drunkard who finds his key under the shine of the lantern! > So one should explore all technical accessible dark matter parameter regions, but according to present-day knowledge it is not excluded that dark matter interacts gravitationally only. Axel Lindner DESY Summer Students 2015 Dark Stuff Page 113

114 Outlook > Next generations of experiments will come and search for dark matter candidates as well as directly and indirectly for dark matter. > Perhaps we (you!) are lucky like the drunkard who finds his key under the shine of the lantern! > So one should explore all technical accessible dark matter parameter regions, but according to present-day knowledge it is not excluded that dark matter interacts gravitationally only. > But never give up! A detection might be close! Axel Lindner DESY Summer Students 2015 Dark Stuff Page 114

Summary III > http://www.phdcomics.com/comics.php?f=1430 http://vimeo.

115 Summary III > Axel Lindner DESY Summer Students 2015 Dark Stuff Page 115

Particles in the Early Universe

Particles in the Early Universe David Morrissey Saturday Morning Physics, October 16, 2010 Using Little Stuff to Explain Big Stuff David Morrissey Saturday Morning Physics, October 16, 2010 Can we explain