1. Dr. Nicolò Masi Dr. Nicolò Masi - Bologna University and INFN May 20 th 2014

2. On Earth Detection

3. The possibility to detect the recoil energy of the nuclei of a low–background detector as a consequence of their elastic scattering with a WIMP. The signal arises if the solar system itself is moving relative to the stationary halo of WIMP as it orbits around the Milky Way center. This recoil can be detected in some ways : Electric charges released (ionization detector) Flashes of light produced (scintillation detector) Vibrations produced (phonon detector) Scattering Rate Local DM density Differential Recoil Energy Spectrum Elastic cross section (SI): Nuclear Form Factor Integral over local WIMP velocity distribution Earth Velocity through the DM Halo

4. Low energy effective Lagrangian for WIMP-quark interaction scalar interaction spin-dep. interaction The other terms are velocity-dependent contributions and can be neglected in the non-relativistic limit for the direct detection. The scalar interaction scales with a power of the the atomic weight and almost always dominates for nuclei with A > 30. q q q q

6. Hypothetical WIMP-Nucleon Scattering: a Summary In the Feynman diagrams, scalars are represented by dashed lines, fermions by solid lines and vector bosons by wavy lines. The mediators , h, Z' and SM Z and h are neutral under both electromagnetism and color, while X, and Q (quarks) transform as triplets under color and carry electric charge Spin-dependent SD and Spin-independent SI interaction

7. Research Landscape

8. Direct Search of Dark Matter: Constraints Anything above the blue lines is now excluded /H 1000 Circumstantial signals A hope only for very massive candidates

9. It won’t be forever Direct detection experiments will inevitably hit the neutrino wall: they will reach the sufficient sensitivity to observe nuclear recoils due to elastic scattering of solar and atmospheric neutrinos. That will constitute an irreducible background to dark matter searches (unless directional detection techniques are developed). LUX currently holds the leader position for DM masses above 6 GeV; the Xenon collaboration is already preparing a nuclear response in the form of a 3 ton detector. Meanwhile, the SuperCDMS experiment will secure a monopoly in the low-mass region.

10. There are also stringent bounds from IceCube for the Spin-dependent DM cross-section …. The principle: WIMPs could be gravitationally captured by massive objects like the Sun and accumulate in the core the Sun itself: for high enough density they would annihilate producing neutrinos, which could be observed by IceCube

11. ...that can be related to the parameters space of different DM models, such as the Universal Extra Dimension Model (UED): SI vs SD 10 -5 pb = 10 -41 cm 2

12. Collider Search: Direct Detection Experiments vs LHC

13. Collider Detection: Interaction Cross Section limits  Look for missing energy signatures.  Problem: Can only find DM candidate (no proof that it is DM)  Model-dependent strategy: Cascade decays with E T CMS Results

14. ATLAS Results

15. A Corotating Dark Disk: do our assumptions survive?

16. Dark Structures Dark Matter Disk

17. If the dominant dark matter contribution to the local high energy e  flux comes from a Dark Disk rather than the spherical halo, we get good fits of Fermi and PAMELA’s data; the boost factor/Sommerfeld enhancement is almost an order of magnitude smaller than what is needed for the standard fits; a (perhaps) corotating DD with small velocity v 0 = 50 ÷ 70 km/s is provided by structure formation simulations of standard ΛCDM cosmology in presence of baryons. Also low energy signals could be TeV-ish Dark Matter hints

18. Dark Matter Candidates: not only an astrophysical necessity

19. Main theoretical Standard Model problems  Hierarchy problem – the mass of the Higgs gets some very large quantum corrections due to the presence of virtual particles (mostly virtual top quarks). These quadratic corrections are much larger than the actual mass of the Higgs. The bare mass parameter of the Higgs must be unnaturally fine tuned in such a way that almost completely cancels the quantum corrections.  Strong CP problem – theoretically it can be argued that the SM should contain a term that breaks CP symmetry in the strong interaction sector. Experimentally, however, no such violation has been found, implying that the coefficient of this term is very close to zero. This fine tuning is also considered unnatural.  Neutrino masses – according to the SM, neutrinos are massless particles. However, neutrino oscillation experiments have shown that neutrinos do have mass. Mass terms, added by hand, need to be extraordinarily small and it is not clear if the neutrino masses would arise in the same way that the masses of other fundamental particles do in the Standard Model.  Matter/antimatter asymmetry – The universe is made out of mostly matter. However, the SM predicts that matter and anti-matter should have been created in (almost) equal amounts, if the initial conditions of the universe did not involve disproportionate matter relative to antimatter. If DM would solve one (or more than one) of these problems, everything would be more consistent and natural

20. Neutralino WIMP Mass Region: 100 GeV ÷ 10 TeV (<100 TeV) Axion Mass Region: 10 μ eV÷1 meV Statistic: dirac or majorana fermion, boson S= 0,1/2, 1, 3/2, 2 Exotic Candidates

21. SUS Y The gauge hierarchy problem is most elegantly solved by supersymmetry. In SUSY models every SM particle has a new, as-yet-undiscovered partner particle, which has the same quantum numbers and gauge interactions, but differs in spin by 1/2. The introduction of new particles with opposite spin-statistics from the known ones supplements the SM quantum corrections to the Higgs boson mass with opposite sign contributions:

22. MSSM : Neutralino The exact properties of each neutralino will depend on the details of the mixing but they tend to have masses in the order of 300-600 GeV and couple to other particles with strengths characteristic of the weak interaction. In this way they are phenomenologically similar to neutrinos. In fact they are Majorana fermions and not directly observable in particle detectors at accelerators. Some MSSM Parameters In the basis - ratio of vev of the two neutral Higgs - Higgsino mass parameter - Bino, Wino mass parameters SUSY dependence: 5 independent parameters Upper bounds now enlarged by LHC results The mixing matrix :

23. Gaugino Higgsino Mixed Neutralino: Classification & Annihilation Channels …and finally Main Models

24. SUSY Constrained The exclusion region in the CMSSM (Constrained MSSM) framework, using charge di-leptons, is narrowing SUSY chances…

25. Discrimination parameter I for signal and background: the AMSB Wino MSSM is the most suitable for AMS-02, both in antiproton and positron channels Expected clear positron signal from heavy Wino 25

26. SUSY Gravitino The gravitino is not a WIMP, but it is a viable dark matter candidate. The gravitino is the supersymmetric partner of the graviton. If it exists, it is a fermion of spin 3⁄2 and therefore obeys the Rarita-Schwinger equation. If supersymmetry is to solve the hierarchy problem of the Standard Model, the gravitino cannot be more massive than about 1 TeV (preferably light). It’s a strange candidate, the only high spin candidate, which give a lot of cosmological problems and it’s not able to produce the correct actual dark matter density of our Universe. It has also a low annihilation cross section and it’s a superpartner of an hypothetical particle, the graviton, which could not exist at all.

27. Possible Gravitino Indirect Detection in Multiple Channels e+

28. antiproton A low signal, compatible with the observed antiproton flux: a hidden signal?

29. Little Higgs Theory As an alternative mechanism to Supersymmetry to stabilize the weak scale, the so- called “Little Higgs” model, has been proposed and developed: the Standard Model Higgs becomes a pseudo-Goldstone boson with its mass protected by an approximate nonlinear global T-symmetry. Although the idea was first suggested in the 1970s, aviable model was only constructed by Nima Arkani-Hamed, Andy Cohen, and Howard Georgi in the spring of 2001. Little Higgs theories were an outgrowth of dimensional deconstruction: in these theories, the gauge group has the form of a direct product of several copies of the same factor, for example SU(3) × SU(3). In the Minimal Moose model these symmetries acquires a clear physical attribute: they’re a chiral symmetry SU(3) L × SU(3) R and a collective spontaneous symmetry breaking produces the vector subgroup from which the Standard Model descends. The quadratic divergence of Higgs mass is removed using bosonic loops with opposite hypercharge. The divergences which remain are present only at the two-loop level: the weak scale can be stabilized in an effective field theory which is valid up to  10 TeV.

30. Little Higgs Dark Matter parameters space: The region above the line can be distinguished from the background: AMS can sweep a wide window Little Higgs Dark Matter parameters space: The region above the line can be distinguished from the background: AMS can sweep a wide window e+e+ Little Higgs Spectrum 30 Massive LTP Photon Annihilation

31. Scalar Singlet/Multiplet  Predictivity and simplicity are undoubtedly their most salient features.  In contrast with other common scenarios that explain the dark matter, it contains only one or few additional fields, the singlet scalar/multiplet, and few new parameters: the singlet mass and the coupling between the singlet and the Higgs boson.

32. The area above the MIN, MED, MAX lines is detectable by AMS-02 in the antiproton channel Scalar Singlet/Multiplet 32

33. Kaluza –Klein Theory: UED In UED all particles propagate in flat, compact extra dimensions of size 10 -18 m or smaller. In the simplest UED model, minimal UED, there is one extra dimension of size R compactified on a circle. Every SM particle has an infinite number of partner particles, with one at every Kaluza- Klein (KK) level n, with mass  nR -1. In contrast to supersymmetry, these partner particles have the same spin. As a result, UED models do not solve the gauge hierarchy problem. The simplest UED models preserve a discrete parity known as KK-parity, which implies that the lightest KK particle (LKP) is stable and a possible dark matter candidate: a heavy vector boson. Another particle produced by the KK theory spectrum is the LZP, i. e. a right-handed neutrino which also may account for the dark matter observations. Kaluza-Klein dark matter particles, unlike neutralinos or Little Higgs dark matter, can annihilate efficiently to light fermions. KK particles may escape from collider events following the fourth spatial dimension (missing energy channel)

34. KK Warped GUT LZP M = 40÷50 GeV theoretical signal Not observed

35. Kaluza-Klein Theories: Universal Extra Dimension Antiproton High Energy Signal Positron High Energy Signal

36. Other Attempts

37. Primordial Quantum Black Holes Sensitivity problem: not a good candidate Antideuteron Antiproton Not observed From CMS results, as of March 2012, PBH should have masses above 3.8 to 5.3 TeV Micro black holes are predicted as tiny black holes, also called quantum mechanical black holes or mini black holes. They could be produced at LHC. It is possible that such quantum primordial black holes were created in the high-density environment of the Early Universe. They might be observed by astrophysicists in the near future, through the particles they are expected to emit by Hawking radiation.

38. Light Sterile Neutrinos (Warm DM) These hypothetical particles are similar to Standard Model neutrinos, but without Standard Model weak interactions, apart from mixing. They were proposed as dark matter candidates in 1993 by Dodelson and Widrow. Stringent cosmological and astrophysical constraints on sterile neutrinos come from the analysis of their cosmological abundance and the study of their decay products: light neutrinos, with masses below a few keV, would be ruled out as dark matter candidates. Sterile neutrinos could also be cold dark matter, if there is a very small lepton asymmetry, in which case they are produced resonantly with a non-thermal spectrum. 4 th SM generation MDM The Minimal Dark Matter adds to the SM the minimal amount of new physics (just one extra EW multiplet X) and search for the minimal assignments of its quantum numbers (spin, isospin and hypercharge). The stability of the successful candidates is guaranteed by the SM gauge symmetry and by renormalizability. MDM is strongly disfavored from searches at LEP (neutrino’s three family bound), and from the LHC and Tevatron searches of the Higgs: MDM models need heavy Higgs (about 0.5 TeV), incompatible with our light Higgs with a mass of ∼ 125 GeV.

39. Singlino

40. Graviton The graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory. The graviton is expected to be massless (because the gravitational force appears to have unlimited range) and must be a spin-2 boson. The spin follows from the fact that the source of gravitation is the stress–energy tensor, a second-rank tensor (compared to electromagnetism's spin-1 photon, the source of which is the four-current, a first-rank tensor). Any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field must couple to the stress–energy tensor in the same way that the gravitational field does. They would have extremely low cross section (almost zero) for the interaction with matter: individual gravitons detection is not possible. String theory predicts the existence of gravitons and their well-defined interactions: a graviton is a closed string in a very particular low-energy vibrational state. As closed strings without endpoints, they would not be bound to branes and could move freely between them: if we live on a brane this "leakage" of gravitons from the brane into higher- dimensional space could explain why gravitation is such a weak force. Gravitons from other branes adjacent to our own could provide a potential explanation for dark matter. Experiments to detect gravitational waves, which may be viewed as coherent states of many gravitons, are underway (LIGO and VIRGO): they might provide information about certain properties of the graviton, such as its mass.

41. Ambitious Theories: DM solving other fundamental problems

42. Asymmetric Theories: Tulin X antibaryonic DM IND: Indirect Nucleon Decay And meson may decay into detectable leptons Asymmetric DM theories take into account the possibility of a DM internal matter- antimatter asymmetry, introducing a DM sector with SM-like violations.

43. Shaposhnikov Neutrinos

44. Advantages of Shaposhnikov Theory …It solves many problems and implies that no new high-mass particle physics lies in ambush up to Planck Scale SHIP in a new proposal for a beam dump experiment at CERN-SPS for hidden Shaposhnikov particles

45. State of Art: DM Candidates Landscape

46. LHC LHCb Little portion of parameter space remains Only Standard Model ?!

47. ATLAS Results

48. A Great Desert

49. Table 1 - DM Candidates properties Light candidates GHP: most relevant HS: Hidden Sector Scalar, vector, Dirac fermion, Majorana fermion, Rarita- Schwinger fermion Wrong relics Also leptophilic models may produce antip by EW corrections S=0,1 Bosons and Majorana Fermions are the most interesting candidates because they’re their own antiparticle and so capable to self-annihilate

50. Table 2 - DM Candidates detection An independent model Difficult to prove

51. Higgs Portal Model Also the HS depends on SUSY! Hidden Sector and Hidden Valley Models generate armies of dark particles including the Dark Photon : does the visible photon have a counterpart, a dark photon, that interacts with the components of dark matter?

52. Without SUSY Little Higgs, KK Theory, Graviton, Singlet/Multiplet Scalar, Axion, MDM, PBH, Sterile Neutrino, Antibaryonic DM… With only our 4 dimensions Little Higgs, Singlet Scalar, Axion... Detectable with AMS-02: Little Higgs and Singlet/Multiplet Scalar A complex scenario A realistic exclusion

53.  The positron signal is the fundamental channel for DM study. In terms of intensity of annihilation products fluxes: space experiments can see a positron peak for all DM candidates capable of producing e+ beyond 100 GeV, testing all DM theories.  AMSB Wino-like neutralino, UED KK LKP particle, Scalar Multiplet and Little Higgs LTP are the most suitable candidates for Earth and space experiment. The first three could be non-leptophilic theories capable to grant a very heavy candidate producing high energy antiproton fluxes measurable by AMS-02; but SUSY and KK UED theory are quite disfavored if a simplicity criterion is invoked and once taken into account LHC evidences. Parameters space for a non-leptophilic candidate DIRECT CONSTRAINTS: XENON100 + EDELWEISS + ICECUBE: Astrophysical and cosmological constraints: compact stars, galaxies clusters, CMB… : New TeV-ish paradigm: with DM without DM fraction with DM 20÷30 fraction without DM 5÷10% Remarks: a heavy WIMP Identity Card

54. Axions: a Bit of Detergent

55. Neutron Electric Dipole Moment Peccei-Quinn Idea: Theta is a new particle field

56. Pseudo Nambu-Goldstone Boson of the PQSB: its vev remove the anomaly, through a potential minimum QCD Instanton Sector Kinetic termFrom Goldstone Theorem: EM Anomaly

57. Maxwell-Chern-Simons Equations Light shining through walls experiments Currents

58. From CDM to BEC a a a a Axions rethermalize and reach T BEC Galactic Halos: Tidal Torque Theory

59. f a – H infl Plots : Experimentally excluded regions (colored ones) Axions production, with the so-called «misallignament angle», and their properties are strongly correlated with Inflation physics and primordial gravitational waves…

60. Perspective after BICEP2 What does this have to do with axion dark matter? There were big uncertainties in the possible properties on axions, depending on whether they were created before or after inflation. The observation by BICEP-2 rules out the creation of axion dark matter before inflation, giving a more precise target for future axion searches. A narrow window

61. Axion Searches  Light Shining Through Wall (BFRS and PVLAS) - In the Italian PVLAS experiment polarized light propagates through the magnetic field of a 5 T dipole magnet, searching for a small anomalous rotation of the direction of polarization: if axions exist, photons could interact with the field to become virtual or real axions. This rotation is very small and difficult to detect, but this problem can be overcome by reflecting light back and forth through the magnetic field millions of times.  Axions can be produced in the Sun's core when X-rays scatter off electrons and protons in the presence of strong electric fields and are converted to axions via Primakoff effect. The CAST experiment is currently underway to detect these axions by converting them back to x-rays in a strong magnetic field.  The USA Axion Dark Matter Experiment (ADMX) searches for light, weakly interacting axions saturating the dark matter halo of our galaxy.ADMX is a strong magnetic field permeating a cold microwave cavity. Axions matching the resonant frequency of the cavity decay into microwave photons.  New italian proposal for an experiment which exploits the axion-electron conversion in the detector, using the galactic axion wind.  Magnetars could convert photons to axions much more efficiently than most laboratory experiments, over a broad axion mass range. This, in turn, would give rise to distinct absorption-like features in the spectra of such extreme objects which can be observed by current telescopes.

62. ADMX ADMX will soon be sensitive to even the more weakly coupled dark matter axions in the range 1μeV to 20μeV.

63. Dark Matter is the simplest and most clever way to deal with astrophysical, cosmological and Standard Model problems: DM has to exist! On Earth experiments are reaching technical limits, whereas indirect searches are still promising for heavy WIMPs Nuclear uncertainties affect every sector of particle physics: DM direct detection (nuclear recoil matrix), indirect searches (spallation in the ISM) and cosmology (primordial nucleosynthesis) A deep study of the dark matter profile and its hypothetical dark disk is challenging but fundamental Exotics candidates, SUSY candidates and SUSY antagonist: a full exhaustive theory which accounts for Dark Matter and fundamental SM problems in not available yet We prefer: minimal scalar and Majorana-like solution, deriving from a Strong or EW Simmetry Breaking, with TeV-ish masses A viable alternative scenario is constitued by the tiny axion, but this field of search is still at an embryonic state AMS-02 will soon demonstrate the presence or absence of WIMPs annihilation products

64. Some open questions