The unknown part of the universe, dark matter. Krasznahorkay Attila MTA Atomki, Debrecen

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2 The unknown part of the universe, dark matter Krasznahorkay Attila MTA Atomki, Debrecen

3 ATOMKI, Debrecen The Institute for Nuclear Research in the downtown of Debrecen! 4 main divisions: Nuclear Physics Division Atomic Physics Division Applied Physics Division Accelerator Centre Size: 100 scientists, 100 other staff

4 Our visible world is beautiful. With our vision we can learn about the surrounding world, recognize the laws of nature, and use them to facilitate our lives. However, our observations with the naked eye have limitations... 4

5 Our visible and invisible world Bacteria (1674, 1865) Viruses (1892) Too small objects Microscope Too far objects telescopes Radioactive radiations 5

6 Discovering a new invisible micro-world Philippe Lenard, examination of cathode rays 1886, phosphorescent screen, thin foil publ Nobel Prize 1905 J.J. Thompson, 1897 Discovering the Electron Nobel Prize in 1906 W.C. Rontgen.: Discovering X-rays, later they are called Röntgen-rays. Wilhelm Conrad Rontgen was first awarded the Nobel Prize in Physics in A new device for detecting invisible radiation, the Fotoemulsion Becquerel, 1899 α, β, γ radiation Nobel Prize 1903 Rutherford, the structure of the atoms, the nucleus Nobel Prize in 1908 Electronic detectors, particle accelerators new particles 6

7 The first motivation to research the dark matter Study of the velocity of stars as a function of distance Dark halo around the galaxies In grammar school we learned that the movements of planets around the Sun can be interpreted precisely with the Newton's laws. Gravitational lensing Dark galaxies Andromeda galaxy Mass: 370 billion M Distance: 2.5 million Light year Census in the Universe Stars and galaxies: 0.5 % Visible matter: 5 % Dark matter: 30 % Dark energy: 65 %

8 What do we know and what we do not about dark matter? We observe its gravitational effect on the visible stars. Their contribution to the mass of the Universe is huge (95%) We are searching diligently for the associated particles with more and more sensitive detectors. We can not turn it on What particle (s) are they? What (new) interactions affect these particles? 8

9 Searching from the basement to the attic already for 30 years, every corner with tremendous strength... With state-of-the-art underground detectors, with high-sensitivity spectrometers built in space 9

10 The physicists of the world's largest accelerator laboratory, the Large Hadron Collider (LHC), built at CERN, are also involved in the search. Lake Genova Jura LEP/ LHC France SPS Switzerland PS 10

11 The nucleus as a discovery machine A The LHC was built on a discovery machine where the collisions of highenergy protons are being investigated. These protons are in the nucleus, too. We investigate the properties and transformations of atomic nuclei in the Institute of Nuclear Research of the Hungarian Academy of Sciences. In fact, however, the nucleus is also a discovery machine like LHC, with only smaller energies. Which perhaps all the interactions of nature are present. Of the four currently known interactions, two were discovered in the nucleus. These are strong and weak interactions. What are they good for? The strong interaction results in the very large binding energy of the nucleus, which is liberated by the nuclear reactors. Without the weak interaction, the Sun would not shine. We started searching for the dark matter in the nucleus. 11

12 The dark force and the dark photon In our visible world, photons, quantums of the light, mediate electromagnetic interaction. In the dark world, light is the equivalent of dark radiation, the quantum of which is the dark photon (2008). Big experiments are under way to detect the dark photon around the world. Under the aforementioned theory, there could be dark atoms and we could start thinking about dark chemistry... Features of the Dark Photon: Well defined (short) life time Decomposition to electron-positron pair 12

13 Searching for the e+ e- decay of the dark photon in nuclear transitions J π e e e So if we measure the angles between the e - and e + particles that are generated in succession for many events, and sketch the angular frequency, the so-called angular correlation, we expect a typical peak. J π e+ e + e + 13 e + e

14 Creation and decay of 8 Be* Decay with proton emission: B(p + 7 Li) 100% With γ-radiation: B( 8 Be + g) 1.5 x 10-5 With internal pair creation: B( 8 Be + e + e - ) 5.5 x 10-8 Smooth, gradually decreasing angular correlation Creating a dark photon: B( 8 Be + X) 5.5 x finding a peak on the curve 14

15 Seeing the invisible (detectors) Multy Wire Proportional Chamber (MWPC):

16 Two dimensional MWPC readout with the help of induced charges on the cathode strips Charpak and Shauli, Nobel Prize

17 Scintillation detectors Scintillating materials: At the deexcitation of excited atoms "scintillation light" is generated. Inorganic crystals (ZnS(Ag), NaI(Tl), CsI(Tl) ) Organic materials (plastics, liquids ) Gases The resulting light is transferred to the photoelectron multiplier by a light guide (Plexiglas, light guide fibers...). A photomultiplier

18 Electrostatic Van de Graaff accelerator A ribbon charged up with needles takes up the charges to a hemisphere that is charged to high voltage. Production of acceleration field with many electrodes with increasing voltage. Among them is a resistance divider. 18

19 Typical high energy γ-ray spectrum

20 Our electron-positron spectrometer 20

21 Our experimental results and their interpretation Interpretation of our results for the electronpositron angular correlation by assuming the creation and decay of a new particle. Experiment points: red points with errors Theoretical curve: dashed line Spectrometer check: empty circles with errors Curves calculated with the assumption of a new particle m 0 c 2 = 16.6 MeV, X(16.6) 21

22 Phys. Rev. Lett. 117, Egy kis statisztika: Szinte minden ország újságai hírül adták Több mint 200 ezer letöltés a világhálóról 2016-ban 17 nemzetközi konferencia meghívást kaptam 22

23 Our result is on the international list Our results will be checked in many of the world's large laboratories. Results are expected in a few years time. CERN experiment in September 23

24 To 8 Be continued More telescopes bigger efficiency Position Sensitive Si Detectors for determining the momentum vectors for electrons and positrons. Precise determination of the invariant mass. Do we see anything in the 17.6 MeV transition? (Predictions of the protofobic model) Measuring the life time of the particle. In E1 transition ( 11 B (p,γ) 12 C) do we see anything? (does parity conserved in the interaction?) Investigating the two γ decay of the particle. 24

25 Our first results at the new accelerator 1. New accelerator 2. New Si DSSD detectors 3. New data acquisition system We could reproduce the published anomaly!!! Published data New data 25

26 We live in a fantastic age. Our physical understanding of the world in the coming years will probably be fundamentally changed. Take part in this process! 26