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A short journey to the infinitely small Fundamentals of Particle Physics Stefania Ricciardi RAL, March 2009 Building blocks: particles and forces Current.

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Presentation on theme: "A short journey to the infinitely small Fundamentals of Particle Physics Stefania Ricciardi RAL, March 2009 Building blocks: particles and forces Current."— Presentation transcript:

1 A short journey to the infinitely small Fundamentals of Particle Physics Stefania Ricciardi RAL, March 2009 Building blocks: particles and forces Current areas of research

2 Warning This journey may change your vision of the Universe. What you will hear may alter your perception of reality. We are entering a Quantum World.. Stay awake and keep an open mind!

3 We and all things around us are made of atoms Human Hair ~ 50 m = m = m Atom ~ m = m Magritte

4 Atoms Atoms are all similarly made of: - protons and neutrons in the nucleus - electrons orbiting around electron proton neutron Protons, neutrons are made up of quarks The electron was the first elementary particle to be discovered (JJ Thomson 1897)

5 From the atom to the quark Atoms and sub-atomic particles are much smaller than visible light wave-length Therefore, we cannot really see them (all graphics are artists impressions) To learn about the sub-atomic structure we need particle accelerators How small are the smallest constituents of matter? ~ m ~ m ~ m < m

6 Wave-particle duality of Nature Central concept of quantum mechanics: all particles present wave-like properties De Broglie showed that moving particles have an equivalent wavelength So high momentum gives us short wavelengths so we can make out small details Example: electron microscope Not only light has a dual nature Electron Microscope Image Gold atoms (0.2 nm apart) Copyright © FEI

7 1911 Rutherford found a nucleus in the atom by firing alpha particles at gold and observing them bounce back Rutherford: atoms are not elementary particles! Precursor of modern scattering experiments at accelerator

8 Quarks detected within protons Stanford (SLAC), California, late 1960s Fire electrons at proton: big deflections seen! 2 miles long accelerator End Station A experimental area Freeway 280

9 Protons and neutrons in the quark model proton (charge +1) neutron (charge 0) ud d uu d Quarks have fractional electric charge! u electric charge + 2/3 d electric charge 1/3

10 Is the whole Universe made only of quarks and electrons? No! There are also neutrinos! Electron, proton and neutrons are rarities! For each of them in the Universe there is 1 billion neutrinos Neutrinos are the most abundant matter-particles in the Universe! 1 cm Within each cm 3 of space: ~300 neutrinos from Big Bang Neutrinos are everywhere! in the outer space, on Earth, in our bodies.. 1 cm

11 Neutrinos get under your skin! Within your body at any instant: roughly 30 million neutrinos from the Big Bang No worries! Neutrinos do not harm us. Our bodies are transparent to neutrinos 14 neutrinos per second from Sun are zipping through you Every cm 2 of Earth surface is crossed every second by more than 10 billion (10 10 ) neutrinos produced in the Sun

12 The particles of ordinary matter e e-e-e-e- u d -1/3 +2/3 0 charge All stable matter around us can be described using electrons, neutrinos, u and d quarks Quarks: u = up d = down Leptons: neutrino e = electron

13 3 Families (or Generations) - c s - t b Ordinary matterCosmic rays Accelerators 1 st generation2 nd generation3 rd generation 3 generations in everything similar but the mass -1/3 +2/3 e e-e-e-e- u d -1/3 +2/3 We believe these to be the fundamental building blocks of matter 00 0

14 Quark masses Top (discovered 1995) 175 GeV E= mc 2 1 proton mass ~ 1GeV ( Kg) The mass grows larger in each successive family

15 Anti-matter For every fundamental particle of matter there is an anti-particle with same mass and properties but opposite charge e e-e-e-e- u d -1/3 +2/3 e e+e+e+e+ u d +1/3 -2/ positron Correspondent anti-particles exist for all three families Anti-matter can be produced using accelerators Matter Anti-Matter Bar on top to indicate anti-particle

16 Matter-antimatter pair creation Electron-positron pair created out of photons hitting the bubble-chamber liquid Example of conversion of photon energy into matter and anti-matter Matter and anti-matter spiral in opposite directions in the magnetic field due to the opposite charge Energy and momentum is conserved

17 Quarks and colour All quark flavours come in 3 versions, called colours ud +2/3-1/3 u u d d up down Quarks combine together to form colourless particles -Baryons (three quarks: red+ green + blue = white) -Mesons (quark-antiquark pair) such as red+anti-red u-ubar state proton u u pion p Strong forces glue quarks together in bound states

18 Building more particles bb J/ cc Y bu B-B- ub B+B+ bd B0B0 db B0B0 B mesons (bq) Many more mesons and baryons…

19 The Particle Physicists Bible: Particle Data Book "Young man, if I could remember the names of these particles, I would have been a botanist! E.Fermi to his student L. Lederman (both Nobel laureates) Most particles are not stable and can decay to lighter particles..

20 THE WEAK FORCE Beta Decay np Antineutrino Electron

21 Neutron -decay A (free) neutron decays after 15 min ud d n uu d p e-e-e-e- d u e - e e 15 min At quark level: Long life time (15min is an eternity in particle physics!) weak without such weak interactions the Sun would shut down!

22 The 4 forces of Nature Weak Beta-decay pp fusion Strong Quark binding Electromagnetic TV, PCs Magnets e- e+ creation Gravity Responsible of Keeping us well-planted on earth Electric charge mass weak charge strong charge

23 Electromagnetic force e-e- e-e- Photon The repulsive force that two approaching electrons feel Photon is the particle associated to the electromagnetic force smallest bundle of force

24 Photon exchange Feynman Diagram e-

25 Weak force: W -,W +,Z 0 decay npe e Electric charge conserved at each vertex W-W-

26 Strong force: gluons Gluons interact with quarks Gluons interact with other gluons

27 Quark confinement There are no free quarks, quarks and antiquarks are confined in colourless doublet (mesons) or triplets (baryons) by the exchange of gluons The new quarks bound to the old quarks and form new mesons until the gluon connection snaps, and other quark-antiquark pairs are created out of the energy released Gluon hold quarks together as they move further apart Z0Z0 Decay ® S.Ward

28 Force Particles (summary) Particles interact and/or decay thanks to forces Forces are also responsible of binding particles together Strong: gluons Only quarks (because of their colour charge) Weak: W +, W -, Z 0 Leptons and quarks (only force for neutrinos) Electromagnetic: Quarks and charged leptons (no neutrinos) Gravity: graviton? Still to be discovered Negligible effects on particles

29 The Standard Model Matter 6 quarks 6 leptons Grouped in three generations Forces Electroweak: (photon) -Z 0, W ± Strong -g (gluon) Very successful to describe all observed phenomena in the subatomic world so far. But there ought to be more.. Framework which includes: Not gravity! No quantum field theory of gravity yet.. H= the missing ingredient: the Higgs Boson

30 Beyond the Standard Model:Unification of forces WEAK STRONGGRAVITY ELECTRO- MAGNETIC UNIFIED FORCE? Looking for a simple elegant unified theory

31 Open question : Why is the Universe made of matter and not equally of anti-matter? We have seen that for every fundamental particle there is a corresponding antiparticle. Where are these anti-particles? Large amount of matter but no evidence of large amount of antimatter in the Universe..

32 Why has all the anti-matter gone? Anti-matter The development of the Universe containing matter and no antimatter requires that matter and antimatter behave differently This phenomenon is due to CP violation.. matter Puff Good thing for us that there is no antimatter around!

33 CP Violation CP = Charge Conjugation (reverse charge) x Parity (reverse spatial coordinates as in a mirror) CP beauty anti-beauty B0B0 B0B0 Nobody is perfect CP-Violation: B 0 and B 0 do not behave exactly in the same way (their decay pattern as a function of time is different)

34 Discovery of CP violation in the B-meson system at Babar (SLAC, 2001) A visible difference is detected, but tiny, not enough to explain the matter-antimatter asymmetry in the Universe

35 The CPV quest will go on at LHC CMS ALICE CERN LHCb experiment: 700 physicists 50 institutes 15 countries LHCb cavern LHCb ATLAS

36 Recent view of the LHCb cavern Its complete! RICH-1 The experiment is fully installed and ready for first collisions RICH2RICH1 Muon detector Calorimeters OT Magnet VELO

37 Another open question: What is the Dark Matter? Astronomical observations have shown that observable mass represent less than 4% of the Universe! What is dark matter? We dont really know … –Perhaps partially composed of neutrinos, or possibly neutralinos particles predicted by super-symmetric theories beyond the Standard Model? Dark Matter Visible Matter False-color images The brightness of clumps corresponds to the densitydensity of mass.

38 Looking for Dark Matter at the Boulby Underground Laboratory

39 Neutrinos do matter to us: If there were no neutrinos the sun would not shine! Almost no interactions (only weak) Can cross light-years of material without being affected Can travel from the most remote corners of the Universe bringing information from the origin of space and time Puzzling neutrinos

40 R. Davis : measuring the solar neutrino flux in a gold mine in South Dakota for 30 years ( ) …and observing only 1/3 of the expected flux!! Why? R. Davis Solar neutrinos pioneer

41 Neutrino oscillations If you let the neutrino travel enough, it can change its flavour! e a huge neutrino detector in the right place exists! A detector here does not see any Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo a huge neutrino detector exists! A detector here sees all

42 in the Kamioka mine in Japan SuperKamiokande is measuring neutrinos born in the atmosphere above the detector.. flux from below only ½ of flux from above!..and below the detector (on the other side of the Earth!!) Total neutrino flux from below = total flux from above _

43 Discovery of neutrino oscillation Super-Kamiokande (1998) Half of the are lost! Oscillated to undetected 2002 Nobel Prize Koshiba (superK Spokesman) shared with Davis Up-going Down-going

44 What have we learnt? A number of surprising things: –A limited number of forces and matter particles describe all the Universe we know about; –A theory of the interactions of matter with forces called the Standard Model describes successfully the phenomena of the subatomic world; –There are evidences that there is lot more that we do not know about and our research should find: such as the missing anti-matter, dark matter, puzzling neutrino properties, but also the Standard Model key-vault..the Higgs!

45 Looking into the future The Higgs should be found at the LHC…please be patient for a few more hours….and you will learn about the Higgs, the LHC, and much more! NOT

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