Nuclear and Particle Physics An Introduction

Transcription

1 Nuclear and Particle Physics An Introduction Spring Monday , Aud. Ø467 Thursday , Aud. Ø467 Web site 2014 Additional material Farid Ould- Saada

2 Web site Course content & goals Practical: teaching, lectures vs exercises, evaluation 2014 Time, pensum, other recommended material Additional material Material from last year (kept) and is being updated Note colour coding: Red=important information; Yellow=working on it; Green=ready for printing CERN visit 2013 International Master Classes - Modern Particle Physics, 2013, Thomson - Particles and Fundamental interactions, 2012, Braibant et al - Introduction to Nuclear and particle physics, A. Das, T.Ferbel - CERN summer student lectures - Review of particle properties - Nobel Lectures in Physics - HyperPhysics

3 Exercise sessions Pensum book has sets of problems with solutions Solve as many as you can Exercise sessions will be organised when needed Compulsory projects and final exam 3 compulsory projects and final oral exam Nuclear physics course in parallel with FYS3510 FYS3520 Nuclear physics, structure and spectroscopy Some related (future) courses: FYS4170 Relativistic Quantum Field Theory FYS4550 Experimental High Energy Physics FYS4560 Elementary Particle Physics FYS4530 Subatomic many- body theory

4 About yourselves Following Nuclear Physics Course (FYS3520)? Quantum mechanics introduction? Special relativity introduction? Including 4- vectors,? Master classes? Heard of? Participated? Visited CERN? About myself Farid Ould- Saada or Farid Ould- Saada Feedback most welcome

5 Feedback is needed in order to plan some trip ~March, April or May Short discussion Institute contributes with 15 knok (in total) So some own contribution is expected CERN Student program us/students Summer student Deadline Technical student Deadline

6 1. Basic Concepts Appendix B Special relativity 3. Particle Phenomenology 2. Nuclear Phenomenology Appendix A Quantum Mechanics, Appendix C Rutherford scattering 4. Experimental Methods (shorter version) 5. Quark Dynamics: The Strong Interaction 6. Weak Interactions And Electroweak Unification 7. Models And Theories Of Nuclear Physics 8. Applications Of Nuclear Physics (only selected topics) 9. Outstanding Questions and Future Prospects 25/01/14 F. Ould-Saada 6

7 1 History and current research The origin of Nuclear Physics The emergence of particle physics The Standard Model and Hadrons CERN LHC Highlights 2 Relativity and Antiparticles. 3 Space- Time Symmetries and Conservation Laws. Parity Charge Conjugation Time Reversal 4 Interactions and Feynman Diagrams. 5 Particle Exchange: Forces and Potentials. Range of forces, The Yukawa potential 6 Observable Quantities Amplitudes, Cross- sections, Decay rates of unstable particles 7 Units: Length, Mass and Energy. 25/01/14 F. Ould-Saada 7

8 Origins of Nuclear Physics (NP) NP distinct from Atomic Physics Becquerel: some nuclei unstable and decay spontaneously Radioactivity: α ( 4 He ++ ), β (e -, e + ), γ (photons) J.J. Thomson 1897: cathode rays are electrons e - Nature of atoms: plum pudding model with + and charges Addresses stability of atoms but no account of discrete wavelengths in emitted spectra of light Rutherford 1911: large angle scattering of particles by thin gold foils very small, electrically charged central nucleus planetary atom model with e - s on discrete orbits around nucleus explains discrete light emission in decay of excited atoms Hydrogen = proton + electron 25/01/14 F. Ould-Saada 8

9 Planetary atom Masses of natural elements are integer multiples of a unit 1% smaller than m H m C =12.0 ; m N =14.0 in such units But not all atoms obey rule! Chlorine=35.5 Soddy Isotopes : atoms whose nuclei have different masses but same charge Natural elements are mixtures of different isotopes à observed masses Chadwick 1932: neutron, n, neutral radiation emitted in α- Be Final ingredients for understanding nuclei? Bohr 1913: Bohr model using Quantum Mechanics (QM) Avoids atom collapse in planetary version based on classical mechanics Phenomena of atomic physics explained by Dirac equation relativistic analogue of Schrödinger equation Heisenberg et al.: application of QM to Nucleus made of nucleons (p,n) Force binding nucleus is not electromagnetism holding electrons in their orbits, but a short- range, charge- independent, Strong Nuclear force Different models are used to interpret various classes of phenomena in Nuclear Physics 25/01/14 F. Ould-Saada 9

10 Early 1930s: elementary particles Electron e - - (Thomson 1897), proton p (Rutherford 1919), neutron n (Chadwick 1932) Photon γ Planck 1900: quantization of EM radiation to explain black- body radiation Neutrino ν Pauli 1930: postulated neutral spin1/2 particle to explain apparent non- conservation of energy and angular momentum in b- decays, 3- body instead of 2- body decay to e- +p) Reines- Cohen- 1956: detection of antineutrino at nuclear reactor 1950s: High energy beams of particles in laboratories Controlled scattering experiments, greater use of computers, sophisticated analysis techniques 1960s: large number of unstable particles with very short lifetimes à Particle Zoo Quark model: Gell- Mann & Zweig à 3 families of more fundamental particles Quarks, q confirmed in deep inelastic scattering en and νn 25/01/14 F. Ould-Saada 10

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13 From Hadrons Model predicts particles like the Ω Particle! to q u a r k s All hadrons are made of a smaller number of yet more fundamental particles, quarks As confirmed by experiments by shooting high energy electrons on nucleons (p,n) Protons and Neutrons are made of quarks bound by gluons.

14 Explains nearly all particle physics phenomena, except Gravity Interaction of a small number of elementary (fundamental) particles Single theory to interpret all HE data, contrary to nuclear physics Elementary particle characterized by quantum numbers: mass m, electric charge q, spin s=0,1/2,1,3/2, Spin : permanent angular momentum in QM no classical analogue Fermions: half- integer spin (electron: s=1/2) Bosons: integer spin (photon: s=1, Higgs: s=0, Graviton : s=2) 3 families of particles in SM 2 spin- 1/2 families of fermions: Leptons (electron, neutrino) and Quarks (u,d) 1 family of spin- 1 bosons (at least) one spin- 0 Higgs boson to explain origin of mass A (scalar) Higgs boson discovered by CERN 25/01/14 F. Ould-Saada 14

15 1 st generation: All ordinary matter belongs to this group Neutrinos needed in most matter transformations 2 nd and 3 rd generations: Existed just after the Big-Bang Now found only in Cosmic rays or produced at high energy Accelerators Each particle also has an antimatter counterpart... sort of mirror image.

16 The 4 fundamental forces of nature are carried by Bosons: - 8 Gluons - 1 Photon - 3 W +, W -, Z 0-1 Graviton?

17 Electromagnetic All electrically charged particles: electron, quarks, W- bosons Massless γ à long range interaction Weak all particles (but gluons and photons), including neutrinos and Higgs Heavy W +,W -, Z 0 m=80-90 GeV à short range interaction Strong interaction Only quarks (and gluons) bound in nucleons Massless gauge bosons but short range due to confinement Strong nuclear forces (in NP) are a consequence of this more fundamental strong interaction 25/01/14 F. Ould-Saada 17

18 Free quarks unobserved in nature Hadrons made of quarks Quark properties deduced from studies of hadron properties Analogy to deducing properties of nucleons by studying nuclei Nuclei are bound states of nucleons Nucleons are bound states of quarks Are properties of Nuclei deducible from properties of quarks and their interaction, i.e. the SM? In practice, it is beyond present calculation techniques NP and PP treated as 2 almost separate subjects However there are many connections between the fields 25/01/14 F. Ould-Saada 18

19 q Quarks are not free, they come in 3 colors and are confined in Hadrons q Only colorless combinations of quarks exist in nature Ø Mesons = quark-antiquark (π +, π 0, π - ) Ø Baryons = qqq (p,n)

20 The four fundamental forces are carried by vector field particles - bosons If you change the strength of any interaction, you would arrive to a totally different world Is the relative strength always Like that? - No, it depends where you live!? Just after the Big-Bang it is believed that all 4 forces had the same strength 25/01/14 F. Ould-Saada 20

21 Our current understanding leads to a coherent picture of the Universe: Astronomy: v=hd Statistics: E=kT Relativity: Quantum mechanics E=hν=hc/λ and a series of phase transitions

22 Student contacts Course evaluation Mid- term evaluation You will have the chance to give feedback in order for me to improve the teaching on the fly Final evaluation Student contact collects input from students Meeting Report

23 (N 2 ) gas (10-8 cm) in a room at NTP (293 o K, 1 Atm) M=28. 1, kg ; k=1, J K - 1 ; 1eV=1, J 1 m 2 v2 = 3 kt ev 2 v 2 = 510m s 1 E k 1, T [ K] [ ] 2, T 2 $ K 2 t s % & ' From S. Braibant et al.; Particles and fundamental interactions

24 Very hot Travel back in time TeV scale!1ps 13.7 M years Very Cold starting totally symmetric with Big Bang some 13.7M years ago cooling towards current 2.7º K while expanding, went through successive phase transitions with associated Symmetry Breakings, led to a diversity of fields responsible for 4 ``fundamental'' forces

25 PV=nRT? 25/01/14 F. Ould-Saada: LHC - Fysikk 25

26 High Symmetry Towards higher symmetries Chaos High Energy Physics Astronomy Chemistry Biology... A simple, single theory Various theories describing Various aspects of Nature Experiment not accessible SM describes Nature up to ~1 TeV

27 Towards unification of all fundamental forces Current experimental limits?

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29 The Standard Theory of Particles and Forces

30 H? All forces in nature obey a form of symmetry. Gauge-symmetry The Standard Model (SM) describes interactions between elementary particles grouped in 3 families of quarks and leptons The Standard Model unifies Electromagnetism (long range, macroscopic, photon has no mass) and Weak force (short range, microscopic, W and Z are heavy) at high energies describes (almost) all current particle physics data The Electroweak symmetry must be broken at low energies in order to give the weak bosons (W,Z), as well as all matter particles, masses. A scalar field requiring a new particle, the Higgs Boson...

31 What is the origin of mass? Newton: Weight proportional to mass Einstein: Energy related to mass... neither explained origin of fundamental particle masses... Although most of mass of ordinary matter (p,n) is due to kinetic energy of its constituents (quarks) what gives mass to quarks and electron? Massless electrons would be flying around at speed of light and there would be no matter Is mass due to the Higgs boson (through its field), the only missing particle of the Standard Model? Whole Universe swims in an invisible, cosmic field, Higgs-field, which acts on particles and provide them with what is called mass. All fields have associated boson. The Higgs-field has its Higgs-boson.

32 Forces are dictated by (gauge) symmetries ú Fermions in 3! = SU(3) C *[SU(2) L *U(1) Y ] à QCD + Electroweak ( = QED + Weak) Symmetries of laws do not necessarily lead to symmetries of outcomes ú ú Electroweak symmetry spontaneously broken Brout Englert Higgs mechanism BEH hides EW symmetry, gives masses to weak gauge bosons and approves fermion masses, predicts couplings of particles to Higgs, and more Higgs boson mass is not predicted by the SM è Must be measured Higgs and more - F. Ould- Saada 25/01/14 32

33 q Particle collisions at LHC Ø Simulated proton + proton à black hole candidate Ø LHC collides also heavy ions: pb- pb and p- pb q Sensitivity to rare phenomena with small cross sections depends on the luminosity Higgs and more - F. Ould- Saada 25/01/14 33

34 Number of collisions N = L. σ (pp X) Luminosity L n. of protons per bunch n. of bunches L = N2 k b f 4πσ x σ y n. of turns per second beam size at IP (σ x,y = 16 µm) Cross-section σ Very small for new processes 25/01/14 F. Ould- Saada: HEPP & ATLAS 34

35 45 m ATLAS superimposed to the 5 floors of building m 7000 Tons 35

36 Let s build ATLAS in ~ 1 minute Higgs and more - F. Ould- Saada 25/01/14 36

37 A real event in a detector Higgs and more - F. Ould- Saada 25/01/14 37

38 Particle detection " the various particles have different signatures in different parts of the detector " by combining the various signatures, we can reconstruct how the particle moved through the detector 25/01/14 F. Ould-Saada: HEPP & ATLAS 38

39 Particle identification Higgs and more - F. Ould- Saada 25/01/14 39

40 Hà ZZ*à µ+µ- µ+µ- Higgs and more - F. Ould- Saada m4=127.4 GeV. m12=86.6 GeV, m34=31.6 GeV 25/01/14 40

41 Hà γγ Higgs and more - F. Ould- Saada 25/01/14 41

42 Hà γγ Higgs and more - F. Ould- Saada 25/01/14 42

43 Anything new? Invariant mass of photons Higgs particle at 126 GeV! 43

44 What about the strong interaction QCD? ú ú Especially at high energies and densities Asymptotic freedom vs confinement p- p vs pb- pb vs p- pb collisions ú ALICE, ATLAS and CMS à observation of jet- quenching Sign of quark- gluon plasma? ú Another phase transition Experimental Particle UiO F. Ould-Saada, 11/

45 ALICE Mission ú High Energy Heavy Ion collisions ú Comparison of pb +pb, p+p and p +pb collisions ú Investigating the Quark Gluon Plasm (QGP), predicted by QCD, in the LHC energy regime. F. Ould-Saada, 11/

46 Pb Heavy ion collisions Pb π + p π -

47 Water phase transition solid liquid vapor

48 QCD phase transition diagram T c Early universe quark-gluon plasma Temperature hadron gas nucleon gas nuclei ρ 0 net baryon density F. Ould-Saada, 11/

49 QCD phase transition diagram Studying the phase transitions of quark-gluon plasma allows us to understand the behavior of matter in the early universe, just fractions of a second after the Big Bang, as well as conditions that might exist inside neutron stars. The fact that these two disparate phenomena are related demonstrates just how deeply the cosmic and quantum worlds are intertwined. Credit: Brookhaven National Laboratory

50 High Energy Physics may provide answers to some outstanding problems in Astrophysics and Cosmology What is the origin of mass? BEH mechanism! What is dark matter? What is dark energy? Do extra dimensions exist? What is the Universe s original symmetry? What happened with the original symmetry? What happened with the original antimatter? How did Universe evolve? Vacuum with scalar field (`Higgs ) Spontaneous symmetry breaking Quark-gluon plasma Supersymmetric particles Extra dimensions, graviton

51 CERN The place where things happen 25/01/14 F. Ould-Saada 51

52 CERN A research laboratory for thepour worldla Recherche Conseil Européen - ~10000 scientists from more than 110 countries Nucléaire Situated between Geneva and France Fundamental research in particle physics - seeking answers to questions about the Universe What is it made of? How did it come to be the way it is? Advancing the frontiers of technology and engineering - Medicine, - IT (WWW, Grid) Training the young scientists and engineers - the experts of tomorrow World s leading Norway is one of CERN s research 20 members centre in particle physics

53 4 large experiments at LHC to explore a new energy era CMS: 2900 physicists 184 Institutions 38 countries Multipurpose LHCB 700 physicists 52 Institutions 15 countries matter-antimatter ALICE; 1000 physicists 105 Institutions 30 countries q-g plasma and 3 smaller experiments TOTEM LHCf MoEDAL Korea and CERN / July ATLAS : 3030 Physicists 174 Institutions 38 countries Multipurpose

54 Feedback is needed in order to plan some trip ~April 7-10 Must start planning very soon Institute contributes with 15 knok (in total) So some own contribution is expected CERN Student program us/students Summer student Deadline Technical student Deadline