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- 1. Exploring the Fundamental Particles in the Universe Exploring the Fundamental Particles in the Universe – p.1/29
- 2. Outline Standard Model of Particle Physics Beyond the Standard Model Astroparticle Physics Exploring the Fundamental Particles in the Universe – p.2/29
- 3. Standard Model of Particle Physics LEP T ON S : e − e+ µ− µ+ τ− τ+ ¯ ¯ νe νe νµ νµ ντ ¯ ντ QU ARKS : u ¯ u d ¯ d s ¯ s c ¯ c b ¯ b t ¯ t GAU GEBOSON S : γ W ± Z g(8) G HIGGSBOSON : φ Antiparticle - same mass, opposite charge Exploring the Fundamental Particles in the Universe – p.3/29
- 4. PARTICLE DISCOVERIESCathode Ray Tube Electron (1897)Compton scattering expt Photon (1923)Cosmic Rays Positron (1932), Muon (1936)Beta decay Electron neutrino (1956)(nuclear reactors) Exploring the Fundamental Particles in the Universe – p.4/29
- 5. ACCELERATORS FERMILAB p¯ p KEK e + e− CERN(LHC) pp BROOKHAVEN HeavyIonCollisions Exploring the Fundamental Particles in the Universe – p.5/29
- 6. CERN - [27km, 100m, 11K rev/s, 1011 p per bunch] Exploring the Fundamental Particles in the Universe – p.6/29
- 7. The LHC tunnel Exploring the Fundamental Particles in the Universe – p.7/29
- 8. Exploring the Fundamental Particles in the Universe – p.8/29
- 9. Decaying Higgs after a p-p collision600mill/s Exploring the Fundamental Particles in the Universe – p.9/29
- 10. PARTICLE DISCOVERIESAccelerators Muon and Tau neutrino, Tau lepton Up and Down quarks s,c,b,t quarks Gluons, W ± , Z (1962-2000) Exploring the Fundamental Particles in the Universe – p.10/29
- 11. PARTICLE DISCOVERIES Accelerators Muon and Tau neutrino, Tau lepton Up and Down quarks s,c,b,t quarks Gluons, W ± , Z (1962-2000)Higgs particle is not yet discovered. (LHC?) Exploring the Fundamental Particles in the Universe – p.10/29
- 12. Theoretical Calculations Quantum Mechanics Non-relativistic particles Quantum Field Theory Relativistic particles Represent each particle by a ﬁeld As in QM, work with a Hamiltonian (or Lagrangian) Use perturbation theory (like in QM) to calculate how particles decay, interact with each other, etc. Compare theoretical and experimental results Exploring the Fundamental Particles in the Universe – p.11/29
- 13. The Lagrangian of the Standard Model 1 i iµν 1 µν 1 j jµν θ2 g2 ˜ L = − Wµν W − Bµν B − Gµν G + 2 Tr Gj Gjµν µν 4 4 4 16π ¯ γ µ (1 − γ5 ) i∂µ − g 1 τ i W i − g Y Bµ − gs 1 λj Gj fD +f D µ µ 2 2 2 ¯γ µ (1 + γ5 ) i∂µ − g Y Bµ − gs 1 λj Gj f +f µ 2 2 2 1 Y 1 + i∂µ − g τ i Wµ − g Bµ − gs λj Gj φ − V (φ) i µ 2 2 2 ¯ ¯ −mf φf1 f1 − mf φc f2 f2 [i = 1, 2, 3; j = 1, 2, .., 8] where f are fermions ( leptons and quarks), Gj , Wµ and µ jBµ are the strong and electroweak gauge bosons irespectively, and φ is the Higgs boson. The Lagrangianhas SU (3)c × SU (2)L × U (1)Y mathematical symmetry,which spontaneously breaks into SU (3)c × U (1)EM . Exploring the Fundamental Particles in the Universe – p.12/29
- 14. Unease with the Standard Model The Standard Model of Particle Physics has 19 parameters. The large number of arbitrary parameters in the Standard Model is a cause of concern. Exploring the Fundamental Particles in the Universe – p.13/29
- 15. Unease with the Standard Model The Standard Model of Particle Physics has 19 parameters. The large number of arbitrary parameters in the Standard Model is a cause of concern. Also neutrinos are massless in the Standard Model. (1998 - ν mass) Exploring the Fundamental Particles in the Universe – p.13/29
- 16. Unease with the Standard Model The Standard Model of Particle Physics has 19 parameters. The large number of arbitrary parameters in the Standard Model is a cause of concern. Also neutrinos are massless in the Standard Model. (1998 - ν mass) Some theoretical calculations of the Higgs mass make it too large (unless one carefully adjusts parameters). Exploring the Fundamental Particles in the Universe – p.13/29
- 17. Unease with the Standard Model The Standard Model of Particle Physics has 19 parameters. The large number of arbitrary parameters in the Standard Model is a cause of concern. Also neutrinos are massless in the Standard Model. (1998 - ν mass) Some theoretical calculations of the Higgs mass make it too large (unless one carefully adjusts parameters). GO BEYOND THE STANDARD MODEL Exploring the Fundamental Particles in the Universe – p.13/29
- 18. Beyond the Standard Model High Energy Theory −→ Standard Model (like Special Relativity −→ Newtonian Physics) Exploring the Fundamental Particles in the Universe – p.14/29
- 19. Beyond the Standard Model High Energy Theory −→ Standard Model (like Special Relativity −→ Newtonian Physics) GRAND UNIFIED THEORIES (GUTs) (larger mathematical symmetry, neutrino mass) Exploring the Fundamental Particles in the Universe – p.14/29
- 20. Beyond the Standard Model High Energy Theory −→ Standard Model (like Special Relativity −→ Newtonian Physics) GRAND UNIFIED THEORIES (GUTs) (larger mathematical symmetry, neutrino mass) SUPERSYMMETRY (controls the Higgs mass) FERMION ←→ BOSON BOSON ←→ FERMION γ (PHOTON) ←→ γ (PHOTINO) ˜ e (ELECTRON) ←→ e (SELECTRON) ˜ Exploring the Fundamental Particles in the Universe – p.14/29
- 21. Beyond the Standard Model High Energy Theory −→ Standard Model (like Special Relativity −→ Newtonian Physics) GRAND UNIFIED THEORIES (GUTs) (larger mathematical symmetry, neutrino mass) SUPERSYMMETRY (controls the Higgs mass) FERMION ←→ BOSON BOSON ←→ FERMION γ (PHOTON) ←→ γ (PHOTINO) ˜ e (ELECTRON) ←→ e (SELECTRON) ˜ Discoveries at the LHC? Exploring the Fundamental Particles in the Universe – p.14/29
- 22. The Standard Model and Beyond THE STANDARD MODEL OF PARTICLE PHYSICS Theory: Lagrangian (Quantum Field Theory) Experiment: Cosmic Rays, Accelerators BEYOND THE STANDARD MODEL Grand Uniﬁed Theories (GUTs) Supersymmetry LARGE HADRON COLLIDER Exploring the Fundamental Particles in the Universe – p.15/29
- 23. What about Gravity? CLASSICAL GRAVITY −− GENERAL THEORY OF RELATIVITY QUANTUM GRAVITY −− ? Exploring the Fundamental Particles in the Universe – p.16/29
- 24. What about Gravity? CLASSICAL GRAVITY −− GENERAL THEORY OF RELATIVITY QUANTUM GRAVITY −− ? SUPERSTRING THEORY Elementary particles like the photon and the electron are not point-like objects but are extended objects. To see the string like behaviour need very high energy probes. Exploring the Fundamental Particles in the Universe – p.16/29
- 25. What about Gravity? CLASSICAL GRAVITY −− GENERAL THEORY OF RELATIVITY QUANTUM GRAVITY −− ? SUPERSTRING THEORY Elementary particles like the photon and the electron are not point-like objects but are extended objects. To see the string like behaviour need very high energy probes. Supersymmetric GUTs are included in superstring theory and the GRAVITON appears naturally in the particle spectrum. So it is a UNIFIED QUANTUM THEORY of PARTICLE PHYSICS and GRAVITY. Exploring the Fundamental Particles in the Universe – p.16/29
- 26. What about Gravity? CLASSICAL GRAVITY −− GENERAL THEORY OF RELATIVITY QUANTUM GRAVITY −− ? SUPERSTRING THEORY Elementary particles like the photon and the electron are not point-like objects but are extended objects. To see the string like behaviour need very high energy probes. Supersymmetric GUTs are included in superstring theory and the GRAVITON appears naturally in the particle spectrum. So it is a UNIFIED QUANTUM THEORY of PARTICLE PHYSICS and GRAVITY. d>4 Exploring the Fundamental Particles in the Universe – p.16/29
- 27. Cosmology and Particle Physics Particle Physics theories ﬁnd applications in astrophysical scenarios and in the context of the Early Universe. Particularly in the latter case, they allow us to test interactions of particles at very high energies. Solar Neutrino Deﬁcit Dark Matter Matter-Antimatter Asymmetry Exploring the Fundamental Particles in the Universe – p.17/29
- 28. Solar Neutrino Deﬁcit Nuclear reactions in the Sun 2 p+p → H + e + + νe p +2 H → 3 He + γ 3 He +3 He → 4 He + 2p 3 He +4 He → 7 Be + γ 7 7 Be + e− → Li + νe 7 8 Be + p → B+γ 8 8 B → Be∗ + e+ + νe 8 Be → 4He +4 He We detect only 1/3 of the neutrinos νe that we expect. Exploring the Fundamental Particles in the Universe – p.18/29
- 29. Neutrino Oscillations No solution from Solar Physics. Exploring the Fundamental Particles in the Universe – p.19/29
- 30. Neutrino Oscillations No solution from Solar Physics. Is something happening to neutrinos as they travel from the sun to the earth? Exploring the Fundamental Particles in the Universe – p.19/29
- 31. Neutrino Oscillations Electron neutrinos emitted by the sun transform into muon and tau neutrinos. Therefore we detect only 1/3 of the neutrinos emitted by the sun. Exploring the Fundamental Particles in the Universe – p.20/29
- 32. Neutrino Oscillations Electron neutrinos emitted by the sun transform into muon and tau neutrinos. Therefore we detect only 1/3 of the neutrinos emitted by the sun. This hypothesis of neutrino oscillations has been conﬁrmed by experiments. (νe ↔ νµ ↔ ντ ) Neutrino oscillations requires neutrino massess Physics of stars tells us about fundamental particles ν Exploring the Fundamental Particles in the Universe – p.20/29
- 33. Dark Matter Velocity Rotation Curves of Galaxies Expect v ∼ √ , 1 r since v2 mr = G M2 and M is constant. r m BUT .... Exploring the Fundamental Particles in the Universe – p.21/29
- 34. Exploring the Fundamental Particles in the Universe – p.22/29
- 35. Take v ∼ constant. How can this be explained? Exploring the Fundamental Particles in the Universe – p.23/29
- 36. Take v ∼ constant. How can this be explained? v2 Mm m =G 2 r rIf M (r) = Ar, then v ∼ constant. Exploring the Fundamental Particles in the Universe – p.23/29
- 37. Take v ∼ constant. How can this be explained? v2 Mm m =G 2 r rIf M (r) = Ar, then v ∼ constant.But M (r) = Ar ⇒ matter beyond the central luminousregion which we can not see.This non-luminous matter (does not emit or scatter light)is called DARK MATTER. Exploring the Fundamental Particles in the Universe – p.23/29
- 38. DARK MATTER does not emit or scatter light so it isdifﬁcult to detect.What is it?Consists primarily of non-Standard Model matter –supersymmetric particles, axions, massive neutrinos, ...High energy physics theories provide possible candidatesfor dark matter Exploring the Fundamental Particles in the Universe – p.24/29
- 39. Matter-Antimatter Asymmetry Observed Universe is made up of only matter. ¯ M + M → photons Antimatter seen in laboratories since 1930s. We believe that at early times (t < 1s) there were equal amounts of matter and antimatter in the Universe. WHERE DID THE ANTIMATTER GO? Exploring the Fundamental Particles in the Universe – p.25/29
- 40. Matter-Antimatter Asymmetry WHERE DID THE ANTIMATTER GO? Disequilibrium in the early Universe 100 M + 100 M −→ 103 M + 101 M −→ 2 M Possible mechanism of creating matter excess is via the decay of GUT bosons X at t ∼ 10−34 s (T ∼ 1026 K). X −→ M −→ M r > r ⇒ N (M ) > N (M ). ¯ Particle physics theories to explain the M-A asymmetry Exploring the Fundamental Particles in the Universe – p.26/29
- 41. Conclusion We have a good understanding of the history and evolution of our Universe, but there are sill important outstanding questions – Big Bang, Dark Matter, Dark Energy The Standard Model of Particle Physics is good but not good enough Need to consider theories Beyond the Standard Model valid at higher energies Exploring the Fundamental Particles in the Universe – p.27/29
- 42. Conclusion Problems in Particle Physics are often linked to Cosmology and vice versa High energy particle physics theories such as String Theory may explain the Big Bang, Supersymmetric models may provide the Dark Matter, GUTs may explain the Matter-Antimatter Asymmetry, Solar Physics provides clues to the nature of Neutrinos Accelerators such as the LHC will (hopefully) discover the dark matter particle Exploring the Fundamental Particles in the Universe – p.28/29
- 43. Cosmology and Particle Physics Books The First Three Minutes by S. Weinberg The Big and the Small, vol. I and II by G. Venkataraman raghavan@prl.res.in Exploring the Fundamental Particles in the Universe – p.29/29

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