Physics 2D Lecture Slides Jan 22. Vivek Sharma UCSD Physics

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1 Physics 2D Lecture Slides Jan 22 Vivek Sharma UCSD Physics

3 Nuclear Fusion : What Powers the Sun Opposite of Fission Mass of a Nucleus < mass of its component protons+neutrons Nuclei are stable, bound by an attractive "Strong Force" Think of Nuclei as molecules and proton/neutron as atoms making it Binding Energy: Work/Energy required to pull a bound system (M) apart leaving its components (m) free of the attractive force and at rest: Mc n 2 2 +BE= mic i=1 He MeV = H + H Helium Deuterium Deuterium Think of energy released in Fusion as Dissociation energy in Chem Sun's Power Output = 4 10 Watts Fusion/Second No wonder Sun is considered a God in many cultures!

4 Nuclear Fusion: Wishing For The Star Fusion is eminently desirable because More Energy/Nucleon (3.52 MeV in fusion Vs 1 MeV in fission) 2 H + 3 H 4 He + n MeV Relatively abundant fuel supply No danger like nuclear reactor going supercritical Unfortunately technology not commercially available What s inside nuclei => protons and Neutrons Need Large KE to overcome Coulomb repulsion between nuclei About 1 MeV needed to bring nuclei close enough together for Strong Nuclear Attraction fusion Need to heat particle to high temp such that kt 10keV tunneling High density plasma at high temp T 10 8 K like in stars Confine Plasma (± ions) long enough for fusion» In stars, enormous gravitational field confines plasma

5 Inertial Fusion Reactor : Schematic Pellet of frozen-solid Deuterium & tritium bombarded from all sides with intense pulsed laser beam with energy 10 6 Joules lasting 10-8 S Momentum imparted by laser beam compresses pellet by 1/10000 of normal density, heats it to temp T 10 8 K for S Burst of fusion energy transported away by liquid Li

World s Most Powerful Laser : NOVA @ LLNL Size of football

0 x 10 14 watts (100 terawatts) 10 laser beams converge onto H

6 World s Most Powerful Laser : LLNL Size of football field, 3 stories tall Generates 1.0 x watts (100 terawatts) 10 laser beams converge onto H pellet (0.5mm diam) Fusion reaction is visible as a starlight lasting S Releasing neutrons

Anti Matter! E = p c + ( mc ) 2 2 2 2 2 2 2 2 2 E =± p c + ( mc ) We conveniently took the +E solution? What does the -E solution imply?

7 Anti Matter! E = p c + ( mc ) E =± p c + ( mc ) We conveniently took the +E solution? What does the -E solution imply? In Nature if something is allowed is allowed, it must happen Dirac 1930: Combined relativity with Quantum Mechanics All negative energy states filled with electrons in a negative energy sea Rules prevent electron from junping into negative energy states But if an electron from negative-energy sea is given E > 2mc 2 Can jump out of sea and become an electron of positive energy leaves behind a positive charged HOLE which behaves like a particle of positive charge POSITRON Positron is antiparticle of Electron, All particles must have anti-particles Tweeduldum and Tweedledee

Energy Energy E =± pc + ( mc) 2 2 2 2 - e - 2 +mc Light with E > 2mc 2 2 +mc mc 0 2 Filled sea of negative Energy electrons mc 0 2 e + +

8 Energy Energy E =± pc + ( mc) e - 2 +mc Light with E > 2mc 2 2 +mc mc 0 2 Filled sea of negative Energy electrons mc 0 2 e + + Filled sea of negative Energy electrons A positron from Outer space (Cosmic Ray) captured on photographic plate : Anderson 1931, Nobel Prize

9 Creating matter-antimatter: ee Annihilating matter-antimatter e γ + + e γ + : Making baby universes : Go back to environment when the Universe was very young Observe it

10 Large Electron-Positron Collider

11 Matter-Antimatter Collider Detector Concentric Onion like Shells of Precision camera Measures Momentum & Energy of Particles

12 ALEPH Detector At CERN

13 Very Fast Signal Readout (DAQ)

14 P ν,ε ν Relativistic Kinematics of Subatomic Particles ν π + Reconstructing Decay of a π Meson At rest µ + P µ, Ε µ + + The decay of a stationary π µ υ happens quickly, υ is invisible, has m 0; µ + leaves a trace in a B field + µ 2 mass=106 MeV/c, KE = 4.6 MeV + What was mass of the fleeting π? Energy Conservation: E = E π µ + E ν m π c ( mµ c ) pµ c pυc Momentum Conservation : also m c π = ( m c ) + p c + p c µ µ µ pµ c Eµ ( mµ c ) ( Kµ mµ c ) ( mµ c ) Substituting for = K + 2K m c 2 2 µ µ µ p c 2 2 µ = mπ c = mµ c + Kµ 2Kµ mµ c Kµ + 2 p = p µ ν = = + 2 Put in all the known #s = m mπ c 111MeV 31MeV 141Me π = 141 MeV / c + = V K m µ µ c 2

16 My Discovery (1993): Beauty With Strangeness

17 Two Faced Particle :Matter & Antimatter Sometimes Matter Sometimes Antimatter May help explain why antimatter In the Universe has disappeared Why Universe is matter dominated

Physics 2D Lecture Slides Jan 21. Vivek Sharma UCSD Physics

Physics 2D Lecture Slides Jan 21. Vivek Sharma UCSD Physics Physics D Lecture Slides Jan 1 Vivek Sharma UCSD Physics Particle Accelerators as Testing ground for S. Relativity When Electron Goes Fast it Gets Fat E = γ mc v As 1, γ c Apparent Mass approaches Relativistic