Transcript mariel_long
Nuclear Physics UConn Mentor Connection Mariel Tader The Standard Model Describes three of the four “fundamental” forces • Electromagnetism, weak and strong interactions • There are 12 different kinds of elementary particles UConn Mentor Connection 2010, Mari Tader 2 The Forces • Electromagnetism: why opposites attract • Biology/ Chemistry • Strong Force: holds quarks together • Weak Force: mediates fundamental particle decay • (Gravity): not included in Standard Model UConn Mentor Connection 2010, Mari Tader 3 Electroweak Theory • Electromagnetism and weak force are two different aspects of the same force: electroweak • The two merge into the same force at high energies and close distance UConn Mentor Connection 2010, Mari Tader 4 The particles • 6 Quarks: make up protons, neutrons, etc. • 6 Leptons: electrons, neutrinos, etc. • Force carriers: gluons for strong force, etc. • Weak force’s range • The three generations UConn Mentor Connection 2010, Mari Tader 5 Antimatter • Each type of particle has a comparable anti-particle • The same properties, except charge • The mystery: why so much more matter? • Annihilation: matter and antimatter collide a Z boson/gluon/photon form decay into new matter/ antimatter pair UConn Mentor Connection 2010, Mari Tader 6 The Nucleus • Quarks: come in threes (protons/ neutrons/ etc.) or twos (mesons) • Gluons: hold quarks together, force carrier particle for strong force UConn Mentor Connection 2010, Mari Tader 7 Quantum Numbers • Electric Charge: all particles except quarks have integer charge, quark charges add to whole numbers • Flavor: different kinds of quarks/ leptons • Spin: goes by 1/2s, particles/ nuclei • Lepton/baryon numbers, etc. • Color Charge: gets its own slide • Angular momentum/ momentum: location • Weak Charge: strength of weak force UConn Mentor Connection 2010, Mari Tader 8 Color Charge • Why quarks come in threes or twos: neutral charge • Why quarks stay together: color force field • Quark: 1 of 3 colors • Anti-quark: 1 of 3 anti-colors • Gluon color charges: 1 color and 1 anti-color combination UConn Mentor Connection 2010, Mari Tader 9 Bosons and Fermions • Pauli Exclusion Principle: “two particles can’t have identical sets of quantum numbers” • Fermions: obey Pauli • Bosons: violate Pauli UConn Mentor Connection 2010, Mari Tader 10 Radiation • Unstable nuclei decay • Alpha: release of 2 protons/2 neutrons (helium nucleus) • Beta: release of an electron • Gamma: release of photons (as gamma rays) • Neutron radiation: like it sounds UConn Mentor Connection 2010, Mari Tader 11 Fundamental Particle Decay • Unlike atoms, fundamentals can not break into constituents • To become a less massive particle: 1. Emit a force carrier (W boson) “virtual” 2. W boson immediately decays into lighter particles UConn Mentor Connection 2010, Mari Tader 12 Virtual Particles • Can not be detected directly • Can break “conservation of energy” for a very short time You can not see virtual particles, but you can see the before and after UConn Mentor Connection 2010, Mari Tader 13 The Project • Thomas Jefferson National Accelerator • The collaboration • Will be the first to observe and study exotic mesons • Will begin 2014 UConn Mentor Connection 2010, Mari Tader 14 gluex • • GlueX hopes to learn about quarks, gluons, and confinement by creating exotic mesons How we “see” the gluons: Polarized beam liquid hydrogen target exotic mesons final particles and radiation data deciphered UConn Mentor Connection 2010, Mari Tader 15 Bremsstrahlung • German for “braking radiation” • A radiation particle interacts with atoms and creates more radiation, while losing the corresponding energy Atom UConn Mentor Connection 2010, Mari Tader 16 Coherent Bremsstrahlung • Must be in a crystal • Particle/crystal must be in correct alignment • A few specific wavelengths are prevalent, “peaks” UConn Mentor Connection 2010, Mari Tader 17 Reciprocal Lattice Vectors • Bravais Lattice: repeating crystalline arrangements of points • Reciprocal Lattice: made from the vectors perpendicular to three of the vectors of the original • Used as a simple geometric model that can interpret diffraction in crystals UConn Mentor Connection 2010, Mari Tader 18 Framing the Crystal • A frame would produce too much unwanted bremms. diamond is mounted on tiny carbon fibers • The resonant frequency of the fibers should be known, to minimize rotation UConn Mentor Connection 2010, Mari Tader 19 Vibration • Interference: two or more superimposed waves create a new wave pattern: need coherent bremss. • Resonant frequency: An objects natural frequency of vibration • Gluonic flux tube vibration is like a string UConn Mentor Connection 2010, Mari Tader 20 The Carbon Wire • The glue ball equation Amplitude vs Frequency 8.E-05 7.E-05 6.E-05 Amplitude (m) • The theoretical model vs. the experimental data • How we modeled it 5.E-05 4.E-05 3.E-05 2.E-05 • How we measured it • Uncertainty bars 1.E-05 0.E+00 61.8 UConn Mentor Connection 2010, Mari Tader 61.9 62 62.1 62.2 62.3 62.4 frequency (Hz) 21 62.5 Polarization • • The orientation of the wave’s electric/ magnetic fields Transverse wave: polarization is perpendicular to wave’s direction • Linear Polarization: the electric or magnetic field is oriented in one direction, i.e. no rotation (chirality) UConn Mentor Connection 2010, Mari Tader 22 Putting it all together • The process: Electron beam diamond wafer polarized photons hit mesons detectors UConn Mentor Connection 2010, Mari Tader 23