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K-Mesons: History and Basic Theory

Francisco Antonio Physics 129 November 23, 2010. K-Mesons: History and Basic Theory. Li Zhengdao and Yang Zhenning , 1953. Overview:. Experimental History of Kaons Evolving Theory of Kaons with respect to CP Current Technologies, Directions for Kaon Science.

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K-Mesons: History and Basic Theory

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  1. Francisco Antonio Physics 129 November 23, 2010 K-Mesons: History and Basic Theory Li Zhengdao and Yang Zhenning, 1953

  2. Overview: • Experimental History of Kaons • Evolving Theory of Kaons with respect to CP • Current Technologies, Directions for Kaon Science

  3. Pre-Gellmann and Pais • The state of the yet to be conceived “Standard Model” • The Neutral  Particle, one among the many particles of the 1953 particle extravaganza • Late 1950’s: The Intermediate Vector Bosons, courtesy of Yukawa • 1964: The quark. • 1960-1980’s: Parallel development of Kaons’ and the Standard Model’s main concepts.

  4. The Gellmann-Pais Paper • Theoretical proposition that there be a property of strangeness to allow for K0 < -- > K0 (Eigenstates of Mass) • CP|K0> = -|K0> • By CP conservation:K1 and K2 were restricted to 2 and 3 decays, respectively Initially thought to be equivalent to KS and KL Later known as the Eigenstatesof Weak Interaction

  5. First Results: • Lederman, 1956. • 1  10^-10 sec. • 2  10^-8 sec. • Goal: Kinematically confirming the events were related to a neutral secondary particle. 36 “ Magnet Cloud Chamber Design with Proton Beam incident on target (Brookhaven Bevatron)

  6. Data On the Vo Events

  7. Ruling Out the Possibilities

  8. CP Violation After All • Cronin and Fitch, 1964. • First evidence for Indirect CP Violation. • Goal: Measured uncharacteristic 2 decays where only KL = K1 should have existed. Again at the Brookhaven Bevatron, this time with spark chamber detectors

  9. CP Violation: The Contenders • Direct CP Violation – Depends on decay process itself, penguin diagrams • Indirect CP Violation – related to mixing the eigenstates of mass to form the eigenstates of decay. Weak interactions of ΔS = 1 and superweak interactions of ΔS = 2.

  10. The Weak Interaction • Asymmetry in the K0/K0 mixing that created KL and KS no longer equivalent to K2 and K1 respectively. Instead a mixture characterized by  of K1 and K2 describe KL and KS in the eigenstate of weak interaction. • Result: Time/Space Dependent Oscillation between KL and KS  Is a measure of CP violation related to the mixing of K0/K0

  11. The Kobayashi-Maskawa Model of Weak Interaction Instead of a diagonal matrix relating the mass eigenstates to the weak interaction eigenstates, the off diagonals are present, allowing a small amount of mixing The amount of mixing is parametrized by three angles ij and phase shift  Weak Interaction Eigenstates Mass Eigenstates

  12. Superweak Interactions • Asserts that the ONLY CP violation in the neutral Kaon system is due to K0/K0mixing • Would accomplish this by allowing ΔS = 2 so that (for the superweak) is much larger than  (from the second order KM weak interaction).

  13. Direct CP Violation Measured! • Alavi et. al. 1999, • Data: from 96-97 Fermilab Run. • Goal: To measure a non-zero Re(/) to a high degree of accuracy Note that in the case of Superweak models Re(/) = 0

  14. Alavi Experiment, Fermilab. KTeV Experiment, E832, First to use Dual Kaon Beams for great suppression of unwanted channels

  15. The Modern Kaon Experimental Setup • Beam – Dual Kaon Beams • Regenerator – Takes advantage of eigenstate oscillations • Photon Veto – Rejects 2 and 2 decays. • EM Calorimeter – particle “shower”. Reconstruction • Magnetic Spectrometer- Phase space measurements (Intensity vs. Momentum) • Collimators – maximize neutral beam acceptance.

  16. Is The Superweak Theory disproven? • At least in the neutral Kaon system it has been found to be “weak”-sauce. • B Systems are currently being tested for similar ratios of Re(/) with results pending.

  17. Kaon Science Today • Direct vs. Indirect CP violation (only Kaons have the former) • The Strong CP Problem (QCD doesn’t break CP Symmetry) • Matter/Antimatter existence due to preferential decays that violate CP • The Standard Model’s take on CP Violation - Insufficient

  18. References • Gell-Mann, Pais. “Behavior of Neutral Particles Under Charge Conjugation”. Phys Rev. 97. 1387. • Alavi et al. “Observation of Direct CP Violation in Ks,l 2Pi”. Phys Rev. Letters. 83. 22. • Cronin et al. “Evidence of the 2Pi Decay of the K2 Meson”. Physical Review Letters. 13. 138. • Landeet al. “Observation of Long-Lived Neutral V Particles”. Physical Review. 103. 1901. • Kobayashi, Maskawa. “CP-Violation in the Renormalizable Theory of Weak Interaction”. Progress of Theoretical Physics. 49. 652 • Biino et al. “The Simultaneous Long and Short lived Neutral Kaon Beams for Experiment NA48”. European Organization for Nuclear Research CERN—SL Division. • Winstein. “The Search for Direct CP Violation”. Reviews of Modern Physics. 65. 1113

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