Francisco Antonio Physics 129 November 23, 2010 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

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.  ’s: Parallel development of Kaons’ and the Standard Model’s main concepts.

The Gellmann-Pais Paper  Theoretical proposition that there be a property of strangeness to allow for K 0 K 0 (Eigenstates of Mass)  CP|K 0 > = -|K 0 >  By CP conservation:K1 and K2 were restricted to 2  and 3  decays, respectively Initially thought to be equivalent to K S and K L Later known as the Eigenstates of Weak Interaction

First Results:  Lederman,   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)

Data On the V o Events

Ruling Out the Possibilities

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

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.

The Weak Interaction  Asymmetry in the K 0 /K 0 mixing that created K L and K S  no longer equivalent to K2 and K1 respectively. Instead a mixture characterized by  of K1 and K2 describe K L and K S in the eigenstate of weak interaction.  Result: Time/Space Dependent Oscillation between K L and K S  Is a measure of CP violation related to the mixing of K 0 /K 0

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 EigenstatesMass Eigenstates

Superweak Interactions  Asserts that the ONLY CP violation in the neutral Kaon system is due to K 0 /K 0 mixing  Would accomplish this by allowing ΔS = 2 so that  (for the superweak) is much larger than  (from the second order KM weak interaction).

Direct CP Violation Measured!  Alavi et. al. 1999,  Data: from 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

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

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.

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.

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

References  Gell-Mann, Pais. “Behavior of Neutral Particles Under Charge Conjugation”. Phys Rev  Alavi et al. “Observation of Direct CP Violation in Ks,l  2Pi”. Phys Rev. Letters  Cronin et al. “Evidence of the 2Pi Decay of the K2 Meson”. Physical Review Letters  Lande et al. “Observation of Long-Lived Neutral V Particles”. Physical Review  Kobayashi, Maskawa. “CP-Violation in the Renormalizable Theory of Weak Interaction”. Progress of Theoretical Physics  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