Francisco Antonio K

Francisco Antonio
Physics 129
November 23, 2010
Li Zhengdao and Yang Zhenning, 1953
 Experimental History of Kaons
 Evolving Theory of Kaons with respect to CP
 Current Technologies, Directions for Kaon
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.
The Gellmann-Pais Paper
 Theoretical
proposition that
there be a property
of strangeness to
allow for K0 < -- > K0
(Eigenstates of
 CP|K0> = -|K0>
 By CP
conservation:K1 and
K2 were restricted
to 2 and 3 decays,
Initially thought to be equivalent to KS and KL
Later known as the Eigenstates of Weak Interaction
First Results:
 Lederman, 1956.
 1  10^-10 sec.
 2  10^-8 sec.
 Goal: Kinematically
confirming the events
were related to a
neutral secondary
36 “ Magnet Cloud Chamber Design with Proton Beam incident on target
(Brookhaven Bevatron)
Data On the Vo Events
Ruling Out the Possibilities
CP Violation After All
 Cronin and Fitch,
 First evidence for
Indirect CP
 Goal: Measured
2 decays where
only KL = K1
should have
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 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.
 Is a measure of CP violation related to the mixing of K0/K0
 Result: Time/Space Dependent Oscillation between KL
and KS
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
The amount of mixing is parametrized by three angles ij and phase shift 
Weak Interaction Eigenstates
Mass Eigenstates
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
Direct CP Violation
 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
Alavi Experiment, Fermilab.
KTeV Experiment, E832, First to use Dual Kaon Beams for great suppression of
unwanted channels
The Modern Kaon Experimental
 Beam – Dual Kaon Beams
 Regenerator – Takes advantage of eigenstate
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
 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
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.
Lande et 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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