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The design has been optimized for the measurement of:
R=R^+-/R⁰⁰=[Γ(KL>π+π-)/Γ(KS>π+π-)]*[Γ(KS>π0π0)/Γ(KL>π0π0)]=1+6*Re(ε'/ε)

In principle one can look for CP violation by counting how many times KS->3π0, but in this case there is a further suppression due to the phase space. So, it's much easier to count how many times KL->2π0.

Drift chamber:
Requirements

• Large tracking volume (K Long decay length= 340 cm)
• High and uniform reconstruction efficiency (due to the K Long decays distribution)
• Good momentum resolution @ 0.6 T (for kinematical rejection of the background for CP events)
• Transparency to reduce regeneration, multiple scattering and conversion of low energy photons

Calorimeter:
It's a fine sampling calorimeter (lead/scintillator), in order to have good direction resolution for photons. Its energy resolution is comparable to homogeneous calorimeters.
Requirements

• Determine the KS/KL neutral vertex with few mm precision
• Discriminate between KL->2π0 and KL->3π0
• Particle identification via time of flight ( electrons vs. Muons vs. Pions)
• Good time resolution
• The volume ratio Pb:scint:glue of 42:48:10 has been chosen to maximize the calorimeter sampling fraction and correspondingly increase the light yield (~1 p.e./MeV/side at 2 m distance). This high light yield reflects in an excellent time resolution which roughly scales as τ/√N_{primary electrons} (τ~2.2ns)

Scintillating fibers:

"K crash": a K Long that does not decay in the drift chamber, but interacts (nuclearly) in the calorimeter:

Equalization of charged/neutral energy scales: by comparing KL>π+π-π0 and K+>π+π0π0.

The KLOE detector is "short" (5 meters long, while it has a diameter of 6 meters): the reason is that the KS+KL pairs from Φ decay have a sin²θ distribution, since they come from a J=1 state.

Peculiarity of KLOE: around the interaction region, the beam pipe is spherical. This is designed to give negligible regeneration effects.