K0 beam line for the E391a experiment

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K0 beam linefor the E391a experiment

• May 27, 2005
• Takao Inagaki (KEK)

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Location
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(No Transcript)
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Collimation scheme
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KL spectrum and n and?profiles
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• Telescope for the profile measurement

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Profiles (meas. vs MC)
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Sizable vacuum effect
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Detectors for energy spectra
SLSD ( lead glass)
Cerberus
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?spectra measured by SLSDlead glass
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Neutron and ? spectra by Cerberus
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C4 suppressor of thermal neutron flux
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Profiles and spectra of the halo
Measured by Cerberus
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Decay vertex distribution for 2?sample at
trigger bias
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How are the halo neutrons generated?

• Scattering at C2
• Hadronic Shower at C6
• Main source of
• lower-energy tail events
• 25 events

• Multiple Scattering
• Main source of
• higher-energy edge events

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Summary

• The profiles and spectra including the absorber
  effects were rather well reproduced by a MC
  simulation using GEANT(G-FULKA) code.
• Beam-line design becomes science from art.
• Further improvement
• suppress the second step scattering
• decrease n/KL ratio

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Supplement
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(No Transcript)
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How are the halo neutrons generated?
It consists of two kinds of source.

• From first look of e391 data, we have to reduce
  halo!!!

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How are the halo neutrons generated?

• Multiple Scattering,
• 1st scattering is in the Pb absorber.
• No. of event is rather large.
• 20 of halo events

Scattering at Vacuum window.
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Summary for halo-neutrons

• Source of halo neutrons
• 1. Multiple scattering
• typical case
• (a) C2?C6?halo
• (b) Pb abs ? C6 ? halo (20)
• 2. Hadronic shower at C6 (ex, C2?C6?shower) (
  25 )
• Possible way
• 1. Position of trimming collimator relative to
  Pb abs.
• 2. Active veto-counter at C6.
• Test of New Collimation Scheme