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A Close-In Detector for the BNL Long Baseline Experiment

A Close-In Detector for the BNL Long Baseline Experiment. Steve Kahn 10 Jan 2003. Requirements for a Close-in Detector for the Long Baseline Neutrino Experiment. This detector should provide flux distributions as a function of E  .

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A Close-In Detector for the BNL Long Baseline Experiment

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  1. A Close-In Detector for the BNL Long Baseline Experiment Steve Kahn 10 Jan 2003

  2. Requirements for a Close-in Detector for the Long Baseline Neutrino Experiment • This detector should provide flux distributions as a function of E. • It should provide flux distributions for all components:  e  e • A magnetic field is desired to distinguish the sign of the leptons. • The detector should provide a flux that can be extrapolated to the far detector. • The most desirable case would be to position the close detector such that the neutrino source position looks like a point. • This would suggest that the close-in detection should be placed greater than 2 km from the target. This is not easily achievable for a beam inclined 11.3o. Close-In Detector

  3. Requirements, continued. • A realistic position for the close in detector is 275 meters from the target. • This is behind a 10 meter beam stop at the end of the decay tunnel and benefits from the additional 60 meters of soil between the beam stop and the detector enclosure. • A study of how to relate the flux distribution at 275 m to that at 2540 km will be necessary. • This will have to be done for J-PARC also. • In order to avoid relying heavily on a Monte Carlo description of the beam-line one would need either: • Two close detectors with some separation between them • A single detector at a distance greater than ~2 km, so that the neutrino source (pion decay position) appears as a point. Close-In Detector

  4. Neutrino Fluxes at Detector Locations Off-axis e fluxes are scaled by 20 in order to be visible. Note the different shapes at 250 m and 2540 km. Close-In Detector

  5. Technology to be used for the Close Detector • It would be desirable to have neutrino interactions off the same nuclei at the near and far detector. • There are nuclear effects such as pion reabsorption. • A resonance event pp can look like np in an Ar detector but not in a H2O detector. • There are Fermi Motion effects that would be different with different nuclear targets. • There different resolutions with different detectors. • One needs to evaluate the size of these effects. There are likely to cause ~10% errors in the knowledge of the beam flux at the far detector. • We might be able to live with it. Close-In Detector

  6. Cartoon Design of the Close-In Detector 3 meters 1.5 m Close-In Detector

  7. Liquid Argon Detector • The major component of this detector is a magnetized liquid argon TPC detector modeled after that proposed in the -LANNDD experiment. • I have chosen as a start the dimensions of -LANNDD: • 0.70.73.0 m3 • These dimensions may have to change to enclose the lateral growth of a shower. • A detector of this size could fit into 120D36 dipole magnet which could give a 1 T field. • This detector would have 2 tons of liquid argon. Close-In Detector

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  10. Typical Shower from a 2.5 GeV Electron in a 1 T Transverse Field Close-In Detector

  11. Ice Target • In order to address the criticism that the near detector has a different target than the far detector, a supplementary target made of ice could be put in front of the liquid argon to provide a sample of events that interacted on water. • The ice would not have active detection. Events would observed as tracks from an interaction upstream. • An upstream veto detector would be necessary to verify that the interaction occurred in the ice. • I have assumed about 0.5 meters of ice which would give 0.22 tons of target. Close-In Detector

  12. Muon Magnet • Liquid Argon has interaction84 cm. This would provide on average ~2 interaction lengths to distinguish pions from muons. An external magnetized iron-scintillator detector could verify muons and provide a measurement of the muon momentum. • The field in the iron is sort of torroidal, à la Minos. • The magnet in the liquid argon only provides the momentum projected in a plane. Close-In Detector

  13. Estimates of Events Seen in this Detector. Estimates are for 5107 sec and don’t include fiducial volume cuts Close-In Detector

  14. What Next? • I am in the process of setting up this detector system in a Geant4 simulation. • This should give insight on whether this system will work. • Also we need to study how to use the flux measured at the close-in detector to determine the flux at the far detector. Close-In Detector

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