BNL Neutrino Long Baseline Neutrino Initiative N. Simos, BNL NWG Baseline = 2540 Km Homestake.
A Near Detector for the BNL Very Long Baseline Facility
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June 11, 2004 S. Kahn -- Near Det ector Facility 1 A Near Detector for the BNL Very Long Baseline Facility Steve Kahn BNL Review AGS Upgrade and Super Neutrino Beam Facility June 11, 2004
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A Near Detector for the BNL Very Long Baseline Facility. Steve Kahn BNL Review AGS Upgrade and Super Neutrino Beam Facility June 11, 2004. The Purpose of a Near Detector. The main purpose of the near detector is to provide knowledge of the composition of the neutrino beam: - PowerPoint PPT Presentation
Transcript of A Near Detector for the BNL Very Long Baseline Facility
June 11, 2004 S. Kahn -- Near Detector Facility
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A Near Detector for the BNL Very Long Baseline Facility
Steve Kahn
BNL Review
AGS Upgrade and
Super Neutrino Beam Facility
June 11, 2004
June 11, 2004 S. Kahn -- Near Detector Facility Page 2
The Purpose of a Near Detector
The main purpose of the near detector is to provide knowledge of the composition of the neutrino beam:
The energy spectrum of the dominant flux. The energy spectrum of the contaminant neutrino species in the
beam: , e, ande. The integrated neutrino flux for overall normalization. Neutrino direction information for extrapolation to far detector.
e elastic scattering Statistically from Quasi-elastic interactions.
Alignment monitoring information from neutrino data during a run. Also it should hopefully have its own physics program.
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Near Detector Location
The near detector facility is planned to be located at 285 m from the target.
It would be desirable to have the near detector further from the target, so that the neutrinos appear to come from a point source.
The steep 11.3° incline limits the choice of location.
At this position the near detector hall is 21 m below the ground level.
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Near Detector Location (cont.)
The near detector hall is behind a 10 meter iron 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. There should be essentially no muon punch through.
A study of how to relate the flux distribution at 285 m to that expected at 2540 km will be necessary. This will have to be done for J-PARC’s near detector
also.
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Comparison of the Flux Distribution at the Near and Far Detectors
Figure shows the flux distribution at the near location (red) and the flux distribution at the far detector (blue) scaled to the near detector position.
The near flux peaks at a lower energy than the flux at the far detector.
Because of the large statistics that will be present at the near detector the flux can be measured as a function of position to provide information for the extrapolation to the far detector.
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Flux Contamination Seen at the Near Detector
Flux distributions can be obtained from a simulation of the target and horn system using both GEANT and MARS programs
MARS gives the , K± and ± produced on the carbon target.
GEANT tracks these particles through the horn system and allows them to decay to channels that produce neutrinos.
At the near detector the flux has: 3% component 1% e component
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Expected Event Rates at the Near Detector
The number of events of each neutrino species produced in the detector can be obtained by integrating the flux with the appropriate cross section.
The table below shows the expected number of events for a 200 ton detector during a 5107 second running period.
200 tons was chosen to be large enough to contain the entire event, but small enough to be affordable.
For this 5107 second period we expect a total of 4109 events in a 200 ton detector. That is 32 events per pulse!
Species Quasi-Elastic Charge Current Neutral Current 1.33109 3.66109 2.01108
7.70106 7.74107 1.37106
e 1.42107 3.99107 3.10106
e 4.89104 3.98105 1.30104
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Desired Attributes of a Near Detector
The technology chosen should be able to handle the high event rate. It should be able to distinguish events from different neutrino species.
Distinguish electrons from muons. Determine the sign of the lepton, particularly the muon.
Do we need a magnetic field? It should be able to distinguish the lepton from hadrons
Muons from pions Electrons from
It would be desirable that the interactions be on a similar nucleus as the far detector so that uncertainties about re-absorption will cancel.
The near detector should have its own physics program to take advantage of the large statistics available.
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The Choice of Near Detector Technology
It is certainly not my intention to choose the Near Detector technology. This should be done by a group of physicists who are
proposing the experiment and should be reviewed by the usual committees.
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What about Water Cherenkov?
High event rate at 285 m may limit the usefulness of a water Cherenkov detector.
The Super-K guidelines requires 2 m from the surface of the fiducial volume to the PMTs. In addition to measure energy up to 1 GeV requires 4 m down stream region.
This says that 100 ton fiducial volume requires 1kton size water Cherenkov detector.
The water Cherenkov detector would be better suited at a distance of 1.5-2 km.
Intermediate Distance Water Cherenkov proposed for JPARCIntermediate Distance Water Cherenkov proposed for JPARC
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Schematic of a Liquid Argon TPC Near Detector
100 ton active liquid argon volume
14 ton fiducial volume
Magnetized Iron-scintillator
Detector for muon identification
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Typical Shower from a 2.5 GeV Electron in a 1 T Transverse Field
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Events in Liquid Argon
Events are clean in liquid argon. Separation of electrons from muons should be easy. Separation of 0 from electrons should be possible.
Expect ~16 events in 100 ton active region or ~2 events in fiducial volume. A typical event should occupy about 6 m3. (The fiducial
volume is about 10 m3)
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Cost Estimate Guess
Liquid Argon TPC Based on A. Rubbia’s numbers for the actual cost of the Icarus
prototype module: M$ 20/kiloton. Estimate that 200 ton Liquid Argon TPC would be ~M$5 0.5 T magnetic field on Liquid Argon would be additional.
Magnetized Iron Scintillator. MINOS near detector was estimated at M$5 in the design report.
This would escalate to M$6.2 today. I am using a smaller iron-scintillator detector behind the Liq-Ar
cryostat. Estimate about 1/3 the cost: ~M$2.1 Expect the Near Detector to cost M$ 7-9
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Summary
The near detector will provide the necessary understanding of the neutrino flux and its contamination.
The detector will be challenging because of its location and its high event rate. Extrapolating to the flux at the far detector will require
some analysis. A liquid argon TPC may be a reasonable technology for this
detector. The cost of this detector should be of the order of 10 million
dollars.
