1 / 32

A Super-Neutrino Beam From BNL to Homestake

A Super-Neutrino Beam From BNL to Homestake. Steve Kahn http://pubweb.bnl.gov/people/kahn/talks/bnl2homestake.pdf. Staging to a Neutrino Factory. Two feasibility studies for a Neutrino Factory have been concluded. These studies indicate a cost of 2-2.5 B$.

ismael
Download Presentation

A Super-Neutrino Beam From BNL to Homestake

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Super-Neutrino Beam From BNL to Homestake Steve Kahn http://pubweb.bnl.gov/people/kahn/talks/bnl2homestake.pdf Neutrino Beams from BNL to Homestake

  2. Staging to a Neutrino Factory • Two feasibility studies for a Neutrino Factory have been concluded. • These studies indicate a cost of 2-2.5 B$. • This does not include contingency and overhead. • This kind of money may not be available in the current climate • They indicate an optimistic turn-on date of 2012. • We might like to do some physics before that. • A staged approach to building a Neutrino Factory maybe desirable. • First Phase: Upgrade AGS to create a 1 MW Proton Driver and target station. • Second Phase: Build phase rotation and part of cooling system. • Third Phase: Build a pre-acceleration Linac to raise beam momentum to 2.5 GeV/c • Fourth Phase: Complete the Neutrino Factory. • Fifth Phase: Upgrade to entry-level Higgs Factory Muon Collider. • Each phase can support a physics program. Neutrino Beams from BNL to Homestake

  3. First Phase Super Neutrino Beam • Upgrade AGS to 1MW Proton Driver: • Both BNL and JHF have eventual plans for their proton drivers to be upgraded to 4 MW. • Build Solenoid Capture System: • 20 T Magnet surrounding target. Solenoid field falls off to 1.6 T in 20 m. • This magnet focuses both + and . Beam will have both  and  • A solenoid is more robust than a horn magnet in a high radiation. • A horn may not function in the 4 MW environment. • A solenoid will have a longer lifetime since it is not pulsed. Neutrino Beams from BNL to Homestake

  4. Types of Capture/Focus Systems Considered • Traditional Horn Focus System • Uses toroidal magnetic field. • Focuses efficiently • B  p • Conductor necessary along access. • Concern for radiation damage. • Cannot be superconducting. • Pulsed horn may have trouble surviving ~109 cycles that a 1-4 MW system might require. • Solenoid Capture System similar to that used by Neutrino Factory • Solenoid Horn System Neutrino Beams from BNL to Homestake

  5. Simulations to Calculate Fluxes • Model Solenoid/Horn Magnet in GEANT. • Use Geant/Fluka option for the particle production model. • Use 30 cm Hg target ( 2 interaction lengths.) • No target inclination. • We want the high momentum component of the pions. • Re-absorption of the pions is not a problem. • Solenoid Field profile on axis is B(z)=Bmax/(1+a z) • Independent parameters are Bmax, Bmin and the solenoid length, L. • Horn Field is assumed to be a toroid. • Pions and Kaons are tracked through the field and allowed to decay. • Fluxes are tallied at detector positions. • The following plots show  flux and e / flux ratios. Neutrino Beams from BNL to Homestake

  6. Solenoid Capture Sketch of solenoid arrangement for Neutrino Factory • If only  and not  is desired, then a dipole magnet could be inserted between adjacent solenoids above. • Inserting a dipole also gives control over the mean energy of the neutrino beam. • Since  and  events can be separated with a modest magnetic field in the detector, it will be desirable to collect both signs of  at the same time. Neutrino Beams from BNL to Homestake

  7. Captured Pion Distributions PT =225 MeV/c corresponding to 7.5 cm radius of solenoid P > 2 GeV/c Decay Length of Pions 66% of  are lost since they have PT>225 MeV/c  = 50 m <L>=7 m PT distribution of  A 15 cm radius of the solenoid would capture 67% of the + PT, GeV/c L, cm Neutrino Beams from BNL to Homestake

  8. Rate and e/ as a function of Decay Tunnel Length Neutrino Beams from BNL to Homestake

  9. Comparison of Horn and Solenoid Focused Beams • The Figure shows the spectra at 0º at 1 km from the target. • Solenoid Focused Beam. • Two Horned Focused Beam designed for E889. • So-called Perfect Focused beam where every particle leaving the target goes in the forward direction. • The perfect beam is not attainable. It is used to evaluate efficiencies. • A solenoid focused beam selects a lower energy neutrino spectrum than the horn beam. • This may be preferable for CP violation physics Neutrino Beams from BNL to Homestake

  10. Horn and Solenoid Comparison (cont.) • This figure shows a similar comparison of the 1 km spectra at 1.25º off axis. • The off axis beam is narrower and lower energy. • Also a curve with the  flux plus 1/3 the anti- flux is shown in red. • Both signs of  are focused by a solenoid capture magnet. • A detector with a magnetic field will be able to separate the charge current  and anti-. Neutrino Beams from BNL to Homestake

  11. Angle Solenoid  QE evts Solenoid  QE Events Horn  QE evts Horn evts 0 4.21106 9.86105 1.38107 1.20105 ¼ 4.11106 9.56105 1.32107 1.06105 ½ 4.10106 9.46105 1.18107 1.05105 1 3.80106 8.83105 8.69106 8.27104 1.5 3.36106 7.89105 5.98106 7.53104 2 2.88106 6.80105 4.01106 4.76104 3 1.94106 4.64105 1.93106 3.31104 4 1.31106 3.20105 1.02106 2.35104  Flux Seen at Off-Axis Angles • We desire to have Low Energy  beam. • We also desire to have a narrow band beam. • I have chosen 1.5º off-axis for the calculations. Neutrino Beams from BNL to Homestake

  12. e/ Ratio • The figure shows the e flux spectrum for the solenoid focused and horn beams. • The horn focused beam has a higher energy e spectrum that is dominated by Koee • The solenoid channel is effective in capturing and holding  and . • The e spectrum from the solenoid system has a large contribution at low energy from ee. • The allowed decay path can be varied to reduce the e/ ratio at the cost of reducing the  rate. • We expect the e/ ratio to be ~1% Neutrino Beams from BNL to Homestake

  13. Running the AGS with 12 GeV Protons • We could run the AGS with a lower energy proton beam. • If we keep the same machine power level we would run at a 5 Hz repetition rate. • This would work for a conventional beam since we are not concerned with merging bunches. • Figure shows Perfect Beam for 12 and 24 GeV incident protons. • 12 GeV profile is multiplied by 2 for the higher repetition rate. • 24 GeV protons • 12 GeV Protons Perfect Beam Neutrino Beams from BNL to Homestake

  14. 12 GeV Protons (cont.) 1.25 degrees off axis On Axis Neutrino Beams from BNL to Homestake

  15. Detector Choices • The far detector would be placed 350 km from BNL (near Ithica, NY). • There are salt mines in this area. One could go deep underground if necessary. • If a massive detector were built at say 2540 km from BNL (at Homestake), this would permit the determination of the CP violation sign using mass effect. • Two possible detector technologies that can be considered are Liquid Ar and Water Cherenkov. • We are considering Liquid Ar TPC similar to Icarus. The far detector would have 50 ktons fiducial volume (65 ktons total.) • Provides good electron and o detection. • The detector will sit between dipole coils to provide a field to determine the lepton charge. • This technology is expensive and may not be practical. Neutrino Beams from BNL to Homestake

  16. Detector Choices (cont.) • Water Cherenkov technology similar to Super-K may be the only reasonable way to achieve a Megaton detector. • Charge determination using a magnetic field may not be possible with this type of detector. The neutrino source must sign select the . • A close-in 1 kton detectors at 1 km and/or 3 km would be needed. • 1 km detector gives  beam alignment and high statistics for detector performance. • 3 km detector is far enough away that  source is a point. Neutrino Beams from BNL to Homestake

  17. Detectors Are Placed 1.5o Off  Beam Axis • Placing detectors at a fixed angle off axis provides a similar E profile at all distances. • It also provides a lower E distribution than on axis. •  from  decays are captured by long solenoid channel. They provide low E enhancement. • Integrated flux at each detector: • Units are /m2/POT Neutrino Beams from BNL to Homestake

  18. Ratio of QE D350/D3 10 1 0.1 0.01 0 1 2 3 4 Enu, GeV Neutrino Oscillation Physics • The experiment would look at the following channels: •  disappearance -- primarily  oscillations. • Sensitive to m232 and 23 • Examine ratio of np (QE) at 350 km detector to 3 km detector as a function of E. • NoN events • These events are insensitive to oscillation state of  • Can be used for normalization. • e appearance • (continued on next transparency) Neutrino Beams from BNL to Homestake

  19. e Appearance Channel • There are several contributions to P(e): • Solar Term: Psolar=sin2212 cos213cos223sin2(m2solL/4E) • This term is very small. • Tau Term: P=sin2213sin223sin2 (m2atmL/4E) • This is the dominant term. • This term is sensitive to 13 and would allow us to measure it with the 1 MW proton driver. • Terms involving the CP phase : • There are both CP conserving and violating terms involving . • The CP violating term can be measured as • This asymmetry is larger at lower E. This could be ~25% of the total appearance signal at the optimum E • The 4 MW proton driver would be necessary for this asymmetry Neutrino Beams from BNL to Homestake

  20. Event Estimates Without Oscillations • Below is shown event estimates expected from a solenoid capture system • The near detectors are 1 kton and the far detector is 50 kton. • The source is a 1 MW proton driver. • The experiment is run for 5 Snowmass years. This is the running period used in the JHF-Kamioka neutrino proposal. • These are obtained by integrating the flux with the appropriate cross sections. • Estimates with a 4 MW proton driver source would be four times larger. Neutrino Beams from BNL to Homestake

  21. Determination of m223 • Consider a scenario where • m212=5105eV2 • 23=/4 • m231=0.0035 eV2 (unknown) • Sin2 213=0.01 (unknown) • This is the Barger, Marfatia, and Whisnant point Ib. • <E> =0.8 GeV is not optimum since I don’t know the true value in advance. • I can determine m223 from 1.27 m223L/E0=/2 Where E0 is the corresponding null point • Note that these figures ignore the effect of Fermi motion in the target nuclei. • This would smear the distinct 3/2 minimum. /2 Neutrino Beams from BNL to Homestake

  22. m232 with Errors • Same plot as previously shown. • The near detector at 3 km and the far detector is at 350 km. • The plot is made comparing quasi-elastic events only. • E is well measured for these events. No corrections are necessary. • This should produce a solid measurement of m232. Neutrino Beams from BNL to Homestake

  23. Barger, Marfatia and Whisnant Table Neutrino Beams from BNL to Homestake

  24. Oscillation Signal • The following transparencies will show Quasi-Elastic event numbers for Solenoid and Horn capture systems. They assume: • 1 MW Proton Driver • 50 kton detector at 350 km with charge determination (Liquid Ar) • 5107 second running period. • For comparison we have 28% of the flux used in Barger et al. • We do not use a necessarily optimum L/E fixed configuration for all cases since the true oscillation parameters are not known in advance. • We use the actual flux distribution, not a monochromatic  beam (as used in Barger et al.). • The size of the e appearance signal will give a 13 measurement since m132 m232 is measured independently by the  disappearance. Neutrino Beams from BNL to Homestake

  25. Going to Homestake • Most of the transparencies shown are based on Snowmass calculations for a far detector placed near Cornell. • We can scale the number of events from these calculations to estimate signals that would be seen at Homestake. • Scale with detector mass • Scale with 1/r2. • Increasing the Proton Driver Power to 4 MW would be very advantageous to a detector at Homestake. 0.38 if 1 MW • With the eventual upgrade to a neutrino factory, the Homestake detector would have a significant event rate. Neutrino Beams from BNL to Homestake

  26. m213 eV2  e signal e background Anti  Anti e signal Anti e BG No Oscillation 15539 455 3455 150 0.002 5065 76 455 1096 18.5 150 0.0035 5284 70 455 1283 16.2 150 0.005 7722 55 455 1762 13.1 150 Solenoid Capture System with 230 m Decay Tunnel Table 1: Oscillation Signal: ·Consider m212=510-5 eV2, 23=/4 and sin2 213=0.01 ·Using a 1 MW proton driver and a 50 kton detector 350 kilometers away. ·Experiment running for 5107 seconds. ·Solenoid capture system with e/flux ratio=1.9 %  e Signal e BG  e signal e BG Ignores e BG oscillations Significance: e signal: 3.3 s.d. e signal: 1.3 s.d. Neutrino Beams from BNL to Homestake

  27. m213 eV2  e signal e background Anti  Anti e signal Anti e BG No Oscillation 10582 249 2560 47 0.002 3600 58 249 878 14.4 47 0.0035 4282 50 249 1090 12.3 47 0.005 5283 43 249 1303 10.6 47 Solenoid Capture System with 100 m Decay Tunnel Table 1: Oscillation Signal: ·Consider m212=510-5 eV2, 23=/4 and sin2 213=0.01 ·Using a 1 MW proton driver and a 50 kton detector 350 kilometers away. ·Experiment running for 5107 seconds. ·Solenoid capture system with e/flux ratio=1.1 %  e signal e BG  e signal e BG Ignores e BG oscillation Significance: e signal: 3.2 s.d. e signal: 1.8 s.d. Neutrino Beams from BNL to Homestake

  28. m213 eV2  e signal e background Anti  Anti e signal Anti e BG No Oscillation 21645 272 228 5.4 0.002 8317 83 272 115 1 5.4 0.0035 5165 95 272 84 1 5.4 0.005 9966 69 272 90 1 5.4 Horn Beam 200 m Decay Tunnel E889 Horn Design Table 1: Oscillation Signal: ·Consider m212=510-5 eV2, 23=/4 and sin2 213=0.01 ·Using a 1 MW proton driver and a 50 kton detector 350 kilometers away. ·Experiment running for 5107 seconds. ·Horn capture system with e/flux ratio=1.08 %  e Signal e BG  e signal e BG Ignores e BG oscillations Significance: e signal: 5.8 s.d. Neutrino Beams from BNL to Homestake

  29. m213 eV2  e signal e background Anti  Anti e signal Anti e BG No Oscillation 691 19 4354 65 0.002 506 4 19 1576 19.7 65 0.0035 305 4.7 19 1018 17.8 65 0.005 331 4.5 19 2074 13.9 65 Anti  Horn Beam 200 m Decay Tunnel E889 Horn Design Table 1: Oscillation Signal: ·Consider m212=510-5 eV2, 23=/4 and sin2 213=0.01 ·Using a 1 MW proton driver and a 50 kton detector 350 kilometers away. ·Experiment running for 5107 seconds. ·Horn capture system with e/flux ratio=1.04 %  e Signal e BG  e signal e BG Ignores e BG oscillations Significance: e signal: 2.2 s.d. Neutrino Beams from BNL to Homestake

  30. Cosmic Ray Background • This table shows the cosmic ray rates for a detector placed on the surface. • The rate reduction factors come from the E889 proposal. • The events shown are scaled to the 350 km detector mass and 5 Snowmass year running period. • The neutron background could be significantly reduced by going 50-100 m underground if it is a problem. • Placing the detector deep below ground in a mine would be more advantageous for proton decay experiments. • The residual cosmic ray background could be reduced to ~0.002 events at ~600 m below ground. Neutrino Beams from BNL to Homestake

  31. Backgrounds to e Appearance Signal • The largest backgrounds to the e signal are expected to be: • e contamination in the beam. • This was ~1% e/ flux ratio in the capture configuration that was used in this study. This yields a ~2% in the event ratio. • Neutral Current oN events where the o are misidentified as an electron. • If a  from the o converts close to the vertex (Dalitz decay) and is asymmetric. • The magnetic field and dE/dx will be helpful in reducing this background. Simulation study is necessary. • I estimate (guess) that this background is ~0.001 of the oN signal. Neutrino Beams from BNL to Homestake

  32. Conclusions • A high intensity neutrino super beam maybe an extremely effective way to study neutrino oscillations. • In particular the 4 MW version of the super beam may be the only way to observe CP violation in neutrino oscillations without a Muon Ring Neutrino Factory. • This experiment is directly competitive with the JHF-Kamioka neutrino project. • Do we need two such projects? I will not answer that! Neutrino Beams from BNL to Homestake

More Related