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Fine-Grained Near Detector(s) at JHF: Purpose and Thoughts

Fine-Grained Near Detector(s) at JHF: Purpose and Thoughts. Kevin McFarland University of Rochester 31 October 2002. Sign of d m 23. d. | U e3 |. Precision P( n m → n e ) and P( n m → n m ). Conventional “superbeams” will be our only windows into n m → n e for a long time…

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Fine-Grained Near Detector(s) at JHF: Purpose and Thoughts

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  1. Fine-Grained Near Detector(s) at JHF: Purpose and Thoughts Kevin McFarland University of Rochester 31 October 2002

  2. Sign of dm23 d |Ue3| Precision P(nm→ne) and P(nm→nm) • Conventional “superbeams” will be our only windows into nm→ne for a long time… • Analogous to |Vub| in quark sector • Long time before m sources or “b beams” • Studying in neutrinos and anti-neutrinos gives us magnitude and phase information on |Ue3| • Comparing two precise n measurements at different E or L/E does same • P(nm→nm) is mixing maximal? Precise dm23 Kevin McFarland

  3. 1ring FC m-like Oscillation with Dm2=3×10-3 sin22q=1.0 Non-QE No oscillation Reconstructed En (MeV) Where do Cross-Sections matter? • nm→nm, dm223, q23 • Signal is suppression in 600-800 MeV bin • Dominated by non-QE background • 20% uncertainty in non-QE is comparable to statistical error • Non-QE background feeds down from En>Epeak Kevin McFarland

  4. Where do Cross-Sections matter? sin22qme=0.05 (sin22qme0.5sin22q13) • nm→ne, q13 • Shown at right is most optimistic q13; we may instead be fighting against background • Equal parts NC p0 and beam ne background • NC p0 cross-section poorly known • We can calculate sCC(ne)/sCC(nm). Is it right? • We must prove to the world we are right with S/N of 1:1 • Precision measurement is the endgame Kevin McFarland

  5. Where do Cross-Sections matter? • nm→ne vs nm→ne, d • Cross-sections very different in two modes • “Wrong sign” background only relevant in anti-neutrino • Crucial systematic in comparison • Need sCC(n)/sCC(n) at high precision in sub- to few-GeV region nm nm Kevin McFarland

  6. n–p0 nn+ Status of Cross-Sections • Not well-known at 1-few GeV • Backgrounds for JHFn • Signal and Background at NUMI 0.70 off-axis proposal Kevin McFarland

  7. Low Energy Neutrino cross-sections Neutrino interactions • Quasi-Elastic / Elastic , nmn→m-p (x =1, W=Mp) • well measured and described by form factors • BUT, need to account for Fermi Motion/binding effects in nucleus, e.g. Bodek-Ritchie prescription • Resonance, nmp→m-pp (low Q2, W) • Poorly measured and only 1st resonance described by Rein and Seghal • Deep Inelastic, nmp→m-X (high Q2, W) • well measured by high energy experiments • well described by quark-parton model (pQCD with NLO PDFs) • but doesn’t work well at low Q2 region. at x = 1 (quasi)elastic F2 integral=0.43 (e.g. SLAC data at Q2=0.22) • Issues at few GeV : • Resonance production and low Q2 DIS contribution meet. • The challenge is to describe ALL THREE processes atALL neutrino (or electron) energies • HOW CAN THIS BE DONE? • QPM model with proper scaling behavior above 1st resonance using ideas from quark-hadron duality Kevin McFarland

  8. Does model work? Ref: Bodek and Yang hep-ex/0203009 Q2= 0.22 GeV2 Q2= 0.07 GeV2 • Can test in electron scattering • Data at right predicted by fit • More complicated in neutrino charged-current • Isospin selection, e.g., np→mD++ • EOI considered by FNAL PAC • Collaboration (FNAL, Hampton, Jefferson Lab, Rochester) being formed • Note that this project requires a JHF 280m type detector • Is NUMI our test beam? Q2= 1. 4 GeV2 Q2= 9 GeV2 Q2= 3 GeV2 Q2= 15 GeV2 Q2= 25 GeV2 Kevin McFarland

  9. Fine-Grained Detector Goals • Observe recoil protons • Important for n–p, n–p0 • Investigate n capture layers? • 0 , – reconstruction • Adds a lot of mass. Muon charge needed for n • Oxygen-rich Target • Water miscible scintillator layers • Exists. Commercially available. Need detailed study of properties • Light output problematic? VLPC readout? • Sampling water + plastic scint? • Acrylic? Is it stable? Lowish oxygen content Kevin McFarland

  10. Fine Grained Location: Off-Axis • Narrow band beam, similar to far detector • NBB crucial for study of cross-sections, particularly for neutral current • Event cannot be fully reconstructed without knowing En • En can be varied by varying position • Bonus: can check beam spectrum, particularly backgrounds for nm→ne • Not clean as in case of “2km” detector Kevin McFarland

  11. Event Spectra in Near Off-Axis, Near On-Axis and Far Detectors at NUMI Far 0.7o OA Far 0.7o OA Near 0.7o OA (LE) Near On-Axis (LE) Near 0.7o OA (ME) Near On-Axis (ME) Kevin McFarland

  12. NUMI EOI (technology test?) • Ideal locations in NUMI tunnel complex exist for 2.5 GeV beam • 1.5 GeV possible. 1 GeV tough. Locate in access drift Kevin McFarland

  13. n Conceptual NUMI Near Detector Active/passive frame around target Active scintillator strip target Kevin McFarland

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