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

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 Sign of dm23 |Ue3| d 31 October 2002 Kevin McFarland

Where do Cross-Sections matter? 1ring FC m-like Reconstructed En (MeV) Oscillation with Dm2=3×10-3 sin22q=1.0 No oscillation Non-QE 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 31 October 2002 Kevin McFarland

Where do Cross-Sections matter? 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 sin22qme=0.05 (sin22qme  0.5sin22q13) 31 October 2002 Kevin McFarland

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 31 October 2002 Kevin McFarland

Status of Cross-Sections Not well-known at 1-few GeV Backgrounds for JHFn Signal and Background at NUMI 0.70 off-axis proposal n–p0 nn+ 31 October 2002 Kevin McFarland

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 at ALL neutrino (or electron) energies HOW CAN THIS BE DONE? QPM model with proper scaling behavior above 1st resonance using ideas from quark-hadron duality 31 October 2002 Kevin McFarland

Does model work? Can test in electron scattering Ref: Bodek and Yang hep-ex/0203009 Q2= 0.22 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= 0.07 GeV2 Q2= 1. 4 GeV2 Q2= 9 GeV2 Q2= 3 GeV2 Q2= 15 GeV2 Q2= 25 GeV2 31 October 2002 Kevin McFarland

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 31 October 2002 Kevin McFarland

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 31 October 2002 Kevin McFarland

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) 31 October 2002 Kevin McFarland

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 31 October 2002 Kevin McFarland

Conceptual NUMI Near Detector Active/passive frame around target Active scintillator strip target 31 October 2002 Kevin McFarland