Preliminary Ideas for a Near Detector at a Neutrino Factory

1. Preliminary Ideas for a Near Detector at a Neutrino Factory Neutrino Factory Scoping Study Meeting 23 September 2005 Paul Soler University of Glasgow/RAL

2. Contents • Near Detector Aims • Flux normalization • Cross-sections • Parton Distribution Functions • Charm production • Sin2qw • Possible near detector technologies • 7.1 Silicon tracking detector • 7.2 Liquid argon TPC or other technologies • Conclusions Neutrino Factory Scoping Study Meeting CERN 22-23 September

3. 1. Near detector aims • Long baseline neutrino oscillation systematics: • Flux control and measurement for the long baseline search. • Neutrino beam angle and divergence • Beam energy and spread • Control of muon polarization • Near detector neutrino physics: • Cross-section measurements: DIS, QES, RES scattering • sin2W - sin2W ~ 0.0001 • Parton Distribution Functions, nuclear shadowing • S from xF3 - S~0.003 • Charm production: |Vcd| and |Vcs|, D0/ D0 mixing • Polarised structure functions • L polarization • Beyond SM searches General Purpose Detector(s)!! Neutrino Factory Scoping Study Meeting CERN 22-23 September

4. 2. Flux normalisation (cont.) • Neutrino beams from decay of muons: Polarisation dependence Need to measure polarization!! Pm=+1: gone! Spectra at Production (e.g. 50 GeV) Number CC interactions Neutrino Factory Scoping Study Meeting CERN 22-23 September

5. 100 m 2. Flux normalisation (cont.) • Rates: • Em = 50 GeV • L = 100 m, d = 30 m • Muon decays per year: 1020 • Divergence = 0.1 mm/Em • Radius R=50 cm E.g. at 25 GeV, number neutrino interactions per year is: 20 x 106 in 100 g per cm2 area. High granularity in inner region that subtends to far detector. Yearly event rates Neutrino Factory Scoping Study Meeting CERN 22-23 September

6. 2. Flux normalisation (cont.) • Neutrino flux normalisation by measuring: • Signal: low angle forward going muon with no recoil • Calculable with high precision in SM • Same type of detector needed for elastic scattering on electrons: E.g. CHARM II obtained value of sin2qW from this Neutrino Factory Scoping Study Meeting CERN 22-23 September

7. 3. Cross sections • Measure of cross sections in DIS, QE and RES. • Coherent p • Different nuclear targets: H2, D2 • Nuclear effects, nuclear shadowing, reinteractions With modest size targets can obtain very large statistics Neutrino Factory Scoping Study Meeting CERN 22-23 September

8. 4. Parton Distribution Functions(s) • Unpolarised and Polarised Structure functions • S from xF3 - S~0.003 • Sum rules: e.g. Gross-Llewelyn Smith • L polarization: spin transfer from quarks to L • NOMAD best data • Neutrino factory 100 times more data Neutrino Factory Scoping Study Meeting CERN 22-23 September

9. 5. Charm Production • Charm production: • Measure of Vcd and strange quark content nucleon • 6-7% of cross-section at 20 GeV3% CC events: about 3x107 charm states per year McFarland • mixing: doubly Cabbibo suppressedSM very small, new physics • Babar: Rmix<4x10-3 (90% CL) hep-ex/0408066 Tagged sample Neutrino Factory Scoping Study Meeting CERN 22-23 September

10. 6. sin2qw • Elastic scattering off electrons: • Deep inelastic scattering: NC/CC • sin2W ~ 0.0001 Good statistical accuracy on sin2W (~0.5x10-4) but hadron uncertainties dominate Neutrino Factory Scoping Study Meeting CERN 22-23 September

11. 7. Near detector technologies • High granularity in inner region that subtends to far detector. • Very good spatial resolution: charm detection • Low Z, large Xo • Electron ID • Does the detector have to be of same/similar technology as far detector? • Possibilities: • silicon or fibre tracker in a magnet with calorimetry, electron and muon ID(eg. NOMAD-STAR??) • Liquid argon calorimeter • Does not need to be very big (eg. R~50-100 cm) Neutrino Factory Scoping Study Meeting CERN 22-23 September

12. 7.1 Vertex detector with spectrometer • R&D in NOMAD for short baseline nt detector based on silicon: NOMAD-STAR • Does not need to be very big (eg. R~50-100 cm) Neutrino Factory Scoping Study Meeting CERN 22-23 September

13. 7.1 Vertex detector with spectrometer • Longest silicon microstrip detector ladders ever built: 72cm, 12 detectors, 50 mm pitch, S/N=16:1 • Vertex resolution 19 mm Neutrino Factory Scoping Study Meeting CERN 22-23 September

14. 7.1 Vertex detector with spectrometer • nm CC event • Secondary vertex • Primary vertex Neutrino Factory Scoping Study Meeting CERN 22-23 September

15. 7.1 Vertex detector with spectrometer • Vertex resolution: 19 mm • Impact parameter resolution: 33 mm • Used NOMAD-STAR to search for charm events: marginal statistical accuracy, but was a good proof of principle Neutrino Factory Scoping Study Meeting CERN 22-23 September

16. 7.1 Vertex detector with spectrometer • Efficiency very low: 3.5% for D0, D+ and 12.7% for Ds+ detection because fiducial volume very small (72cmx36cmx15cm), only 5 layers and only one projection. • From 200 million events, about 600,000 charm events, but efficiencies can be improved. Neutrino Factory Scoping Study Meeting CERN 22-23 September

17. 2.5 GeV e, 1.5T • Maybe the UA1/NOMAD magnet will live on again as a near detector for a neutrino factory? 7.2 Other technologies • Liquid argon TPC in a magnetic field would be able to perform as a near detector as well • Other possible technologies that have been used or are being proposed to be used as near detectors: scintillating fibre tracker, standard gas TPC with target (T2K near detector) … Neutrino Factory Scoping Study Meeting CERN 22-23 September

18. Conclusions • The Near Detector(s) needs to meet two physics goals: • Flux control and measurement for the long baseline • A dedicated near detector neutrino physics programme • Silicon detectors could provide a solution for the near detector technology. • Other options include liquid argon TPC, SciFi tracker, or gas TPC associated with a target. Neutrino Factory Scoping Study Meeting CERN 22-23 September