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. 2 Neutrino Factory Scoping Study Meeting CERN 22-23 September Contents 1.Near Detector Aims 2.Flux normalization 3.Cross-sections 4.Parton Distribution Functions 5.Charm production 6.Sin 2  w 7.Possible near detector technologies 7.1 Silicon tracking detector 7.2 Liquid argon TPC or other technologies 8.Conclusions

3. 3 Neutrino Factory Scoping Study Meeting CERN 22-23 September 1. Near detector aims o 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 o Near detector neutrino physics: –Cross-section measurements: DIS, QES, RES scattering –sin 2  W -  sin 2  W ~ 0.0001 –Parton Distribution Functions, nuclear shadowing –  S from xF 3 -  S ~0.003 –Charm production: |V cd | and |V cs |, D 0 / D 0 mixing –Polarised structure functions –  polarization –Beyond SM searches General Purpose Detector(s)!!

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

5. 5 Neutrino Factory Scoping Study Meeting CERN 22-23 September 2. Flux normalisation (cont.) o Rates: — E  = 50 GeV — L = 100 m, d = 30 m — Muon decays per year: 10 20 — Divergence = 0.1 m  /E  — Radius R=50 cm 100 m E.g. at 25 GeV, number neutrino interactions per year is: 20 x 10 6 in 100 g per cm 2 area. Yearly event rates High granularity in inner region that subtends to far detector.

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

7. 7 Neutrino Factory Scoping Study Meeting CERN 22-23 September 3. Cross sections o Measure of cross sections in DIS, QE and RES.  Coherent  o Different nuclear targets: H 2, D 2 o Nuclear effects, nuclear shadowing, reinteractions With modest size targets can obtain very large statistics

8. 8 Neutrino Factory Scoping Study Meeting CERN 22-23 September 4. Parton Distribution Functions(s) o Unpolarised and Polarised Structure functions o  S from xF 3 -  S ~0.003 o Sum rules: e.g. Gross-Llewelyn Smith   polarization: spin transfer from quarks to  — NOMAD best data — Neutrino factory 100 times more data

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

10. 10 Neutrino Factory Scoping Study Meeting CERN 22-23 September 6. sin 2  w o Elastic scattering off electrons: o Deep inelastic scattering: NC/CC Good statistical accuracy on sin 2  W (~0.5x10 -4 ) but hadron uncertainties dominate  sin 2  W ~ 0.0001

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

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

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

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

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

16. 16 Neutrino Factory Scoping Study Meeting CERN 22-23 September 7.1 Vertex detector with spectrometer o Efficiency very low: 3.5% for D 0, D + and 12.7% for D s + detection because fiducial volume very small (72cmx36cmx15cm), only 5 layers and only one projection. o From 200 million events, about 600,000 charm events, but efficiencies can be improved.

17. 17 Neutrino Factory Scoping Study Meeting CERN 22-23 September 7.2 Other technologies o Liquid argon TPC in a magnetic field would be able to perform as a near detector as well o 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) … 2.5 GeV e, 1.5T o Maybe the UA1/NOMAD magnet will live on again as a near detector for a neutrino factory?

18. 18 Neutrino Factory Scoping Study Meeting CERN 22-23 September Conclusions 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.