Near Detector Report International Scoping Study Detector Meeting 4 July 2006 Paul Soler University of Glasgow

2 International Scoping Study CERN, 4 July 2006 Contents 1.MINOS near to far ratio methods 2.Beam diagnostics 3.Near Detector flux and event rates 4.Near Detector design 5.R&D plans

3 International Scoping Study CERN, 4 July MINOS Near to Far Ratio Methods Ranged out in ECAL: momentum measurement Prediction far detector spectrum from near detector SciBooNE Proposal hep-ex/ SciBooNE is less peaked, and has a much smaller high-energy tail Look for a deficit of ν μ events at Far Detector Unoscillated Oscillated ν μ spectrum Monte Carlo Spectrum ratio The Million $ Question: How to predict the Far Detector spectrum? Last ISS meeting: talk by Weber

4 International Scoping Study CERN, 4 July 2006 o Problems – Hadron production uncertainties – Cross-section uncertainties Ranged out in ECAL: momentum measurement Three beams in MINOS o Near and Far Detector energy spectra are not identical –Both detectors cover different solid angles –Near Detector sees extended line source ff to Far Detector Decay Pipe   (soft) (stiff) nn target ND 1. MINOS Near to Far Ratio Methods

5 International Scoping Study CERN, 4 July 2006 o Four possible methods for beam flux extrapolation – NDFit method – 2D Grid method – Near to far ratio – Beam matrix method o NDFit: Reweighting hadronic distributions LE-10/185kA pME/200kApHE/200kA Weights applied as a function of hadronic x F and p T. LE-10/ Horns off Not used in the fit LE-10 events 1. MINOS Near to Far Ratio Methods

6 International Scoping Study CERN, 4 July 2006 Ranged out in ECAL: momentum measurement o 2D Grid method –Bin data in reconstructed E ν & y –Fit weight as a function of true E ν & y o Near to far ratio –Look at differences between data and MC in Near Detector as a function of reconstructed Energy –Apply correction factor to each bin of re-constructed energy to Far Detector MC: c = n data / n MC o Beam matrix –It uses the measure Near Detector distribution and extrapolates it using a BEAM Matrix to the Far Detector. 1. MINOS Near to Far Ratio Methods

7 International Scoping Study CERN, 4 July 2006 o Predictions for far detector do not give perfect agreement but well controlled. o Four methods agree very well –Different systematics Predicted FD true spectrum from the Matrix Method Predicted spectrum Nominal MC 0.93  POT 1. MINOS Near to Far Ratio Methods

8 International Scoping Study CERN, 4 July 2006 o Flux determination at a neutrino factory (Blondel) 2. Beam Diagnostics  polarization controls e flux:  + -X> e in forward direction Main parameters to MONITOR 1. Total number of muons circulating in the ring: BCT, near detector for purely leptonic processes 2. muon beam polarisation, polarimeter 3. muon beam energy and energy spread, race-track or triangle. NO BOW-TIE! +polarimeter 4. muon beam angle and angular divergence. straight section design +beam divergence monitors e.g. Cerenkov? 5. Theory of  decay, including radiative effects OK We believe that the neutrino flux can be monitored to IF + design of accelerator foresees sufficient diagnostics. + quite a lot of work to do to design and simulate these diagnostics.

9 International Scoping Study CERN, 4 July Beam Diagnostics o Beam Current Transformer (BCT) to be included at entrance of straight section: large diameter, with accuracy ~ o Beam Cherenkov for divergence measurement? Could affect quality of beam. storage ring shielding the leptonic detector the charm and DIS detector Polarimeter Cherenkov BCT

10 International Scoping Study CERN, 4 July Beam Diagnostics o Muon polarization: Build prototype of polarimeter Fourier transform of muon energy spectrum amplitude=> polarization frequency => energy decay => energy spread.

11 International Scoping Study CERN, 4 July Near Detector Beam Flux o Near detector(s) are some distance (d~ m) from the end of straight section of the muon storage ring. o Muons decay at different points of straight section: near detector is sampling a different distribution of neutrinos to what is being seen by the far detector storage ring shielding the leptonic detector the charm and DIS detector Polarimeter Cherenkov d o Different far detector baselines: ̶ 730 km, 20 m detector:  ~30  rad ̶ 2500 km, 20 m detector:  ~8  rad ̶ 7500 km: 20 m detector:  ~3  rad If decay straight is L=100m and d =30 m, at 8  rad, lateral displacement of neutrinos is mm to subtend same angle.

12 International Scoping Study CERN, 4 July Near Detector Beam Flux d=30 m, r=0.5 m Flux d=130 m, r=0.5 md=1km, r=0.5 m e Anti   17.8 GeV 15.3 GeV 21.6 GeV 34.1 GeV 29.2 GeV18.5GeV Neutrino point source (muon decays not taken into account)

13 International Scoping Study CERN, 4 July Near Detector Event Rates d=30 m, r=0.5 m Event rates d=130 m, r=0.5 md=1km, r=0.5 m Anti   e 25.5 GeV 22.3 GeV 26.6 GeV 37.1 GeV 32.5 GeV 23.2 GeV

14 International Scoping Study CERN, 4 July Near Detector Event Rates Compared to far detector: d=2500 km, r=20 m Event rates Anti   e 35.8 GeV 30.0 GeV 38.1 GeV 33.3 GeV Flux ND at 1 km has similar spectra to FD

15 International Scoping Study CERN, 4 July Near Detector Design o Overall design of a near detector ̶ Vertex detector: Choice of Pixels; eg. Hybrid pixels, Monolithic Active Pixels (MAPS), DEPFET; or silicon strips. ̶ Tracker: scintillating fibres, gaseous trackers (TPC, Drift chambers, …) ̶ PID: ̶ Calorimeter ̶ Muon ID o Old UA1/NOMAD/T2K magnet offers a large magnetised volume with a well known dipole field up to 0.7 T. o Use NOMAD/T2K as basis for design

16 International Scoping Study CERN, 4 July Near Detector Design VERTEX DETECTOR Dipole Magnet: T Tracker (SciFi or TPC?) Electromagnetic Calorimeter PID Hadronic Calorimeter Nuclear Target

17 International Scoping Study CERN, 4 July Near Detector Design o Vertex detector ̶ Identification of charm by impact parameter signature ̶ Charm has similar decay time to tau particle search used in NOMAD-STAR

18 International Scoping Study CERN, 4 July Near Detector Design o Longest silicon microstrip detector ladders ever built: 72cm, 12 detectors, S/N=16:1  Detectors: Hamamatsu FOXFET p+ on n, 33.5x59.9 mm 2, 300  m thick, 25  m pitch, 50  m readout  VA1 readout: 3  s shaping NOMAD-STAR

19 International Scoping Study CERN, 4 July Near Detector Design  CC event Primary vertex Secondary vertex NOMAD-STAR

20 International Scoping Study CERN, 4 July Near Detector Design  Vertex resolution:  y = 19  m  Impact parameter resolution: 33  m  Double vertex resolution: 18  m from K s reconstruction Pull:  ~1.02  x ~33  m  x ~18  m  z ~280  m Point resolution: 6  m

21 International Scoping Study CERN, 4 July Near Detector Design o Charm event selection: 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 10 9 CC events/yr, about 3.1x10 6 charm events, but efficiencies can be improved.

22 International Scoping Study CERN, 4 July Near Detector Design o Passive target can provide target mass, but affects vertex and tracking reconstruction efficiency due to scatters o Improve efficiency by having 2D space point measurement and more silicon planes.  For example: 52 kg mass can be provided by 18 layers of Si 500  m thick, 50 x 50 cm 2 (ie. 4.5 m 2 Si) and 15 layers of B 4 C, 5 mm thick  Optimal design: fully pixelated detector (could benefit from Linear Collider developments in MAPS, DEPFET or Column Parallel CCD). With pixel size: 50  m x 400  m  200 M pixels, ~0.4 X 0  Could also use silicon “3D” detectors or double sided silicon strips (with long ladders of 50 cm x 50  m  360 k pixels). o Will start R&D on MAPS and DEPFET at Glasgow from October this year – MI3 collaboration (MAPS) & Bonn University (DEPFET)

23 International Scoping Study CERN, 4 July Near Detector R&D Plans o What needs to be measured: 1) Number of muons in ring (BCT) 2) Muon beam polarisation (polarimeter) 3) Muon beam angle and angular divergence (Cherenkov, other?) 4) Neutrino flux and energy spectrum (Near Detector) 5) Neutrino cross-sections (Near Detector) 6) Backgrounds to oscillations signal (charm background, pion backgrounds, ….), dependent on far detector technology and energy. (Near Detector) 7) Other near detector physics: PDF, electroweak measurements, ….

24 International Scoping Study CERN, 4 July Near Detector R&D Plans oR&D programme 1)Vertex detector options: hybrid pixels, monolithic pixels (ie. CCD, Monolithic Active Pixels MAPS or DEPFET) or strips. Synergy with other fields such as Linear Collider Flavour Identification (LCFI) collaboration. 2)Tracking: gas TPC (is it fast enough?), scintillation tracker (same composition as far detector), drift chambers?, cathode strips?, liquid argon (if far detector is LAr), … 3)Particle identification: dE/dx, Cherenkov devices such as Babar DIRC?, Transition Radiation Tracker? 4)Calorimetry: lead glass, CsI crystals?, sampling calorimeter? 5)Magnet: UA1/NOMAD/T2K magnet?, dipole or other geometry? oCollaboration with theorists to determine physics measurements to be carried out in near detector and to minimise systematic errors in cross- sections, etc.

25 International Scoping Study CERN, 4 July Near Detector R&D Plans o Request plan : 40k/yr 80k/yr 120k/yr

26 International Scoping Study CERN, 4 July 2006 Conclusions  There is important synergy between existing (or planned) experiments such as MINOS and T2K and the technology for future near detectors. Cross-sections and fluxes remain an issue. Learning the techniques that these experiments are adopting helps to formalise the problem that we will face at a neutrino factory.  A near detector at a neutrino factory needs to measure flux and cross- sections with unprecedented accuracy. Beam diagnostic devices need to be prototyped  It is worth noting that the beams measured by a near detector if it is close to straight sections (<100m) are quite different from far detector. However, at 1 km, beams start to look very similar.  We should start having some idea of what a near detector should look like. One proposal is to use the old UA1 magnet (like in NOMAD and T2K) once more.  The near detector should have a vertex detector, tracking planes, particle identification, calorimetry and muon identification. The dipole filed between T can provide good muon momentum resolution.  R&D plans are not very well defined at the moment