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Near Detector Working Group for ISS. Neutrino Factory Scoping Study Meeting 24 January 2006 Paul Soler University of Glasgow/RAL. Contents. Near Detector Aims Organisation Flux measurement and control Muon polarization Cross-sections Charm production Possible technologies.
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Near Detector Working Group for ISS Neutrino Factory Scoping Study Meeting 24 January 2006 Paul Soler University of Glasgow/RAL
Contents • Near Detector Aims • Organisation • Flux measurement and control • Muon polarization • Cross-sections • Charm production • Possible technologies Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
1. Near detector aims • Control of the systematics for the long baseline oscillation measurement • Flux measurement and control • Neutrino beam angle and divergence • Beam energy and spread • Control of muon polarization • Near detector neutrino physics: • Neutrino cross-section measurements (DIS, QES, RES scattering) • Determination of charm production spectra for background studies at far detector • Parton Distribution Functions (polarized and unpolarized?) • Other physics: • sin2W - sin2W ~ 0.0001 • S from xF3 - S~0.003 • D0/ D0bar mixing • L polarization • …. Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
2. Organisation • What has been done so far? • Set up webpage: http://ppewww.ph.gla.ac.uk/~psoler/near_detector.html • I have contacted an ad hoc group of people from different communities: theoreticians interested in near detector physics (eg. PDFs …), experimentalists working on near detectors at neutrino experiments, … • List can be found on webpage: not exhaustive, so please contact me if you would like to be included. • Not much else! • What (I think) needs to be done? • Set-up a generic simulation of a near detector • Define a series of potential detector geometries to run on near detector • Carry out physics studies needed for the ISS report: • Study flux normalisation through: • Use quasi-elastic and elastic interactions to determine neutrino spectrum • Reconstruct muon polarization from spectrum • Sensitivity for cross-section measurements: low energy? • Determination of charm: remember this is main background for golden channel! • ….suggestions …. Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
3. Flux normalisation • 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 KEK, 23-25 January, 2006
100 m 3. 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 per 100 g/cm2. With 50 kg 109n interactions/yr High granularity in inner region that subtends to far detector. Yearly event rates Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
3. 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 KEK, 23-25 January, 2006
4. Muon polarization • Fit neutrino spectrum for polarization: Compare fitted polarization to measured one from polarimeter: Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
5. Cross sections • Measurement 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 • What is lowest energy we can achieve? E.g. with LAr can go down to ~MeV Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
not detected Hadron decay CC NC 6. Charm Production • Remember that main background to golden channel is production of charm: • Qt = Pm sin2q cut eliminates backg at 10-6 Cervera et al. • Can use near detector to measure Pt and Qt distribution of charm, if we can reconstruct explicitly: • With silicon detector can reconstruct more than 106 charm states per year Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
6. Charm (cont.) • NOMAD-STAR silicon detector was able to reconstruct 45 charm events in NOMAD. • Measured charm rate: • Fully active silicon target (ie. 52 kg with 18 layers of Si 500 mm thick, 50 x 50 cm2 =4.5 m2) for full charm event reconstruction. • Optimal design: fully pixelated detector (e.g. Monolithic Active Pixels MAPS) Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006
2.5 GeV e, 1.5T 7. Possible technologies • Apart from silicon, there are other possibilities: • Liquid argon TPC in a magnetic field would be able to perform as a near detector as well. Can it withstand the rate? • Scintillating fibre tracker • Scintillator (like Minerva) • Standard gas TPC (like T2K near detector) • …. • Need to develop proper simulation to compare options. Neutrino Factory Scoping Study Meeting KEK, 23-25 January, 2006