Large and Small (Far and Near)Liquid Argon Detectorsfor an Off-Axis NuMI BeamKirk T. McDonaldPrinceton [email protected] Off-Axis Experiment Detector WorkshopSLAC, Jan. 23-24, 2003http://puhep1.princeton.edu/˜mcdonald/nufact/1Post-Nobel OpportunitiesData from atmospheric and solar neutrino experiments⇒ Rich follow-up physics at accelerators and reactors.Parameter Atmos. Solar Accel. Reactor β Decay¯¯¯¯∆M223¯¯¯¯ID PMθ23ID PM¯¯¯¯∆M212¯¯¯¯ID PM PMSign(∆M212) ID = PMθ12ID PM PMνsterileID, PMSign(∆M223) ID = PM ID = PMθ13ID, PM ID∆CPID, PMMνID(ID = Initial Discovery, PM = Precision Measurement)No evidence for proton decay, “theories” apparently not falsifiable,⇒ Linkage with neutrino expts. should be driven by the latter.2Off-Axis NuMI Beam (P929)• 14-mrad off-axis beam, 735 km, ⇒ 2-GeV ν’s @ 1st oscillationmax for ν2-ν3.0510152025300 1 2 3 4 5 6 7 8 9 10Eν (GeV)νµ CC evts/kt/3.8E20 POT/0.2 GeVOn Axis 7 mrad off-axis14 mrad off-axis27 mrad off-axis10-310-210-11101020 1 2 3 4 5 6 7 8 9 10Eν (GeV)CC evts/kt/3.8E20 POT/0.2 GeV14 mrad off axisνµνe+ν_eEν (GeV)(νe+ν_e)/νµ10-310-210-110 1 2 3 4 5 6 7 8 9 10• ≈ 50 νµCC events/kton in 4-5 year run.• νe/νµ≈ 5 × 10−3, ⇒ Measurement of sin22θ13via νµ→ νelimited to ≈ 0.01 by backgrounds.• At this limit, a signal of 10 νµ→ νeoscillations⇒ 1000 νµCC events,⇒ Need (at least) 20 kton detector.• ⇒ Will eventually want bigger detector (>∼100 kton) andhotter beam (0.4 MW → 2 MW).3δCPand Sign of ∆M223• Can untangle δCPfrom matter effects (sign of ∆M223) withNuMI off-axis beam only if sit close to 1st 2-3 osc max (and ifsin22θ13>∼0.03), ⇒ helpful to know ∆M223better.• Some improvement in sensitivity to sign of ∆M223if go to largerdistance (and slightly smaller off-axis angle), with little cost insensitivity to sin22θ13.• ⇒ Very likely will need 2 generations of detectors (and beams!)to exploit full potential of off-axis superbeams.4The Neutrino Horn Issue for Superbeams• 2-4 MW proton beams are achieved in BNL, CERN and FNALscenarios via high rep rates: ≈ 106/day.• Classic neutrino horns based on high currents in conductorsthat intercept much of the secondary pions will have lifetimesof only a few days in this environment.• Consider instead a solenoid horn with conductors at larger radiithan the pions of interest (c.f., Neutrino Factory Design).• Adiabatic reduction of the solenoid field along the axis,⇒ Adiabatic reduction of pion transverse momentum,⇒ Focusing.• No sign selection in horn, ⇒ Both νuand ¯νµ,⇒ Detector must measure sign of final-state µ or e.See, http://pubweb.bnl.gov/users/kahn/www/talks/Homestake.pdf5Liquid Argon the Best Detector to Study sin22θ13inthe NUMI Beamline• ≈ 10 times better per kton than waterˇCerenkov for νµ→ νeappearance at 1-2 GeV (Harris).• Density = 1.4; X0= 14 cm; can drift electrons 3-5 m.• 100% sampling tracking and calorimetry.• Construction is simplest of large neutrino detector options.• Best rejection of neutral current backgrounds, including softπ0’s.6Liquid argon time projection chamberconceived by C. Rubbia (1977).Largest implementation to date is theICARUS T600 (600 ton) module,on the surface in Pavia, Italy.http://www.aquila.infn.it/icarus/7Liquid Argon TPC Properties• 3D tracking + total-absorption calorimetry.• Pixel size: 3 mm × 3 mm (wire planes) × 0.6 mm (via 400 ns timesampling).• ρ = 1.4 g/cm3, T = 89K at 1 atm., X0= 14 cm, λint= 80 cm.• A minimum ionizing particle yields 50,000 e /cm.• Drift velocity of 1.5 m/msec at 500 V/cm ⇒ 5 m drift in 3 msec.• Diffusion coef. D = 6 cm2/s ⇒ σ = 1.3 mm after 3 msec.• Can have only 0.1 ppb of O2for a 5 m drift,⇒ Purify with Oxisorb.• Liquid argon costs $0.7M/kton – and is “stored” not “used”.• Large modules (>∼100 kton) can be built using technology of liquid methanestorage. (Total cost of a 100-kton detector is estimated to be $200M.)• Detector is continously “live” and can be “self-triggered” using pipelined,zero-suppression electronics.• Operates at the Earth’s surface with near zero overlap ofcosmic ray events.• Detector is compatible with operation in a magnetic field.8Events from the ICARUS T300 Cosmic Ray TestAbove: 3 views of alow-energy hadronicinteraction.Right: Computerreconstruction.Below: Cosmic rayshower that includesa muon with a δ-ray, a stopping muon,and an electromag-netic shower.9LANNDD – 100 kton Liquid Argon Neutrino andNucleon Decay Detector10LANNDD Top ViewMax drift length of 5 m (limited by O2purity),⇒ Several drift cells.11Is a 100-kton Liquid Argon Detector Feasible?• Use mature, low-cost technology of liquid methane storagetanks (up to 300 kton based on existing structures).Preliminary budget estimate from industry of < $20M for a100-kton tank, IF built on the SURFACE.• 100 kton of liquid argon = 10% of USA annual production.⇒ Deliver one trailer-load every 2 hours from Chicago,....Only 5 ppm O2grade available in large quantities,⇒ On-site liquid-phase purification via Oxisorb (MG).Raw material, delivery + purification ⇒ $0.8M/kton.• ICARUS electronics from CAEN @ $100/channel.3 mm wire spacing ⇒ 300k ch ⇒ $30M.9 mm wire spacing ⇒ 100k ch ⇒ $10M.High capacity of long wires ⇒ signal may be too weak to use3 mm spacing.• With neutrino beam, record every pulse (10−3duty factor).Cosmic rays occupy ≈ 10−3of active volume,⇒ ≈ 10 MB data per trigger.⇒ Modest (< $10M) DAQ/computer system.12200-kton Cryogenic Tanks Used for LNG StorageChicago Bridge & Iron: can build 100-kton LAr tank for < $20M.13Strong Interest by PraxairPraxair is the leading USA vendor of liquid argon.The Praxair R&D Lab in Tonawanda, NY is same Union Carbidelab that provided the expertise to build the Oak Ridge gaseousdiffusion plant in the 1940’s.14Extrapolation to Very Large ModulesPreliminary cost estimate for a liquid argon detector of 100 kton total mass.Component Scaling CostLiquid argon (industrial grade) M $70MCryo plant, including Oxisorb purifiers M $10MSurface site preparation M2/3$10MCryogenic storage tank M2/3$20MElectronics (300k channels) M2/3$30MComputer systems M2/3$10MSubtotal $150MContingency $50MTotal $200MFiducial mass is for νeappearance events ⇒ contain EM showers.1000100101Total Mass (kton)1.00.80.60.40.20.0Fiducial Mass Fraction1000100101Liquid Argon Fiducial