T2K-LAr A liquid Argon TPC for the T2K neutrino experiment

1. ne QE T2K-LAr A liquid Argon TPC for the T2K neutrino experiment D.Autiero (IPNL) GDR neutrino, Marseille 14/3/05

2. low En (<1 GeV) Super-Beam: 1021 pot/year • (3.3x1014 50 GeV pot/s x 130 days x 5 years) • SK detector: 22.5 kton x year • @ 2°  3000 nm CC/year (x10 w.r.t. K2K) • 0.2% ne contamination and p° BG Tunable off-axis beam ne contamination m decay K decay

4. T2K nm disappearance P(nm nx) ~ cos4q13sin22q23 sin2 (Dm223 L/ 4E) Assume q23 = p/4 5 years running • measure Dm223 with 10-4 eV2 error • know if sin22q23 = 1 (0.01 uncertainty) Assumed systematic errors (to be reduced by using near detectors!) Far-near ratio: 10% Non QE/ QE ratio: 20% Energy scale: 4%

5. The experience of K2K has shown that a fine grained detector in front of the WC near detector is necessary for oscillation analysis since: the energy spectrum measured by the WC (Evis = Em) cannot be used to predict the oscillated spectra at SK due to the lack of knowledge of all the details of the neutrino interactions (En = Em + Ehad) In fact, in K2K the original near Sci-fi has been replaced by the improved SCI-bar detector. The fine grained detector mass of K2K must be accordingly scaled up in the T2K 2 km site (~ 100 ton). This is not a practical solution for a volume-instrumented detector. dE~60MeV <10% measurement non-QE resolution QE inelastic 1-sin22q En (reconstructed) – En (true) Dm2

6. When adding protons and detector mass isn’t enough… D. Harris, proton driver review For any of these experiments, detectors see different mixes of events between near and far. Cross section uncertainties don’t all cancel! Looking for differences between n and anti-n probabilities of at most 15-20%…need to measure probabilities to 5% or better for a 3s determination! Problem: no cross sections at these energies are known any better than about 20%... Minerna will provide precise n measurements, but we still need anti-n cross sections… NOvA pre-PD rates

7. T2K neappearance: measurement of q13 5 years, OA2° Sensitivity: Expected events in 5 years for : Total Bck uncertainty should be less than 10 % Beyond 5 years For the appearance search the two main BGs (prompt ne and p0) have very different systematics: measure them separately ?? Ideal: fine grained detector with good e/ p0 separation capabilities

8. low En low x-section Japanese program phase 2: short L, low E • intensity up to 4 MW • detector mass up to 1 Mton • no matter effects: assume mass hierarchy determined elsewhere Major T2K beam upgrade, new Hyper-K detector 1) low energy: low p° BG 2) gigantic water Cerenkov: good e ID demanding requirements: 2% syst. from BG subtraction and 2% from data selection

9. The 1 kton WC detector at the 2km locationwould profit if operated in conjunction with a muon ranger and a 100 ton fine grained detector, able to reconstruct recoiling protons, low momentum hadrons, asymmetric decays of p0, etc., in an unbiased way. A liquid Argon (LAr) Time Projection Chamber (TPC) allows to reach the required mass while maintaining the high granularity. The T2K experiment will profit of its distinctive features of a fully active, homogeneous, high-resolution device. A LAr TPC will provide means to perform: an independent measurement of nm CC events; a measurement of n NC events with clean π0 identification for an independent determination of systematic errors on the NC/CC ratio; the measurement of the intrinsic neCC background; last but not least, the collection of a large statistical sample of neutrino interactions in the GeV region for the study of the quasi-elastic, deep-inelastic and resonance modelling and of nuclear effects. Measurement of antineutrino QE CC events via topological id ?

10. ne QE p0 coherent Liquid Argon TPC at 2 Km High granularity : 0.02 X0 sampling Tracking + Calorimetry 100 Ton mass easely feasible Real neutrino in ICARUS

11. August 2004: T2K general meeting Sept 2004-now: Discussion at the level of the 2km working group Design of the T2K LAr detector Optimization of geometry and definition of the T2K-LAr detector layout in underground hall Definition of dedicated infrastructure for LAr Since Nov 2004, a working group is active at writing a “comprehensive” and “scientific” document. Deadline ≈ May 2005. The baseline detector parameters are frozen and initial performance studies have been accomplished. Innovative features and recent technological advances are well included in the detector implementation. We have extracted the relevant information for the 2km Appendix. Milestones

12. T2K-LAr working group (17 institutes, 41 members) Columbia University: E. Aprile, K. Giboni, M. Yamashita IPN-Lyon : D. Autiero, Y. Déclais, J. Marteau ETHZ: W. Bachmann, A. Badertscher, M. Baer, Y. Ge, M. Laffranchi, A. Meregaglia, M. Messina, G. Natterer, A. Rubbia Granada University: A. Bueno, S. Navas-Concha L’Aquila University: F. Cavanna, G. Piano-Mortari UCLA: D. Cline, B. Lisowski, C. Matthey, S. Otwinowski Yale University: A. Curioni, B. Flemming INFN Naples: A. Ereditato, G. Passeggio, V. Vanzanella CIEMAT: I. Gil-Botella, P. Ladron de Guevara, L. Romero Silesia University (Katowice): J. Holeczek, J. Kisiel Warsaw University: D. Kielczewska INFN Frascati: G. Mannocchi LNGS: O. Palamara Torino University: P. Picchi Soltan Institute (Warszawa): P. Przewlocki, E. Rondio Wroclaw University: J. Sobczyk Niewodniczanski Institute (Krakow): A. Szelc, A. Zalewska UK has expressed interest but is presently committed to 280 m

13. Dedicated simulation tools for T2K-LAr geometry have been developed to assess detector performance Results are available on e/p0 separation Hadron identification Event reconstruction, selection and classification Stand-alone muon momentum resolution Neutrino and hadronic system energy resolution Event kinematics reconstruction Events in inner target Nus/antinus statistical separation (work in progress) Write-up available for 2km Appendix Further integration of the liquid Argon software into official 2km SW on-going Physics items to be studied next: Prediction of nm events at SK Prediction of ne events and p0 background at SK LAr detector performance studies

14. e/pi0 separation Sampling : 0.02 X0 dE/dx cut efficiency: When vertex known, combine with prob to convert within 1 cm:  5.4% Combined, aim at:  0.2% π0 efficiency by imaging for 90% electron efficiency

15. T2K nmdisappearance P(nm nx) ~ cos4q13sin22q23 sin2 (Dm223 L/ 4En) QE e.g. : nQE/QE measurement in LAr: nQE (work in progress)

16. Neutrino energy reconstruction nQE

17. The proposed design takes advantage from the experience of ICARUS. However, innovative features and technological advances are included in the detector design. In particular: Cryostat has a design that follows the codes of conventional cryogenic-fluid pressure storage-vessels (ASME Boiler & Pressure Vessel Code, Sect. VIII (www.asme.org)). Design and construction according to these standards will ensure a reliable and safe cryogenic operation Cooling is based on heat engine with Ar as medium (avoid LN2) Inner detector has an innovative and simple design (to limit complexity & cost) Immersed Cockroft-Walton to generate uniform drift of 1 kV/cm over 2 m (to exploit very high electric rigidity of LAr) Inner target allows to measure events on Water / CO2 New LAr purity monitoring systems Scintillation light readout based on DUV sensitive PMT Electronics based on commercial preamps and newly designed digital part (since triggered by beam timing). Design features of T2K-LAr

18. Artistic view of LAr integration in 2km underground site ≈15m Incoming neutrino beam ≈28 m Total LAr mass ≈ 315 tons, 100 tons fid., total cryostat weight ≈ 100 tons

19. Close view(open endcap) Racks Supporting structure 5 m Liquid Argon Active volume 7,2 m 4.5m 4.5m 8,5 m

20. Front view Charge readout electronics HV Liquid Argon imaging volume Scintillation light readout Cathode and H2O/CO2 inner target 5 tons Wire chambers ≈7,2 m

21. Liquid Argon process Linde-Hampson refrigeration LAr Vent + compressor Liquid Purification Pressure-relief valve High p GAr 3500 lt/hr Qpurif ≈ 1kW Burst-disk Vent valve Heat exchanger and expansion valve Electrical power (5% eff): W/o recirculation ≈ 10kW W recirculation ≈ 30 kW Buffer Qin ≈ 500W Boiloff ≈200 lt/day 10–3 / day Dewar Vacuum insulation + Double liquid Argon containment

22. Adopted strategy: Assemble detector at surface (e.g. assembly hall with crane at KEK or JAERI) Transport and lower detector into underground hall as a single item (≈ 100 tons), however this requires the full shaft diameter (≈8.5 m) Minimize underground activities Main phases: Installation procedure Year 3 Year 1 Year 2

23. Proposal to lower detector as single item Shock absorber

24. Proposal to lower detector as single item Shock absorber

25. Comprehensive LAr TPC document progressing well. Expect to complete it by May 2005, to include all latest achievements and integration, to be used as a reference for scientific case and financial requests. The T2K-LAr baseline detector parameters are frozen. Innovative features and recent technological advances are well included in the detector implementation. No major R&D required. However, detailed technical work is in progress in all sub-items. Initial physics performance studies have been accomplished Extracted enough information and included it into the 2km Appendix. Next steps: Final assessment of the physics added-value of LAr detector in T2K More detailed studies on installation & integration issues Detailed costing, spending and construction profiles as soon as principle approval of the 2km physics programme. Ideally within Fall 2005. Outlook

26. Chris Walter 2km review, last week

27. Chris Walter 2km review, last week

28. Engineering design of cryostat Total LAr mass ≈ 315 tons, total weight ≈ 100 tons, two independent stainless steel vessels, multilayer super-insulation in vacuum. Likely to be constructed and assembled in Japan to avoid costly transportation.

29. 3D engineering: Thermal analysis: Finite element analysis:

30. Inner target: two geometrical options Geometry to be defined following laboratory results and MC simulations

31. Reconstruction of MC events in inner target Recoil proton p=660 MeV QE event

32. Inner detector structure 4.5 m x 4.5 m x 5 m stainless-steel supporting structure for wire planes, PMTs, auxiliary systems, cathode, inner target. Two independent readout chambers (LR) Conceptual design, stress calculation. Engineering design in progress. Supporting beams Field shaping electrodes Cathode + inner target Wire frame

33. Main parameters of the TPC

34. Details of wire planes Baseline option: two perpendicular planes per chamber; simple wire sustaining design with wire pre-tensioning anchored by slipknots and pins onto wire frame. Optional third vertical plane under study.

35. Needed for T0 definition and possibly independent trigger Two possible options (A) 8” PMT with WLS coating (B) 2” PMTs with MgF2 window glass for DUV sensitivity Immersed in LAr Number of PMTs : 60150 HV distribution designed (minimize #feed-through, power dissipation, …) Light readout system High voltage system • Cathode @ 200 kV + field shaping electrodes designed • Uniform drift field ≈ 1 kV/cm • Immersed Cockroft-Walton HV generator (no HV feed-throughs) • Mechanical tolerance studied • Field mill for field measurement Readout electronics • Commercially available front-end analog board (CAEN, 32 channels) • Custom-made digital boards to interface to PCs • ≈10’000 channels in total LAr purity monitors and slow control • Improved designs of previously custom-built devices. Study of UV laser calibration

36. Underground cryogenic infrastructure A: Detector dewar B: LAr Purification C: Buffer D: Heat exchanger and expansion valve E: Argon pipes F: Shock absorbers G: Dedicated shaft (ventilation+piping) G E D B A C F