Uni-Geneva in the T2K experiment

1. Uni-Geneva in the T2K experiment Aim: following involvement in HARP / K2K, take part in the concept/construction of the T2K experiment as part of the T2K-Europe team and be there for the first data taking and results of the experiment in 2009. This will be scientifically exciting.

4. The T2K experimental programme Disappearance 1. improve measurement of Dm213 (after MINOS, CNGS) 2. improve measurement of sin22q12 These require good knowledge of -- flux shape -- absolute energy scale, -- experimental energy resolution. Here the fact that the 2km flux is much similar to the SK flux than at 280 m is clearly an argument in favor of 2km detector location. 3. Appearance search fornm neoscillation  q13 This is probably the highest priority measurement Appearance experiment. The main problem here is the understanding of the backgrounds from anything that produces or mimics an electromagnetic shower. - beamne from K and mu decay - p0 - pions and secondary interactions etc…

5. disappearance: ratio of events seen/expected appearance events seen over background

6. Off Axis Beam (another NBB option) Far Det. Decay Pipe q Horns Target (ref.: BNL-E889 Proposal) p+ m+ nm WBB w/ intentionally misaligned beam line from det. axis Decay Kinematics • Quasi Monochromatic Beam • x2~3 intense than NBB

9. p p n 0 m 140 m 280 m 2 km 295 km The (J-PARC-n) T2KBeamline Neutrino spectra at diff. dist Problem with water Cerenkov: not very sensitive to details of interactions. Either 280 m or 2 km would be good locations for a very fine grained neutrino detector Planned: a scintillating fiber/water calorimeter. Liquid argon TPC would be a very good (better) candidate! Event numbers: near/SK = m(near[tons]) / 22500 . (300/2)2 = m(near[tons]) => Need 10-50 tons fiducial or so at 2km 200-500 kg fid @ 280m 1.5km 295km 280m

10. 1. Flux Decay tunnel 280m 2.5 deg=42mrad 12m target 130m 84m@2km 1. Detector at 280 m in 42 mrad position sees angles from 42 to 80 mrad! (target to end of DK tunnel) 2. This spread is 2X larger than detector size, +- 2m at 200 m is +-10 mrad. detector is able to tell the position (yes) but not the angle of the Neutrinos Fermi motion gives +- 200 MeV/c Pt… vs 600MeV/c neutrino mom. 42 to 45 mrad at 2km 1X at 2km +-3m at 2km is +-1.5 mrad

12. Some coments about the off-axis beam The off-axis technique is, really, a way to tune the pion-neutrino beam energy. The fact that the ne component is 0.2-0.3% under the pion neutrino energy peak is true more or less in any wide-band beam. There is a loss of neutrino events wrt on axis wide-band beam due to the fact that the neutrino cross-section is proportional to E. In addition, the beam systematics are very different from those we are used to. In first order the flux is now insensitive to the secondary particles energy but is is now sensitive directly to angular variables in the beam (alignment, pion production angular distribution etc…. A NEW GAME! Finally the oscillation experiment is performed for neutrino energies of 500-800 MeV for which very little is known. (e.g. in GGM, a cut was placed at 1 GeV for neutrino energy) Precise measurement of the properties of these events (and of neutral currents with this visible energy) is crucial for the experiment.

13. Flux: Pions, muons and kaons. The dominant source of electron neutrinos at the off axis peak is from muons. How do we know muons -- and their polarization ? (pion decay -- but the muons go in the walls.) This is not true of the high energy tail, which can feed into the peak Kaons give a secondary off axis peak at high energy (from K->mn) Which is never seen in the pictures. MRD should monitor this quite well.

14. What we know and dont know 2. Cross-sections Well known: how to simulate Cherenkov light emission and detection in a water detector. This should take care of the acceptance calculations IFF we knew the production cross-sections and topologies. Not well known: how to simulate emission of secondary p0 & photons from neutrino, nuclear or secondary interactions in water. (let alone carbon or argon) There are some interesting models but no certainty. We do not know inclusive or exclusive cross-sections on water target. We do not know the difference between electron- and muon-neutrino cross-sections at 300-600 MeV. => These measurements must be made. Detector needs to have at least 10-20 times rate of far detector That is 200-400 kilos at 280 meters (10 to 20 tons at 2km) and to be able to measure the detail of interactions, Including low energy photon detection. This is the crux.

15. idea; loverre

16. loverre loverre, sanchez, radicioni

17. loverre, sanchez, radicioni The present detector concept suggested detectors: water targets empty targets

18. sanchez charge ID of pions is relevant since pi+, mu+ and pi-, mu- have different stopping properties in water.

19. I think I have some good news for you. After discussion with the DG, I can say that CERN would be in favour of making  the ex UA1 magnet available to the T2K experiment. We have to see what would be the best procedure (loan or  donation). Ilet you know more details soon which we could also discuss next time you are coming to CERN. Best regards Dieter Schlatter

20. One of the important design constraints is the rate: 0.2 event per ton per spill at 280 m. Each spill contains 11 bunches in 2 microseconds about. The 1 kton water cerenkov would be swamped and there will be many interaction in the iron joke and calorimeter. to be able to associate photons seen in the calorimeter to the interactio vertex one must be able to have their time precisely and possibly a pointing. => Lead glass blocks, (There exist many 'mines' of lead glass blocks, Tristan, Opal, that could be used for the purpose … under investigation (OPAL's is at CERN) but also active converters inside the tracker.

21. At Uni-Geneva: Our participation in the 280 m detector is very natural in the framework of the T2K-Europe group. We would like to contribute to the tracker, and preferably with the same technology as will be used for MICE. TPC (we have some 2000 channels available from HARP) or scintillating fibers… see MICE talk tomorrow. The forces liberated at the end of HARP/K2k constitute a bare minimum, further evidently welcome.

22. CONCLUSION: The T2K experiment will bring considerable improvements in neutrino mixing parameters with emphasis on q13 from appearance search fornm neoscillation In line with the involvement in HARP K2K Gva will get involved in T2K. This will of course be more direct than for K2K and we are foreseing to contribute directly to the hardware (tracker of the fine-grained detector) The concept of a magnetic detector is specially appealing since it allows a detailed measurement of the properties of the final state of neutrino events, the understanding of which will be crucial for the background estimates for the nm ne search. This should take place within the European effort in T2K.