NEUTRINO OSCILLATIONS: T2K AND NA61 EXPERIMENTS, R&D TOWARDS A FUTURE NEUTRINO PROGRAM 1 Research Plan The field of neutrino physics is certainly one of the most active in particle physics today. It is by now well established that neutrinos have mass and that the three families mix. In the minimal Standard Model, neutrinos are massless; massive neutrinos require either a new ad- hoc conservation law or new phenomena beyond the present framework, with a possible link to the grand unification scale via the see-saw mechanism. A deep field of research is thus open, that could last several decades and culminate with the discovery of leptonic CP violation – a key ingredient in the understanding of the baryon- anti-baryon asymmetry of the universe. Because observation of CP violation in neutrino oscillations requires appearance experiments, accessible at accelerators only, an important investment in accelerator-based neutrino beams and experiments is called for. The CHIPP Roadmap considers neutrino physics as one of the three pillars of particle physics in Switzerland, and so does the 15 years research plan of the DPNC at University of Geneva1. The neutrino group at DPNC has been actively involved in this quest since the nomination of Prof. A. Blondel in early 2000, where participation in the HARP experiment at CERN led us to the K2K experiment in Japan, in which the first observation of neutrino oscillation with a neutrino beam was achieved. The group received an added boost with the nomination of Alessandro Bravar (MER) in 2006. The research program comprises a progression of on- going experiments and far-reaching R&D activity as described in the SNF reports of October 2007 and October 2008. The main effort of the group is the preparation of the T2K experiment. The J-PARC off-axis !µ beam aims at the SuperKamiokaNDE detector, and a new complex of near detectors is being built for flux control and cross-section measurements. T2K will allow a sensitive investigation of the !µ " !e transition, sensitive to the yet unmeasured angle #13, and, at a later stage to CP violation. T2K will provide a broad set of other measurements including the precise measurement of #23 and $m23 and various poorly known neutrino low energy cross-sections. A first beam is scheduled for April 2009 and the first physics run starting in December 2009 aims at providing 100kW of 30 GeV protons on target for 107 s by the time of the summer conferences in 2010. These data should be enough to match the best existing measurements and improve the reach in the search for !µ"!e oscillations. The group of UNIGE contributed in a major way in the design, prototyping, construction and quality assurance of the magnetic near-detector (ND280) tracking device, a TPC with micro-pattern readout, in collaboration with groups in Canada, France and Spain. The Swiss groups have leadership in the procurement of the magnet for ND280. The T2K beam line, partly because of the very high foreseen intensity, comprises no device suited for absolute flux normalization. We have therefore engaged in the measurement of pion and kaon particle production by 30-50 GeV protons on carbon (the T2K conditions) using the NA49 apparatus at CERN, which was approved in 2007 under the name of SHINE (SPS Heavy Ion and Neutrino Experiment) NA61. We noticed the need for an extension of the TOF system to cover the forward angular region most relevant for T2K measurements, and built it in five months (May-September 2007) in collaboration with UniBE. A first data- taking run took place successfully in September 2007 where a small sample of data was accumulated to satisfy the needs of the first year of T2K operation. A high statistics runs will take place in 2009, for which an upgrade of the TPC and TOF is necessary. The need of a high intensity neutrino facility for future neutrino experiments was recognized by ECFA in 20012, SPSC in 2004, and the CERN Council Strategy for Europe in 20063. The exploratory generation of neutrino experiments, including T2K, will determine the order of magnitude of the mixing angle #13. A dedicated precision neutrino facility will be needed to discover or study precisely leptonic CP violation. The University of Geneva has been one of the main players in the definition of this future program4 5 6, now within the European Network BENE7 and an International Design Study. BENE has been extended under the 7th EU framework program FP7 under the name of EUCARD – NEU2012, in which we lead the work-package on future neutrino facilities. Alain Blondel led a study8 on future detector for future neutrino facilities with a clear conclusion that a number of key questions remain as for the performance of the leading candidate for neutrino factory detector. A program of test beam studies was outlined and we will begin to prepare the infrastructure for it. The ultimate facility is a neutrino factory based on a muon storage ring; this is a challenging novel accelerator for which a substantial R&D program is needed. We played a leading role in the concept and design of the International Muon Ionization Cooling Experiment (MICE). We are now responsible for the data acquisition and trigger of this experiment, which is presently in the commissioning process. The construction of the calorimeter designed in Geneva will be concluded within the duration of this request. This detector constitutes a first step in a detector R&D program for future neutrino detectors. The program of activities for 2009-2010 is as follows: ! T2K experiment: completion and commissioning of the Micromegas-TPCs; data taking and analysis of first data, first physics results in summer 2010 (section 2). ! NA61/T2K experiment: further TOF upgrade, 2009 data taking and analysis; inclusion of data in the T2K beam simulation (section 3). ! MICE experiment operation, commissioning of the sandwich calorimeter, observation of ionization cooling in MICE step IV(section 4) ! Future neutrino studies: preparation of test beam infrastructure for detector R&D at CERN (section 5). 1.1 Participants The neutrino group at University of Geneva consists of 10 physicists: one professor, one MER, three post-docs, and five PhD students. Prof. Alain Blondel (Prof. Ordinaire, Etat) Dr. Alessandro Bravar (MER Etat since September 2006) Dr Jeremy Argyriades (MA FN since September 2008) Dr. Jean-Sebastien Graulich (MA, Etat, since June 2005) Dr. Andrea Ferrero (MA Etat since July 2008) Raphael Schroeter (Assistant FN November 2004 to November 08, to be replaced) Nicolas Abgrall (Assistant FN since April 2006) Vassil Verguilov (Assistant FN since June 2006) Sebastien Murphy (Assistant FN since August 2007) Melody Ravonel (Assistant since 2007, FN from November 2008) Departmental mechanical and electronic engineering support groups: Didier Ferrere, Pierre Bene, Eric Perrin, Fran Cadoux, Florian Masciocchi, Yann Meunier. 2 The T2K experiment The case for the !µ " !e oscillation search and the T2K experiment (Figure 1) have been described in the SNF request submitted in February 2008. The status of the experiment is as follows: -- The beam line and the beam line monitors are in the construction phase with first beam expected in April 2009 and a first run aiming at an intensity of 100kW of 30 GeV protons on the neutrino target scheduled to start in December 2009. With 107 seconds of data taking, first physics results should be possible for the summer of 2010. -- The ND280 detector is under construction: the first module of FGD has been completed and placed in a test beam. The first TPC prototype has been equipped with two Micromegas readout chambers built in collaboration between CERN, Saclay and University of Geneva, and the first tracks have been observed in test beam at TRIUMF (Figure 2). Figure 1: Schematic description of the detectors along the T2K beam line. The 280m detector station is part of the approved project. The 2km station is part of a possible upgrade. Figure 2 Top left: cut-away view of the ND280 magnetic detector; right: the first full-size TPC module; bottom: first test beam tracks in that TPC. University of Geneva produces the mechanics of the TPC modules, stiffeners, gas seals, and handling tools. We have designed and constructed a test bench for calibration of gain and resolution of every pad of the chambers, which have now demonstrated: gain uniformity of about 2%, reproducibility of 2% and a 9% resolution for the 55Fe. 11 Micromegas modules have now been completed and 6 modules been successfully passed through the test bench. Two TPCs will be complete and installed at Tokai by October 2009. Construction and test of the third TPC will be taking place in the 2009-2010 period covered by this request. This will require still some construction and the upkeep of the clean environment lab at CERN. A substantial expense will be incurred for travel to Vancouver and Tokai for commissioning of the TPCs. We estimate that about 30kCHF will be needed for travel of technician and scientific personnel. Important scientific activity will take place in 2009-2010 to achieve the goal of providing first physics results for summer 2010. Our group is well placed since Alain Blondel is convener of the global oscillation analysis group. 3 NA61 experiment at CERN The aim of the NA61-T2K measurements is to reduce the impact of the geometry induced differences in neutrino flux between the near (ND280) and far (SuperK) detectors of T2K. This requires a precise measurement of particle production by 30 GeV (the initial energy of J-Parc) to 50 GeV (the possible maximum energy). There exist no data in this energy range. The UNIGE group has taken responsibility to push this experiment in 2006, with A.