LAGUNA Collaboration. Liquid Argon option - some physics goals Ionel Lazanu Faculty of Physics, University of Bucharest

21 beneficiaries in 9 countries: 9 higher education entities, 8 research organizations, 4 private companies and 4 additional universities Romanian teams: Horia Hulubei National Institute of Physics and Nuclear Engineering: R. M. Margineanu, B. Mitrica, I. Brancus, A. Apostu, A. Saftoiu, S. Stoica, M. Petcu, G. Cata Danil, A. Oprina, F. Chipesiu University of Bucharest, Faculty of Physics: A. Jipa, O. Duliu, I. Lazanu, O. Sima

LAGUNA - Physics goals (1) Grand Unification - proton decay, as well as: WIMPs, DM, Q-balls (2) MeV-GeV neutrino “astronomy” (3) Long baseline neutrino oscillations: looking for mixing angles, CP- violation, type of hierarchy; θ 13, δ, sgn(ΔM 2 ) High intensity low energy conventional neutrino sources New neutrino production technology Astrophysical origin: ★ Sun’s interior (day&night) ★ Supernova core collapse ★ Diffuse supernova relic neutrinos ★ Dark Matter annihilation Terrestrial origin: ★ Atmospheric neutrinos ★ Geo-neutrinos (Earth natural radioactivity) ★ Nuclear reactor

LAGUNA - R&D strategy Small prototypes ton-scale detectors 1 kton LAGUNA Scalable principles (materials, technologies, design) Exemplification for LAr detector ArDM detector TPC/calorimeter Prototype unit for large LAr detectors Single module; Cylindrical shape with excellent surface / volume ratio; Simple, scalable detector design, possibly up to 100 kton Single very long vertical drift with full active mass A very large area LAr LEM-TPC for long drift paths Possibly immersed visible light readout for Cerenkov imaging or possibly immersed (high Tc) superconducting solenoid to obtain magnetized detector Excavation < m 3 Measure of WIMP recoil E-spectrum

Needed: Large volume high electric field Large area position sensitive charge readout (3rd-dimension from drift time) Large area VUV sensitive light readout with good time resolution (=> trigger) Efficient liquid argon purification system Careful choice of used (non radioactive) materials Energy threshold ~30 keV, 3-D imaging Event-by-event interaction type identification Trigger rate below 1 kHz Estimated event rates on argon target: cm 2 ≈ 100 events/ton/day Estimated sensitivity ≈ pb ( cm 2 ) Background recognition strategies: Topology: (e.g. multiple elastic scatters from neutrons) Localization: (fiducial volume, 3D imaging) Ionization density discrimination: ratio of ionization to scintillation: primary rejection against electron recoils time distribution of the scintillation light is used to discriminate further (promising in Ar)

ArDM Detector and R&D are in the final stage LAr/TPC technology could provide the means to develop very large highly sensitive multi purpose detectors Next step: tests in underground conditions

Conceptual design of a 100 kton LAr TPC detector GLACIER: Giant Liquid Ar Charge Imaging ExpeRiment The geometry was implemented in a simulation based on the GEANT4 toolkit. Simulation of cosmic muon-induced background

(1) Nucleon Decay Searches with large Liquid Argon TPC Detectors

(1) Nucleon decay signal simulation For each event generated within the liquid Argon volume, final state particles are transported through the medium, with the possibility of secondary interactions. The detector effects have been included in the production and transport of the events by simulating the liquid Argon response.

If the neutrinos have non-zero masses then there is no reason for the three neutrino interaction (or flavour) eigenstates to coincide with the three mass eigenstates. In general there will be mixing between them. Lepton mixing for massive neutrinos Some pedagogical aspects of the neutrino mass and mixing phenomena (neutrino oscillation) The transition probability is given by the equation: Six parameters: two mass-squared differences three mixing angles one phase and have rather complex forms.

The determination of the unknown elements of the PMNS matrix is possible via the study of oscillations at the baseline and energy relevant Pontecorvo-Maki-Nakagawa-Sakata matrix Long baseline neutrino physics

Open problems concerning the theory of neutrino oscillations: Is non-stationarity a characteristic feature of neutrino oscillations? If the evolution of the state of flavour neutrinos is determined by the Schrodinger equation for quantum states, neutrino oscillations are a non-stationary phenomenon. If the evolution of emitted neutrinos is determined by the Dirac equation and the propagation is described by coherent wave function, both non-stationary and stationary phenomena are possible. Is the wave packet approach necessary? If the answer is yes, then the coherence length L coh must be added to the proper oscillation length L osc ; so that if the distance Source – Detector is greater than L coh, the particle oscillation disappears. MSW – effect. Matter enhancement (resonant conversion) Has gravity any contribution? The problem of neutrino masses and mixing: normal hierarchy or inverted hierarchy?

Conclusions The LAGUNA community is studying the feasibility of a new large underground infrastructure in Europe able to host the next generation neutrino physics, astroparticle physics and proton decay experiments. Future long baseline in Europe should consider: an upgraded CNGS and/or a new beam line towards one of the LAGUNA sites an upgrade of PS2 is needed (PS2++ at 1.6 MW ?) advanced neutrino beams like for instance beta-beams or neutrino factories Longer baselines (>900 km) will provide better physics performance LAGUNA will be also strongly linked to other project world-wide (Japan, USA) that considers the same physics goals.

References A. Rubbia, 22nd International Workshop on Weak Interactions and Neutrinos, September 2009, Perugia, Italy A. Bueno et.al., JHEP 0704:04, 2007 ArDM Collaboration (M. Laffranchi et. al.), Invited talk at 3rd Symposium on Large TPCs for Low Energy Rare Event Detection, Paris, France, Dec 2006, e-Print: hep-ph/ S. M. Bilenky, F. von Feilitzsch, W. Potzel, Neutrino telescopes Conf. 2009, p.315 S. Nussinov, Phys. Lett. B63 (1976) 201 Marek Zralek, The XXXVIII Cracow School of Theoretical Physics, Zakopane, June 1-10, 1998 D. P. Roy, arXiv: ] Takaaki Kajita, Neutrino telescopes 2009, p 440 A. Rubbia, arXiv: A. Badertscher et. al., arXiv: physics/ V. Boccone et. al., arXiv: