LAGUNA Collaboration. Liquid Argon option - some physics

goals

Ionel LazanuFaculty 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; θ13, δ, sgn(ΔM2)

• 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 <250000 m3

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 kHzEstimated event rates on argon target: 10-42cm2 ≈ 100 events/ton/dayEstimated sensitivity ≈ 10-9pb (10-45 cm2)

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 recoilstime 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 asimulation 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.

eventep 0

eventepofkinematics 0

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)

'll

2

3

1

2'

2

''

iil

E

Lmi

illl UeUPki

The transition probability is given by the equation:

Six parameters: two mass-squared differencesthree mixing anglesone 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

n

a baabkikikbibkaiakaiaik E

LmUUUUUULP

1;

2**22

2cos2

**; arg kbibkaiaabki UUUU

2

224

ki

xkicoh

m

EL

2

kicohL

x

e

2det

2 xprodxx

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 Lcoh must be added to the proper oscillation

length Losc; so that if the distance Source – Detector is greater than Lcoh, 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 sitesan 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, 14-19 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, 11-12 Dec 2006, e-Print: hep-ph/0702080 • 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: 0809.1767]• Takaaki Kajita, Neutrino telescopes 2009, p 440• A. Rubbia, arXiv: 0908.1286 • A. Badertscher et. al., arXiv: physics/0505151• V. Boccone et. al., arXiv:0904.0246