KM3NeT: Status and Prospects Juan José Hernández ‒ Rey Instituto de Física Corpuscular (CSIC- Univ. of Valencia) On behalf of the KM3NeT Collaboration 1 RICAP 2013 – Roma International Conference on Astroparticle Physics, May 2013, University La Sapienza, Roma

Status of HE ν-Astronomy as of 2013 “Facts as found”: – No doubt HE ν’s are a most interesting messenger (HECR origin, acceleration mechanisms, unexplored territory,…). – Technical feasibility of HE ν telescopes is proven (under ice, under water …and under icy water). – Southern sky (Galactic centre) better studied in Northern hemisphere. – First evidence of signal from IceCube (most of the events in a region where the visibility is exceedingly good for Med Telescopes). A large Mediterranean ν- telescope – Volume? Cost? Main target? Timeline? 2 …they are challenge, though!

Goals of ν-telescopes (in a nutshell) 3 Galactic neutrino sources These should be the (natural) main aim of a Mediterranean NT. They are the closest sources (SNRs are the main targets). Extragalactic sources Fluxes might be still weaker. If you have to make a choice go for Galactic. Transient sources Don’t forget the γ-ray lessons: the HE Universe is extremely variable and the multi-messenger approach is of paramount importance. Diffuse neutrino flux Possibly the first type of signals to be observed. Be prepared. The usual suspects: AGNs SNRs GRBs

Goals of ν-telescopes (in a nutshell) 4 Neutrinos from Dark Matter annihilations Indirect DM searches in NTs are extremely interesting and complementary to direct searches. However, the experimental constraints can go in a somewhat different direction than that of astrophysical sources. Particle physics with atmospheric neutrinos This has always been a possibility, but lately some new opportunities have come up: elucidation of the neutrino mass hierarchy (more about that, later.) Search for exotics (monopoles, nuclearites,…) NTs are very well suited for the search of these objects without major detours in the detector design. Go for them.

KM3NeT Parameters 5

KM3NeT 6 Main physics goals: – Galactic neutrino “point” sources (energy TeV) – Extragalactic sources – High-energy diffuse neutrino flux EU-funded Design Study and Preparatory Phase Decisions taken: – Multi-km 3 NT in Mediterranean Sea (exceeding IceCube substantially in sensitivity). – Technology: Strings with 18 multi-PMT optical modules. – Multi-site installation (France, Greece, Italy). – 6 building blocks of ~115 strings each. Collaboration established "If your experiment needs statistics, you ought to have done a better experiment.” Ernest Rutherford

Multi-site Infrastructure m Capo Passero Sicily Italy NEMO m Pylos Peloponnese Greece NESTOR The advantage of additional funding and human resources resulting from adopting a multi ‑ site solution significantly outweighs any financial or scientific advantage from adopting a single site solution.  Site properties known (long term site characterisation measurements performed).  Political and funding constraints.  Distributed implementation is the best option m Toulon PACA France ANTARES

Multi-PMT OM ” PMTs in 17-inch glass sphere (cathode area~ 3x10” PMTs) –19 in lower, 12 in upper hemisphere –Light collection rings (20-40% gain) (D)31 PMT bases (total ~140 mW) (D) (B,C)Front-end electronics (B,C) –FPGA readout –Sub-ns time stamping –Gb/s speed (A)Al cooling shield and stem (A) Single penetrator Calibration: –LED and piezo inside sphere Advantages (wrt large photocathode): –increased photocathode area –1-vs-2 photo-electron separation  better sensitivity to coincidences –directionality A B CC D PMT

Strings as detector units 9 Mooring line: – Buoy (probably syntactic foam) – 2 Dyneema © ropes (4 mm diameter) – 18 storeys (one OM each), 30-36m distance, 100m anchor-first storey Electro-optical backbone (VEOC): – Flexible hose ~ 6mm diameter – Oil-filled – fibres and copper wires – At each storey: connection to 1 fibre+2 wires – Break out box with fuses at each storey: One single pressure transition

Deployment strategy 10 Compact package self-unfurling – Eases logistics (in particular in case of several assembly lines) – Speeds up and eases deployment; several units can be deployed in one operation – Self-unfurling concepts is being thoroughly tested and verified Connection to seabed network by ROV “String compactification” First successful test in December 2009 More about recent test later

Building blocks Building block: – Smallest detector with optimal efficiency – detection units. – Technical reasons impose segmentation. – Above ~75 strings sensitivity for muons is independent of block size. – One block ~ one IceCube. Geometrical parameters optimised for galactic sources (E cut-off). Final optimisation in progress. 11 Example configuration: 120 DUs, 100 m distance on average abs scaling factor events / year number of lines

KM3NeT Implementation 12 Staged implementation: Phase-1 in progress, 40 M€ available. Science from very early stages of its construction Overall investment ~220 M€. Operational costs of full detector 4-6 M€ per year (2-3% of capital investment), including electricity, maintenance, computing, data centre and management. Node for deep-sea research of earth and sea sciences.

KM3NeT reach 13

KM3NeT Performance 14 Energy resolution ~0.3 in log 10 (E ) if E µ >1 TeV E [GeV] Probability Angle [degrees] Area [m 2 ] Effective neutrino area Angular resolution muon neutrino Angle between incoming neutrino and reconstructed muon. Dominated by kinematics up to ~1TeV

KM3NeT field of view 15 KM3NeT has an excellent view towards the inner part of the Galaxy (including Galactic centre) Map in Galactic coordinates Visibility for upgoing ν μ events (other possibilities exist). > 75% > 25%

SNRs are good candidates 16 RXJ Standard belief : SNRs origin of Galactic CRs Fermi-LAT results on IC 443 and W44. Hints from VHE  but no conclusive evidence about CR acceleration in RXJ and Vela JR best candidates. RXJ1713 is a good candidate due to the high gamma flux measured up to 100 TeV. Very reliable calculation of flux and spectrum assuming all  is of hadronic origin (via π 0 ’s) Observable with 5σ in 3-5 years of full KM3NET provided all gammas come from hadronic acceleration.

Fermi Bubbles 17 Giant gamma-ray structures with sharp edges that appear below and above the Galactic centre observed in Fermi data. They extend up to 50⁰ (~8.5 kpc) and are well centred on longitude zero and close to latitude zero. Fermi detected hard  emission (E -2 ) up to 100 GeV. They are correlated to the haze detected by WMAP.

Fermi Bubbles 18 E -2, no cut-off E -2, 100 TeV cut-off E -2, 30 TeV cut-off 3 50% 5 50% expected flux Origin and acceleration mechanism are under debate. If it is hadronic acceleration, it can be a copious source of neutrinos. Some theoretical models predict that a high-energy neutrino flux of the order of GeV cm -2 s -1 could come from the Fermi bubbles. KM3NeT is well located to observe these structures.

Recent progress 19

Pre-Production Model DOM 20 PPM-DOM installed on the instrumentation line of ANTARES Fully equipped DOM (31 PMTs + acoustic positioning sensors + time calibration LED beacon) Mounted on the ANTARES instrumentation line. Instrumentation line installed and connected on 16 April 2013 PPM-DOM fully operational and working correctly

First PPM-DOM data from the deep sea 21 Coincidence rate  PMT efficiencies   Up to 150 Cherenkov photons per decay e - (β decay) 40 K 40 Ca Concentration of 40 K is stable (coincidence rate ~5 Hz on adjacent PMTs) PRELIMINARY Coincidence rate on 2 adjacent PMTs Peak position  time offsets PRELIMINARY Number of Coincident hits in a DOM

String deployment tests, April String rolled up for self-unfurling: Deployment and unfurling successful Problems occurred during recovery operations (heavy currents) Detailed analysis ongoing Further tests necessary

Tower deployment in Capo Passero (Sicily) 23 Tower with 8 storeys 4 OMs / storey One 10‘-inch PMT / OM) See Carlo Alessandro Nicolau’s talk at this conference Touchdown at 3500 m

Tower deployment in Sicily 24 Taking data, fully operational. 31 (32) PMT’s working at nominal HV. All 18 hydrophones working. DAQ system working All voltages/current at nominal values All Optical transmission parameters are OK Commissioning still ongoing. ~52 kHz Δt (μs) Rate (kHz) time 2 hours mins Confirmation of previous measurements: Capo Passero site is a very quiet place: Optical background : 52.1 kHz (on average during 10 days), i.e. compatible with 40 K only. Bioluminescence burst rate very low: In 10 days: Burst fraction (>100kHz) =0.4% Burst fraction (>1.2 x Gaussian-mean value)=3.8%

A Detour? (ORCA) 25

Mass hierarchy with atmospheric neutrinos? 26 MSW effect in Earth induces difference in oscillations. Resonance around E ν ≈ 3 –10 GeV (L=D earth, ρ≈ 4–13 g/cm 3 ) Could be measurable since at these energies: Differences in the (E ν, cosθ ν ) plane between normal and inverted hierarchies

ORCA If feasible, it is worth doing it → study group. Caveat: agreed KM3NeT technology, must be used, only minor changes (e.g. length of strings, distance, connection techniques) Given the funding profile, decision should be taken soon. An (scalable) example of detector has been studied: – 50 strings, 20 OMs each – 31 3-inch PMTs / OM – 20 m horizontal distance – 6 m vertical distance – Instrumented volume: 1.75 Mton water 27 Not only “can we see low energy events?”, Long list of questions: What are the trigger/event selection efficiencies? How and how efficiently can we separate different event classes? How can we reconstruct these events and what resolutions can we reach on E and  ? How can we control the backgrounds? What are the dominant systematic effects and how can we control them? What precision of calibration is needed and how can it be achieved?

ORCA 28 significance All the questions above are still under investigation. Results of a toy analysis: Experimental determination of mass hierarchy at 4-5  level requires ~20 Mton-years Improved determination of seems possible

Summary 29

Summary and Conclusions 30 ANTARES has demonstrated the feasibility of a deep-sea neutrino telescope. KM3NeT will provide a multi-km 3 installation in the Mediterranean Sea sensitive enough to detect Galactic sources and more. The design process has concluded in an agreed technology (strings with multi-PMT digital OMs). KM3NeT will be a multi-site installation (France, Greece, Italy). It will provide nodes for earth/sea sciences. A first construction phase in underway. A low-energy option (ORCA) is under investigation.

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