ANTARES neutrino telescope: status and first results

1. ANTARES neutrino telescope: status and first results TeV Particle Astrophysics Beijing, September 2008 Juan de Dios Zornoza (IFIC - Valencia) on behalf of the ANTARES Collaboration

2. Neutrino Astronomy • Advantages w.r.t. other messengers: • Photons: interact with CMB and matter • Protons: interact with CMB and are deflected by magnetic fields • Neutrons: are not stable • Drawback: large detectors (~GTon) are needed.  n  p

3. Production Mechanism • Neutrinos are expected to be produced in the interaction of high energy nucleons with matter or radiation: Cosmic rays • Moreover, gammas are also produced in this scenario: Gamma ray astronomy

4. Scientific scopes Detector size • Origin of cosmic rays • Hadronic vs. leptonic signatures Supernovae Limitation at high energies: Fast decreasing fluxes E-2, E-3 Oscillations Limitation at low energies: -Short muon range -Low light yield -40K (in water) Dark matter (neutralinos) Astrophysical neutrinos GZK, Topological Defects MeV GeV TeV PeV EeV Detector density Other physics: monopoles, Lorentz invariance, etc...

5. The ANTARES Collaboration • NIKHEF, Amsterdam • KVI Groningen • NIOZ Texel • ITEP,Moscow • University of Erlangen • ISS, Bucarest • IFIC, Valencia • UPV, Valencia • CPPM, Marseille • DSM/IRFU/CEA, Saclay • APC Paris • IPHC (IReS), Strasbourg • Univ. de H.-A., Mulhouse • IFREMER, Toulon/Brest • C.O.M. Marseille • LAM, Marseille • GeoAzur Villefranche • University/INFN of Bari • University/INFN of Bologna • University/INFN of Catania • LNS – Catania • University/INFN of Pisa • University/INFN of Rome • University/INFN of Genova 5

6. CRAB CRAB VELA SS433 SS433 Region of sky observable by Neutrino Telescopes ANTARES (43° North) AMANDA/IceCube (South Pole) Mkn 421 Mkn 501 Mkn 501 RX J1713.7-39 GX339-4 Galactic Centre V. Bertin - CPPM - ARENA'08 @ Roma

7. Installation

8. The ANTARES detector • 12 lines (900 PMTs) • 25 storeys / line • 3 PMT / storey Buoy Storey Horizontal layout 14.5 m Detector completed in May 2008 350 m Junction box 100 m Electro-optical cable ~60-75 m Readout cables

9. The Optical Module contains a 10” PMT and its electronics The Optical Beacons allows timing calibration and water properties measurements It receives power from shore station and distributes it to the lines. Data and control signals are also transmitted via the JB. The Local Control Module contains electronics for signal processing It provides power and data link between the shore station and the detector (40 km long) Detector elements

10. Milestones • 2001 – 2003: • Main Electro-optical cable in 2001 • Junction Box in 2002 • Prototype Sector Line(PSL) & Mini Instrumentation Line (MIL) in 2003 • 2005 – 2006: • Mini Instrumentation Linewith OMs(MILOM)running since April 2005 • Line 1running since March 2006,firstcomplete detector line • Line 2 running since September 2006 First Physics analysis started with first line • 2007 – 2008: • Line 3-5 running since Jan 2007 • Line 6-10+IL07 since Dec 2007 • Line 11-12 since May 2008 • 2008+: Physics with full detector !

11. Deployment

12. Connection Victor (ROV) Nautile (manned)

13. Pictures from the seabed Detector layout

14. Operation

15. Days in the sea (26/9/08) • A problem with the electro-optical-cable prevented operation during July and August 2008. • The cable has been repaired and the detector data taking had continued smoothly

16. Detector operation Live channels: 90%

17. Median rate 2/3/06 1/5/08 Fraction of time above rate 1(2) lines (2005) 5 Lines (2007) 12 Lines (2008)

18. Active time

19. Detector footprint • Detector as seen by atmospheric muons: position of the first triggering hit

20. Example: Muon bundle height time

21. Example: Neutrino candidate height time

22. Potassium 40 • K40 decays in water produce electrons which induce Cherenkov photons which can be detected in coincidences in two neighboring OMs  Cherenkov light 13.4 Hz in average 20% spread beta decay 40K 40Ca

23. ±100 ns between storey Preliminary Coincidence rate

24. Acoustic detection • Modules for acoustic detection are installed in several storeys (6 storeys in total in L12 + Instrumentation Line) • Distance between sensors ranging from 1m to 340m Status: • Continuous data taking since Dec 2007 with 18 hydrophones • Full system running since May 2008 with 36 acoustic sensors

25. Calibration

26. DR - OB offset difference σ = 0.4 ns RMS 0.7 ns Time calibration with LED beacons • Four LED beacons/line (with 36 blue LEDs each) allow to illuminate the neighbouring OMs • Good technical performance (45/47 are working) • Additional output: water optical parameter measurement Electronics contribution less than 0.5 ns Lines 1-10 • Residual time offset grows with distance (early photon + walk effect) according to a straight  offsets measured in the dark room before deployment can be corrected • Checked with independent K40 tests Only 15% are larger than 1 ns

27. Positioning • Acoustic system: • One emitter-receiver at the bottom of each line • Five receivers along each line • Four autonomous transponders on pyramidal basis • Additional devices provide independent sound velocity measurements Measure every 2 min -Distance line bases to 5 storeys/line andtranspoders -Headings and tilts

28. Positioning results Comparison among storeys Larger displacements for upper top floor Comparison among lines Coherent movement for all the lines of the detector

29. K40 coincidences • K40 coincidence rates reveal a decrease in the OM efficiency • The most likely explanation is a reduction in PMT gain • By retuning the thresholds (every 2-3 months), the rates are recovered • Eventually, PMT voltages can be increased. Threshold retunning Old runsetup used by mistake

30. First Physics analysis

31. Preliminary estimation of systematic errors (I) Zenith angle Azimuth angle Data MC Detector systematics • systematic error due to +/- 10% on absorption length = +25%/-20%; • syst. err. due to -15% on PMT efficiency (QE, eff. area etc) = -15%; • syst. err. due to cutoff in angular accept. = +20%/-15%; • total systematic uncertainty +/- 30%.

32. Preliminary estimation of systematic errors (II) Zenith angle Azimuth angle Data MC Flux model systematics • +30% for primary flux; • +25% for the hadronic shower model; • total systematic uncertainty +40%.

33. Line 1: Intensity-depth distribution • The intensity-depth relationship is obtained from the zenith distribution for down-going muons

34. 5-line data • The 5-line data (Jan07-Dec07) correspond to 140 active days. • Two alternative reconstruction algorithms agree in identifying neutrino candidates. Reconstruction strategy #1 Reconstruction strategy #2

35. Neutrino candidates by A. Heijboer First neutrino candidates have been reconstructed with the 5 lines deployed

36. 10-line data • The 10-line data (Jan08 –May08) correspond to 100 active days. Multi line fit (strat #2) Single line fit (strat #2) 88 neutrinos 208 neutrinos

37. Point-like searches with 5 lines • First analysis looking for point-like sources are underway with five-line data • Two methods are considered (cf. S. Toscano’s talk): • Binned (cone search) • Unbinned (expectation maximization algorithm) • The estimated sensitivity with only 5-line data is already comparable to the best limits in Southern sky so-far. • A blinding policy is followed: unblinding recently approved (yesterday!) • First limits (or discoveries!) on specific sources and skymap will come very soon

38. Expected Performance (full detector) Angular resolution Neutrino effective area Ndet=Aeff × Time × Flux • For E<10 PeV, Aeff grows with energy due to the increase of the interaction cross section and the muon range. • For E>10 PeV the Earth becomes opaque to neutrinos. • For E < 10 TeV, the angular resolution is dominated by the - angle. • For E > 10 TeV, the resolution is limited by track reconstruction errors.

39. Expected Performance Point Sources of neutrinos Diffuse flux of neutrinos ANTARES 1 yr

40. Neutrino candidate with 12-line detector

41. Conclusions • ANTARES has already been completed and is taking data for several months. The collaboration has shown good response capability for solving the different technical difficulties arisen during the process. • It will complete the coverage of the neutrino sky, with an unsurpassed angular resolution. • First analysis have already started (muon flux intensity with one line, search for point-like source with five lines…) • The expected sensitivity for point-like sources of ANTARES for 365 days is comparable to the limits set by AMANDA in 1001 days (2000-2004) • The technical success of ANTARES paves the way for the cubic kilometer detector in the Mediterranean Sea: KM3NeT

43. Particle Physics

44. Model Selection in EM • The parameter used for discriminating signal versus background is the Bayesian Information Criterion, which is the maximum likelihood ratio with a penalty that takes into account the number of free parameters in the model weighed by the number of events in the data sample. D: data set 0: parameters of bg 1: parameters of signal M: model k: number of parameters to be estimated BIC distribution for different number of sources events added (at =-80), compared with only background

45. Neutralino search : Amanda II (2006) : SuperKamiokande (2004) : Macro (1999) : Baksan (1996) μflux from the Sun excludable by Antares per km2 per year vs. mχ : Excl. models, 0.094 < Ωχh2 < 0.129 : Excl. models, Ωχh2 < 1 : Non-excl. models, 0.094 < Ωχh2 < 0.129 : Non-excl. models, Ωχh2 < 1 c.f. G. Lim’s talk 24-09-'08

46. Comparison with CDMS 2008 limit “spin-independent” = -> models where the Higgsino fraction of the χis relatively large are dominant -> the regions excludable by Antares and direct detection experiments are correlated (CDMS : Direct detection experiment sensitive to the spin-independent χp -> χp cross section)

47. Expectation Maximization • The EM method is a pattern recognition algorithm that maximizes the likelihood in finite mixture problems, which are described by different density components (pdf) as: signal: RA,  bg: only  pdf position of event proportion of signal and background • The idea is to assume that the set of observations forms a set of incomplete data vectors. The unknown information is whether the observed event belongs to a component or another. zi is the probability that the event comes from the source

48. Astrophysical Sources • Galactic sources: these are near objects (few kpc) so the luminosity requirements are much lower. • Micro-quasars • Supernova remnants • Magnetars • … • Extra-galactic sources: most powerful sources in the Universe • AGNs • GRBs • GRBs are brief explosions of  rays(often + X-ray, optical and radio) In the fireball model, matter moving at relativistic velocities collides with the surrounding material. The progenitor could be a collapsing super-massive star • Neutrinos could be produced in several stages: precursor (TeV), main-burst (100TeV-10PeV), after-glow (EeV) • Isolated neutron stars with surface dipole magnetic fields ~1015 G, much larger than ordinary pulsars • Seismic activity in the surface could induce particle acceleration in the magnetosphere • Event rate: 1.5-13 (0.1/) ev/km2· y • Active Galactic Nuclei includes Seyferts, quasars, radio galaxies and blazars • Standard model: a super-massive (106-108 Mo) black hole towards which large amounts of matter are accreted • Detectable neutrino rates (~10-100 ev/year/km2) could be produced • Micro-quasars: a compact object (BH or NS) accreting matter from a companion star • Neutrino beams could be produced in the MQ jets • Several neutrinos per year could be detected by ANTARES • Different scenarios: plerions (center filled SNRs), shell-type SNRs, SNRs with energetic pulsars… • 2 ev/km2 for RX J1713 and Vela Junior Refs: astro-ph/0404534, astro-ph/0607286, astro-ph/0204527

49. Expected Limits Point Sources of neutrinos Diffuse flux of neutrinos ANTARES 1 yr

50. Detector response to power law flux Detector response function for neutrino flux E events /E  105 2 Tev -1 Pev Log10 (E /GeV) Neutrino Telescopes naturally much more sensitive to high energies