antares neutrino telescope: status and first results tev particle astrophysics beijing, september...

ANTARES neutrino telescope: status and first

resultsTeV Particle Astrophysics

Beijing, September 2008

Juan de Dios Zornoza (IFIC - Valencia)on behalf of the ANTARES Collaboration

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.

p

n

Production Mechanism

• Neutrinos are expected to be produced in the interaction of high energy nucleons with matter or radiation:

YYKXN )(...)(

)()(

eee

Cosmic rays

0 N X Y Y

Gamma ray astronomy

• Moreover, gammas are also produced in this scenario:

Scientific scopes

MeV GeV TeV PeV EeV

Astrophysical neutrinos

Dark matter (neutralinos)

Oscillations

Supernovae

GZK, Topological Defects

Limitation at high energies:Fast decreasing fluxes E-2, E-3

Limitation at low energies:-Short muon range-Low light yield-40K (in water)

Other physics: monopoles, Lorentz invariance, etc...

Detector density

Detector size Origin of cosmic rays Hadronic vs. leptonic signatures

5

CPPM, MarseilleCPPM, Marseille DSM/IRFU/CEA, Saclay DSM/IRFU/CEA, Saclay APC ParisAPC Paris IPHC (IReS), StrasbourgIPHC (IReS), Strasbourg Univ. de H.-A., MulhouseUniv. de H.-A., Mulhouse IFREMER, Toulon/BrestIFREMER, Toulon/Brest C.O.M. MarseilleC.O.M. Marseille LAM, MarseilleLAM, Marseille GeoAzur VillefrancheGeoAzur Villefranche

University/INFN of Bari University/INFN of Bari University/INFN of Bologna University/INFN of Bologna University/INFN of Catania University/INFN of Catania LNS – CataniaLNS – Catania University/INFN of PisaUniversity/INFN of Pisa University/INFN of Rome University/INFN of Rome University/INFN of Genova University/INFN of Genova

IFIC, ValenciaIFIC, Valencia UPV, Valencia UPV, Valencia

NIKHEF, Amsterdam NIKHEF, Amsterdam KVI GroningenKVI Groningen NIOZ TexelNIOZ Texel

ITEP,MoscowITEP,Moscow

University of University of ErlangenErlangen

ISS, BucarestISS, Bucarest

The ANTARES Collaboration

V. Bertin - CPPM - ARENA'08 @ Roma

Region of sky observable by Neutrino Telescopes

Mkn 501

Mkn 421

CRAB

SS433

Mkn 501

RX J1713.7-39

GX339-4SS433

CRAB

VELA

GalacticCentre

AMANDA/IceCube (South Pole)AMANDA/IceCube (South Pole) ANTARES (43° North)ANTARES (43° North)

Installation

The ANTARES detector

Horizontal layout

• 12 lines (900 PMTs)• 25 storeys / line• 3 PMT / storey

14.5 m

~60-75 m

Buoy

350 m

100 m

Junctionbox

Readout cables

Electro-optical cable

Storey

Detector completed in May 2008

Detector elements

The Local Control Module contains electronics for signal processing

The Optical Beacons allows

timing calibration and water properties

measurements

The Optical Module contains a 10” PMT and its electronics

It receives power from shore station and distributes it to the lines. Data and control signals are also transmitted via the JB.

It provides power and data link between the shore station and the detector (40 km long)

2001 – 2003: Main Electro-optical cable in 2001 Junction Box in 2002 Prototype Sector Line (PSL) &

Mini Instrumentation Line (MIL) in 2003

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 !

2005 – 2006: Mini Instrumentation Line with OMs (MILOM) running since April 2005 Line 1 running since March 2006,

first complete detector line Line 2 running since September 2006

Milestones

First Physics analysis started with

first line

Deployment

Connection

Nautile (manned)

Victor(ROV)

Pictures from the seabed

Detector layout

Operation

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

Detector operation

Live channels: 90%

Median rate

1(2) lines (2005)5 Lines (2007)12 Lines (2008)

2/3/06 1/5/08

Active time

Detector footprint

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

Example: Muon bundle

height

time

Example: Neutrino candidate

height

time

Potassium 40

• K40 decays in water produce electrons which induce Cherenkov photons which can be detected in coincidences in two neighboring OMs

40K

40Ca

Cherenkov light

beta decay 13.4 Hz in average20% spread

13.4 Hz in average20% spread

Coincidence rate±100 ns between storey

Preliminary

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

Calibration

Time calibration with LED beacons

Lines 1-10

DR - OB offset difference

Only 15% are larger than 1

ns

RMS 0.7 ns

σ = 0.4 ns

Electronics contribution less than 0.5

ns

•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

•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

•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

•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

Positioning

Measure every 2 min

-Distance line bases to 5 storeys/line andtranspoders

-Headings and tilts

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

Positioning results

Larger displacements for upper top floor

Coherent movement for all the lines of the detector

Comparison among storeysComparison among storeys

Comparison among linesComparison among lines

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

First Physics analysis

Preliminary estimation of systematic errors (I)

• 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%.

Zenith angle Azimuth angle

DataMCDetector systematics

Preliminary estimation of systematic errors (II)

Zenith angle Azimuth angle

DataMCFlux model systematics

• +30% for primary flux;• +25% for the hadronic shower model;• total systematic uncertainty +40%.

Line 1: Intensity-depth distribution

• The intensity-depth relationship is obtained from the zenith distribution for down-going muons

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

by A. Heijboer

First neutrino candidates have been reconstructed with the 5 lines deployed

Neutrino candidates

10-line data

• The 10-line data (Jan08 –May08) correspond to 100 active days.

Multi line fit (strat #2)

208 neutrinos

Single line fit (strat #2)

88 neutrinos

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

Expected Performance (full detector)Neutrino effective area Angular resolution

•For E < 10 TeV, the angular resolution is dominated by the - angle.•For E > 10 TeV, the resolution is limited by track reconstruction errors.

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.

Expected PerformancePoint Sources of neutrinos

Diffuse flux of neutrinosANTARES 1 yr

Neutrino candidate with 12-line detector

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

Particle Physics

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 set0: parameters of bg1: parameters of signalM: modelk: number of parameters to be estimated

BIC distribution for different number of sources events added (at =-80), compared with only background

Neutralino search

45/2324-09-'08

: Excl. models, 0.094 < Ωχh2 < 0.129

: Excl. models, Ωχh2 < 1

: Non-excl. models, 0.094 < Ωχh2 < 0.129

: Non-excl. models, Ωχh2 < 1

μ flux from the Sun excludable by Antaresper km2 per year vs. mχ

: Amanda II (2006): SuperKamiokande (2004): Macro (1999): Baksan (1996)

c.f. G. Lim’s talk

Comparison with CDMS 2008 limit

“spin-independent” =

-> models where the Higgsino fraction of the χ is relatively large are dominant

-> the regions excludable by Antares and direct detection experiments are correlated

(CDMS : Direct detection experiment sensitive to thespin-independent χp -> χp cross section)

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:

proportion of signal and background

pdf signal: RA, bg: only

position of event

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.

),( }{ raiii xx ),,( }{ ra

iiii zyy zi is the probability that the event comes from the source

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

• 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

• 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

• 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 (100 TeV-10 PeV), after-glow (EeV)

Refs: astro-ph/0404534, astro-ph/0607286, astro-ph/0204527

Expected LimitsPoint Sources of neutrinos

Diffuse flux of neutrinosANTARES 1 yr

Detector response to power law flux

Log10 (E /GeV)

even

ts /E

Detector response function for neutrino flux E

105

Neutrino Telescopes naturally much more sensitive to high energiesNeutrino Telescopes naturally much more sensitive to high energies

2 Tev -1 Pev

Muon reconstruction

• On shore data filtering

– Local trigger L1 : coincidence < 20 ns on storey– At least 4 L1 in coincidence « Physics event »

• A single line poor sensitivity to azimut use 4 parameters chi2 fit

220i

2c0i0i sin)zz(dtgcos)zz()tt(c

V. Bertin - CPPM

C. Distefano et al, ApJ 575, 378(2002)

Model of Levisson and Waxman:Model of Levisson and Waxman:Proton interactions on synchrotron gamma from electronsProton interactions on synchrotron gamma from electrons - assuming 10% of jet energy in protons- assuming 10% of jet energy in protons

Event rates from Microquasars in ANTARES


MILOM Singles Counting Rates

2 mn

Burst-fraction:fraction of time whenrate > baseline + 20%

3 months

Baseline rates

~15% higher counting rate of OM1 due to

lower threshold

Baseline (40K+biolum.)

Bursts frombiolum.

Deployment

Acoustic detection(upper part of line 12)


Front-end electronics

M. Circella – Status of ANTARES VLVnT08

The full-custom Analog Ring Sampler (ARS) chip performs the front-end elaboration of the PMT signals (pulse shape discrimination, threshold detection, time stamp, digitisation) and data transfer toward the DAQ processor

Data digitisation is performed when a threshold condition is met. A mixed analogue-digital pipeline is used for temporary data storage.

Time stamp: the arrival time of the signals is recorded by means of a counter incremented by the master synchronization signal (20 MHz) and an internal TVC

Pulse shape discrimination (PSD): • amplitude and time are recorded for single photoelectron (SPE) signals• the entire waveform is digitized for non-SPE signals

Inputs from the anode and last dynode of the PMT

Threshold detection: level-0 trigger signals are generated by the ARS when the input signal exceeds a predefined threshold level. This trigger signal may be used to search for local coincidencies among the PMT signals of one storey

A serial output transfers the data to the DAQ processor (20 Mb/s)

56

3 ARS chips, arranged on a single motherboard, serve an individual PMT: data acquisition is performed by two of them in a “token ring” configuration, the third one being used for trigger purposes


M. Circella – Status of ANTARES 57VLVnT08

100 Mb/s linkSCM

MLCM 2

MLCM 3

MLCM 4

MLCM 5

1 Gb/s link

MUX

deMUX

to shore

(MEOC)

JBLine 1

Line 2

LCM

LCM

LCM

LCM

OM

OM

OM

OM

OM

Shore StationLa Seyne-sur-mer

Demux/Mux

Computerfarm

LCM MLCM 1

ANTARES: a large undersea LAN…

Data acquisition architecture



Clock distribution

START STOPTDC

STARTSTOPGPS E/O/E

TXRX

Main Electro-Optical Cable 40 km

from shore to Junction BoxSingle bidirectional fibre

(1534 nm / 1549 nm)

Junction Box116 passive splitter

String Control ModuleBIDI modules

O/E and E/O convertersby sectors (5 storeys)

Local Control ModulesLCM clock boards

1534 nm1549 nm

1310 nm1550 nm

On-shore Station Link Cables200-500 m fibre

1534 nm1549 nm


M. Circella – Status of ANTARES VLVnT08

ARS ARS ARS ARS ARS ARS

Trigger

Ethernet switch

Trigger Trigger

PC n-1 PC n PC n+1

Time (slices ~100ms)

x,t,Q

off-shore

on-shore

DAQ: all data to shore

~1 MB/s

591-10 MB/s


Standard trigger…MajorityMulti-directional

log10(E)

effic

ienc

y

5 local coincidences or large pulses

• L0: PMT hit above 1/3 p.e.

• L1: local coincidence (2 L0 in the OM triplet in t<20 ns) or a large pulse (> 3 p.e.)

350 m

180 m200 m

200 m

100 m

TRIGGER:• 5 L1• causal connection between L1:



…and specialized triggers (e.g.: GRB)


Out of 198 GCN triggers 176 have been handled by Antares DAQ

In some cases, data are recorded even before the alert



Examples of seismic eventsExamples of seismic eventsExamples of seismic events


Multi line fit Single line fit

0.78/day

0.005/day

0.70/day

0.36/day

0.45/day

0.07/day

Fit quality cut to select neutrino


Data Taking efficiency

Detector with 5 lines Detector with 10 lines


Coincidence rate between adjacent optical modules

Calibration with Potassium-40

40K decay

(β or EC)

on average~35 photons

tuning 2tuning 1

40K coincidence rate during 18 months


ANTARES Optical Beacons

The complete detector has 49 Optical Beacons:

• LED OB: 4 per line in floors 2, 9, 15 and 21

• Laser OB: at the anchor in lines 7 and 8.

• Special LED OBs in the UV (~400 nm) (L11 F2 + L12 F2).

Allow the measurement of the optical water properties for a different wavelength.

60 m

300

m

60 m

300

m


Reconstructed events with 5 line dataReconstructed events with 5 line data

Multi line fit Single line fit

78 neutrinos 36 neutrinos

Data: June 2007 – Dec 2007 : 100 active days

Original reconstruction algorithm

75 neutrinos

Data: Feb 2007 – Dec 2007 : 140 active days


Mozambique

Feb. 22, 2006

Lavandou (France)

Feb. 9, 2006

Multidisciplinary research activity:

real-time broadband seismometerReadout by MILOM and now by Line 12


69

Multidisciplinary research activity:cetacean survey

Moon shadow

• In principle, the Moon shadow can provide a (anti)test-beam for the absolute pointing accuracy of ANTARES

ANTARES angular resolution for high energy muons (0.3deg) is smaller than the size of the Moon (0.5 deg)

Large statistics are needed since the moon covers only a tiny fraction of the sky (~10-

5)

Moon shadow

Moon shadow detection with 5 line detector is marginal

The expected significances after one year is 0.4 , scaling with time as T

Similar perspective can be concluded for the 12 line detector.

From JP Ernewein at vlvnt08

Calibration with surface array

Floating stations Atmospheri

c Muon

ANTARES

A floating array of EAS detectors can be used as a sea-top calibration infrastructure over ANTARES. Such an array can detect atmospheric shower muons and the collected data can be used for the reconstruction of the direction and the estimation of the impact parameter of the shower axis.

HELYCON station: scintillation counter + GPS antenna + digitization and control electronics

Floating array• The marine operation could be

done on CASTOR in a five day campaign

• Preliminary studies predict a calibration resolution of 0.5 degrees in identifying a possible zenith offset (1.5 deg for azimuth)

• Cost estimation: 90 k€

Median 4°

(surface array above ANTARES)

antares neutrino telescope: status and first results tev particle astrophysics beijing, september...

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