First detection of extensive air showers with the EEE

experiment

CRIS 2010, Catania, September 13-17

Introduction to EEE project The MRPC detector The EEE telescope Telescopes in high school of L’Aquila Data analysis and first results Conclusions and future prospects

Roberto Moro for the EEE Collaboration

The EEE (Extreme Energy Events) project

The EEE Project is a Centro Fermi initiative, in collaboration with INFN, CERN and MIUR (the Italian Ministry of Education, University and Research).

The EEE project

ALTAMURA (Bari)BARIBOLOGNACAGLIARICATANIACATANZAROFRASCATI (Roma)GROSSETOL’AQUILALECCE

PARMAPISAREGGIO EMILIASALERNOSAVONATERAMOTORINOTRINITAPOLI (Barletta)VIAREGGIO (Lucca)

Map of high schoolsinvolved in the project

Carbon layer

MylarPick-up electrode

Glass

The detector

Gas gaps ~ 300 μm

The MRPC has six gas gaps obtained by means of a sandwich of seven glass plates spaced 300 μm (commercial fishing line is used as a spacer), with a volume resistivity of the order of 1013 Ωcm.

The high voltage applied to the outer glasses generates a uniform electric field between glass electrodes.

σX,Y ≈ 1 cmσt ≈ 100 ps

MRPC: Multi-gap Resistive Plate Chambers

The detectorFishing line is used to create uniform small gaps (300 m) between glasses

The detector

The MRPC is equipped with 24 copper strips 160 cm long, with a pitch of 3.2 cm acting as pick-up electrodes to collect the electric signals generated by the passage of particles through the detector.

Pick-up electrode

The detectorThe MRPC provides 2-dimensional position information: 24 copper strips (3.2 cm pitch) give the position in the transverse direction (X); the right-left time difference gives the position in the longitudinal direction (Y).

X

Y

An ultra-fast and low power front-end amplifier/discriminator ASIC specifically designed for the MRPC is being used (NINO ASIC).

v

tty rl

2

The EEE telescope

● Each telescope is made by 3 MRPC modules, approx. 160 x 82 cm

● Gas mixture of C2H2F4+SF6 (98%-2%), continuous flow

● Special FEA cards for readout and trigger

● DC/DC converters for HV (max ±10 kV) to chambers

● GPS time-stamp of the collected events

● VME-based data acquisition

● Each MRPC provides a two-dimensional position information

● Efficiency close to 100% and excellent time resolution

● Good reconstruction of the muon orientation

82 cm

160 cm

Schools and telescopes in L’Aquila

ITIS

Liceo

NordGeo.

α ~ 11.7°

Distance between schools ~ 220 m.

NordMagn.

d ~ 2°

The schools involved in L’Aquila are two: Liceo Scientifico “A. Bafile” and ITIS “A. di Savoia”, at present the distance between telescopes is about 220 m

(180 m before earthquake) .

Schools and telescopes in L’ Aquila

EEE telescope in Liceo “Bafile” EEE telescope in ITIS “di Savoia”

Data analysisData reported refer to 2 different periods:

2008 (300 hours acquisition time) - telescopes distance 180 m

2009 (400 hours acquisition time) - telescopes distance 220 m

Two typologies of events are selected:

• Single track events• Multi hit events

M. Abbrescia et al. NCB 125 B, N.2 (2010) 243-254.

Data analysisSingle track event

One only track can be reconstruct

Multi hit eventThere are a number of hits ≥ 4 and you can reconstruct more than one track

A single track is defined from the presence of hits in each of the three MRPC chambers of the telescope, with no more than 2 adjacent strip signals per MRPC, fitted by a good χ2 straight line on both views.

Data analysisTo fully exploit the tracking capability of EEE telescope, the data have been subdivided into three samples:

Single track-single track (S-S) coincidences: one single track is present in each telescope;

Single track-multihit (S-M) coincidences: a single track is present in one telescope, while the other telescope has a high-multiplicity event.

Multihit-multihit (M-M) coincidences: both telescopes have high-multiplicity events.

Data analysisTelescopes distance 180 m

S-S sample

Time difference (ΔT=T1-T2) between the signals of two telescopes in L’Aquila

The measured rate ofcoincidences R (area of aGaussian fit) is 3.26events/hour.

The values Signal/Noise 0.93, ∼ where Signal is

the area of a Gaussian fit within ±1σ and Noise is the flat background, due to accidental coincidences, within ±1σ

R=3.26 events/hourS/N=0.93σ=155 ns

Data analysisTelescopes distance 180 m

S-S sample

The time difference ΔT = T1−T2 depends on the distance L between the telescopes and on the angle θ’ between the shower axis and the imaginary line joining the centres of the two telescopes. THIS EFFECT CAN BE CORRECTED by means of the muon direction

ΔT is proportional to cos θ’ according to

this relation

Lcos θ’ = cΔT

Data analysisTelescopes distance 180 m

S-S sample

ΔT as a function of cos(θ’)

We expect a straight line distribution of experimental points. The dispersion observed is mainly due to the GPS resolution (σGPS * �√2 60 ns)∼

Data analysisTelescopes distance 180 m

S-S sample

S-S sample

σ =155 70 nsSignal/Noise = 0.93 2

S-M sample

R=3.62 events/hourS/N=26σ =59 ns

ΔT distribution corrected taking into account the shower axis direction.

Data analysisTelescopes distance 180 m

S-S sample

Muons belonging to the same EAS are expected to be nearly parallel.

The Signal/Noise ratio improves by selecting events which tracks have a small relative angle.

EAS axis

Data analysisTelescopes distance 180 m

S-S sample

Corrected time difference distribution, as obtained byselecting the tracks with an angular divergence less than θ.

θ S/N R 2 3.26

50° 2.4 3.05

40° 2.8 2.88

30° 3.8 2.47

25° 4.7 2.35

20° 6.4 2.18

10° 18.3 1.61

7° 27.6 1.35

5° 38.8 0.95

Data analysisTelescopes distance 180 m

M-M sample

R=0.8 events/hour

S/N=75

For this sample no time correction and no angular cut has been applied.

Data analysisTelescopes distance 220 m

S-S sampleWith time correctionRaw data

R=2.64 events/hour S/N=0.56σ=193 ns

R=2.64 events/hour S/N=1.6σ=86 ns

Preliminary !

R= 3.26 (180 m) 2.64 (220 m)

Data analysisCatania

146 m 450 m

82 m40 m

Conclusions

• Extensive Air Showers have been detected with the EEE experiment.

• The MRPC allows the track reconstruction, that is essential to improve the signal to noise ratio (shower direction and noise rejection).

• Soon analysis of coincidences between “close” stations (400 m<L< 4 km).

• Search of coincidences between faraway stations.

Thank you for your attention