First detection of extensive air showers with the EEE experiment CRIS 2010, Catania, September  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) BARI BOLOGNA CAGLIARI CATANIA CATANZARO FRASCATI (Roma) GROSSETO L’AQUILA LECCE PARMA PISA REGGIO EMILIA SALERNO SAVONA TERAMO TORINO TRINITAPOLI (Barletta) VIAREGGIO (Lucca) Map of high schools involved in the project

Carbon layer Mylar Pick-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 Ωcm. The high voltage applied to the outer glasses generates a uniform electric field between glass electrodes. σ X,Y ≈ 1 cm σ t ≈ 100 ps MRPC: Multi-gap Resistive Plate Chambers

The detector Fishing 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 detector The 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).

The EEE telescope ● Each telescope is made by 3 MRPC modules, approx. 160 x 82 cm ● Gas mixture of C 2 H 2 F 4 +SF 6 (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 Nord Geo. α ~ 11.7° Distance between schools ~ 220 m. Nord Magn. 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 analysis Data 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)

Data analysis Single track event One only track can be reconstruct Multi hit event There 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 analysis To 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 analysis Telescopes distance 180 m S-S sample Time difference (ΔT=T1- T2) between the signals of two telescopes in L’Aquila The measured rate of coincidences R (area of a Gaussian fit) is 3.26 events/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/hour S/N=0.93 σ=155 ns

Data analysis Telescopes 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 analysis Telescopes 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 (σ GPS * √2 ∼ 60 ns)

Data analysis Telescopes distance 180 m S-S sample S-S sample σ =155  70 ns Signal/Noise = 0.93  2 S-M sample R=3.62 events/hour S/N=26 σ =59 ns ΔT distribution corrected taking into account the shower axis direction.

Data analysis Telescopes 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 analysis Telescopes distance 180 m S-S sample Corrected time difference distribution, as obtained by selecting the tracks with an angular divergence less than θ. θ S/N R ° ° ° ° ° ° ° °

Data analysis Telescopes 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 analysis Telescopes distance 220 m S-S sample With time correctionRaw data R=2.64 events/hour S/N=0.56 σ=193 ns R=2.64 events/hour S/N=1.6 σ=86 ns Preliminary ! R= 3.26 (180 m)  2.64 (220 m)

Data analysis Catania 146 m450 m 82 m 40 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.

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